Development of a novel bioassay for determining the available lysine contents of foods and feedstuffs

Abstract

Lysine is an important indispensable amino acid, and describing the lysine content of a food or feedstuff provides useful information about nutritional value. However, when a food or feedstuff is subjected to heating the lysine present can be altered to nutritionally unavailable derivatives. These derivatives can revert back to lysine during the acid hydrolysis step used in amino acid analysis causing an overestimate of the lysine content. There have been many chemical methods developed to determine the reactive (unmodified) lysine content of foods and feedstuffs, but these do not take into account the incomplete absorption of lysine from the small intestine. There are also a number of animal-based assays for determining available lysine (the lysine that can be absorbed in a form that can be used for protein synthesis). The true ileal amino acid digestibility assay is commonly used to determine amino acid availability and is accurate for application to unprocessed foods and feedstuffs but is not accurate for lysine and possibly other amino acids when applied to heat-processed foods or feedstuffs. For such protein sources, assays such as the slope-ratio assay, indicator amino acid oxidation assay and the BIOLYSINEe assay (true ileal digestible reactive lysine assay) have been developed to determine available lysine. The present paper discusses the efficacy of the BIOLYSINEe assay as well as other assays for determining available lysine in processed foods and feedstuffs.

Rat Bioassay for Evaluation of Protein Quality of Soy-Fortified Complementary Foods

“…This is probably due to compositing cereals with legumes which yield high protein quality (FAO/WHO, 2002). It may also be attributed to the fact that the current study used milk powder with 30% protein as the reference instead of casein which has 90% protein (Baskaran et al, 2001;Rutherford & Maughan, 2007). The significantly high PER in the banana-soy diet could be attributed to reduced amount of phytic acid and other anti-nutritional factors to complex with the protein and other nutrients which made the protein more bioavailable (Bukusuba et al, 2008;Aremu, Osifade, Basu & Ablaku, 2011).…”

Amino acid digestibility of heat damaged distillers dried grains with solubles fed to pigs

“…Lysine is particularly susceptible to undergo Maillard reactions because of its free amino group, which easily reacts with reducing sugars. If the amino group of an AA reacts with a reducing sugar to form early or advanced Maillard reaction products, it becomes unavailable to pigs [2,5]. During the acid hydrolysis step of AA analysis, however, Lysine that has reacted with reducing sugars is partially recovered, thus leading to an overestimation of available Lysine.…”

Amino acid digestibility of animal protein ingredients for bullfrogs in different phases of post-metamorphic development

“…). According to Rutherford and Moughan (), the low digestibility of these feed ingredients may be due to the high content of peroxide, which can trigger a Maillard reaction that renders some nutrients non‐degradable and non‐absorbable by the intestinal mucosa. Comparison of the amino acid results and their availability between different species is impaired by the variability in feed ingredients over the years and the use of different sources and processing (Li et al .…”