Search

Modification of dairy proteins during processing impacts structural assemblies, influencing textural and nutritional properties of dairy products, and release and availability of amino acids during digestion. By modifying only pH, acid heat-set bovine dairy gels with divergent textural properties were developed to alter protein digestion. In vitro assay confirmed faster digestion of protein from a firm gel (pH 5.65) versus a soft gel (pH 6.55). We hypothesised that firm gel (FIRM-G; pH 5.6) would result in greater indispensable amino acid (IAA) appearance in circulation over 5 h and corresponding differences in gastric myoelectrical activity relative to soft gel (SOFT-G; pH 6.2). In a randomised, single-blind cross-over trial, healthy females ( n = 20) consumed 150 g of each gel; plasma amino acid appearance was assessed over 5 hours. Iso-nitrogenous, iso-caloric gels were prepared from identical mixtures of bovine milk and whey protein concentrates; providing 17.7 g (FIRM-G) and 18.9 g (SOFT-G) of protein per serving. Secondary outcomes included gastric myoelectrical activity measured by body surface gastric mapping, glycaemic, triglyceridaemic, and subjective appetite and digestive responses. Overall plasma IAA (area under the curve) did not differ between gels. However, plasma IAA concentrations were higher, and increased more rapidly over time after SOFT-G compared with FIRM-G (1455 ± 53 versus 1350 ± 62 μmol L -1 at 30 min, p = 0.024). Similarly, total, branched-chain and dispensable amino acids were higher at 30 min with SOFT-G than FIRM-G (total: 3939 ± 97 versus 3702 ± 127 μmol L -1 , p = 0.014; branched-chain: 677 ± 30 versus 619 ± 34 μmol L -1 , p = 0.047; dispensable: 2334 ± 53 versus 2210 ± 76 μmol L -1 , p = 0.032). All other measured parameters were similar between gels. Peak postprandial aminoacidaemia was higher and faster following ingestion of SOFT-G. Customised plasma amino acid appearance from dairy is achievable by altering gel coagulum structure using pH during processing and may have minimal influence on related postprandial responses, with implications for targeting food design for optimal health. The Clinical Trial Registry number is ACTRN12622001418763 (https://www.anzctr.org.au) registered November 7, 2022.

Novel animal-derived fibers are of interest for the pet food industry. We here introduce a method for extracting wool proteins using controlled hydrolysis of wool. This results in an appropriate form and we demonstrate its application in pet food using the domestic cat. The effect of the wool hydrolysate on biomarkers of digestive health (e.g., fecal short-chain fatty acids and fecal microbial composition, apparent amino acid (AA) and protein digestibility), are also described. In a feeding study, a cohort of cats (n = 8 per treatment) were fed a basal diet (Control), or the basal diet supplemented with 2% wool hydrolysate, 2% inulin (Synergy1; as is) or 2% cellulose (Novagel; as is). The concentration of butyric acid was not significant (P = 0.102) between treatment groups. The concentration of fecal lactic acid was greatest (P = 0.007) in cats on the Novagel diet. Valeric acid was increased (P = 0.001) in cats fed Synergy1. Supplementation of cat diet with a wool hydrolysate showed similarities to Novagel supplementation in terms of its effects on fecal short-chain fatty acid concentrations and fecal microbiota composition. Wool hydrolysate increased apparent cysteine digestibility compared to Synergy 1 or Novogel. In terms of fecal health, intake, and palatability, the diet supplemented with wool hydrolysate was not detrimental, being similar to currently used dietary fiber supplements. These findings indicate that wool hydrolysates offer promise as an animal-derived supplement source for pet diets.