M a y , 1916
T H E J O L;R N A L O F I S D U S T RI A L A X D E S G I S E E RI A-G C H E M I ST R Y
AZELAICACIDFOUND Before saponification After saponification 0 . 6 per cent 9 8 per cent
TOTAL 10 4 per cent
T h e crude acid had a n equivalent weight of 1 1 2 (calc. 94). A “shredded” (laundry) soap, which had developed 2 per cent of free acid on storage, was also worked u p for azelaic acid. A4bout 0 . j per cent ‘was found. T h e most remarkable thing about t h e oxidized cottonseed oil described is, however, not so much its abnormally high content of azelaic acid, as t h e form in which it was evidently present. Only about oneeighteenth of t h e total amount was present as free acid. T h e rest was in a form t h a t was insoluble in hot water, and became soluble only after saponification. T h e simplest assumption t o explain this behavior is t h a t the oxidation proceeded practically independently of hydrolysis, and thus gave rise t o the formation of glycerides of a hitherto unknown type, t h e semiglycerides of dibasic acids. T h e simplest one t h a t might be present here may be called trisemiazelain, C H P O C O(CHz);COOH C H O C O ( CH2) i C O O H
I CHzOCO ( C Hz) ;COOH T h e formation of mixed glycerides is of course not excluded. For instance, a-palmito diolein might be expected t o give a-palmito disemiazelain, CH20COCijH3i C H O C O (CH2)i C 0 0 H 1
C Hz0 C 0 ( C H2) ;.COO H . These results t e n d also t o justify t h e modern tendency t o regard rancidity of fats and oils as due not simply t o hydroiysis of t h e glycerides present, b u t a t least equally t o oxidation phenomena which are not necessarily dependent on such hydrolysis. I n the case described, it is evident t h a t the oxidation and hydrolysis were entirely independent processes. MELLOS INSTITUTE OF INDUSTRIAL RESEARCH UNIVERSITYOF PITTSBURGH ~
~~~~~~~~
JELLY INVESTIGATIONS By W.V. CRUESS
AND
J. B. MCNAIR
Received February 14, 1916
A great deal of work has been done upon the chemistry of pectin and related bodies from both t h e purely scientific and practical standpoints. One of t h e best pieces of work has been done b y Th. von Fellenberg,‘ who seems t o have obtained more definite information upon t h e derivation of pectin from more complex compounds and upon its composition and chemical behavior t h a n any of t h e other investigators. Bigelow and Gore in Bull. 94 of the U. S. Dept. of -4gric., Bureau of Chemistry, gave a very good summary of the literature a t t h a t date. Miss N. E. Goldthwaite* studied jelly making largely from the practical side and dealt with such factors as effect of acid concen1
T h . von Fellenberg, M i l l . Lebensm. H y g . , 1914, 2 2 6 - 2 5 6 . X. E. Goldthwaite, THISJOURXAL,1 (1909) 333; 2 (19101, 457.
417
tration, character of acid, sugar concentration, character of sugar, temperature, pectin concentration a n d source of pectin, on quality of jelly. The experiments discussed in the following paper were undertaken t o throw light upon some of the practical phases of jelly making, rather than t o add anything t o t h e knowledge of t h e chemical composition of pectin. The main points investigated were: ( I ) Suitability of rarious fruits and vegetables for jelly making; ( 2 ) yields of jelly from various fruits; ( 3 ) clarification of jelly stock;’ (4) loss of fresh fruit flavor in jelly making by hydrolysis and evaporation and production of jellies without application of h e a t ; and ( j ) effect of sugar and acid concentrations on jelly. These topics will be discussed in t h e order given. S C I T A B I L I T Y O F \ - A R I O U S F R U I T S A X D V E G E T A B L E S FOR
1ELLY MAKISG
T o produce a jelly of the proper consistency when t h e liquid, obtained from the fruit by cooking with or without addition of water. is mixed with sugar in t h e proper proportion and cooked, the fruit must contain a good supply of both pectin and acid, or if not a large supply of pectin, a large amount of compounds t h a t break down into pectin at the temperature of boiling water. Some fruits were found t o contain sufficient acid and pectin while others lacked one or the ot,her of these necessary constituents. Where t h e fruits were low in acid, attempts were made t o produce jelly without additLon of acid and also with addition of citric acid or lemon juice. I n most cases the pectin was extracted in the usual way b y cutting the fruit into small pieces, adding water t o cover, boiling slowly until tender and expressing the hot juice b y pressing in a small fruit press or b y straining through a coarse cloth with gentle pressure. The solution so obtained was analyzed for Balling or Brix degree (per cent dissolved solids) and acidity, and if much more dilute t h a n the juice of the fresh fruit itself, was concentrated before being made into jelly. In making jelly, sugar was added in most cases a t t h e rate of I ’ / ~volumes of sugar t o I of solution. The mixture was then heated t o boiling and boiled down t o a boiling point of 1 0 4 - 1 0 j ~ C. or t o a concentration of 65-70 per cent dissolved solids. A t these concentrations, a jelly will form if the fruit is suited t o the purpose. The tests enumerated in Table I show t h a t cull blackberries, loganberries. Isabella grapes, Tokay grapes, oranges, lemons. and pomelos can be used as jelly stock without addition of acid. These fruits are produced in from moderate t o very large quantities in California. The culls resulting during picking and packing are in many instances a total loss. Of those noted, only t h e loganberry is used t o any great extent as jelly stock. Commercially, this fruit is boiled with a small amount of water, pressed and the juice is sterilized in j-gal. cans. I t is stored in these cans until needed. The liquid settles in t h e cans so t h a t when
’
By “jelly stock” is meant t h e pectin-containing solution obtained from fruit or vegetables by heating t h e material with or without addition of water, and pressing or straining t o separate liquid from pulp.
418
T H E J O l - R S d L OF I-VDCSTRIAL A N D ENGINEERISG CHEMISTRY
the can is opened and t h e juice is decanted from the sediment, only a small amount of the total need be filtered. T h e other fruits noted above can be treated similarly with good results, as small scale tests have shown. Oranges do not always contain sufficient acid f o r jelly making, while lemons are too high in acid t o make a palatable jelly. A mixture of the two fruits in t h e ratio of two oranges t o one lemon gives more uniform and satisfactory results. Tokay grapes give a jelly of neutral flavor and should. therefore, be mixed with highly flavored grapes such as Muscat, Isabella or Concord. Muscat and Tokay culls are obtainable in great quantities in California for 8.3 t o $IO per ton. Cull apples, apple cores, and peels, are, of course, used i n large quantities €or jelly stock, both for apple jelly and blended jellies. By one of the most common methods, the waste apples are dried, baled, and sold to bakeries and jelly manufacturers. The manufacturer then boils t h e dried fruit with water as t h e TABLEI-COMPOSITION OF
JELLY
extracts were kept separate and tested individually for their jelly making properties. They were also combined in various amounts t o ascertain maximum amounts of pectin solutions from the last extractions t h a t could be blended Jrith the first two extracts and still give a jelly. Oranges and lemons mixed in the ratio of t w o oranges t o one lemon gave a maximum yield of I j 8 j cc. jelly per 1000 g. of fruit, or approximately 392 gals. of jelly per ton of fruit. or 8363 6 - o z . glasses of jelly per ton. Yields of 300 gals. of jelly from the mixed h i t s have been obtained often in t h e laboratory. Red loganberries gave a maximum yield of 1890 cc. jelly per 1000 g. fruit or approximately 467 gals., or 9962 6-oz. glasses per ton. Similarly, LIammoth blackberries gave 2 9 0 gals. jelly per t o n . With addition of acid, these yields were considerably increased so t h a t the yields were limited rather b y lack of acid t h a n lack of pectin. CLARIFICATION--A jelly t o be most attractive should be clear. Two methods of clarification are in general
STOCKS FROM VARIOUSFRUITS, AND SUITABILITY OF VARIOUSFRVITS FOR PSCTIN SOLUTION Citric Balling
FRUIT OR VEGETABLE
(a)
Acidity
(b)
Acid Added
Final Acidity
Apple, Yellow Newtown, Smith Cider, Gravenstein Winesap Apricot. . . . . . . . . . . . . ... .., Cherry Black Tartarian . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Citron Melon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Citron Melon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Citron Melon . . . . . .......................... Cranberry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Currant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Currant (2nd boiling of pulp). . . . . . . . . . . . . . . . . . . . . . . . . . . Blackberry, Mammoth Variety, . . . . . . . . . . . . . . . . . . . Blackberry, Himalaya Variety. . . . . . . . . . . . . . . . . . . . Fig, Mission Variety, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
....
....
....
23.2 7. 1 7.1 7.1
0.55 0.32 0.32 0.32
0 0.30 0 0.68 2.68
0.80 0.32 1 .oo 3.00
7.0 1.3 7.6
1.86 0.28 1.18
0 1.22 0
1.86 1.50 1.18
.... ....
13.1
. . . . . . . . . . . . . . . . . . 13.1 . . . . . . . . . . . . . . . . . . 20.0
....
i
. . .
0 : ‘(app.) 0 . 2 (app.) 0.8 0.7
20.0 ........ .... ..................................... 4 . 0 (app.) i:O’ .................................... 13.5 1.85 .............. 7.0 0.96 ng . . . . . . . . . . . . . . . . . . . . . . . . 0.40 ng) . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . 3 . 0 0.65 . . . . . . . .. . . . . . . . . . . 8 . 0 2.0 0.27 ........ . . . . . . 1.0 0.10 . . . . . . . . . . . . . . . .. . . . . . . . . . . . . .
7.0 0.64 Orange (Valencia) -1Lemons in ratio 7 : 1 by w t . . . . .... .... Peach, Muir.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . .... .... .............. Pear, Bartlett . . . . . . . . . . . . . . . . . . . . . 6.3 0.61 . . . . . . . .. . . . . . Pomegranate. . . . . . . . . . . . . . . . . . . . . . 1.60 Pomegra . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . 1 2 . 6 .... ..... .... Pomelo. . . . . . . . . . . . . . .. . . . . . . . 0.65 Pomelo plus Lemons in ratio 6 : 1 by. wt.. . . . . . . . . . . . . . . . 8 . 0 0.76 . . . . . . . .. . . . . . . . . . . 5 . 8 Strawberry. ....................... (a) Balling degree equals per cent dissolved solids, principally sugars. (6) Acidity as citric or malic.
......
fruit is needed for jelly making. Loganberries and citrus fruits have been treated similarly in this laboratory with good results. Citron melons were found t o be high in pectin, b u t low in acid. They could possibly be mixed with acid fruits when used for jelly. The suitability of cranberries and currants for jelly is so well known t h a t they need not be dwelt upon. Peaches, pears, pomegranates and strawberries were found t o be t o o low in pectin for jelly. llission figs contain sufficient pectin, b u t are too low in acid t o make jelly. The localities t h a t produce figs often produce lemons; thus t h e two fruits could be mixed t o advantage. YIELDS-The amount of jelly obtainable from a n y fruit without addition of acid will depend on the pectin and acid content of t h a t fruit. Maximum yields from several fruits were obtained b y making from four t o six successive extractions of pectin by boiling t h e fruit with water a n d pressing. The several
s‘ol. 8, 1-0. 5
....
0,3(am 0 0 0
...
0 0 0 0 0 0.5
0.5 0
0 0
....
0 0
....
JELLY
MAKING
CHARACTER OF RESULTIXGJELLY Good jelly in all cases except where fruit was overripe Good jelly in some cases. Does not always jell Very soft jelly. Not satisfactory Did not jell Soft jelly, b u t fairly satisfactory Stiff irllv
Good jelly .... Good jelly 0.5 0 . 2 (app.) Did not jell Good iellv 0.8 Good leu+ 0.7 .... Did not jell 3.0 Good jelly (this represents dilution of one-half) Very good jelly 1.85 Fair jelly, a little soft 0.96 Did not iell 0.40 Good jeliy 0.65 Good jelly 0.77 0.65 Did not jell 0.64 Good jelly Did not jell Did not jell .... 0.61 Did not jell 1.60 Did not jell Good jelly .... 0.65 Good jelly Did not jell 0.76
commercial use. The most common practice is t o filter t h e hot pectin solution. Often t h e boiled fruit and liquid are thrown together into some form of cloth or felt bag filter. This process is slow and troublesome and does not ordinarily give a brilliantly clear filtrate. The second method consists in sterilizing t h e hot juice from t h e press in j-gal. cans. These are stored until t h e sediment deposits. This will ordinarily be a period of several months. T h e settled juice is then decanted or siphoned off from t h e sediment directly into the cooking kettles. The process is often modified t o t h e extent of giving t h e hot juice a bag filtration before canning. Laboratory tests were made t o ascertain the effect of Spanish clay and infusorial earth on t h e rate of filtration. These substances were added in powdered form t o the hot juice and t h e rates of filtration and clearness of filtrates compared with those of t h e untreated juice. T h e Spanish clay, when added dry.
hIa>-, 1916
T H E J O C R S A L O F I N D U S T R I A L An‘D E N G I N E E R I N G C H E U I S T R Y
gave a n “earthy” t a s t e a n d did not appreciably hasten filtration. Infusorial e a r t h , when added a t t h e rate of j g. per IOO cc., greatly increased t h e rate of filtration a n d gave a clearer filtrate with one filtration t h a n could be obtained without t h e addition of this substance. I t was also found t h a t t h e filtration through short fiber asbestos pulp in t h e Seitz t y p e ol filter wab very much more rapid a n d resulted in a clearer filtrate t h a n was obtained with t h e bag filter. A mixture of Seitz asbestos N o . j a n d Seitz “Brilliant” asbestos added t o a n d mixed with juice t o give a filtering layer about % 8 in. thick gave good results. T h e flavor of t h e juice is not impaired. f i l t r a t i o n in all cases is made before a n y sugar is added t o t h e juice. Jelly stocks from loganberries, currants, and a mixture of oranges a n d lemons were prepared b y boiling t h e fruits with a small amount of water until soft a n d pressing through a coarse cloth. T h e oranges a n d lemons were mixed in t h e ratio of two oranges t o one lemon before boiling. T h e juices were divided into small portions. T o these portions were added casein from a 2 per cent solution in dilute NH40H at t h e rate of 20, 40, 6 0 a n d I O O g. per hectoliter. respectively. T o other portions were added egg albumen in t h e same amounts as noted for casein. T o others were added 2 5 0 , joo, 1000, ~ j o oa n d 2 0 0 0 g. Spanish clay per hectoliter from a I O per cent suspension of this substance in water. Untreated checks were also prepared. The various lots were bottled a n d sterilized one-half a n hour a t 100’ C. It was found t h a t t h e lemon-orange jelly stock settled very satisfactorily in 24 hrs. after sterilization without t h e addition of a n y clarifying material. T h e untreated loganberry a n d currant checks did not settle very satisfactorily in 24 hrs., b u t after several weeks’ storage did settle fairly well. Currant juice prepared b y heating t h e crushed fruit t o 8;” C , pressing and sterilizing a t 8 j ’ C., settled better t h a n t h e juice from t h e same fruit heated t o 100’ C. The casein a n d eggalbumen findings gave poor results in all cases a n d resulted in making t h e liquids more cloudy t h a n t h e untreated checks. Spanish clay a t 2 50 g. per hectoliter did not aid i n clearing; joo g. per hectoliter seemed to aid considerably in clearing. I n some cases, 1000 g. per hectoliter gave a perfect clarification in 24 hrs.; in other cases, 1500 t o 2 0 0 0 g. of Spanish clay per hectoliter were needed t o effect clearing of t h e juice. This was especially t r u e of loganberry juice. I n applying this method in practice, preliminary tests on a few hundred cc. of t h e material should be made before clarifying a n y large amount. T h e Spanish clay was prepared b y soaking it in a small amount of water until soft. It was t h e n worked u p with t h e water into a finely divided, thin “mud” or suspension. This can be made t o a definite concentration; e. g., 2 0 per cent or I O per cent mixtures were found satisfactory. T h e flavor of t h e juice is not impaired b y t h e use of t h e clay i n this form. Preliminary tests with fire clay iridic-ate t h a t this substance can probably be used in a way similar t o t h a t employed with Spanish clay.
419
AROMA A N D F L A V O R C H A N G E S IPi J E L L Y M A K I N G
Fruit jellies when made in t h e ordinary way usually have a different aroma a n d flavor t h a n those of t h e fresh fruits from which t h e y are made. Ordinarily, jellies are made b y extracting t h e pectin b y boiling, followed b y addition of sugar a n d boiling until t h e mixture boils a t about 2 2 0 ’ F., or until t h e mixture jells, or until a Balling or Brix degree of 6 j ’ (corrected for temperature) is obtained. The high temperatures resulted in marked changes in flavor, giving a socalled “cooked” t a s t e t o t h e resulting jelly. It was thought t h a t this change in flavor a n d aroma might be due in part t o hydrolysis a n d in part t o loss b y volatilization. T o throw light on loss by evaporation, a t t e m p t s were made t o make jelly from currants, loganberries, blackberries, a n d a mixture of orange and lemons. a t temperatures of room temperature, 60°, 7 0 ° , go’, 90’ a n d 100’ C. The fruits were crushed and heated in water-jacketed aluminum pots t o t h e temperatures indicated and pressed Cane sugar was added t o increase t h e Brix degree t o 6 5 ’ and t h e juices were heated t o t h e temperatures indicated t o dissolve t h e sugar. T o note whether loss of flavor was also due t o hydrolysis, a second series a t t h e same temperatures indicated above was carried out in a joo-cc. flask fitted with a long water-cooled reflux condenser. T h e jellies made b y t h e t w o methods were compared shortly after t h e y were made. The jellies made in t h e open kettle a t t h e lower temperatures were superior t o those made a t t h e higher temperatures as regards amount of fresh fruit flavor a n d aroma retained The same applied t o t h e jellies made under t h e reflux condenser. After two t o three months’ storage, t h e differences in flavor and aroma were not so pronounced. The orange jelly, after long storage, developed a “turpentine”-like taste, probably due t o oxidation of t h e orange oil. The jellies made a t room temperature were especially close t o t h e flavor of t h e fresh fruits from which t h e y were made. Loganberry a n d i n one or t w o cases blackberry and orange jelly were made without application of heat, b u t strawberries did not yield a jelly in a n y case. Loganberries very readily give a highly flavored aromatic and firm jelly in this way. So far as known, this method has not been described in t h e literature before. T h e jellies made under t h e reflux condenser were superior in flavor a n d aroma t o those made a t t h e corresponding temperatures in t h e open kettle. T h e facts t h a t jellies made a t high temperatures (8;-105’ C.) were poorer in fresh fruit flavor t h a n those made a t room temperature and 6 c - 7 j 0 C., a n d t h a t jellies made under t h e reflux condenser were stronger in fresh fruit aroma a n d flavor t h a n jellies made a t t h e same temperatures in a n open kettle, indicate t h a t loss of flavor a n d aroma is due both t o volatilization a n d t o decomposition of flavoring a n d aromatic bodies. EXPERIMENTS
O N R ~ L EO F
SUGAR
IN
JELLY
YAKII~G
T h e addition of sugar in jelly making is necessary t o raise t h e concentration of dissblved solids sufficientl;
t o cause jelling of the pectin. The amount of sugar necessary t o cause jelling will depend upon t h e pectin and acid concentrations, b u t the amount used normally is controlled b y the concentration of sugar necessary t o prevent fermentation or molding. Tests with loganberry a n d orange jellies showed t h a t jellies could be obtained a t 6 0 " Brix or lower, but t h a t in such cases molding or fermentation took place unless jellies were sterilized in sealed containers. Jellies with varying amounts of sugar were inoculated with mold and yeast and caps were placed on the glasses. I t was found t h a t 65' Brix prevented spoilage b u t t h a t much below this concentration. mold growth took place. Tl'here t h e sugar concentration was increased from 7 2 O t o 7 j " Brix crystallization of sugar often took place. This crystallization depends on t h e amount of cane sugar present. The tendency t o crystallize was most noticeable in jellies of low acid content and in which little hydrolysis of the cane sugar had probably taken place. n'here glucose is used for jelly making, the concentration may be considerably above 70' Brix without crystallization. In the ordinary household method of jelly making, equal parts of volume of juice and sugar are used. T h e mixture is then boiled down until i t jells This results in prolonged boiling a t temperatures above 100"C. and consequently in considerable loss in flavor and aroma. Jellies were made b y this method and compared with jellies from t h e same fruits made by adding enough sugar t o bring t h e juice t o the proper concentration ( 6 j " Brix) a t once and only heating enough t o dissolve t h e sugar. The latter method gave jellies of better flayor and aroma t h a n the former. X simple method for calculating the amount of sugar t o add t o a juice of a given degree Brix t o bring t h e liquid t o 6 j " Brix is as follows: Let a = Brix of juice. V = Volume of juice. S = Grams sugar necessary t o bring t o 65' Brix Then (65 - a ) V / 3 5 = S Example: V = 250 cc. a = Brix. (65 - 5 ) 250,,35 = S = 428.5 g. sugar.
For practical purposes, a little more t h a n 1 1 , ' ~ of sugar t o one of juice by Tveight will be found satisfactory. If this method is used, t h e fruit juice cannot be so dilute as where a mixture of one of sugar to one of juice is used and where t h e pectin is concentrated by boiling off excess water. The juice must contain enough pectin t o give a jelly without concentration of t h e juice. Sugar added t o the crushed fruit before pectin extraction seemed t o help retain t h e flavor a n d t h e jelly so made appeared t o be superior in this respect t o jelly made b y the usual methods. X solution of 6 j" Brix mill boil a t 103.9' C.or 2 1 9 . 0 2 ~ F. a t sea level. This point can be used t o determine the proper density of the boiling jelly if the proper allowance is made for elevation of locality in which the jelly is made. The boiling point of water for a n y gi\*en locality may be determined and then t h e boiling point of jelly a t the proper concentration will be 3 . 9 ' C. or j . 0 2 ~F. above the boiling point of water.
T E S T S O S E F F E C T O P .&CID I S J E L L Y MAK1L-G
I t 15-as found t h a t pectin solutions made by boiling and pressing fruit and containing less t h a n 0 . j per cent acid as citric or tartaric usually did not jcll, b u t it Tl-as also found t h a t if t h e acid were increased t o 0.7 or 0 . 8 in such cases. it almost invariably gave a jelly. This was noticed especially with citron melon and fig solutions. both naturally deficient in acid. b u t containing sufficient pectin for jelly making. Tests made with a I per cent solution of pure orange.pectin1 in distilled lyater indicated t h a t a concentration of 0 . 3 per cent acid in t h e final jelly was necessary t o give a firm jelly. Increase of acid in the final jelly t o 1.9 per cent acid resulted in softening of the jelly; I per cent acid in the final jelly gave good results and corresponds t o about I . j acid in a fruit juice before addition of sugar. 0.3 per cent acid in the final jelly would similarly correspond t o about 0.; per cent acid in the fruit juice before addition of sugar. This v,-ould indicate a range of 0 . 5 t o I . j per cent acid in the original fruit juice for t'he proper concentration of acid calculated as citric acid. This corresponds lrery well with results obtained lyith pectin-containing orange juices made b y boiling this fruit and pressing. I n this case an acidity of 1 . j per cent in the juice gave a finished jelly t h a t set quiclily b u t which finally softened. while 0 . j per cent gave a fairly good jelly, and less than 0 . j per cent did not give a jelly or resulted in a very soft jelly. Working with purified pectin and different amounts of pure citric acid, it was found t h a t for the same treatment as regards amounts of sugar added, time of boiling. etc.. the color of the resulting jelly was darkened in direct proportion t o the amount of acid used. T h e colors were compared by means of a Dubosq colorimeter. This darkening is probably due t o caramelization of the sugar. SU 11 M A R Y
I-It was found t h a t of the fruits produced in any great quantity in California, namely. grapes, apples, loganberries. blackberries, lemons and POmelos in all cases contained. sufficient acid and pectin t o gi7-e satisfactory jellies. Oranges always contained enough pectin, b u t were found t o give better results if mixed with lemons t o increase the acidity. -1pricots and cherries occasionally gave jellies, b u t in general v,-ere not satisfactory because of deficiency in pectin. Pomegranates and strawberries did not have enough pectin t o gire jellies. although the acidity was sufficient. Peaches, pears, and the huckleberries lacked sufficient pectin and acid. Figs and citron melon gave satisfactory jellies when acidified v i t h citric acid or lemon juice. 11-Naximum yields of 392 gals. jelly per ton of oranges and lemons mixed in ratio of two oranges t o 1 This pectin was prepared by boiling the sliced oranges under a reflus condenser with 95 per cent alcohol three successive times v i t h three different lots of alcohol. This rerno\Tes most of the sugars, acid, etc. T h e residual pulp as then heated with distilled water under pressure. T h e hot liquid was pressed out a n a filtered. T h e pectin ,$-as precipitated with 95 per cent alcohol and purified by redissolving in water and precipitating with 95 per cent alcohol. This purification was twice repeated The resulting pectin was white and friable.
May, 1916
T H E JOCR.VAL O F I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
one lemon, 467 gals. per ton of loganberries and 290 gals. per ton of blackberries were obtained in this laboratory. 111-Orange jelly stock was found t o clear satisfactorily b y settling twenty-four hours; other juices required a longer time and did not settle so completely as t h e orange jelly stock did. All juices tested were clarified satisfactorily b y t h e addition of 1000--2000 g. Spanish clay per hectoliter (from a I O or 2 0 per cent suspension of t h e clay in water), followed by heating t o 100' C. and settling. IT'-Changes in and loss of fruit flavors a n d aromas in jelly making were found t o be due t o decomposition by heat and t o direct loss b y volatilization. V-Jellies with practically all of t h e aroma and flavor of t h e fresh fruit were made by crushing fruits high in pectin, pressing out t h e juice, and adding sufficient sugar t o increase the Brix degree to 65". Loganberries and currants were especially adapted t o this procedure VI-An acidity between 0.5 and 1.5 per cent for fruit juices t o be made into jelly seemed t o be the optimum range for production of satisfactory jellies. VII-A Brix degree of 6 j O was necessary t o prevent spoilage by mold and yeasts where jellies were inoculated with these organisms. UNIVERSITY OF CALIFORAIA EXPERIMENT STATIOK BERKELEY
THE ANALYSIS OF NON-ALCOHOLIC LEMON AND ORANGE EXTRACTS B y E. I,. RFDFERN Received November 29, 1915
During the last year there have appeared on t h e market various flavoring extracts containing no alcohol b u t made u p with gum tragacanth a n d glycerine in which the essential oils are held in suspension. It is obvious t h a t the amount of oil present cannot be determined by t h e ordinary methods a n d an attempt was made t o devise Some method b y which t h e oils could be determined quantitatively t o see if this class of extracts was up t o t h e legal standard. These extracts are quite viscous and unless warmed slightly, pour with difficulty, but. by warming for a few minutes they can be measured in an accurately graduated cylindrical graduate. The use of a pipette for measuring is not satisfactory. as a considerable amount of the mixture adheres t o the inside of the pipette and is difficult t o remove. while with a graduate it can be removed by letting the graduate drain for a few minutes into the flask t o be used in t h e analysis and then rinsing with a little alcohol. A standard extract containjng j per cent of lemon oil was made u p as follows: Ijo cc. gum tragacanth, which had been soaked in water and reduced t o the proper consistency, 40 cc. glycerine and I O cc. pure lemon oil. First a n a t t e m p t was made t o extract t h e oil in a separatory funnel with ether b u t an emulsion was formed which could be only partly broken u p b y running in the centrifuge. The ether was drawn off through a small dry filter into a tared flask, evaporated off spontaneously and dried for a few hours in a
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desiccator. T h e final weight of oil obtaiiied from I O cc. of the j per cent extract was 0 . 2 6 6 4 and 0 . 2 2 4 6 g. in duplicate determinations. Ten grams of extract were then mixed with anhydrous CuSOd t o apparent dryness and extracted in a Soxhlet extractor with anhydrous ether b u t only 1 7 per cent of t h e oil was recovered. Distillation with steam gave 24 per cent recovery of oil. The fact t h a t gums are precipitated with alcohol suggested a possible solution of the difficulty: 2 j CC. of the standard extract were measured out and transferred t o a 200-cc. Erlenmeyer flask, 2 j cc. of 95 per cent alcohol were added and the flask was then shaken vigorously. The alcohol was filtered o n a Gooch crucible and collected in a 100-cc. graduated flask, care being taken t o prevent a n y of t h e precipitated gum from running into t h e crucible. The precipitate was washed several times with 9 j per cent alcohol and t h e filtrate made u p t o IOO cc. The precipitation method using j o cc. of this solution did not give uniform results, owing t o the fact t h a t with this high strength of alcohol a considerable quantity of t h e oil was held in solution. The method suggested b y Howard1 was then used which gave 4 96 and j per cent oil in duplicate tests on the j per cent standard. An orange extract was made u p as in the case of lemon, using orange oil, and gave in duplicate tests with Howard's method 4 . 8 0 per cent of oil. Duplicate tests of a n unknown extract gave j 2 and j . 0 4 per cent. I n these tests a Babcock milk bottle graduated t o I per cent was used t o insure more accurate reading as t h e amount of oil in t h e dilutions is small. Especially is this t r u e in substandard extracts. If the analysis of an extract shows t h a t it is much below standard, t h e author has found it advisable t o repeat t h e analysis using a skim milk bottle graduated t o 0.01per cent, which makes it possible t o read very small amounts of oil. The supernatant liquid in t h e skim milk bottle can be easily drawn off b y attaching a suction tube t o t h e filling tube on t h e bottle and decanting off the remaining small amount through the capillary tube as the chloroform carries t h e oil present and remains on t h e bottom. The method has been used in this laboratory for several months a n d has given uniform results. IOWADAIRYA N D FOODCOMMISSION DES MOINES
THE ANALYSIS OF MAPLE PRODUCTS, VI11 The Application of the Conductivity and Volumetric Lead Subacetate Tests to Maple Sugar By J. F. SNELLA N D G . J. \'AX ZOEREN Received August 27, 1915
I n Papers I 2 and VI13 of this series a conductivity test and in Paper VI4 a volumetric lead subacetate test for purity of maple syrup have been described. The question remained how these tests could best be applied t o sugars. Two methods of procedure suggested themselves: ( I ) A quantity of sugar sufficient 1
J. A m . Chem. SOC.,1908, 608.
2
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a 4
(19131, 740.
Ibid., 8 (1916), 331. I h i d . , 8 (19161, 241.
