The Impact of Processing on Amino Acid Racemization and Protein Quality in Processed Animal Proteins of Poultry Origin

Abstract

Re-authorization of processed animal proteins (PAPs) in EU, derived from by-products of human food production, could increase manufacturing of proteins for feed ingredients and reduce the need of imported proteins mainly of plant origin. The PAPs production is largely done by the rendering process during which authorized animal by-products are heat treated to extract valuable protein and animal fat, ensuring sterilizing conditions of raw incoming materials. Proteins exposure to certain processing conditions induces two important chemical changes, racemization of amino acids and formation of cross-linked amino acid. These changes are associated with appreciable reduction of protein digestibility and nutritional value. The aim of this study was to verify the effect of heat treatment on amino acid racemization in processed animal proteins of poultry origin and related nutritional implications by evaluation of their in vitro digestibility. The results reported confirm the detection of racemized amino acids in processed animal proteins, especially D-aspartic acid, as realistic indicators of thermal treatments during PAP manufacturing. In our results, the severe (115°C) and prolonged heat treatment (180 minutes) revealed a D-Asp content of 28.1%.Prolongation of temperature treatment (20, 30 and 180 min, at 115°C) significantly (P<0.05) affects in vitro protein digestibility, which decrease from 86.0%, in no-treated sample, to 78.3% and 79.1% after 20 and 30 min, respectively, and to 76.3% after 180 min. The processing conditions applied during PAPs preparations and the racemization of proteins amino acids may reasonably be involved in the loss of protein quality.

Processing techniques of selected oilseed by-products of potential use in animal feed: Effects on proximate nutrient composition, amino acid profile and antinutrients

“…These losses could be nutritionally detrimental since these EAA cannot be synthesized by fed animals. This is in support of Papadopoulos (1989) and Bellagamba et al. (2015) who concluded that heat processing of feedstuff causes the racemization of amino acids and the formation of cross-linkages with resultant reduction in amino acid digestibility.…”

Over-processed meat and bone meal and phytase effects on broilers challenged with subclinical necrotic enteritis: Part 1. Performance, intestinal lesions and pH, bacterial counts and apparent ileal digestibility

“…Further, over-processing might have resulted in the isomerization of l -AA into d -AA and mesoisomers which are poorly digested and unavailable for absorption ( Finot, 2005 ). Cross-linking of peptide bonds between a carbonyl group and amino group (Mallard reaction) during such severe heating processing is another possibility ( Heck et al., 2013 , Bellagamba et al., 2015 ).…”

Growth of Tea Nursery Plants as Influenced by Different Rates of Protein Hydrolysate Derived from Chicken Feathers

“…Furthermore, short-chain peptides and certain amino acids, such as phenylalanine, have been reported to increase the production of endogenous auxin by functioning as signaling molecules, resulting in favorable effects on roots and improved vegetative growth [20,40]. The presence of small quantities of cysteine (0.79%) and threonine (2.42%) in CFPH may have resulted due to the aggressive reaction of alkali that ended up in the loss of these amino acids [41]. The peptides and amino acids present in the PH might be directly occupied by plants through the roots and leaf, reaching the target tissues and potentially acting as plant biostimulants [11].…”