A scheme of aspartame hydrochloride (Usal) decomposition in relation to the pH and temperature which takes into account the possibility of phenylalanyl-aspartic acid dipeptide formation is suggested and experimentally confirmed. Aspartyl-phenylalanine and diketopiperazine were found to be the main decomposition products. The concentration of diketopiperazine increases and that of aspartyl-phenylalanine decreases with increasing pH. At pH 2.9 less aspartyl-phenylalanine and more diketopiperazine is formed with increase in temperature; twice the concentration of phenylalanine methyl ester was found at 80" and 90°C when 50% of the Usal present in the medium was decomposed, as compared to that determined at 25" and 40°C. The distribution of the remaining products remained constant over the entire range measured. INTRODUCTIONIT IS WELL KNOWN that both the aspartame (l-methyl-N-L-a-aspartyl-L-phenylalanine) and its hydrochloride (prepared in Czechoslovakia under the trade mark Usal), i.e. dipeptidic sweeteners composed of two amino acids -methyl ester of phenylalanine and aspartic acid, exhibit only limited stabilities in aqueous solutions (Scott, 1974; Prude1 and Davidkova, 1981). The decomposition of this sweetener corresponds to a first order reaction and its stability is significantly affected by the pH value and temperature of the medium. The optimal pH range from the point of view of stability, ranges between 2.5 and 5.0; lower temperatures being more favourable.Aspartame decomposition products were first identified by Furda et al. (1975) who applied gas chromatography and proved that dipeptide aspartyl-phenylalanine resulted after splitting off methanol, aspartyl-phenylalanine then either hydrolyzes into individual amino acids or the 3-carboxymethyl-6-benzyl-2,5-dioxopiperazine (diketopiperazine) may form by cyclization. The hydrolysis of aspartame into aspartic acid and phenylalanine methyl ester had also been proved. Boehm and Bada (1984) investigated the racemization kinetics of aspartic acid and phenylalanine in solutions of aspartame heated at 100°C and pH 4 and 7.The purpose of this study was to investigate the kinetics of decomposition of aspartame hydrochloride in aqueous solutions in relation to pH and temperature.

SUMMARY —Fresh chicken muscle contained about 1.1% lipids, of which more than half was made up of phospholipids. Lipids from fresh muscle also contained about 30% triglycerides and small amounts of cholesterol, cholesterol esters, and free fatty acids. During storage at — 10°C, the phospholipid content of the muscle decreased and the free fatty acid and triglyceride contents increased. The decrease in phospholipid content resulted from loss of lecithins and cephalins. The sphingo‐myelin content remained the same, and the lysolecithin content increased. The results suggest that lipolysis occurred during frozen storage, and that lipid hydrolysis and protein denaturation may be interdependent phenomena.

In this paper have been studied properties of a product that arose from the interaction of malonaldehyde with collagen. It has been shown by an amino acid analysis that malonaldehyde reacts in a significant way on lysine and tyrosine residues. The partcipation of tyrosine in the reaction with malonaldehyde has been further demonstrated by means of spectrophotometry. It has also been found that the hydrolysis by pronase is considerably modified with the cross linked collagen.

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