Food Jerry C. Cavagnol General Foods Research Center, Tarrytown, N. Y.
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review (247) covered advances in food analysis to December 1, 1958. The present review covers the interim period to October 1, 1960. During this time three books, devoted wholly to the analysis of foods, were published. Revisions have brought up to date the third edition of Jacobs’ standard text (165) and the ninth edition of the A.O.A.C. (858). One text covered analytical methods for fats and oils (136). The principal changes made in the 11th edition of “Standard Methods for the Examination of Dairy Products” have been itemized, although the book was not available (37). Analytical procedures were given in appropriate sections of books on proteins (e), milk (169), and large food groups (240, 299). I n four books, individual chapters were devoted to meat (380), carbonated beverages (166), fats and oils (187), and cereals (233). HE PREVIOUS BIENNIAL
ADDITIVES
The need for accurate reproducible methods for food additives to support petitions to the FDA has produced a tremendous surge of activity for new methodology in a variety of food products. This is especially pertinent where edible fats and oils are present. A comprehensive review included specific tests, spectrophotometric and chemical methods, and biological assays (326) for butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), nordihydroguaiaretic acid (KDGA) [4,4’(2,3 dimethyltetramethy1ene)dipyrocatechol], propyl gallate (PG), and others. The methods and results of the collaborative A.O.A.C. study have been reported (78). Where mixtures of antioxidants have been employed, methods mere reported for determining each component by distribution between solvents (378) and reversed-phase paper chromatography (388). In one publication, unidimensional paper chromatography was used to separate a mixture of BHA, BHT, PG, and NDGA (93). Methods have also been reported for qualitative (207) and quantitative ($9) analyses of twocomponent mixtures. For those fats containing a single antioxidant a number of methods have
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ANALYTICAL CHEMISTRY
been suggested. Reagents for determining gallate esters include mercuric acetate (323), ferrous ammonium sulfate (66), and cerous ion (41). A rapid method for the determination of butylated cresol was reported (381) but was unsuitable for lards containing smoke substances, BHA, and NDGA. Silver nitrate in buffer solution was used to measure NDGA quantitatively (322). The detection of BHA (380) and BHT (388) has been effected after refluxing with ethanolic KOH under specified conditions. The antienzyme bromoacetic acid has been added to fruit juices, beverages, sirups, and milk. It was determined polarographically (363), by conversion to lysine and measurement with ninhydrin (375) and by ascending paper chromatography (304). Chloroacetic acid was estimated by treatment with thiosalicylic acid and subsequent ouidation to the red thioindigo, extractable with chloroform (238). The hydrolysis of isopropyl 3-chlorophenylcarbamate to m-chloroaniline and subsequent conversion of the latter with hypochlorite and phenol-NHs to a blue color have been reported as a quantitative method for determining this sprout inhibitor in potatoes and potato chips (184). Iodophors in milk have been detected by the blue color produced after reaction of the iodide with a-napthoflavone and hydrogen peroxide (107). Rromates added to flour to increase the volume of bread may be estimated with sulfofuchsin reagent. Specificity was achieved since peroxide, nitrites, persulfates, and perborate did not interfere (105). Two articles have appeared that outline procedures for detecting, identifying, and determining a variety of food preservatives using various spray reagents on paper chromatograms (67,80). The low levels of preservatives in foods continue to present a problem for analysts. Publications have appeared for microquantities of N , N -diphenyl-pphenylenediamine in chicken fat, organs, and egg yolk determined by the red color formed with sulfuric and nitric acids (sa), and in milk by ascending paper chromatography (98). Methods were reported for the quantitative determination of dehydroacetic acid (3acetyl 6 - methyl 2,3 dihydropyran-
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2,4-dione) in various foods (184, 199, 339). A nitration procedure developed for the determination of benzoic acid in foods (337) was critically exarnincd (137) and found to require better control of reaction conditions. A method has been proposed for the colorimetric determination of o-phenylphenol in oranges with 4-aminophenazone (353). Chlortetracycline and oxytetracycline in fish and poultry were estimated by growth inhibition of Ban‘lleis cereus var. mycoides (246). Recent work on emulsifiers has vielded publications on the analysis of b e a d and cakes for polyethylene esters (39, 248) and on edible fats for polyethylene glycol (11). Milk product. suspected of containing a stabilizing agent have been quantitatively analyzed for carrageenin in a recent paper (146). Traces of silicone antifoamer were detected by application of the silicomolybdate procedure to the ashed sample (157). Infrared was used to determine the particular type of silicone present. A paper on antibiotic methods will be of interest to those concerned with milk assays. Penicillin G or V, chlortetracycline, oxytetracycline, and tetracycline h a w been estimated by both a n inoculation procedure and a disk assay method (163). The interference of essential oils in th; determination of biphenyl in citrus fruits has been 4 m i nated by oxidizing the oils with permanganate and convert ~g the biphenyl to the sulfonic acid der’vative so that the ultraviolet absorption may be measured in a a t e r bolution (191). The unique method for p-hydrouybenzoic acid esters in wine i: based on the solubility of the p - n i t r cDnzene,~~ diazonium chloride coupling pi odlict in rhloroform (52). The azo dyc 1 ielded a sensitivity of 10 p . p m The utility of column chromatography mas well illustrated in a paper giving the polycyclic aromatic hydrocarbon levels in oysters collected ic polluted n-ater. Separations were spectrophotometrically distinct for benzo[ghilperj lene, benzo [alpyrene, benzo[alanthracene, benzo [k] Auoranthene, benzo [elpyrene, chrysene, pyrene, and fluoranthene (57). Thiobarbituric acid was used to assess the vanillin content of foods. Interferences by sugars are
eliminated by extracting the vanillin with ether (20). An improved procedure for detecting and measuring alkaloid in foods such as sausages, meat, milk, flour, and jam has been reported (193). Separations were effected by paper chromatography utilizing the descending technique and potassium iodoplatinate as the developer. After separation by paper chromatography both furazolidone [N(5 - nitro - 2 furfurylidene) 3 amino2-oxazolidone] and nitrofurazone (5 nitro - 2 - furaldehyde semicarbazone) have been detected visually a t levels as low as 0.5 p.p.m. in chicken tissues (150). The determination of hexamethylenetetramine in fish preparations (40) and other foods (99) is effected by hydrolysis to formaldehyde, which is estimated colorimetrically. Foods and drinks have been analyzed polarographically for saccharin (152). Quantitative methods reported for sorbic acid include absorption of bromine (838), a spectrophotometric determination at 252, 258, and 264 mp on the methanol extract (306), and a modification of the Luckman and Melnick distillation procedure (260).
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ADULTERANTS
Purr's articles continue to yield valuable information on analytical methods for detecting substitute fats in cocoa and chocolate products (289, 290, 291, 292). Other workers have publiqhed methods for palm-kernel oil in cocoa butter (365), foreign fats in cocoa products utilizing gas chromatography (373), and a paper chromatographic separation method for small amounts of adulterants in chocolates and other confections (275). Several methods have been suggested for the detection and estimation of various substitutes in coffee. Specific tests for coffee grounds, chicory, and cereal have been submitted (123, 280). A column chromatographic technique has been reported for coffee containing mineral oil (82). The presence of roasted date seed or tamarind seed powder in coffee blends can be established by estimating the cyanidin colors formed after hydrolysis (254). Analysis for aldoses on paper chromatograms has made it possible to determine 10% adulteration in coffee (333). The level of honeydew in honey can be estimated by substituting the data for ash, pH, and reducing sugars in a linear discriminant function (188). The value of the function serves to classify a sample as floral or honeydew in origin. The level of sugar sirup in honey can be estimated by paper strip chromatography using a n l-propanolethyl acetatewater developer (376). The presence of sucrose in milk has been detected by procedures using
chemical (36) and paper chromatographic (296) methods. The color reaction of reconstituted milk with resazurin permits its estimation in raw or pasteurized milk (26). Cow's milk in goat's milk, cheese, and butter can be detected from the 0-carotene content (203). Adulteration of olive oil presents problems similar to those encountered with cocoa butter. The applications of infrared spectroscopy (43) and spectrofluorimetry (91) have provided some assistance on this problem. Of greater specificity are methods involving hydmlysis to fatty acids, followed by gas chromatography (76), the detection of rape oil by paper chromatography after oxidation of the unsaturated CIS fatty acids (180), and by the melting point of the sterol acetate isolated (362). Vanilla extracts containing adulterants have been examined successfully by a method that utilizes gas chromatography on the noncarbonyl volatile fraction (56). By increasing the sensitivity of detecting vanillin, ethyl vanillin, and coumarin down to 4 p.p.m., it has been possible to uncover imitation vanilla extract in ice cream, cupcakes, cake mix, and candy (109). A lengthy but systematic procedure has been reported for low levels of adulteration (287). Application of paper chromatographic techniques to the nonsaponifiable portion of a fat mixture permitted separation of cholesterol from phytosterols making it possible to detect animal or vegetable fat in the presence of the other (268). Using a similar technique ghee was differentiated from other fats (295). Other gas and paper chromatographic techniques have been applied to the detection of fish oil in butter (61), groundnut oil in edible oil (47), and rapeseed oil in peanut oil (577). Several papers have reported the use of paper chromatography for separating and detecting adulterants such as blackberries, bilberries, and raspberries in black currant juices (374),sweet potato in tomato ketchup (25), and opium in food (327). Adulteration of cayenne, red, and chili peppers has been disclosed by a combined chemical treatment and taste test (354). The fluorescence of certain particles served as a means of detecting soy flour in wheat flour (281). ALIPHATIC COMPOUNDS
The conversion of micro quantities of citric acid to pentabromoacetone electrolytically was reported as suitable for fruits, berries, vegetables, and dairy products. Details of the electrolytic apparatus are given (510). A micromethod for formic acid was described using a special apparatus to esterify and distil the ethyl ester, and converting
it to the colored ferric hydroxa,mte (196). The hydrocyanic acid conttilt of canned apricots, cherries, and prunes was measured a t 520 mp after conversion to the cyanide-benzidine complex (220). A modification of the current A.O.A.C. method for malic acid in maple sirup by the use of a n ion exchange resin provides greater specificity (969). A new method for determining tartaric acid in wine (229) was based on the precipitation of the barium salt and subsequent iodometric titration. The use of nitron hydrochloride as an extraction indicator for determining organic acids in colored solutions has been reported (18). A mixture of 2-propanol and 2butanol, distilled from fermented liquids, was oxidized to ketones and the total ketone determined with hypoiodite (127) on one fraction. The second fraction was used to determine t h e acetone colorimetrically with salicyladehyde. Diacetyl in butter and starters has been measured by steam distillation followed by conversion to the quinoxaline derivative with o-phenylenediamine and photometric measurement a t 335 mp (163). The gas chromatograph was used to determine fusel oil in grape brandy but the results were not in agreement with those of the standard colorimetric procedure (46). Glutamine in sugar factory juices was estimated by conversion to glutamic acid followed by electrophoresis (318) and under the conditions used no pyrrolidonecarboxylic acid was produced. A method for determining both glycerol and 2,3-butanediol in wines is based on the determination of the sum by periodic acid oxidation and on the reaction of glycerol with chromotropic acid to form formaldehyde (557). Various methods for the determination of methanol in alcoholic spirits have been reviewed (165). A method for methyl mercaptan in irradiated meat has been offered based on the reaction with N , N '-dimethyl-pphenylenediamine (336). Folin reagent was used to determine the oxymethylene glycol aldehyde content of heated milk (2). The estimation of trimethylamine oxide in muscle extract is achieved by reducing the compound with titanium trichloride and estimating the triethylamine colorimetrically as the picrate (66). A rapid distillation method was reported for the quantitative determination of malonaldehyde in rancid foods using thiobarbituric acid as the colorimetric reagent (550). Good correlation of TBA numbers with rancid, odor in cooked meats was established. AROMAS AND PLAVORS
The objective evaluation of aroma and flavor continues to intrigue food analysts. A review of the field of V O L 33,
NO. 5, APRIL 1961
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citrus flavors inrluded a section on analytical techniques (341). The relative elution rates of 21 2.4-dinitro~~liciiylli!~drazone~ from Y chroniatographic column composed of Hyflo Super Cel activated with nitromrthane was reported (170). The carbonyls were encountered i n the analysis of fl:ivoring materials. Several papers have dealt with the composition of carbonyls present before and after heating pork fat (121. 122). The degree of rancidity of fats can be estimated spectrophotometrically by the red color produced after reaction with sumdiphenylcarbazide ( 3 2 4 ) . The estimation of the lower fatty x i d s has been presented (319) as a means of screening foods to detect early decomposition. In a study of vacuum padeurizntion of milk, the anal) g:iq chromatography shon-ed xhether co\vs were fed alfalfa silage, onion tops, or beet tops (383). Tecliniqucs have been v-orked out for the determination of aldehydes in bread during rising and during various baking times (306). The taste values n-ere found to be relnted to the aldehyde content. -1rapid nictliod for estimating volatile aldehydes, ketones, and acids in vegetables \vas proposed based on the conversion to 2.4-dinitrophcnylhydrazones.TT'hen the combined derivatives were 1ie:itcd n-ith 0-ketoglntkric acid, the regenerated compounds iverci volatilized directly into a gas chromatography unit (294).
exchange resin in the formate form for the separation of purines, pyrimidines, and nucleosides permits subsequent determination by ultraviolet spectrophotometry (173). Ingestion by cows of certain green plants gives rise to I.-5vinyl-2-thiooxazolidone in the milk which can be determined spectrophotometrically with fair accuracy (198). Total phenols, leucoanthocymins, flavanols, and anthocyanins were distinguished on the basis of specific reactions carried out on the same extract of canned plums (346). Anthocyanins in red must and red wine have also been separated and measured by viewing papcr chromatography in ultraviolet light (103). A useful addition t o the literature on the paper chromatography of sterols was reported (396) describing in detail the separation achieved by reversed-phase partitioned chromatography of sterols and their functional derivative. Kumerous solvent systems, part'ition coefficients, and developing reagents were also cited. COLORING AGENTS
hlethodq have been examined for the determination of 17 coloring materials recently banned in Italy in foodstuffs. The initial report deals with the polarographic determination of Xaphthol Yelloir , Aniline Yellow, Chrj soidine, Orange I, Acid Bordeaux, Ponceau 2R, Biebrich Scarlet, Eosine, and Phloxine (58). Details have been presented for the identification of and Rj values for AROMATIC AND HETEROCYCLIC COMPOUNDS 41 food colors ( 8 1 ) . Water-soluble dyes nere isolated from foodstuffs by The incre:iird use of decaffeinated fixation on wool. Extraction with coflce has yxirred interest in improving quinoline is preferred over ammonia for microc.l~em;r,al methods for caffeine. subsequent circular paper chromatogPrcocedurcs \\-ere based on precipitation raphy (261). Other methods have n.ith Iicriodide (138, 147') and iodide been presented for dyes utilizing ion ex(166j,and ?lie use of pliosphotungitic change and paper chromatography (94) :icic! for a turbidimetric determination or initial extraction with quinoline (262). (3'0). Othclr studies on coffw have In the latter procedure, modifications yielded methods for chlorogenic acid are introduced for foods containing ( I l l ! 'Sf) and mixtures of chlorogenic, large amounts of fat, protein, or starch. 1.3.4.5 - tetrahydrosycyclohexanecarSeveral papers dealing with the deterhoxylic, and 3,4-dihydroxycinnarnic mination of individual dyes in mixtures :ivi(ls (297). Polarographic and specby paper electrophoresis have been retrophotometric methods suitable for the ported (86, 197, 209). Methods have dc termination of the 1,4-cinnamyl ester of 1,3,4,5-tetrahydroxycyclohexanecar- been presented for the analysis of the four oil-soluble colors now certified for bosylic acid (quinic acid) in artichokes food use (332). were reported ( 6 9 ) . Suitable equat'ions have been derived for calculating the levels of chlorophylls and pheophytins in ENZYMES grern vegetable extracts by measuring The modified Scharer phosphatase absorbances at four wave lengths (5.59). test for multiple sample testing in the Methods for the determination of 5control of pasteurized milk and cream hydroxymcthyl-2-furfural have been rehas been used by the Bureau of Laboraported for glucose sirups (389, 390) tories of Baltimore City Health Deusing the benzidine reagent, and in partment for more than ten years (178). milk products b y rcaction with 2-thioSince alkaline phosphatase is associated barbituric acid (183). An interesting with the immune globulin in skim milk test for the same compound in honey the incidence of mastitis influences the ut,ilizes the formation of a brilliant red concentration of this enzyme in skim color after rcaction with fresh sesame milk. The phenol liberated from dioil (242). Application of a basic anion
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ANALYTICAL CHEMISTRY
sodium phenylphosphate with alkaline phosphatase n a s measured colorimetrically after treatment with Gibbs' reagent (379). It was recommended that the results of the phosphatase test on butter be expressed in terms of either the phenol content of the butter or the protein-free filtrate (283). The aamylase activity of flour and pulverized grain was measured by determining the times required to gelatinize and liquify flour suspensions. A diastatic number is calculated from these times which are related linearly to the a-amylase activity (139). Peroxidase in whole kernel sweet corn is determined quantitatively by the absorbance a t 420 mp when HZ02 oxidizes o-phenylenediamine in the presence of the enzyme (360). FATS, OILS, AND FATTY ACIDS
hlilk products dominate the field of fat and fatty acid analyses. Rapid methods introduced include the sequence of hydrolysis, acidification, extraction, and titration of liberated fatty acids as a measure of fat in milk caramels (S),and a modified Babcock test, called the TeSa test (9),that utilizes a solubilizing agent, a dispersing agent, and a buffer salt to isolate the fat in ram milk. The introduction of a heated centrifuge and a shaker (116) served as a basis for modifying the Gerber method for dried milk. Work in the nearinfrared region has shown (133) that a single turbidity measurement a t wave lengths of -1.2 microns on diluted milk gives accurate fat values. Gentilini's procedure has been modified to yield butter fat values (162) in close agreement with those by the Gerber met'hod. The fat' content of milk, cream, cheese, and creamy curd determined by Gerber's, Koehler's, and 1.m Gulick's routine methods were compared (219) lyith the Roese-Gottlieb method and A the data analyzed statistically. quick gravimetric method for fat in casein (272) was based on rendering casein penetrable to fat solvents by dispersal in alcoholic-SHa followed by precipitation with alcoholic-HC1. Photometric measurement of turbidity in milk (148) and ice cream mix (274) after dilution compares favorably with standard fat methods. 'The use of amyl alcohol in the Koebler butyrometer for determining eream fat was reported (397). A rapid modified Babcock method using acetic acid-perchloric acid was recommended (302) for fat in canned fish. One group of investigators reviewed and compared seven met'hods for determining fat in mayonnaise and recommended benzyl alcohol (100) according to Hadorn and Jungkunz. Methods based on the density of a solvent-fat solution have been proposed using trichloroethylene for saiusages
(130) and o-dichlorobenzene for peanuts, 3alm nuts, and karite seeds (140). 3xcept for varying results with copra ~e methods agreed with the Soxhlet method within 1%. A rapid method for fat in canned foods includes the design of a special grinder that mixes and expresses the filtered fat solution into a pipet (134). For bakery products where the kind and relative quantities of fat mixtures are known, the total fat may be estimated quickly by a refractometric method (190). A number of papers deal with the efficiencies of various solvents used for defatting soybean, sunflower and flax seeds and oil cakes (309), flaxseed, rapeseed, and wheat flour (328), and feeds, and meat products (329). Oils from apricot, peach, almond, castor, cottonseed, and fish have been determined in emulsions using IC1 as the reagent. Of the nine emulsifiers studied-apricot gum, gum arabic, gelatin, starch, salep, dextrin, gum tragacanth, and yolk, only the last reacted with IC1 (128). The reaction between mercaptoacetic acid and unsaturated glycerides was used t o separate and determine ( I f 3) saturated glycerides in a number of commercial fats and oils. I n a n extended work various mixtures of 12 synthetic and 17 natural fats were separated by means of paper chromatography (181) by making the papyrographs hydrophobic with undecane or paraffin. Fatty acids in fatty oils were analyzed with the Cu-triethanolamine reagent (164) by a combination of paper chromatography and polarography with copper acetate (179) and colorimetrically with F e and Hg salts (300). E:mploying a-naphtholphthalein as a n indicator simplified the titrimetric procedure for fatty acids in milk (271). Isomerization of unsaturated fatty acids in K tert-butoxide in place of the KOHethylene glycol (A.O.C.S.) method gave good agreement with linoleic acid but higher results with linolenic acid (368). Fatty acid analyses employing gas chromatography have received a tremendous impetus from improved instrumentation. This was illustrated by the work on vegetable oils (84), and milk, butter, cheese, bread, and alcoholic beverages (101, 1 4 , $67). I n a study on meat fat (159), fatty acids separated from large amounts of unsaponifiables on an anion exchange resin, were converted to methyl esters on the resin and analyzed by gas chromatography. Paper chromatography was used to determine quantitatively the four lowest fatty acids in leaven, dough, and bread made from wheat and rye flours (85). Improved techniques for fatty acid determinations by circular paper chromatography include articles on milk products (136, 171, 346) and fish oils
(8.43). The annual review of the literature on fats and oils ($77)was continued under a new reviewer (308). Published reports have appeared (270, 317) on estimating the degree of fat oxidation with thiobarbituric acid. A method for the peroxide value of edible fats uses peracetic acid for forming the fat peroxides (347). The peak areas of gas chromatograms have been related to weight percentages of fatty alcohols (212) derived from soybean oil. A unique method of determining lipides involves acetylation with C14 acetic anhydride, separating acetylated amines, monoglycerides, and diglycerides, and estimating lipides by radiography (227). Five different glycerides in soybean oil were determined quantitatively by paper chromatography followed by saponification on the paper and measurement of each acid mixture (182). GASES
The level of ethylene in air above apples stored under various conditions has been measured down to 0.1 p.p.m. using a gas chromatograph with a flame ionization detector (237). Gas chromatography has also been applied in evaluating the headspace gases of cans (340). An accurate and rapid electrochemical method has been proposed for determining oxygen in beer (331). A description of the apparatus for automating the method is included. Butter has been analyzed for dissolved or occluded air by measuring the oxygen in the air absorbed by pyrogallol solution when the butter is heated (349). Errors resulting from loss of carbon dioxide when heavily carbonated beer containers are opened were eliminated by the use of specially designed tools and improved techniques (2.8). A collaborative A.O.A.C. study on the determination of carbon dioxide in wines using a newly designed all-glass apparatus gave encouraging results (288). The determination of sulfur dioxide has been improved by using methanol as a solvent in a modified Monier-Williams method (394), and by application of cathode ray polarography (162). INORGANIC IONS
Potatoes have been analyzed for small amounts of arsenic by extraction and reduction of molybdoarsenic acid to the heteropoly blue and subsequent colorimetric estimation (213). A novel estimation of ash in clarified cane juice utilizes the exchange of hydrogen ions for inorganic ions on a strong cation exchange resin (73). The eluted acids were titrated and gave equivalent ash values within *lo% of those found directly. Iodide and bromide have been determined in cabbage polarographically without preliminary separa-
tion (17). New procedures have been published for the determination of calcium in cane juice (28, 164), in milk and cheese (104, 17 6 ) , and in milk and whey (211). The mercurimetric method for chloride has been applied with modifications to milk (161, 367), beer and malt (145), and salted fish, cheese, and bread (19). Errors in determining chloride in cheese by the Mohr and Ehrbacher methods were eliminated almost completely after improvements in techniques were incorporated (68), Milk Tvas titrated directly with silver without interference by protein if the solution was acidified to p H 2 with nitric acid (151). A cost saving feature was introduced by transforming sodium chloride into hydrochloric acid on a cation exchange re3in and titrating the acid directly. It is claimed that 100 grams of resin replaces 2 kilograms of silver nitrate ($78). Copper was ietained by an ion exchange resin while color impurities and interferences in alcoholic spirits passed through (282). Use of a n alumina column impregnated with potassium ferrocyanide has been offered as a method for determining copper in canned goods. The length of the colored zone of copper ferrocyanide produced is compared n-ith a standard curve (259). The use of 2,2’-biquinoline has been suggested for copper in milk following deproteinization (364). Publications have appeared on the simultaneous determination of copper and iron in wine without ashing (%), in starch sirup polarographically ( I S ) , and in a collaborative study among six laboratories with beer (168). For iron, 1,lO-phenanthroline was preferred over 2,2’dipyridyl. Wet ashing with oxidizing acids followed by colorimetric determination with sodium diethyldithiocarbamate is still the preferred method for copper. Cathode ray polarographic methods have been described for the simultaneous determination of copper, lead, and zinc in various foods and drinks (162). Improving methods for fluorides in food continues to be of interest to analysts (32, 2.93). A modified apparatus for distilling fluosilicic acid was described and illustrated (61). A modification of the E D T A titration method for iron utilized the iron-sulfosalicylic acid complex as a n indicator (14). I n another paper iron was determined in wine by using 2,4,6-tripyridyl-striazine (77). The violet complex can be extracted with nitrobenzene and measured at 595 mp. A rapid and convenient method for potassium iodide in cooking salt utilizes the complex formed with Brilliant Green (205). Sugar beets have been analyzed for potassium and sodium by extraction, clarification, and passage of the filtrate through a n VOL. 33, NO. S, APRIL 1961
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ion exchange column. The column is first saturated with calcium and the calcium determined before and after passage of the sample (224). It is claimed that potassium, cesium, ammonium, and rubidium ions can be determined by high frequency titration using sodium tetraphenylboron. Although polyvalent ions interfere, the method has been applied to the determination of potassium in m o l a w s ( 3 5 8 ) . -4routine method for magnesium in milk was proposed by measuring the turbidity produced with the potassium salt of erucic acid and potassium oxalate (230). Free mineral acids have been detected in wine by utilizing the oxidation of iodide with ferric iron in acid solution ( 1 2 9 ) . The interference 'of calcium in the determination of manganese in milk is circumvented by using a chelating agent while precipitating the phosphate as calcium phosphate (149). The manganese is then determined by oxidation to permanganate ion. Foods have been analyzed colorimetrically for molj.bdenum after ashing by convtwion to molybdenum thiocyanate and extraction ir-ith isoamyl alcohol (31). Methods are still under investigation for determining nitrites in meat products. Polarography has been applied directly to aqueous extract after removal of albumin (ZOO) and conversion to the 1-nitroso-2-naphthol formed from the nitrite and 2-naphthol ( 9 8 ) . In another publication (2lO), the nitrite was used t o diazotize procaine which was coupled u-ith thymol to produce a red dye having an absorption masimum at 450 mp. In a n analogous fashion the nitrate content of meat can be estimated by nitration of phenoldisulionic acid and subsequent polarographic determination of the nitro compounds ( 9 7 ) . The yellow color produced by adding ammonium vanadate and ammonium molybdate to phosphate is used to determine total phosphate and inorganic phosphate in sugar products ( 7 6 ) . Careful control of acidity is essential to prevent interference by silicate. Another colorimetric determination utilizes the sodium molybdatehydrazine sulfate reagent to produce a blue color that is measured spectrophotometrically (24). Tin in canned fruits, vegetables, meats, liquids, and fish has been determined colorimetrically using reagents such as 3,4-dimercaptotoluene (sa), cacotheline (2.95)) and gallein plus gelatin (6). Oscillographic polarography has also been applied to this determination (225). By using phosphorus as a n internal standard the tin content of canned foods may be determined rapidly by alternating current arc spectroscopy (3.90). Strontium levels down to 0.1 p.p.m. in the presence of 1000 p.p.m. of calcium were determined in milk and vegetables by direct
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ANALYTICAL CHEMISTRY
current arc spectra. These workers compared strontium levels in five milk ash samples by neutron activation, s-ray fluorescence, emission spectroscopy, and flame photometry (175). Similarly, strontium in milk powders was measured by neutron activation and by stable isotope dilution (217). The problem of determining thallium in wine in the parts per billion range has been attacked by measuring the thallium level electrolytically (112). Addition of sodium salts to food samples produces uniformly enhanced and reproducible spectral lines for measuring the (Sf1). strontium-to-calcium ratio Radionuclides in milk have receivcd increasing attention from dairy analysts n n d health agencies. Methods have been proposed for the rapid ashing of milk samples ( 2 4 9 ) and for the elimination of the ashing procedure (251). Separation procedures have been rei orted for CS'~' (385). 113* (141, 25O), and SrN (131, 253). In an estmbive investigation a method suitable for monitoring by determining Ba14' and Srx(Ys) was described ' (252): Recoveries of added nuclide averaged 77 to 96%. Separation techniques have been described for isolating Cs13' from grain, meat, vegetables, and milk porrder ( 3 8 6 ) . MOISTURE
Problems concerning moisture eyuilibrium and the determination of water were reviewed (343). Spray-dried milk ponder containing known added amounts of water was used as a standard (15) for determining the moisture content of whole and nonfat milks. The times needed to dry the reconstituted products a t 100" C. are given for the various milks. X simplified procedure for estimating the water content of meat was developed by pressing strips of indicator paper on the freshly cut smooth surface, Two types of paper were used nhich gave a gradation in color with nater content (216). An interesting approach to the measurement of water in potato starch was presented in which bhe vapor pressure of water in the air before and after passing over the starch sample was measured ( 2 5 6 ) . The problem of assessing water added to wheat, either as a liquid or as a humid atmosphere, is complicated by the fact that different wheats give different per cent recoveries for the same amount of water added (265). In another publication a n apparent interaction between cereal and oven method was disclosed. The values obtained for the moisture content of a grain sample by various methods were different and in many cases when more than one type of grain was run no two methods gave the same results (d64). A fully automatic Karl
Fischer titration apparatus has been described (326). Determinations on a variety of cereals, flours, doughs, and bread gave results in good agreement with those of oven drying methods. The carbide method has been applied to the quality control of soft sugars (l77), and to grain samples where the percentage of moisture is read directly from the gage that records the pressure of the reaction mixture (83). PHYSICAL MEASUREMENTS
A significant increase in precision R as attained by rewiring a commercial Bloom Gelometer and adding a relay with a built-in transistor amplifier circuit (314). The reliability of several spectrophotometers and tristimulus photoelectric colorimeters has been evaluated in determining color differences and absolute color values and comparing Rith a General Electric recording spectrophotometer (214). The application of a coffee hydrometer to the determination of soluble solids I R beverage coffee has been described (If6). Several papers have applied infrared and nuclear magnetic resonance spectroscopy to problems on fats. These techniques include the nondestructive determination of functional groups, polymorphism, and liquid-solid content of fats (YO, 7 1 ) . A new method for molecular neights of edible fats was presented based on data obtained from a temperature-heat content plot (336). A self-balancing photoelectric polarimeter of high sensitivity capable of measuring sugar concentrations up to 1000 p.p.m. with a sensitivity of 2 p.p.m. has been developed ( 2 2 6 ) . A device for continuous measurement of ultraviolet light absorption of eluent from columns used to chromatograph a commercial food dye permits the determination of residual %naphthylamine ( 7 9 ) . A measurement of absorbance at 500 mp has been proposed as a more reliable index of the color of edible oils (279). Forward-scattering a t an angle of 20" n i t h respect to the incident light beam has been shown to increase the sensitivity of the turbidity measurement on commercial sugar solutions (301). A relationship between shear stress and rate of shear has been established for the flow constants of nontime-dependent, non-Newtonian food materials. These constants permit the calculation of heat transfer and flow characteristics for various conditions (72). PROTEINS, A M I N O ACIDS, A N D NITROGEN
Work on milk proteins has received increasing attention. The methods of Steinacher, Schultz, and Walker have been reviewed critically and evaluated experimentally in comparison with the Kjeldahl method (208). The Schultz
modification of the Steinacher method w a s satisfactory for total protein while the Walker method was best for casein. I t was reported (344) that milk protein heated with sodium hydroxide releases a consistent amount of ammonia. The method is rapid and linearly related to the Kjeldahl nitrogen determination. Several applications of dye binding have been reported involving the use of Amido Black 10B (342) and Buffalo Black (356). I n a n extended study of the Orange G dye binding method (16) an excellent correlation coefficient was established with the Kjeldahl method. Variations in the butter fat and lactose content were shown to be without effect. Advantage was taken of the fluorescence of tyrosine and tryptophan in the protein molecule to assess the total protein content (194). On the premise that more than half of the total acidity in milk is due to casein, the percentage casein was calculated from a function involving the milk acidity and the whey acidity (167). The noncasein proteins of milk were partitioned by the aid of paper electrophoresis. QuantitRtive separation of a-lactalbumin, j3lactoglobulin, globulins, and proteose peptone was effected (316). The method is simple and suitable for routine analytical work. Albumin was determined directly on diluted milk by fluorescence (196). By measuring the volume of phosphotungstic acid-precipitated serum proteins (10) it was possible to measure the serum protein in milk. The method correlates well with the Kjeldahl procedure, but the acid-precipitated casein and denatured serum protein must be removed first. An improved procedure for determining hydroxyproline in a-casein utilized the new ninhydriri-isatin-triethylamine reagent (303). This led to significant improvement in the accuracy and precision of the method. Reaction with 2,4-dinitrofluorobenzene was suggested as a method of determining the available lysine in milk (4). The procedure for determining amino acids by converting them to aldehydes followed by chromatography and thermal cracking to methane has been modified. The oxidation to aldehydes takes place in a microreactor connected to a gas chromatography column as a continuous gas flow system. Applicstion of the method to a casein hydmlyzate resulted in a complete analysis ?f B mixture of seven amino acids in 1;c.s than 1 hour (392). Sulfosalicylic acid was used for the rapid determination of protein in barley (108). An improved procedure was described using diethylaminoethylcellulose for the separation and analysis of proteins in chicken breast muscle extract, cabbage extract, egg white, and livetin fraction of egg yolk (226). It appears that thc modified cellulose
shows more detail than the patterns obtained by electrophoresis. In applying the formol titration to the speeding up of nitrogen determinations in cereals. interference due to metal catalysts in the preliminary Kjeldahl digestion was avoided by using hydrogen peroxide as catalyst (42). The formol titration was carried out electrometrically and the results agreed very well with the standard Kjeldahl titration. Current methods for determining proteins in chocolates were reviewed and tannin-acetic acid and sulfosalicylic acid were compared as protein precipitants (298). Sulfosalicylic acid has also been applied to the rapid determination of protein in wheat by measuring the turbidity of the treated alkaline extract (116). Potassium ethyl tetrabromophenolphthalein has been suggested as a reagent for the detection of protein in starch (244). This indicator is yellow in acid solution but in the presence of protein i t remains blue. Another rapid method utilizes the violet color produced by the reaction between copper sulfate and the protein in rye, oats, barley, and wheat (361). The results of a formol titration for proteins in milk were used directly to calculate the solids-not-fat of milk since approximately 40% of the solidsnot-fat of normal milk is protein (@). The gluten level in wheat has been determined accurately by measuring the turbidity after precipitation of the neutral extract with sodium chloride (33, 34). A high quality gluten is indicated if a low turbidity is obtained when a homogeneous paste is shaken with borate buffer at constant temperature. Glutamic and aspartic acids in sugar factory juices are readily isolated by two acid cation exchange resins (186). Good agreement with chemical and microbiological methods is claimed for a polarographic method for cystine in flour (89). A simple procedure was proposed for determining tryptophan in wheat, rye, oats, and barley directly without prior separation, but the method is not applicable to red corn (361). A similar test has been worked out for glutamic acid on various food hydrolyzates (391). A new and rapid method for total nitrogen in casein, albumin, soybeans, and rice was introduced (241). The semimicro sample was decomposed by the Kjeldahl method and the ammonia determined by reaction with sodium hypobromite. SUGARS, STARCHES, A N D CARBOHYDRATES
Methods for the determination of starch and sugar in potatoes were reviewed, and a rapid method for sugar reported involving clarification of the
solution and measurement of the sugar content refractometrically or interferometrically (234). There is still considerable interest in the determination of lactose in milk. Colorimetric methods include the use of orcinol and ferric iron in concentrated acid solution (S34), and the phenol-sulfuric acid reaction (110). Rapid physical methods applied to lactose in milk include a determination in the near infrared (131) and the use of a refractometer on the filtrate after clarification with alkaline lead acetate (206). A publication described the isolation of pure lactose from skim milk using cation and anion exchange resins for isotopic dilution analysis (218). The copper salt of trihydroxyglutaric acid has been investigated as a substitute for Fehling’s solution for sugars, fruits, and fruit juices (1). The accuracy of optical methods was examined for sucrose in sugar beets by use of the isotope dilution method (168). Lack of agreement was attributed to the formation of compounds having greater optical activity than sucrose, which had been indicated previously by paper chromatographic analysis. The construction of an instrument for partial automation of a scheme for analyzing sugar in sugar beets was described (266). Measurement was made with a polarimeter and the results recorded on punched cards. Calcined glass fiber paper has been applied to the separation of sugars from sugar factory juices, which were determined colorimetrically after reaction with triphenyltetrazolium chloride (286). Raffinose was determined with codeine solution in concentrated sulfuric acid (184). A claim was made that errors in reducing sugar analyses from copper reagents arising from autoxidation of the cuprous oxide could be obviated by using ferricyanide and ceric sulfate (351). Methods have been developed for the determination of 3,6-anhydrogalactose and galactose in agar, Carrageenin, and furcellaran (387). Fehling’s solution has been applied to the gravimetric determination of mannan in coffee extracts (35.2). A rapid method is reported for the determination of glucose, maltose, sucrose, and dextrin in malt extract (312). Congo red was used for the colorimetric determination of amylose in starch (62). The absorptivity of the absorbed dye is the same for both amylose and dextrin. Amylose was determined by addition of potassium iodide solution and amperometric titration with potassium iodate using a rotating platinum electrode (48). Digestion with amylase was used to estimate damaged starch in flour. Since the amylase attacks both damaged and undamaged starch the digestion was run hourly and extrapolated back VOL 33, NO. 5, APRIL 1961
55 R
to zero time for the per cent damaged starch (313). Rapid methods for the determination of dextran and starch in cane juices have been developed for quality control to indicate delay in harvesting or spoilage of juicc (257). Methods for betaine in sugar juices continue to be investigated. One method described a cleanup procedure using ion exchange resins and subsequent precipitation by ammonium reineckate (64). A more rapid procedure utilized only one ion exchange resin and tn-o indicators to show the beginning and end of acid elution. A titration nith base completed the determination (348). The determination of galacturonic acid in pectins is based on the color intensity of the red compound formed n-ith carbazole (208). Corrections for sugars present were made by measuring absorption at two wave lengths. Total carbohydrates and proteins can be determined by a micromethod utilizing total oxidation with dichromate and concentrated sulfuric acid. The procedure is applicable to all materials obtained in chromatographic eluates (142). The determination of sodium carboxymethylcellulose was successfully applied to ice cream by the naphthalenediol method. Alginic acid, propylene glycol alginate, pectin, tragacanth, gum arabic, gelatin, methylcellulose, milk, sugar, or flavors did not interfere (120). The presence of alginate in foods can be readily detected by acid hydrolysis to mannose and mannuronic acid (102). A new method specific for the direct determination of pectic acid in ram beet juice was described in addition to a method for araban (63). Crude fiber analyses have been speeded up by raising the boiling point of the reflux mixture. This was achieved by mixing ethylene glycol, water, and concentrated sulfuric acid to give a temperature of 133' to 135' C. (239). VITAMINS
An A.O.A.C. collaborative study was reported on a chromatographicspectrophotometric method for vitamin A in oleomargarine (119). The dehydration of vitamin A to anhydrovitamin A in benzene solution results in an increase in the absorbance at 399 mp, The method is highly specific, not affected by unsaponifiable extracts, and has been applied to fish oils, margarine, butter, and poultry mashes ( 5 4 ) . A procedure proposed for vitamin A in beverages depends on the destruction of vitamin A by ultraviolet radiation. The absorbance at 326 mp before and after irradiation was measured (189). Vitamin Biz can be determined microbiologically with Oehromonas mal-
56R
ANALYTICAL CHEMISTRY
hanensis in fresh milk and milk products ( 2 2 ) . The colorimetric determination of niacin in cereal products has been improved by using calcium hydroxide in placc of sulfuric acid in the digestion (269). A procedure for measuring the bound nicotinic acid in the prescnce of free nicotinic acid in rice and n-heat bran was sho\\-n to be reliable on the basis of recovvry experiments. The colored compound formed nith cyanogen bromide and p-aminobenzoic acid is not extractable. The bound and free forms are determined before and after alkaline hydrolysis (88). A new lalioratory proeedurc was developed for the estimation of pantothenic acid in foods bnscd on the use of double enzymc. system of intestinal phosphates and pigeon livcr extract for the release of pantothcnic acid, followed by a niicroliiological assay with Lactobacillus plantarum (3.95). Over a 2-year period the rvsults w r e shojvn to agree well with those obtained by rat bioassay. l h e use of a cation exchange resin permits the complete separation of pyridoxine, pyridoxal, and pyridoxaniine in aqueous food extract (221). Oxidation of these substances to 3-hydroxy-
5-(hydroxymcthyl)-2-methylisonicotinic acid (4-pyridoxic acid) followed by a fluorometric measurement is consistent but does not give quantitative results. Vitamin B6 in milk products has been assayed by a cup-plate technique using Streptomyces carlsbergensia as a test organism (393). Manipulations in acid media lead to loss of pyridoxyl components (355). Modifications in bhe A.O.A.C. method aimed at obviating low results include the use of a mixed solvent in place of HC1 for desorbing the vitamin (95). By irradiating aqueous solutions of food with an incandescent lamp, riboflavin was converted to lumiflavin, extracted with chloroform, and determined photometrically (125). Riboflavin in complex foods requires an extended cleanup and final adsorption on Fuller's earth. After elution with acetone, the riboflavin concentration was estimated polarographically (186). Progress in thiamine analysis on bread has been marked by a collaborative verification of improvements in methodology, A 2-year investigation of previously recommended changes was followed by a collaborative study that involved seven analysts and four samples ($23). In a second study a variety of cereal products was used in three series of collaborative tests to prove out the new procedure (2s). The time required was reduced from 2 days t o 6 hours. For difficult extractions of thiamine the use of an HCI-KCI solution assisted in the desorption of the vitamin from the surrounding material (96). A laborious
but esact method for thiamine based on the transformation into tliioc.hrome r a s reported (278). A review of analytical methods for ascorbic acid has been published with special reference to polarography (872). The specificity of polarography has been cited as an advantnge over conventional titrimetric niethods that often include interferences (106). The w e of n-broniosucciriiii?itic. ic finding increasing application (11,;). Extracts of vegetables, meat products., and milk were titrated Kith this reagent before and after destruction with ascorbinase (192).
A simple apparatus consisting of a galvanometer connected to platinum electrodes carrying a current of 50 mv. has been employed for the electrometric determination of ascorbic acid in orange juice (276). RIercapto groups that interfere with the determination of ascorbic acid in soybeans may be blocked with p-chloroniercuribenzoic acid (566). The presence of sulfur dioxide in wine and must presents no problem in the determination of asi corbic acid if it is combined ~ - i t laeetaldehyde before titrating xvith iodine (186). A rapid and senbitive method for ascorbic arid was ba.wl on tlic diffusion of a ~ n i p l esoaked in paper disks and placed on tile surface of an agar gel containing 2,6-dichlorophenolindophenol or pot,assiuiii prrniunganate. The diameter of the zone of reaction was related to the vitamin concentration (69). Inhibition of color formation between antimony trichloride and vitamin D using acetic anhydride 1va3 11' : to estimate interferences by vitamiri 11 decomposition products in nie:isuririg vitamin D in evaporated milk ( 1 7 4 ) . Various systems for tno-dimensional paper chromatography of tocopherols have been employed for maize, rice, and cottonseed oils (225), oils and foods (8), cereals, and flour milling products (232). The removal of peroxide as a n interference has becn effected by distillation under reduced pressure (117), and by the use of pyrogallol prior to column chromatography (143). The specific method for tocopherol in oils and food requires a combination of extraction, column chromatography, and partition chromatography on impregnated paper (204). The plication of infrared spectrophotonictry to the determination of all vitainiris in vcgetables and fruits has been thi subject of an extensive revicw (44). MISCELLANEOUS
The application of chromatogr:rphy to the analysis of various food c.mstituents has been the subject uf an extensive revicw (60). -4 critic:il review of analytical methods for n1imcnt:u-y
doiigli produrts c.oiit:iining eggs has b-c.n publiehrd (?). The partial solubility of gluten in acetic acid has been used as a method of estimating denat,nration (315). The light absorption method \vas preferred over liglit transniittancc, sedimentation, catalase activity, and light reflectance methods as a means of estimating the total smut eontarnination in wheat. I t was selected because of practicality and suitability for routine testing (172). The presence of decay, greening, blacks y k , and hoilow heart in potatoes can be detected by absorbance measurements at 710 and 800 mp (36). A novel indirect method for determining the IIanus iodine number has been suggrsted where the Zeiss Butyro refrrictomcter number is multiplied by R factcir, giving sgreement kvithin &3% of the chi.niica1method (118). .!rni1crc~ictric titrations with mercuric iiitrxte gave consistent values for thiol p w u p c , being unaffected by the r d i ! i i n . I-iomver, titration with silvcr nitrate in various buffer solutions .~-i~bldt~i 'i-ariahle results, depending on t h c pII xnd tlie type of buffer used (38). coloration produced by of sodium nitroprusside rc.agmt t o cwnpounds containing thiol ~ Y ( J U ~ha. S hecn stabilized by adding .iri:Ll .iinoiints of zinc salt (384). Eggs in food have been detected by several i i n t l i o d ~ ' 1 1 1 ~ proportion of egg to +ermined by ether extraction :in,l .i!ter acid hydrolysis ( 4 5 ) . iethod utilized the enzyme D t o hydrolyze the phos:tiid liberate choline which
-
Intern. Dairy Congr. Proc. 15th Congr., London 3. 1829-34 (1959). (297) Rauscher, K., 'Voigt, J., Ernahrungsjorsch. 2, 647-56 (1959). (298) Reith, J. F., Intern. Chocolate Rev. 14, 536-9' (1959). (299) Societv of Chemical Industrv. "Re-
. ports , on tke Progress of Applied-Chem-
istry," Val. XLIV, pp. 145-82; 327408, London, 1959. (300) Rhodes, D. N., J . Appl. Chem., 10, 122-4 (1960). (301) Rieger. C. J.. Caruenter. F. G.. J . '
Researci21'atl. B u r , Standards 638,20511 (1959).
60R
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ANALYTICAL CHEMISTRY
(302) Risley, H. M., J . Assoc. Ofic. Agr. Chemists 42, 261-2 (1959). (303) Roberts, H. R., Kolor, 11. G., A'nture 181, 837 (1958). (304) Romani, B., Bastianutti, I., Boll. lab. chim. provinciali (Bologna) 10 (3), 216-20 (1959); -4nal. Abstr. 7, 2990 (1960). (305) Roos, J. B., Versnyl, 1., Chem. Jl'eekblad 55, 521-5 (1959,. (306) Rothe, II., Thomas, B., Sahrung 3, 1-17 (1959). (307) Rowland, S. J., Wagstaff, A. 'A'., J . Dairy Research 26, 83-7 (1959). (308) Rusoff, I. I., J . Am. Oil Chemists' SOC.37, 223-42; 329-58 (1960). (309) Rzhekhin, V. P., Pogonkina, N. I., T r u d y Vsesoyuz. Sauch. Issleclovatel. Inst. Zhirov., S o . 15, 73-94 (1954). (310) Safronov, -4. P., Zhur. Anal. K h i m . 13, 360-4 (1958). (311) Sahlimoff, G. V., Conway, J. G., Pitzer. S. E., Appl. Spectroscopy 12,
120-2 (1958). (312) Sampietro, C., Invernizzi, I., A7ahrung 3, 1065-74 (1959). (313) Sandstedt,, R. M., Mattern, P. J., Cereal Chem. 37, 379-90 (1960). (314) Schachat, R. E., Kacci, .4.,Food Technol. 14, 117-18 (1960). (315) Schaefer, W. C., \%sham, R. AM., Dimler. R. J.. Senti. F. R.. Cereal Chem 37, 411-12 (1960). ' (316) Schaffenburg, R., Drewry, J.,Intern. Dairy Congr., PTOC.16th, London, 3, 1631-7 (1959). (317) Schmidt, H., Fette, Seijen, Bnstrichmittel 61, 127-33 (1959). (318) Schneider, F., Reinefeld, E., Forth, H., Zucker-Beih. 3, ?;a. 4, 102-8 (1959). (319) Schwartzman, G., J . Assoc. Ofic. Agr. Chemists 43,428-30 (1960). (320) "Science of Meat and Meat Products," 222-54, American Meat Institute Foundation, W. H. Freeman and Co., San Francisco, Calif., 1960. (321) Scott, W. C., Morgan, D. A., Veldhuis, 11. K., Food Technol. 14, 423-8 (1960). (322) SedlSEek, B. A . J., Fette, Seijen, Anstrichmittel 62,669-72 (1960). (323) SedlBEek, B. A. J., Z . Lebensm.Cntersuch. u.-Forsch 111, 108-11 (1959). (324) SedlAEek, €3. -4.J., Rybin, R., Fette, Seifen,Anstrichmittel 61, 134-8 (1959). (325) Seher, A., Ibid., 60, 1144-53 (1958). (326) Seibel, W., Bolling, H., Getreide u. Mehl 8 , 73-6 (1958); Anal. Abstr. 6 , 3184 (1959). (3273 Sengupta, P. N., Mitra, S. Tu'., Roy, B. R., J . Proc. Inst. Chemists ( I n d i a ) 31, Pt. 3, 124-5 (1959). (328) Shearer, D. 4.,Carsen, R. B., J . .eSsoc. O&. Agr. Chemists 41, 414-16 (1958). (329) Sherman, I. R., Ibid., 42, 646-7 (1959). (330) Shubina, S. B., Shaebrich, A. B., Prostakov, M. E., Basova, E. P., Konseru. i Ovoshchesushil. Prom. 14,No. 12, 30-1 (1959). (331) Silbereisen, K.,Weymar, C., Brauerei. Wiss. Beil. 12 (lo), 155-61 (1959); Anal. Abstr. 7 , 2988 (1960). (332) Si,lk, R. S., J . Assoc. O ~ C Agr. . Chenizsts 42,427-30 (1959). (333) Skjrka, B., RadPj, Z., Priimysl potravan 9, 484-5 (1958). (334) Slater, T. F., Analyst 82, 818-25 ( 1957).. (335) Sliwinski, R. A . , Doty, D. M., J . Agr. Food Chem. 6,4 1 4 (1958). (336) Smit, W. M.,Ruyter, J. H., Van Wiik. H. F.. Anal. Chim. Acta 22, 8-16, (19'60). ' (337) Spanyar, P., Iievei, E., Kiszel, M,.Z Lehensm.-Cntersiich 21. -Forsch. 107, 11824 (1958). (338) Spanyar, P., Sandor, d.,Ibid., 108, 402-5; Anal. Absfr. 6 , 2339 (1959).
(339j SpPrlich, H., Deut. Lebensnc.-Run& schau 58,70-3 (1960); J . Sci.Food A g r . 11, ii--135 (1960). (340)Stahl, W. H., Voelker, W. -k, Sullivan, J. H., Food Technol. 14, 14-16 (1960). (341) Stanley, fir. L., Flavor Research and Food Acceptance 344-68 (1958). (342) Steinsholt, K., Xeieriposten 46, 259-64, 279-84(1957). (343) Stitt, F., Fundamentai Aspects D e hydration Foodstiifls, Papers Conf. A b r r deen 1958, 67-88. (314) Stone, \V. K., Creniers, L. F., Thompson, N . R.. J . Dair?] Sci. 43,335 i~i q m -) -. , . -~
(345) Sulser, H., Jlitt. Gebiefe Lebensm. i(. Hyg. 50 ( 4 ) , 287-91 (1959'1; Dairi/ Sci. dbstr. 22, 1436 (1960). (346) Swain, T., Hillis, JY. E., J . Sc?. Food Agr. 10, 63-8 (19-59;. (347) Swoboda, P. A. T., Lea, C. H.; Chem. &- Ind. (London) 1958, 1090-1. (348) Szabolcs, O., Prey, V., Z- Zuck~rind. 9, 517-18 (1959); .4naZ. Ahstr. 7 , 3-497 (1960). (349) Taneva, S., Kenki/lislio H6Xoku. *: 5 35, 8 pp.-(l957). (350) Tarladgis, B. G.! \Vntts, B. M , Younathan, M. T., J . A i ? i . Oil C h e m i w ' SOC.37, 44-8 (1060). (351) Thaler, H., Sahrlinq 2, 111-16 (1958). (352) Thaler, H Z. Leberas,,i.-linlers,Ilh. u.-Forsch. 110,442-9 (19591. (353) Thole, LY., Ibad , 109,40-3 1354) Todd, P. H., Jr., Food Techno'. 12, 468-9 (1958). (355) Torpfer, E , Xachrthur, )I., Li.11mann. J.. J . Assoc. Ofic. - AUT.Chem7sts 43, 57-9 (1960). (356) Vanderzant. C., Te~~nison, \V. It., ' J.'Dairy Sci. 43, 435 (1960). (357) Vecher, -1.S., Ulitina, 0. A , !mest. ~
Vysshibh Ucheb. ZavedeniZ, Pishcheoap Tekhnol. 1958,KO. 1, 103-8. (358) Veis, -4.R., Ievinsh, A . F.,U:r/zenBe Zapiski Latv. Unit). 22, 95-9 (1958); Anal. Abstr. 7, 369 (1960). (359) Vernon, L. P., ASAL. CHEM.32,
1144-50 (1960). (360) Vett,rr, J. L., Steinberg, &I. P., Selson, A. I., J . Agr. Food Chem. 6 , 3941 (1958). (381'*'Vigorov, L. I., Selektsiya i Senianovodstco 22, KO.4, 66-7 (1957). (362) J-itagliano, &I., D'.1mbrosio, .I., Olearia ll,, 169-84 (195i). (363) Vivano, R., Fouassin, .4., Rev. fermentations et in&. aliment 12, 223--30 (1957). (364) Vleechauwer, A. de, Baere, A . v:in den, Saudts, M.,Mededel Landbouioliogeschool en Opzoekingsstations Staat Gent 23, KO.1, 55-63 (1958). (365) Wachs, W., Petscha, P., Z . Lebensm.-Untersuch. u.-Forsch. 108,244-
55 (1958). (366) Keakley, F. B., McKinney, L. L., J . A4n~.Oil Chemists' SOC.35. 281-1 (1958). (367) Xenner, V. R., J . Dairy Sci. 43, 22-7 (1960). (368) White, H. B., Jr., Quackenbush, F. W..J . A4m. Otl Chemists' SOC.36, 653-6 (1959). (369) Willits, C. 0 . )J . Assoc. O$c. Agr. Chemists 42, 349-52 (1959). (370) Wise, C. S.,Mehltretter, C. L., ANAL.CHEX 30, 174-5 (1958). (371) Wittfogel, H., Fbchwaren u. Feinkost-Ind. 30,4-8 (1958). (372) Woggon, H., Erndmmg,$for.diu n g 4, 35-43 (1959). (373) Woidich, H., Gnauer, H., Riedel, 0.) Z . Lebensm.-Unters7ich. ZL. -Forxh,. 112, 184-90 (1960). (374) Woidich, H., Langer, T., FritciitsajtInd. 4. 234-38 (1959): Food ,Uanuf. 35, 444 (lk60).
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(383) Wynn, J. D., Brunner, J. R., Trout, G. hl., Food Technol. 14, 248-50 (1960). (384) Yamada, Y., Kishi, H., S z p p o n k'agaku Zasshi 76, 48-50 (1955). (385) Yamagata, N., Yamagata, T., Bull. Chem. SOC.Japan 31, 1063-8 (1958). (386) Yamagata, N., Yamagata, T., Matsuda, s., Tajima, E., Watanabe, s., Japan Analyst 7, 433-8 (1958); Anal. Abstr. 6, No. 1849 (1959) (387) Yaphe, W.,X.u.4~.CHEM.32, 132730 (IQAOl.
(388)'Yaiuhara, S., hlasuyama, S Kagaku to Kogyo ( O s a k o ) 31, 399-401, (1957). (389) 1-oshihiro, Y., Nakumura, AI., J . Chem. SOC.Japan, lnd. Chern. Sect. 61, ( 8 ) , 972-5 (1958); Anal. Abstr. 6, No. 191.5 - - - - (19.m) ~-"-~,. (390) Ibid., 62 (2), 208-10 (1959); Anal. Ab&. 7, 609 (1960). ~
(391) Zimmerman, H., 2. Lebenstn.-Gntersuch. u.-Forsch 112, 46-9 (1960). (392) Zlatkis, A, Orb, 3. F., Kimball, A. P., A s . 4 ~ CHEX. . 32, 162-4 ( 1 960). (393) Zoet, B.,.I7&. M z l k Dairy J . 13 (4), 306-16 (1959): Dairn Sci. Abstr. 22. 1442 (1960). (394) Zonnt veld, H.. X c y e r , .L, 2. Leberis,,~.-Irnlersurh.'zc.-For,.ck. 111,'19820; (1960). (395) Zook, E. G., MacArthur, >I. *J., Toepfer, E. \I-,,U . S.Dept. Agr., Agr. Hiln~!liookS o . 97, 23 pp. (1956). (386) Zotti, G., de, Capella, P., Jacini, G.- Felte. Seifen. Anstrichmittel 61, 1114-9 (1059). (397) Ziihlsdorf. >IDeut. ., .lfikh. Wirtschafl 63-1 i 1959). '
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I
lid and Gaseous Fuels W. H. Ode and Theodore Chrisfos E ~ e o of t ~ Mines, U. S. Department of the Interior, Pittsburgh, Pa.
1% iiie seventh of a series of rev i e w on methods of sampling, anal) zing, and tccting solid and gaseous fuels. The revim covers a 2-year period ending September 1960, and iolloas the general pattern of previous revsew.
'HIS
SOLID FUEL5
'I'his s e h o n discusses sampling, ardysis, and ttxting of such solid fuels as
ic roal samplers and
i ! .thwr:; ~ ?f mil saniplhg. Of the m t :i nietliods > J S I : ~f c t ~calculating varis
~
i
ioux! more rational. o y i l nil2 Scnxerd (,?A) listed the s o i a niechanical coal &cm+>rL:
7
:tnd spout anti rotatirig slotted cone. The! also iiescritxd n method for testing the aLc:uracy qf Lampling. P ~ L I(7.4) I made an investigation of th- nun:i:cr of iricrements that should ~
be taken for raw coals and for prepared coals. Examples showed the relation of errors of sampling, sample preparation, and analysis to the total error. Norman (6A) investigated a n automatic device for sampling coal from railroad cars as they are unloaded by tipping. H e concluded that, although the sampler may have bias for coals difficult to sample, it is better than taking samples from tops of cars or from under cars during discharge. Chakraborty, Tarafdar, Ghosal, and Dah Gupta ( I A ) proposed a sampling procedure designed for preparation of laboratory samples of coke. The procedure is based on a statistical consideration of the magnitude of errors occurring a t different stages of size and weight reduction of the original sample. Liplavk and Boliter (5A) described a method for determining the degree of mixing for multicomponent coal charges using radioactive sulfur as an indicator. Different types of mixing apparatus were evaluated by the method. Proximate Analysis. Elphick ( I S B ) developed a niethod for proximate analysis of coal a h e n only a small amount of sample is available for analysis -4 0.5-gram sample IS suffioient for a complete proximate analysis and determination of calorific value. MOISTURE. Blanzat (6B) described a n all-glass apparatus for determining moisture by entrainment in xylene or toluene. The ascending column is insulated Kith a silvered vacuum jacket; the descending column assures that all of the water falls into the graduated receiver. The apparatus is designed for use with 50- t o 100-gram samples of
coal of lrss than 3-mm. size. The principle, apparatus, reagents, and procedure for the distillation method adopted in Spain by the Instituto Xacional dcl Carb6n also were described (15B). Banerjee and Paul (6B)reported that, in determining moisture in coal and coke by loss of weight during heating, a cooling period up to 40 minutes has no effect on the moisture value if the empty dish and n-ell-fitted lid are cooled for the same length of time as the dish containing the coal or coke. GAl, Lbsz16, and Varga (I4B) proposed for the rapid determination of moisture in coal that the sample be dried a t 120" ?Z 2" C. for 30 minutes rather than a t 105" to 110" C. for longer periods of time specified in several standards. Comparative results indicated that the method is accurate. Zagrodzki and Kicdzielski ( 2 M ) modified the standard Karl Fischer met,hod by extracting the moisture from coal with anhydrous methanol and titrating the resulting solution. Tyman (bfB) found that the Fiwher method gave results agrccing with those obtained by sylvne distillation. In detcrmining moisture in brown COSlS, Jandisek (16B) showed that rapid drying hy high-frequency heating has advaritngrs over usual ovcn mcthods in that ovrrheating and oxidation are minimized. Iiiihn ( I i B ) rc.portcd that moisture in various matc~ialsincrluding coal could be determined by measuring the thermal neutrons in the immediate virinity of a fast-neutron sourcc anti the nnatc>ri:d. ASH AND ~ I I N E R A MATTER. L hrsin VOL. 33, NO. 5, APRIL 1961
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