In vitro digestion of protein-enriched restructured beef steaks with pea protein isolate, rice protein and lentil flour following sous vide processing

Abstract

The effect of plant protein inclusion in cooked meat upon in vitro gastro-intestinal (GI) digestion was investigated. Pea protein isolate, rice protein and lentil flour were used to increase the protein content in a meat model system restructured using two transglutaminase enzymes [Activa®EB (TG) and Transgluseen™-M (TS)]. Restructured beef steaks were subjected to simulated GI digestion using the static INFOGEST method. Samples taken at different digestion times were analysed using SDS-PAGE, size exclusion-HPLC, free amino acid analysis and microscopy. SDS-PAGE analysis revealed significant protein hydrolysis during GI digestion. Most soluble peptides had a molecular weight smaller than 500 Da, corresponding to peptides of <5 amino acids, regardless of food treatment. The amounts of released, free amino acids isoleucine, lysine, phenylalanine and valine were higher (P < 0.05) in lentil-enriched restructured beef steaks following GI digestion. Confocal laser scanning microscopy (CSLM) revealed pronounced aggregation in digested samples. In vitro digestates of protein-enriched restructured beef steaks showed lower production of small molecular weight peptides. This study demonstrated how the bioaccessibility of protein-enriched restructured beef steaks are influenced by formulation and processing.