Protein and lipid gastro-small intestinal digestibility in vitro of pasture-fed beef, grain-finished beef, and meat alternative : a comparative study : a thesis presented in partial fulfilment of the requirements for the degree of Master of Technology in Food Technology at Massey University, Palmerston North, New Zealand

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This study addresses the protein and lipid digestibility of meat and a plant-based meat alternative using a static model in vitro digestion system. Three commercially relevant beef cuts (tenderloin, striploin and topside) from five carcasses of two different production system namely, pasture-feeding and grain-finishing along with a plant-based meat alternative (Beyond Burger® from Beyond Meat™) were chosen for this study. Breakdown of proteins and the release of peptides during digestion were analysed using tricine SDS-PAGE. The free amino nitrogen released during in vitro digestion was determined using ninhydrin assay. The results showed that there were no significant differences (p<0.05) between the pasture-fed and grain-finished meat digests in terms of in vitro protein digestibility. Both striploin and tenderloin gave good in vitro protein digestibility, but the topside did not perform well, mainly due to the longer cooking time and higher cook loss. The plant-based meat alternative performed relatively poorly in in vitro protein digestion experiments, possibly due to the formation of digestion-resistant protein aggregates formed during the manufacturing process. In terms of in vitro lipid digestibility, this study concludes that pasture-fed beef showed higher amounts of total long chain (LCn-3) polyunsaturated fatty acids (PUFAs) and lower amounts of many free individual saturated fatty acids (SFAs) than those from grain-finished animals. However, grain-finished meat digests were high in total monounsaturated fatty acids (MUFAs) when compared to pasture-fed meat digests. The plant-based meat alternative digests had the highest amount of total SFAs, mostly contributed by lauric acid (C12:0), myristic acid (C14:0), palmitic acid (C16:0) and stearic acid (C18:0). The MUFAs were also significantly higher (p< 0.05) in the Beyond Burger® owing mainly to high amounts of individual free oleic acid (C18:1c9) and vaccenic acid (C18:1c11). In Beyond Burger® there was an abundance of n-6 PUFAs in the form of the individual free linoleic acid (C18:2). However, no LCn-3 PUFAs were detected in the plant-based meat alternative.
Figures 2.2, 2.3 & 2.5 are re-used with the publishers' permission.