Journal Articles
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Item Heat-induced dissociation and association of proteins in hempseed protein bodies(Elsevier Ltd, 2025-10) Do DT; Ye A; Singh H; Acevedo-Fani AProtein bodies (PBs) are naturally occurring storage organelles in seeds. In hempseeds, the major storage proteins, including edestin (11S globulin) and albumin, are primarily located in the crystalloids and proteinaceous matrices of hemp protein bodies (HPBs), respectively. The retention of native PB structures in flours and dry-fractionated protein ingredients has important implications for protein functionality and digestibility, especially when heat treatment is applied during processing. While the thermal behaviour of hempseed proteins has been studied in protein isolate systems, to the best of our knowledge, it has not yet been explored in HPB systems. In this study, we isolated native HPBs using an enzymatic method. Aqueous suspensions of HPBs (4 % protein, w/w) were heated at selected temperatures (60–100 °C) and pH 7 for 20 min, followed by hydrolysis with trypsin at pH 7 and 37 °C for 120 min. The thermal aggregation of proteins in HPBs was characterised using confocal laser scanning microscopy (CLSM) and sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). The hydrolysis of HPBs by trypsin was monitored over 120 min by measuring the degree of protein hydrolysis (DH) and analysing SDS-PAGE. Aggregation of edestin in HPBs, primarily driven by disulfide bond formation, occurred upon heating, most noticeably at temperatures above 80 °C. Heating increased DH and altered protein degradation patterns of both acidic and basic subunits of edestin. This may be related to conformational changes in the HPB structure resulting from heat-induced dissociation-association of multiple HPB protein fractions, including 11S edestin, 7S globulin, and 2S albumin. These findings contribute to our understanding of the structure-hydrolysis relationships of HPBs, potentially leading to their use as a new plant-based material for food applications.Item The impact of heating and drying on protease activities of ruminant milk before and after in vitro infant digestion(Elsevier Ltd, 2023-12-15) Leite JAS; Montoya CA; Loveday SM; Mullaney JA; Loo TS; McNabb WC; Roy NCThis study investigated the effect of heating (63°C/30 min or 75°C/15 s) and drying (spray-drying or freeze-drying) on plasmin, cathepsin D, and elastase activities in bovine, ovine, and caprine milk, compared to non-dried raw milk counterparts. Protease activities and protein hydrolysis were assessed before and after in vitro infant digestion with or without gastric and pancreatic enzymes. At 75°C/15 s, plasmin activity in caprine and ovine milk decreased (69-75%, p<0.05), while cathepsin D activity in spray-dried bovine milk heated increased (2.8-fold, p<0.05). Plasmin and cathepsin D activities increased (<1.2-fold, p<0.05) after in vitro digestion with pancreatin, regardless of milk species. Endogenous milk enzymes hydrolyzed more proteins than gastric enzymes during gastric digestion and contributed to small intestinal digestion. In summary, milk proteases remained active after processing with effects dependent on the species of milk, and they contributed to in vitro protein hydrolysis in the stomach and small intestine.Item Metabolizable energy and standardized ileal amino acid digestibility of full-fat soybeans for broilers are influenced by wet-heating, expansion temperature, and autoclaving time(Elsevier Inc. on behalf of Poultry Science Association Inc, 2022-09) Abdollahi MR; Wiltafsky-Martin M; Zaefarian F; Ravindran VThe influence of wet-heating (WH) and expansion temperature (ET), and autoclaving time (AT) on the nitrogen-corrected apparent metabolizable energy (AMEn) and standardized ileal digestibility (SID) of AA in full-fat soybeans (FFSB) for broilers was examined in 2 experiments. The AMEn and SID AA of FFSB were determined by the difference and direct methods, respectively. In Experiment 1, raw FFSB (K0) were either treated by WH at 80°C for 1 min and expanded at 115°C (K1-115) or 125°C (K1-125), WH at 100°C for 6 min and expanded at 115°C (K2-115) or 125°C (K2-125), or WH at 100°C for 16 min and expanded at 115°C (K3-115) or 125°C (K3-125). Wet-heating and ET significantly (P < 0.001) increased the AMEn in FFSB. Among heat-treated FFSB, K1-115 and K1-125 resulted in the lowest and highest AMEn values, respectively, with all samples wet-heated at 100°C being intermediate. The K3-125 had AMEn values similar (P > 0.05) to K1-125. Among heat-treated FFSB, the highest average SID AA was recorded for K3-125. In Experiment 2, K3-125 from experiment 1 was divided into 9 batches and autoclaved at 110°C for 15 (Z1), 30 (Z2), 45 (Z3), 60 (Z4), 120 (Z5), 180 (Z6), 240 (Z7), 300 (Z8), and 360 (Z9) min. A quadratic (P < 0.01) pattern was observed for the effects of AT on AMEn. The AMEn was unaffected until 300 min AT and then declined at 360 min. The AT quadratically (P < 0.001) affected the average SID AA where the SID increased from K3-125 to Z1, plateaued to Z5, and then declined to Z9. In conclusion, the results demonstrated that WH at 100°C for 16 min followed by expansion at 125°C as the most optimal wet-heating and expansion processing, associated with the highest SID AA. Autoclaving at 110°C for 30 min enhanced energy utilization and AA digestibility in FFSB, suggesting that further advantages may be achieved by short-time autoclaving of previously wet-heated and expanded FFSB samples.Item Tuning heat-‐induced colloidal aggregation of whey proteins, sodium caseinate and gum arabic: effect of protein composition, preheating and gum arabic level(ELSEVIER SCI LTD, 2014) Loveday, SM; Ye, Aiqian; Anema, Skelte G; Singh, HarjinderHeating can drive the colloidal complexation of negatively-‐charged proteins and polysaccharides by strengthening hydrophobic interactions and denaturing proteins, thereby exposing reactive sites for covalent and noncovalent bonding. We have previously shown that stable colloidal aggregates comprising whey protein, sodium caseinate and gum arabic can be produced by careful selection of heat treatment, pH and protein type. Here we tested how the size, composition, charge and morphology of colloidal aggregates are affected by the amounts of whey protein, sodium caseinate and gum arabic, as well as the thermal history of the proteins. Increasing amounts of whey protein resulted in larger particles, which were more prone to precipitate. Preheating whey protein slightly enhanced aggregation, and this effect was mitigated when sodium caseinate was present during preheating (chaperone effect). Increasing amounts of gum arabic produced larger particles with less charge, but the gum arabic effect was statistically confounded with ionic strength. We believe that both covalent (disulphide) and noncovalent interactions among protein molecules are required to overcome electrostatic repulsion at pH 7 and form stable aggregates.