Nov., 1916
T H E J O l r R N A L O F I A V D C S T K I d L A N D ELVGI~VEERINGC H E X I S T R Y
THE INSPECTION OF CANNED FOODS’ By W. D BIGSLOW
Received August 1 5 , 1916
T h e first principle in t h e inspection of a n y article is t h a t t h e inspector or analyst should be thoroughly familiar with t h e normal product. Methods of analysis a n d d a t a for t h e interpretation of analytical results should always be standardized b y t h e normal product. Iron a n d steel analysts standardize their analytical technique b y t h e examination of s t a n d a r d samples of known composition. T h a t practice is also followed in colleges a n d universities where instructors often procure for their students samples t h a t have been analyzed b y experts in various fields. T h e same practice must be observed in t h e examination of canned foods. An analyst who is not thoroughly familiar with a normal product is entirely incompetent t o determine whether or not a given sample is normal. T h e examination oE canned foods m a y be undertaken t o assist in controlling t h e character a n d quality of t h e product; to establish its commercial value a n d grade; t o fix t h e responsibility for defect in food or package; or in connection with t h e enforcement of food laws. Whatever the ultimate object of t h e work, t h e immediate purpose is t h e same-to ascertain as exactly as possible t h e nature, character a n d quality of t h e product under examination. This includes a knowledge of t h e raw product and method a n d conditions of manufacture as far as t h e y affect t h e character a n d quality of t h e finished article. I n packing a n d labeling a product, therefore, t h e canner needs t h e same information t h a t Federal a n d S t a t e officials need in enforcing t h e law. T h e frequent inquiries received b y t h e writer regarding t h e examination of canned foods h a v e suggested t h a t a n outline of t h e methods employed b y technical laboratories would be of interest. T o give such a n outline is t h e purpose of this paper. E X T E R N A L A P P E A R A X C E OB THE C A N
I n t h e examination of canned foods, t h e external appearance of t h e can should be carefully noted. If t h e can appears “flat,” as i t is called i n t h e industry (i. e . , if t h e ends are roncave), it should be “knocked” with considerable force on one end on a substantial table or block of wood t o determine whether a suitable vacuum exists. If t h e lower end of t h e can does not remain concave on being struck in this manner, t h e vacuum in t h e can is not as great as i t should be. T h e temperature at which t h e can is examined must be considered in this connection, for it is obvious t h a t if t h e temperature of t h e contents were a few degrees higher t h e can would be a springer. A lot of cans can be springers i n t h e summer a n d t h e ends concave t h e following fall a n d winter. They m a y be springers during a hot wave a n d “flat” in t h e same location t h e following week. Samples of springers sent t o t h e laboratory b y a packer during a hot wave have reached us “flat” (Kith t h e ends concave) a 1 Read before the Chemical Section of the Association of American Dairy, Food and Drug Officials, August 8, 1916.
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couple of days later, because t h e weather was cooler. T h e fact t h a t a can does not have a good vacuum or even t h a t i t has bulged ends means nothing in itself, b u t m a y be significant when considered in connection with other d a t a . S W E L L S AXD SPRINGERS
Cans whose ends bulge ever so slightly are not merchantable a n d their sale t o consumers should not be permitted. T h e bulged end is a reasonable “warning sign” a n d should be so regarded. Yet t h a t condition does not usually mean decomposition when found in t h e retail trade. Very frequent a n d very serious errors have been made i n t h e inspection of food b y assuming t h a t all “swells,” as t h e y are popularly termed, are due t o decomposition. With non-acid foods, such as peas or corn, swells are usually due t o decomposition, be t h e a m o u n t of swelling ever so little. On t h e other hand, spoilage rarely occurs with acid fruits unless t h e can be leaky. I n this class of products t h e swelling of t h e can (in t h e absence of leaks) is almost invariably due t o hydrogen set free b y t h e action of t h e fruit acid on t h e metal of t h e container. T h e amount of hydrogen liberated in this manner depends t o a certain extent on t h e age of t h e sample, b u t t o a much greater extent on t h e conditions of storage. It is influenced little b y t h e method of canning, or b y conditions within t h e control of t h e packer. A shipment of canned fruit may leave t h e packer in perfect condition a n d yet, owing t o improper storage, t h e cans may become springers within a few months or even within a few weeks. A single shipment of California canned fruit may be split, one portion being sent t o Texas or Oklahoma a n d t h e other t o Boston; or one portion m a y be stored under a hot iron root“ a n d t h e other in a relatively cool warehouse. Under such circumstances, t h e goods stored i n t h e cooler location remain in perfect condition long after t h e others have become springers. This is due solely t o t h e acceleration of t h e higher temperature on t h e action of t h e fruit acids on t h e metal of t h e container. In t h e inspection of cans with concave ends a n d apparently normal in every way, t h e analyst often desires t o know whether t h e y are likely t o become springers i n t h e near future. I n such cases, before opening t h e can, its vacuum is determined b y means of a suitably equipped gauge. T h e vacuum in t h e can has no significance in itself, b u t is often of value when considered in connection with other d a t a . VENT HOLES
T h e number of vent holes appearing in t h e can is a matter which has occasioned frequent error. N o opinion can be formed of t h e character or history of canned foods b y t h e number of vent holes in t h e can. T h e old process of canning many products, including canned beef a n d salmon, used t w o vent holes. This was described by t h e writer as applied t o canned beef in Bureau of Chemistry Bulletin 13, P a r t ‘Io, published in 1901. Although t h e piactice is not as prevalent now as it was a t t h a t time, it is still found a t many plants. T h e procedure which gives two vent holes is this.
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T H E J O C R h - A L O F I S D C ‘ S T R I A L A S D ELVGISEERIlF7G C H E M I S T R Y
The cans are sealed, tipped and given a kettle exhaustt h a t is, they are heated in t h e process kettle about half an hour and again vented t o permit the escape of air. The new vent hole is then sealed and t h e cans are again placed in t h e process kettle and sterilized. I t sometimes happens t h a t t h e closing of t h e second vent hole is prevented b y a piece of solid material such as meat lying against it. When this occurs, a third vent hole is made in order ,to have a n opening when t h e second one is closed. If anything lies against the can where the third Vent hole is made, the can is vented in still another place and this is continued until a spot is found t h a t is not in contact with t h e contents of t h e can. Even when the method just described is not employed, two or more vent holes are occasionally found in hole and cap cans containing foods of all descriptions. This occurs when t h e can is not properly closed. At t h e end of every hole and cap line in the cannery, a man is stationed t o inspect the cans as t h e y pass and set out on a table those not properly sealed. Some packers carry the cans on a conveyor through a trough of hot water, when “cap leaks” and “vent leaks” due t o defective sealing may be detected b y bubbles of air escaping from the top of t h e can. Whatever the method of sorting, there are often enough cans there t h a t are not properly sealed t o keep a. man with a hand-soldering iron busy patching them. These cans can be patched only with an open vent hole t o permit the escape of air \\-bile the hot steel is on the cap. This is generally accomplished b y removing t h e solder from t h e old vent hole with a hot soldering iron. Frequently, however, a new vent hole is made. This second vent hole is in no respect a mark of inferiority. The cans are patched immediately and their sterilization is rarely delayed more t h a n a few minutes. Again, with sanitary cans, there are various reasons why a vent hole may be found. One incident came t o the writer‘s attention n few weeks ago in which, by misunderstanding, t h e brine vias omitted from several hundred cans of shrimp. T h e workmen understood t h a t they \\.ere t o be packed “ d r y “ ” I t was the intention of t h e superintendent t o pack t h e m with brine and he could not spare a process kettle long enough t o give these cans the process necessary for dry shrimp. What he did vias t o make two vent holes in t h e cans, introduce hot brine and close the vent holes again. I t was 211 done in a few minutes and the cans so treated were sterilized in t h e same process kettle as those t h a t followed t h e m through t h e sealing machine. The contents of these cans were identical with those of t h e cans filled and brined before closing. Again, one crabrneat packer of t h e writer’s acquainance, buys his sanitary cans with t h e tops already vented in order t h a t he may continue his former practive of giving the cans a retort exhaust with open vent, One not familiar with t h e industry might suspect reprocessing on seeing the cans described in these two illustrations. If he would investigate t h e matter further, however, he would .find t h a t reprocessing
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would cook the shrimp t o pieces and would darken t h e crabmeat t o such an extent t h a t it would be unmerchantable. On the other hand, some foods can be sterilized a second time without materially changing their appearance. Presence of vent holes is never proof of decomposition. The question of vent holes is merely one of t h e points t h a t should be noted from the external inspection of t h e can and considered in connection with d a t a obtained from t h e examination of the contents. ODOR. ELAVOR A S D APPEARAKCE
On opening the can, the odor, flavor and appearance of t h e contents should be carefully observed. I n this manner the analyst should be able to determine approximately the quality or commercial grade of t h e sample. He may thus judge whether t h e product complies with t h e grade for which it is sold, or with t h e representations on t h e label. The importance of establishing the true commercial grade is not always fully understood. I t is not merely a commercial question. A fancy or first quality article, for instance, can be prepared only from a ram product grown under proper conditions, harvested a t the best stage of maturity. and canned promptly. Moreover, in many varieties of foods, a fancy or first grade product can be prepared onlp b y experienced and skilled men. If t h e ram material is not of suitable grade an experienced man will recognize t h a t fact by the appearance or flavor of the finished product. If the raw material is not properly handled, if ii is allowed t o stand for even a fraction of the time t h a t is cust,omary with fresh vegetables in our city markets, t h a t fact is often apparent in t h e canned food. I t may be suitable for consumption and comply v-ith the law if properly labeled and still not be of thc highest commercial grade. For instance, if not handled promptly, peas lose in flavor and asparagus has a tendency t o become tough and bitter. T o retain LL high quality, they must be canned as soon as possible after they are harvest e d . A movement is under way t o make the commercial grades more uniform and to have the products so labeled t h a t these grades will be understood b y the purchaser. A s this movement progresses, the importance of holding t h e products true t o label will increase. El-en a t t h e present time, this matter is very important and should be considered in the enforcement of food l a m . The importance of odor and taste in t h e inspection of canned foods cannot be overstated. If the odor and flax-or of a sample be not entirely normal, t h e possibility of delay in manufacture and consequent bacterial change should be considered. I n such a case, a microscopical examination is often of value. X I C K 0 S C 0 1’1 C .A L E X .A 111 ?*T A T 1 0X
This method is applied to the liquor if the product has a distinct liquor. TE the sample be thick and pasty, enough n-ater may be added t o give it a suitable consistency. In either case, water should be added if necessary. so t o thin the sample t h a t t h e number of microscopic partic!es ill n o t be too great for their
S o v . , 1916
T H E J O U R J A L O F I L V D U S T R I A L A N D E N G I iliEE RI.VG C H E M I ST R Y
careful s t u d y , a n d this liquid or mixture should be allowed t o s t a n d in a beaker or cylinder for a moment until t h e heaviest particles settle. The proper technique must be worked out with each product. A mount should t h e n be made a n d examined microscopically. If bacteria are recognized b y size and shape, their presence may be confirmed b y bacteriological stains. If either yeasts or bacteria are found in considerable numbers, t h e analyst should endeavor t o find t h e reason for their presence. Obviously, this method is not applicable t o products made b y process of fermentation. Kra.ut, for instance, is prepared by such a process a n d contains a very large number of bacteria, b u t should contain few if a n y yeasts. The presence of dead bacteria in considerable n u m bers is merely an indication of t h e beginning of bacterial change a t some time i n t h e history of t h e product. It m a y be due t o allowing a few cans t o s t a n d too long (because of a breakdown in t h e machine) after filling a n d before sterilizing, or t o storing t h e raw product for a number of hours in boxes or baskets as is done with fresh vegetables in our city markets. I t m a y be due t o a n y 'delay in t h e process of canning. This method may help or mislead a n analyst according t o his ability a n d experience. It can be used intelligently only i n connection with t h e other .methods described. The method requires special aptitude, long training an'd unremitting care. There is no other analytical method applied t o foods which is now used so badly a n d with so little aptitude or judgment as t h e method for determining t h e presence of bacteria with t h e microscope. Mention is made of t h e importance of special aptitude i n judging t h e odor, taste a n d flavor of t h e food. I t is necessary t o no less extent in a microscopic examination. Both methods are largely subjective. Experience with samples of known character, both fresh a n d canned. is absolutely necessary. Without such experience, t h e analyst can be sure only of making serious mistakes. It should be borne in mind t h a t this is a microscopical a n d not a bacteriological method. It is used in determining t h e presence of dead microorganisms. It is therefore widely different from t h e bacteriological method lyhich follows. B ACT E R I 0 L 0 G I C A L E XA M I N A TLO S
I n t h e inspection of canned foods, a bacteriological examination is of value only when considered i n connection with other methods of analysis. A food t h a t has undergone bacteriological decomposition m a y be sterile because of t h e inhibiting action of products of t h e life functions of the organisms causing t h e decomposition. On t h e other hand. it is believed by some t h a t canned foods may contain aerobic bacteria which cannot develop because of t h e absence of oxygen a n d which m a y therefore remain dormant for a considerable time. I t is also believed by some t h a t certain organisms may remain quiescent in some foods because t h e food does not provide a suitable medium for their growth. The t r u t h of the last twc ideas suggested has not been
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demonstrated a n d in f a c t it is well known t h a t canned foods are almost universally sterile. At t h e same time, until questions of this nature are settled, bacteriological methods are of more value in research investigations relating t o canned foods t h a n in their inspection. I n t h e case of goods very recently packed a n d t o determine whether t h e process of t h e plant is sufficient, a bacteriological examination is of value when used i n connection with t h e other methods described above. The results of t h e bacteriological examination of freshly packed goods can be confirmed b y incubating cans for several days a n d noting t h e odor, flavor, and acidity of their contents. D E T E R M I N A T 1 0 N 0 F A C I D I T I'
This is a method with which relatively little has been done i n t h e examination of canned foods. T h e laboratories t h a t have used it have not tabulated their results a n d t h e d a t a now existing from t h e titration of normal samples is therefore n o t available. I t is desirable t h a t authentic d a t a of this nature be secured. The separated liquor should be titrated when practicable. I t need not be filtered unless i t contain finely divided solids t h a t m a y obscure t h e end-point. I n t h e absence of a distinct liquor, t h e sample should be finely comminuted and a weighted portion placed in a beaker with water. I n either case a n excess of standard acid should be added, t h e sample boiled, cooled in water t o approximately room temperature and titrated back with standard alkali, using phenolphthalein as indicator. An abnormally high acidity. o;, under some circumstances, a n abnormally low acidity, may be of much value when considered in connection with t h e results of t h e methods mentioned above. FILL OF THE C A S
When t h e can is opened, t h e fill should be carefully noted. If t h e can be opened b y cutting around t h e side, near t h e end, it is often convenient t o pour t h e liquor through t h e opening t h u s made before turning back t h e t o p , It is important t h a t in t h e examination of a single product a uniform method of separating t h e drained solids be employed. If t h e food under examination consists of insoluble material, such as fruits or vegetables surrounded with water, syrup or brine, t h e amount of food present should be noted. I t may be well t o weigh t h e drained solids a n d liquor after separation with a suitable screen t h e size of whose mesh will depend on t h e product under examination. With some products, a l/e-in. screen is appropriate; with others a smaller mesh is necessary. It is often important for t h e analyst t o consider t h e relation between t h e drained solids found in t h e can a n d t h e weight of food originally weighed into t h e can. For instance, with dry pack shrimp, t h e cutout weight is less a n d with wet pack shrimp it is greater t h a n t h e amount of shrimp originally weighed into t h e can. I n working with fruit packed in syrup, t h e specific gravity of t h e syrup may be determined. Then,
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T H E J 0 C R ; T A L O F I S D L - S T R I AL A N D E A - G I X E E R I S G C N E M I S T R I ’
taking into consideration t h e average sugar a n d water content of t h e fruit present and t h e proportion of t h a t fruit in t h e contents of t h e can t h e analyst can calculate approximately t h e weight of fruit and strength of syrup t h a t was used originally. T h e influence of syrup of different strengths on t h e weight of t h e drained contents has been worked out b y Bitting’ for a m d e range of fruits. Whether the drained solids and liquor be weighed or n o t , a record should be made of whether t h e solid portion of t h e contents appears t o be present in the right amount. I n this connection, care should be taken t h a t t h e analyst be not deceived b y t h e solids floating at t h e top of t h e liquor, thus giving the appearance of a good fill, even if the fill be slack. Here again t h e analyst is not competent t o form an opinion unless he knows what is normal with t h a t particular variety of food. Some foods m a y shrink in processing or become softened so t h a t they settle down, leaving a can which is apparently slack filled although it may have been full a t t h e beginning. Let us take canned shrimp as a n illustration. Even if t h e can be packed so full of shrimp t h a t it will mat together and be unattractive t o the eye. t h e product will often soften on processing so t h a t the fill will appear slack t o one not familiar with the product. T h e analyst must bear in mind t h a t t h e examination of one or two cans will often lead t o incorrect conclusions. S o matter how careful a packer may be, i t frequently happens t h a t the amount of brine in t h e can is either too much or too httle. In a well managed corn cannery. for instance, there i s always one m a n whose d u t y is t o open cans a t frequent intervals t o determine whether the corn is of the right consistency. The character of t h e corn changes from hour t o hour, requiring t h e relative amount of corn a n d brine t o be changed from time t o time in order t o give t h e proper result in t h e finished product. EXAMISATIOK O F THE C A N
Cans should be carefully examined t o determine whether they are tight. This is more important in constructive work checking up the efficiency of a plant t h a n in t h e enforcement of food laws. I t is just as essential for t h e canner t o know when his cans are defective as when t h e y are not completely sterilized. I n both cases he may expect spoilage. An adequate description of t h e exact procedure t o be followed in determining whether a lot of cans is tight is scarcely practicable within t h e scope of this paper. Some types of cans may be emptied through a small opening, thoroughly cleansed, again sealed up, air pumped into t h e m under pressure and leaks detected b y bubbles of air escaping when t h e can is held under water. This can may be sealed in a partial vacuum and t h e vacuum determined after t h e can has stood a number of days. The crimped edges of sanitary cans may be laid bare b y filing and examined with a lens. Soldered seams may be “stripped” (pulled a p a r t ) and carefully inspected for possible imperfections of workmanship. If a large percentage 1 U. S Dept of Agriculture, Bull 196, May, 1915, National Canners .4ssociation, Bull 4, February, 1915
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of t h e cans of a given lot of food is found t o leak because of a common fault in their construction. the entire lot of food may have spoiled. Such cases are almost always discovered a t t h e plant a n d therefore come within t h e experience of the packer’s chemist rather t h a n t h a t of a n official enforcing a food lan-. If they should come t o t h e attention of a food inspection official, t h e examination of t h e can is important in t h a t i t gives fuller information regarding t h e nature of the product, and may confirm other d a t a . Cans containing foods likely t o produce pin-holes should be gone over in great detail with a needle. If the analyst has not exceptionally good eyes, a simple lens of reading glass is sometimes useful. The application of t h e same method of examination t o the inside of t h e can will disclose whether the can is pitting and thus likely t o form pin-holes. For this, both ends of t h e can must be cut off and the body opened bycutting down the side. I n t h e examination of t h e can as in t h e examination of t h e contents, it is obvious t h a t the results obtained from a single can may be misleading. There are many reasons for this. For instance, small leaks. after admitting contaminated air or contaminated water from the cooling t a n k , may be closed b y particles of food o r , , a s in the case of water pipes, b y rusting. If we find leaks in something like half t h e cans from a lot, of swells, we assume t h a t they probably all leaked a t t h e beginning. This explains t h e fact rdiich so many find it difficult t o understand--that z swell may be and frequently is due t o a leak in t h e can. I n such a case, a sample consisting of a single can or a small number of cans is frequently not representative of t h e lot of goods from which it is taken. After examining a half dozen cans, the writer frequently sends for a case and sometimes several cases. Even t h e n a n inspection of t h e entire lot in t h e storeroom will often throw additional light on t h e cause of t h e difficulty. SLTBSEQLTENT E X A M I N A T I O N
T h e nature of any further examination must depend on the particular variety of food and, t o some extent, on t h e character of the sample and t h e reason for the examination. A chemical examination may be made to determine whether certain standards are complied with as t h e determination of f a t and solids in evaporated or condensed milk. T h e cause should be understood of various discolorations t h a t are sometimes found on t h e inside of t h e can and on t h e surface of t h e food. For instance, with some products like kidney beans and, t o a certain extent, with peas, t h e entire inner surface of t h e can which comes in contact with t h e food is more or less dark in color, owing t o a slight film of insoluble tin sulfide. With peas, t h e portion of t h e can which stands uppermost for a few hours immediately after processing and cooling, has a number of spots consisting apparently of iron oxide. These spots gradually become dark until they are quite black, probably owing t o the conversion of a portion of t h e oxide t o sulfide. As just stated, these spots on t h e inside of canned peas are universally present. Apparently they cannot
Nov.. 1916
T H E J O U R N A L OF INDUSTRI.4L A N D ENGINEERING C H E M I S T R Y
be avoided a n d t h e y are not in a n y way objectionable. T h e y sometimes startle a canner who sees t h e m for t h e first time a n d the chemist inspecting his product should be able t o explain them. K i t h some products, patches of iron sulfide, apparently in colloidal form a n d sometimes mixed with particles of food, adhere t o t h e sides of t h e can. These patches of iron sulfide are not frequent on t h e whole but have been found in considerable numbers. They vary in size and sometimes their thickness is so great t h a t they become mixed with t h e food in their immediate vicinity and are objected t o b y buyers who do not understand their nature. When large, a n d especially when they become mixed with t h e food, these patches are unsightly b u t t h e amount of iron present is really exceedingly small. T h e cause of these patches is only partially understood. They always form like the spots just referred t o on pea cans on the portion of t h e can t h a t is uppermost after processing and cooling, which therefore does not come in contact with t h e food. On storage, t h e spots gradually become less conspicuous. T h e conditions leading t o their formation are not entirely understood, b u t i t has been determined t h a t t h e y are less numerous and smaller as t h e can is fuller and freer from oxygen. Before opening a can of food, i t is often of value t o determine t h e vacuum in t h e can b y means of a suitably equipped gauge. This is a matter which has no significance in itself b u t may be of value when considered in connection with other data. T h e amount of tin (or perhaps soluble tin) and iron in acid fruits may be significant when considered in connection with other d a t a . On t h e other hand, with vegetables, such as asparagus, string beans and pumpkin, whose action on t h e t i n is believed t o be due t o amino bodies, .there is no relation between t h e amount of t i n in t h e food and t h e amount of hydrogen in t h e gas content of t h e can. We are just beginning t o understand this subject and all d a t a bearing on it is of value. I t m a y sometimes be of interest t o determine t h e composition of t h e gas in a can with bulged ends. When t h e can is sealed t h e air is not entirely removed. Some carbon dioxide is formed in processing and some may be present in t h e food before processing, especially if it is not sterilized very promptly. Hydrogen is formed b y the action of fruit acids on t h e metal of the container. It has been pointed out b y Baker’ t h a t hydrogen is not found in t h e gases of t h e can until oxygen has disappeared. T h e composition of t h e gas present, therefore, m a y sometimes serve t o confirm d a t a obtained b y other methods of examination. XATIONAL CANNZRS ASSOCIATION, WASHINGTON, D. C.
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THE CHEMICAL COMPOSITION OF COMMERCIAL GLUCOSE AND ITS DIGESTIBILITY By J . A . WESEHERAND G. L. TELLER Received June 29, 1916
T h e t e r m commercial glucose has been applied t o a product obtained b y the action of certain catalytic agents upon refined starch, until t h e starch has lost 1
Original Contributions, 8th Inlevn. C O I Z RA~p .p l . Chem., 18, 45.
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its identity as such a n d has been converted into a series of products, consisting of d-glucose, maltose and different forms of dextrin. The dilute liquid thus produced is clarified b y passing over boneblack a n d is t h e n carefully evaporated, either t o a solid substance or t o a syrupy condition known as glucose syrup. T h e glucose t h u s produced in this country is made entirely from corn starch and, for this reason, t h e syrup is designated as corn syrup. It consists of about onefifth its weight of water, very minute traces of nitrogenous bodies, a very small amount of ash a n d a group oE carbohydrate bodies, consisting of dextrose, maltose and probably several forms of dextrin, and paralleling closely t h e bodies of a similar nature obtained b y t h e action of malt diastase and other diastases upon starch. There is apparently a bbrder line between t h e bodies commonly known as dextrin and, t h a t known as maltose, which has led t o great confusion in t h e minds of t h e chemists who have investigated this subject, largely because of the difficulties attendant upon t h e separation of such bodies from maltose on t h e one hand, and t h e different forms of dextrin, on t h e other, a n d t h e consequent confusion with these bodies and with mixtures of them. This confusion of ideas concerning glucose syrup has been participated in b y a large number of investigators, extending in time over a period of 2 0 or 30 years, a n d has led t o t h e introduction into t h e literature of such terms as “gallisin,” “isomaltose,” “malto-dextrin” a n d others. T h e voluminous literature on this subject appears t o have been reviewed completely b y various writers without coming t o a n y definite conclusions as t o results. T h e latest edition of such a n authoritative work as Allen’s“Commercia1 Organic Analysis” (4th Ed., 1701. I , I ~ I Z ) , dismisses t h e matter with t h e following brief summary: “Gallisin as hitherto obtained is not a definite compound, and i t appears advisable only t o retain the term as synonymous with unfermentable matter. The whole question of the structure of starch, the nature of the various dextrins and of isomaltose still remains a vexed question in carbohydrate chemistry and the utmost confusion exists as regards the subject. [The reader is referred t o Ling’.; article on Starch in Sykes’ ‘TextBook of Brewing’ (1g07).”] A review of t h e earlier literature is quite fully set forth in t h e third edition of the same work, published in 1898, and in Brown’s “Handbook of Sugar Analysis’’ (1912),under t h e title of Iso-maltose. A clear and concise statement of what appears t o be t h e general understanding of these terms, as they are used, is embodied in t h e following definitions, as given in t h e “Century Dictionary and Encyclopedia:” “Gallisin, in chemistry, a substance analogous t o dextrin, obtained by fermenting with yeast a solution of commercial glucose or starch sugar and adding t o the residual liquid absolute alcohol in excess. Gallisin is precipitated as a white powder, of faintly sweetish taste, hygroscopic, dextrogyrate, incapable of fermentation and yielding dextrose by prolonged heating with dilute sulfuric acid. Probably identical with iso-maltose, CIZH z z O ~(Sadtler, ~. “Handbook of Industrial Chemistry,” p. I 78.) “Iso-maltose, a substance formed together with maltose from starch on diastatic digestion. It has been produced synthetically from dextrose, does not ferment and is isomeric with maltose, C12H2?011. “Malto-dextrin, a variety OF dextrine or starch-gum, produced in ‘mashing’ brewers’ malt as an intermrdiate product between
