Effects of Different Protein Sources on Amino Acid Absorption and Plasma Appearance of Tryptophan, Large Neutral Amino Acids, and Tryptophan Metabolites in Pigs.

BACKGROUND: Absorption of tryptophan (TRP) across the gut epithelium is potentially modulated by competing large neutral amino acids (LNAAs), which could affect the appearance of TRP and its metabolites in the bloodstream. OBJECTIVES: This study aimed to determine, in a growing pig model of an adult human, the absorption of TRP and other LNAAs from the gastrointestinal tract, and plasma appearance of TRP, LNAAs, and TRP metabolites, in response to dietary proteins varying in TRP content. METHODS: Pigs were adapted for 7 d to each of 4 diets that differed in their protein source and TRP content: 1) alpha-lactalbumin (AL; 9.95 mg TRP/g diet DM), 2) whey protein (6.59 mg TRP/g), 3) casein (3.73 mg TRP/g), or 4) zein (0.14 mg TRP/g). On day 8, pigs were euthanised after a 12-h fast (baseline), or 1, 2, 3, 4, or 6 h after they received a test meal consisting of 45 g protein, or a protein-free meal (n = 6 pigs at each time in each meal group). Tryptophan and LNAA absorption from the small intestine, and appearance of TRP, LNAAs, and TRP metabolites (melatonin, serotonin, kynurenine pathway metabolites), in the portal vein and systemic circulation, were determined. RESULTS: AL intake resulted in sustained elevated plasma TRP concentrations after an overnight fast. The amount of TRP absorbed was dose-dependently related to protein TRP content (P = 0.028), with fastest rates for pigs fed AL (371 mg/h). Portal and systemic plasma TRP, TRP/LNAA, and the TRP metabolites were highest (P ≤ 0.05) after AL intake, and remained above baseline levels for ∼4 h postprandially. Absorption rates of TRP correlated with postprandial plasma TRP and TRP metabolites (P ≤ 0.05). CONCLUSIONS: In adult humans, postprandial plasma TRP and TRP metabolite concentrations can likely be modulated by the TRP content of the meal.

Profiling the novel plant-based meat alternative category: Consumer affective and sensory response in the context of perceived similarity to meat.

Plant-based meat alternatives (PBMAs) are increasingly popular and may contribute towards reduction of negative environmental impacts associated with the meat industry. Inferior sensory characteristics of PBMAs, compared to conventional meat products, remain a barrier for uptake of these products. This study aimed to profile a wide range of PBMAs for perceived similarity to meat, consumer liking, emotional response and sensory experience, and to determine consumer drivers of liking for this product category. Twenty-one PBMAs, spanning a broad range of product types (burger patties, sausages, meatball alternatives, chicken/beef pieces, bacon alternative, turkey roast alternative) and main protein ingredients (extruded plant proteins, tofu, or legumes/vegetables) representative of PBMAs available to Aotearoa New Zealand consumers, were tasted and evaluated by 140 Aotearoa New Zealand residents. Samples ranged widely in their perceived similarity to meat (median value range: 1.0-4.0 on a 5-point-scale) and overall liking ratings (mean ± SD, range: 35.1 ± 1.2--77.7 ± 17.4 on a 100-point hedonic scale). Overall liking ratings were driven mostly by liking for flavour, followed by texture, and less so by appearance. Sensorially, sample differentiation was mostly associated with variation in meat-related flavours and textures, or vegetable-related attributes. Notably meat flavour was the main driver of liking, and a very strong relationship (r = 0.92) was observed between perceived similarity to meat and overall sample liking ratings. Meat-like samples were also associated with positive emotional terms, whereas samples made from wholefoods were associated with negative emotional terms. Textural terms ('gluey/slimy', 'pasty/doughy') associated with wholefood products were also negative drivers for liking, and should be avoided in future PBMA products. In conclusion, the general population maintains a strong preference for PBMAs that are similar to meat, validating ongoing efforts to improve the meat-like properties of new and emerging products. PBMAs made from wholefoods require extensive product development to achieve consumer satisfaction across the category.

Effects of Green and Gold Kiwifruit Varieties on Antioxidant Neuroprotective Potential in Pigs as a Model for Human Adults.

Kiwifruit (KF) has shown neuroprotective potential in cell-based and rodent models by augmenting the capacity of endogenous antioxidant systems. This study aimed to determine whether KF consumption modulates the antioxidant capacity of plasma and brain tissue in growing pigs. Eighteen male pigs were divided equally into three groups: (1) bread, (2) bread + Actinidia deliciosa cv. 'Hayward' (green-fleshed), and (3) bread + A. chinensis cv. 'Hort16A' (yellow-fleshed). Following consumption of the diets for eight days, plasma and brain tissue (brain stem, corpus striatum, hippocampus, and prefrontal cortex) were collected and measured for biomarkers of antioxidant capacity, enzyme activity, and protein expression assessments. Green KF significantly increased ferric-reducing antioxidant potential (FRAP) in plasma and all brain regions compared with the bread-only diet. Gold KF increased plasma ascorbate concentration and trended towards reducing acetylcholinesterase activity in the brain compared with the bread-only diet. Pearson correlation analysis revealed a significant positive correlation between FRAP in the brain stem, prefrontal cortex, and hippocampus with the total polyphenol concentration of dietary interventions. These findings provide exploratory evidence for the benefits of KF constituents in augmenting the brain's antioxidant capacity that may support neurological homeostasis during oxidative stress.