SummaryEvidence is presented which suggests that epihydrin aldehyde and its derivatives are not necessarily solely responsible for the Kreis color reaction of oxidized fats. Malonic dialdehyde has been shown to give a positive reaction in the Kreis test and the resulting color demonstrated to be spectrally similar to the Kreis colors obtained with epihydrin aldehyde diethyl acetal, acrolein treated with H2O2 rancid lard, and oxidized milk fat. Characteristics of a water‐soluble, low molecular weight, Kreis positive, carbonyl compound from oxidized milk fat were observed to be very similar to those reported for malonic dialdehyde, i.e., strongly acidic, enolic as indicated by the ferric chloride test, and relatively stable to heating with dilute mineral acids. These properties would not be expected of epihydrin aldehyde. Three highly sensitive colorimetric reactions, involving reactions with ferric chloride, 2‐thiobarbituric acid or the Kreis reagents, might well serve as the basis for quantitative measurement of malonic dialdehyde.
IZTZ with the technical assistance of JOHN J. McMULLEN AND LUCIUS V. THOMAS Qitartermaste~ Food and Container InstittLte for the iZr?iieti Forces Chicago, IllinoisMost natural fats have been shown to be readily digested, but in the case of naturally-occurring fats of high melting point and of fats hardened by hydrogenation, the coefficient of digestibility may be reduced. Two major theories have been propounded to explain differences in digestibility :(1) that digestibility is inversely proportional to and dependent upon melting point (3, 9 ) ; or (2) that digestibility is limited by the amount of saturated fatty acids of carbon chains 18 or longer (8, 10). Other recent findings deserve coiisideration : Cheng, Morehouse, and Deuel ( 2 ) reported that monostearin was more digestible than either the triglyceride or the free fatty acid and Mattson, Baur, and Beck (12), that long-chain saturated fatty acids were better utilized as cliacetin fat than as triglyceride. These results indicate that not only is the chain length of the fatty acids imporant but also their association within the glyceride structure.To provide basic information for the development of fats which will meet the Armed Forces' stability requirement of 160" F. these various factors were explored. Preliminary studies of lipid materials formed by interrsterification with hexahydric alcohols were also conducted. METHODS AND MATERIALSDiets varying only in source of f a t were fed to adult male albino rats, 5 to 7 per group, for 15 days and feces collected on the last 5 days f o r digestibility measurement. I n each test a reference cottonseed-oil diet and a fat-free diet were fed. The amount of food offered was constant for all groups in each test and sufficient to permit small weight gains with the reference diet; i n most cases consumption was complete.The diets were composed of 80 parts of a diet base, as shown in Table 1, and 20 parts of test fat. Fats were dissolved in warm ethanol and mixed with the diet base; the diets were then placed on shallow trays and held at room temperature until the alcohol evaporated. This procedure was followed to insure intimate mixing of f a t with other diet components. The fat-free diet was treated in the same manner with 80 parts of base added to 30.7 parts of sucrose to yield a diet iso-nitrogenous when equal calories were fed.Fat content of the diet and of the feces was detcrmined by a modified Association of Official Agricultural Chemists (1) procedure as follows:To approximately 2 g. of wet feces was added 5 ml. of concentrated hydrochloric acid and digestion carried out at low boiling temperature, with
Palmitic, oleic, and butyric acid esters of cetyl alcohol were fed to mature rats. Cetyl palmitate was quantitatively excreted in the feces and produced no physiologic aberration. While cetyl oleate was 75% absorbable, it was of little value as an energy source and was partially excreted through the skin. Feeding of cetyl butyrate also induced seborrhea. Data on free fatty acids in gastrointestinal contents and on the specificity of seborrheic lipids indicate that cetyl esters are largely absorbed without hydrolysis, if the fatty acid moiety is readily absorbable, and excreted by way of the skin without modification.
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