278
IiVDUXTRIAL A N D ENGINEERING CHEMISTRY
of the other oils used, as much as 116 to 130 g. were eaten per day with no laxative effect. I n the case of cocoa butter, however, a decidedly laxative effect accompanied by slight nausea was noted, indicating that the limit of tolerance of this fat is not so high as that of the other oils. A similar effect was also noted with cupuassu fat, which comes from a tree rather closely related to the theobroma cocoa. It is also worth mentioning that a laxative effect was noted when goose fat was eaten in quantity but was not noted with a comparable amount of chicken fat. It seems not unlikely that studies undertaken t o explain these observed divergencies would yield very interesting results. CONCLUSION From the investigations as a whole it seems fair to conclude that fats are wholesome, useful foodstuffs, which are well assimilated, and that for such reasons they deserve the im-
Vol. 15, No. 3
portant place they have in the diet. The fact that they are often carriers of vitamins is another reason for the esteem in which they are held. No attempt can be made here to discuss their effect upon palatability of the diet and their important relation to the texture, flavor, and quality of the foods into which they enter, though these and other matters relating to fats are being studied in the Office of Home Economics, where it is also proposed to continue the work on the digestibility of fats when new ones or new processes of manufacture add to the list of material available for such purposes. ACKNOWLEDGMENT No account of this work carried on in the Office of Home Economics would be complete without noting the fact that much of its success is due to Mr. Arthur D. Holmes and Mr. Harry J. Deuel, who assumed direct charge of the experiments.
Fats in t h e Evaporated Milk Industry’ Certain Physical and Chemical Requirements By Harper F. Zoller NIZERLABORATORIES C O . , D E T R O ~ MICH. T,
T
HE ICE-CREAM and cheese industries generally have a large surplus of skim milk to dispose of during certain seasons of the year. For the last few years a certain amount of this skim milk has been turned into sweetened condensed skim milk, which is sold to the baking industry and some to the candy manufacturers. Attempts have been made to put up the skim milk as straight evaporated skim in gallon cans for the candy trade, etc., but owing t o certain properties possessed by skim milk, it is necessary to run the total solids very low (around 20 per cent) in order that it will stand up under sterilization treatment. Certain companies have, therefore, conceived the idea of adding to this skim milk a fat from some suitable source, so that its total solids can be run to around normal content for evaporated whole milk (28 per cent) and still withstand sterilization. The addition of this fat was welcomed by the candy and baking industries, as it was thus a suitable cooking product in the place of whole evaporated milk. This fat-filled skim milk has earned the name in trade of “filled milk” or “milk compound.” So valuable has it become to the household in certain localities that it is canned in regular size evaporated-milk containers and is retailed as “milk compound” at many grocery stores a t a price of two to three cents less per tall can of product. Without entering upon a discussion of the commercial ethics of such a product-such discussions have engrossed the attention of certain factions in both state and federa1 government during the past few months-certain very fundamental research problems which have been uncovered by the manufacturers and laboratories connected with the production of compound milk will be described. The aim of the producers of the product has always been to secure a highly refined oil and to incorporate it under the most sanitary condition possible. I n many instances the character and physical conditibn of this fat-filled milk have been much superior to some whole-milk batches in its working conditions in the vacuum pan and in subsequent sthrilization. 1 Presented before the Division of Agricultural and Food Chemistry a t the 64th Meeting of the American Chemical Society, Pittsburgh, Pa., September 4 to 8, 1922.
PROCESSING OF FATSI N
THE
COMPOUND MILK IKDUSTRY
The evaporation of milk in a vacuum pan a t the temperature and pressure under factory operation, and the subsequent sterilization of the product a t high temperatures, necessitates the consideration of factors in connection with the constitution and physical make-up of fats, which are uncommon in all other industries in which fats are used. We might say that those who were pioneers in the compoundmilk industry were the unquestionable recipients of luck in the choice of fats for their purpose. I n England and Denmark where the nut-margarine industry first flourished, and subsequently in the United States, coconut fat and palmnut fat were, and are yet, extensively used to manufacture their product. These two fats are reasonably cheap and are easily refined. The coconut oil is imported into the United States markets from our insular possessions. Inasmuch as the margarine people were using tons of this oil annually in the production of their product, it was but natural that the evaporated-milk people should look to this fat as the first possibility for compound milk. It filled the bill admirably. Just why it bhould be SO valuable for the evaporated filled-milk industry will be seen in that which follows, It is fitting that we should turn first to the properties of butter fat to ascertain the factors that render it capable of standing up fairly well during the evaporation in the vacuum pan and during sterilization. An authorative table of its properties is compiled beJow9 FACTOR
TABLB
1
Melting point C.......................... Solidifying point ............................ Saponification, lbs.. ......................... Iodine Ibs .................................. Specifik gravity ............................. Refractive index.. ........................... Acetyl, lbs.. ................................
RANGE 28-36 19-24 220-241 26-38 0.86E-0.870 1.4527-1.4566 1.9-8.4
Comparison figures of the various fats suitable and those which are not suitable for evaporated milk as they exiat naturally, appear in Table 11. 2 Leach and Winton’s “Food Analysis,” 1920, p. 486; Allen’s “Commercial Organic Analysis,” 2 (1910),1.
INDUSTRIAL A N D ENGINEERING CHEMISTRY
March, 1923
279
TABLE I1 Melting Point Butter. . . . . . . . . . . BUTTER-FAT Coconut GROUP Palm-nut. . . . . . . . I Cottonseed. . . . . . . . . . . Peanut, . . . . . . . . . . . . . GROUP Corn . . . . . . . . . . . . . . . . Soybean . . . . . . . . . . . .
c.
.........
i
....
....
.... ....
Solidifying Point O
c.
19-24 14-23 20-27 5-0 0-3 12-10 14-15.3
I n the first place, butter fat is soft a t ordinary room temperature, which bespeaks a fairly moderate content of stearin and palmitin. It contains a very moderate amount of unsaturated glycerides, thus yielding an iodine number of low order. I n fact, the iodine number of butter fat is from onefourth to one-third as high as that of either cottonseed, peanut, corn, or soy-bean oil. The saponification number is quite high, higher than the same index for the oils named above.
COMPARISON OF BUTTER FATS AND COTTON-OIL FATS
.
We can now compare the group of food fats which have been termed the butter-fat group, and which includes butter fat, coconut, and palm nut, with another group called the cotton-oil group and which includes cottonseed, peanut, corn, and soy-bean oil. The melting-point range for all the fats in the butter-fat group is from 20” to 36” C., whereas the cotton-oil group are all liquid fats a t room temperatures and do not solidify until 3 ” C. or lower is reached. The solidifying point of the butter-fat group ranges from 14” to 27” C. The iodine numbers of the butter-fat group range between 8 to 10 for coconut, to 26 to 38 for butter fat, with palm-nut fat intermediate. Now with the cotton-oil group this factor is from 83 to 139, soy-bean oil being least saturated and corn oil next, then following peanut and cottonseed in order. The saponification numbers for the butter-fat group are between 220 and 261, whereas those of the cotton-oil group lie between 186 and 212. The acetyl numbers for the butter-fat group are all smalli. e., 0.9 to 12.3-while the cotton-seed oil yields 21 to 25 and peanut oil greater than 9.1. These group differences among the physical and chemical factors which have been determined for these fats are sufficient to indicate the close relationship to butter fat of coconut fat and palm-nut fat. The volatile fatty acids resulting €rom the hydrolysis of butte: fat and coconut oil are quite similar in qualitative and quantitative features (Table 111). The three fats in this group also contain much myristin. The margarine people have chosen a product very similar to butter in both chemical and physical properties, except that coconut oil needs to be hardened in some manner to raise its melting and solidifying point, either by direct hydrogenation or the addition of some other hardened fat.
EFFECT OF HYDROGENATION Now why is it that the fats in the cotton-oil series are unsuited, as they exist, for evaporated-milk production? In the first place, they all develop more or less rancidity3 in the vacuum pan and this is not improved in the sterilization process. I n the second place, some of them possess certain characteristic flavors in themselves which makes their presence in the sterilized milk obnoxious. These certain characteristic flavors are tied up intimately with certain protein traces, unusual glycerides, or other bodies, and the consequent difficulty of refining the oil so as to eliminate these from the finished product. The highest quality of refined oils as they 8 The term “rancidity” is here used in a loose sense and refers to actual hydrolysis of the f a t taking place in both vacuum pan and sealed cans during heat treatment.
Iodine
Saponification
Acetyl
Lbs.
Lbs. 26-38 8-10 13-18 104-117 83-105 116-130 114-139
Lbs.
220-241 246-261 242-255 191-195 186-196 189-194 207-212
1.9- 8.4 0.9-12.3 1.9- 8.4 21-25 9.1-.
... .... ....
exist on the market, of this group, is not suitable for regular production of compound milk. We have tried to hydrogenate several of these oils to certain degrees so that we would have a product with a satisfactory melting point for pan use, and a fat with an iodine number low enough to fall within the butter group, and we made a very interesting and important observation. As is well known, fats when partially or completely hydrogenated develop a very marked tallowy odor (and this odor becomes a real flavor in practice); this is more pronounced the greater the hydrogenation, and is characterized in trade parlance as “hydrogenation flav~r.” This tallowy odor or flavor is entirely removed in the vacuum pan in the presence of the milk. This does not mean that the milk absorbs the product causing this odor, but that it is carried out in the condenser water during the concentration. Therefore, this constitutes a clue from which it is possible to work out a process of removing “hydrogenation flavor.” These partially hydrogenated fats can be used in the compound-milk industry provided the iodine number has been reduced to about 30 or lower, and the melting and solidifying point is not greater than 50” C. It is very definitely shown that the iodine number (an index of unsaturated glyceride content of a fat) is the controlling factor in rancidity development. But why use these products when coconut fat is the natural substitute for butter fat in the United States, both economically and nutritionally? The term nutritional is used in its broader sense, and should not be construed to indicate any connection to the vitamin controversya controversy which has been used inconsistently and with unfortunate results in connection with filled milk-at this time. TABLE111-FATTY ACIDS
OF
HYDROLYZED BUTTERAND COCONUT FATS Butter Coconut Fat1 Fat2
F a t t y Acid Caproic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Capryllic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Butyric . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Oleic., . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Dihydroxy stearic., ......................... 1 Brown J. A m . Chem. SOC. 21 (18991, 807. 2 Elsdod, Analyst, SS (1912):8.
2.09 0.49 5.45 0.32 2.57 9.89 32.50 38.61 1.83 1.00
2 9
..
10 45 20 2 7 5
..
The coconut oil used to incorporate with the milk is of selected stock. It must have no rancidity, foreign odor, or tallowiness, and it should show only a faint greenish yellow tint when melted. These requirements are met without any difficulty on the part of the coconut oil refiners. It has been urged, in connection with the tariff bill, that coconut oil receive a heavy tax, because it is an imported oil and is jeopardizing our home-grown oil industry. While such legislation, if any is to be directed a t vegetable fats, could without much hardship tax palm-nut fat, the author is opposed to the inclusion of coconut fat. Research has very definitely shown that the glyceride balance in coconut fat is closely analogous to butter fat. It has further revealed the similarity in physical properties. While this is also true of palm-nut oil, the latter is not so extensively produced in United States territories, and could be dispensed with provided a large production of coconut oil could be guaranteed.
