Journal Articles
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Item Investigation of various plant protein ingredients for processed cheese analogues: physical properties and microstructure compared with milk proteins(Oxford University Press on behalf of the Institute of Food Science and Technology (IFST), 2025-01-08) Lu D; Roy D; Acevedo-Fani A; Singh H; Ye AThis study evaluated various structural and physical properties of several plant proteins in the context of processed cheese analogues (PCAs). A total of 9 plant protein sources were selected to formulate PCA samples. The samples were processed at 90 ◦C for 10 min using either a rapid visco analyzer or water bath for different tests. Rheological analysis revealed that PCA samples formulated with plant proteins all exhibited solid-like behaviour. PCAs containing legume proteins had a higher storage modulus (G’) than that of rennet casein (RC) cheese samples, while canola protein samples showed the lowest G’ values. Zein-based PCA had the highest hardness and chewiness but softened when subjected to heat during the stretchability test. In contrast, PCAs containing chickpea, mung bean, or pea proteins exhibited similar hardness to RC-based cheeses but had poorer springiness, cohesiveness, and resilience. Plant protein-based PCAs also lacked melting and stretchability properties due to the absence of a continuous protein network. When ranking all proteins in PCAs based on viscosity, rheological, and textural properties, lentil protein scored the highest, followed by hemp and quinoa proteins, performing most similarly to casein protein. The presented comparison of different plant proteins in PCAs provides valuable insights for cheese analogue development.Item Kinetics of pepsin-induced hydrolysis and the coagulation of milk proteins(Elsevier Inc and the Federation of Animal Science Societies on behalf of the American Dairy Science Association, 2022-02) Yang M; Ye A; Yang Z; Everett DW; Gilbert EP; Singh HHydrolysis-induced coagulation of casein micelles by pepsin occurs during the digestion of milk. In this study, the effect of pH (6.7–5.3) and pepsin concentration (0.110–2.75 U/mL) on the hydrolysis of κ-casein and the coagulation of the casein micelles in bovine skim milk was investigated at 37°C using reverse-phase HPLC, oscillatory rheology, and confocal laser scanning microscopy. The hydrolysis of κ-casein followed a combined kinetic model of first-order hydrolysis and putative pepsin denaturation. The hydrolysis rate increased with increasing pepsin concentration at a given pH, was pH dependent, and reached a maximum at pH ~6.0. Both the increase in pepsin concentration and decrease in pH resulted in a shorter coagulation time. The extent of κ-casein hydrolysis required for coagulation was independent of the pepsin concentration at a given pH and, because of the lower electrostatic repulsion between para-casein micelles at lower pH, decreased markedly from ~73% to ~33% when pH decreased from 6.3 to 5.3. In addition, the rheological properties and the microstructures of the coagulum were markedly affected by the pH and the pepsin concentration. The knowledge obtained from this study provides further understanding on the mechanism of milk coagulation, occurring at the initial stage of transiting into gastric conditions with high pH and low pepsin concentration.