Evauation of lysinoalanine determinations in food proteins

Abstract

A comparison is made between lysinoalanine (LAL) determinations both with an automatic amino acid analyzer (AAA) and with thin layer chromatography-densitometry (TLC) in different types of food and food ingredients, taken from the Dutch market. Generally there is a reasonable agreement between the LAL content obtained by both methods. However, some results indicate that a single technique is not always conclusive about the real identity of the ninhydrin-positive compound at the same position as LAL on the chromatogram. By TLC for instance, in yeast a content of about 800 mg of LAL/kg in protein is found, but according to the AAA method no LAL is present. In heated milk and milk products the LAL content determined by the TLC method is also higher than that found by the AAA method. This is caused by a preceding unknown ninhydrin-positive compound in TLC, occurring in all heated milk products and practically coinciding with LAL. In the AAA technique similar interferences of unknown ninhydrin-positive compounds could be avoided by choosing a suitable elution temperature; however, application of this temperature modification to foaming agents gave no satisfactory results.

Lysinoalanine in foods

“…This portion of the review will be relatively short for two primary reasons. First, not a wide variety of diverse methods have been developed specifically for the analysis of LAL, and second, a relatively recent review has appeared in this area (Haagsma and Slump, 1978).…”

“…Forms of thin-layer chromatography (TLC) have also been used (Woods and Wang, 1967;Sternberg et al, 1975a), and although the lower level of sensitivity is rather low (3 ng), it requires a long separation time (Haagsma and Gortemaker, 1979), and when compared to ion-exchange techniques, large standard deviations (Haagsma and Slump, 1978) make the widespread use of the technique somewhat limited. It should be noted that separation time has now been shortened to approximately 4 h (Aymard et al, 1978).…”

Carboxypeptidase inhibition by alkali-treated food proteins

“…Although alkali treatment is widely used in food processing (Sternberg et al, 1975;Sternberg and Kim, 1977;Haagsma and Slump, 1978;Raymond, 1980;Friedman and Masters, 1982), such treatments may not always be as severe as those shown in Tables V and VI. The possible inhibition of metalloenzymes by commercially processed food proteins merits further study, especially since some D-amino acids may have antinutritional properties (Friedman and Gumbmann, 1984a,b).…”

EFFECT OF ADDED CYSTEINE AND LYSINE UPON LYSINOALANINE LEVELS IN VARIOUS ALKALINE TREATED FOOD PROTEINS1

“…Other evidence suggests that the damage in rats is reversible when LAL is removed from the diet (Struthers et al 1978). While a number of questions about the hazards of LAL in the human diet are unanswered, several studies have investigated the occurrence and formation of LAL in food systems (Aymard et al 1978;Creamer and Matheson 1977;Haagsma and Slump 1978). LAL accumulation in foods and food ingredients is generally associated with an alkaline treatment, but Sternberg et al (1976) surveyed a number of foodstuffs and found LAL in some processed foods that had not been alkaline-processed.…”