IND I7STRIAL AND ENGINEERING CHElcllSTRY
408
Vol. 20, No. 4
Pure Food Gelatin' Physical Properties Related to the Economy of Manufacture M. Briefer and J. H. Cohen ATLANTIC GELATINE COMPANY, W O B U R N . I\IASS.
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N THE manufacture of ice cream, marshmallows, and
the same for all grades when used in this ratio. This, howother confections the use of edible gelatin has become ever, is not always the case. an established practice. Gelatin finely ground and VISCOSITYDETERMINATION-ViSCOSitY is determined from mixed with suitable amounts of sugar and flavors (jelly a 62/3 per cent solution at 40" C. by the efflux method and powders) has found generous acceptance for the preparation of expressed in millipoises. This method was also described desserts, broths, and a variety of other dishes. Recent work in the previous paperq4 at the Mellon Institute2 has shown the value of gelatin when PREPARATION OF SAMPLES-Having determined the jelly added to infant diet and a small amount of gelatin has been strength of the sample and computed the required amount reported to be a desirable addition to buttermilk. Whipped as explained above, a quantity of gelatin sufficient for twenty cream has been found tests (one more than the rei m p r o v e d in texture and quired number) is carefully flavor and more economical weighed out and transferred A means for determining, and numerically expressin use when a small proto a dry liter beaker and ing, the value of the effective concentrations of gelatin, portion of gelatin has been 800 ml. of cold d i s t i l l e d as used in food products, is discussed. Jelly conadded. Research work in sistency is defined and a method for evaluating it is I water are added, with stirthis laboratory has shown ring to avoid lumping. The developed. The effect of pH on jelly consistency and t h a t g e l a t i n may be adgelatin is allowed to swell turbidity is studied. vantageously used in the for l/2 h o u r if i n g r o u n d Comparisons of the physical properties of gelatins preparation of mayonnaise, form, or longer if in flake or extracted from different classes of raw stock are shown yielding a smooth product sheet form, depending on by means of curves. of better flavor and appearthe thickness of the pieces. The significance of viscosity on the specific gravity of ance than when gelatin is marshmallow cream is discussed and the relation of jelly The beaker is then placed omitted. strength to weight of gelatin required to obtain equal in a water bath and the specific gravities is studied. The foam cells of marshg e l a t i n melted at 40" C. This paper d e a l s w i t h mallow creams are examined microscopically, and their for a b o u t */z hour. The s o m e of t h e fundamental approximate size, relative to specific gravity, shown g e l a t i n s o l u t i o n is then physical properties of edible photographically. cooled to 25' C. and made gelatin relative to its use in up to 1 liter with distilled food products. water, also at 25" C. Effect of pH on Jelly Consistency Kineteen jelly jars of fairly uniform dimensions6 are The term "jelly consistency" is used here as representing numbered consecutively and exactly 50 ml. of the gelatin solution pipetted into each jar. Twentieth normal hythe product of jelly strength and viscosity. I n the manufacture of ice cream, marshmallow confections, drochloric acid or sodium hydroxide is added from a buret, baker's marshmallow, and similar products, from 0.5 to in amounts shown by the titration curves (Figure 1). When the pH of the sample is approximately 5 or 6, jar number 3 per cent of gelatin is used, based on the total weight of the ingredients. Usually the quantity of gelatin taken 10 is zero or blank and the pH varied plus or minus from is roughly proportional to the jelly strength, but it is subject this point. If the pH of the sample is above or below these to variation since jellies of equal strength do not always limits, the blank or zero jar is shifted accordingly. The result in like quality of finished product. The effect of pH pH range for the group is from about 3.5 to 11.0. The volume on jellies of approximately 1 per cent gelatin concentration in each jar is then carefully made up to 120 ml. with distilled water and pasteurized for 20 minutes a t 65" C. Each jar will be discussed here.3 is closed with a S o . 9 perforated rubber stopper and the JELLY-STRENGTH DETERMINATION-This test has been described in an earlier papere4 Briefly, it consists of chilling entire group transferred to a constant-temperature coldwater bath. The time of chilling is 16 to 18 hours a t 10" C. a 62/s per cent gelatin solution for about 16 hours a t 10" C. At the end of the chilling period the jelly consistency is and measuring the jelly so formed with the Bloom G e l ~ m e t e r . ~ measured by the method described below. The results are expressed as "Bloom grams." MEASUREMENT OF JELLY COKSISTENCY-Gehtin jellies The ratio of one jelly strength to another may be taken as X:200, where X is equal to Bloom grams; thus, a speci- prepared as described above are too weak to permit of any men of gelatin testing 100 Bloom requires 2 grams, while one measurement based on depression, either by the finger test testing 180 Bloom requires 1.11 grams. All things being or the Bloom gelometer. The method described below equal, the effect due to gelatin, in any product, should be has therefore been devised. A p p w a t u s . The principle of the apparatus depends upon 1 Presented before the Division of Leather and Gelatin Chemistry at the 74th Meeting of the American Chemical Society, Detroit, Mich., Septhe fall of a very small shot of definite weight, from a fixed tember 5 to 10, 1927. height, through the jelly, in which the fall is arrested a t 2 New Orleans Medical Sursicnl J., 78, 12 (1925); Nation's Health, different levels according to the consistency of the jelly. 7 (May, 1925). I n its simplest form the apparatus may consist of a glass a Acknowledgment is made to Harper F. Zoller for the original suggestion upon which this method of testing is based. tube beneath which is placed the jar containing the jelly
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5
Briefer and Cohen, Ind. Eng. Chem., 19,252 (1927). I b i d . , 18, 310 (1924).
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For speciacations see reference 5.
IiVDUSTXIAL A N D ENCI AVEEIKND CHEXISTX I
April, 19%
to be tested. (Figure 2, left) The top of tito tube is adjusted to 50 cm. above the level of the jelly surface. One shot is taken up with fine tweezers and dropped centrally t,hrough the tube into the jelly. The fall is measured with a fine pair of dividers and the value read froin a milliinctor scale. A precision instrument may be constructed from the diagram (riglit hand) in Figure 2. A stand, 9,wit11 platform, ~.
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