Journal Articles
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Item Heat-induced modifications of pea protein: Implications for solubility and digestion behaviour(Elsevier B.V., 2025-08-20) Li D; Ma Y; Acevedo-Fani A; Lu W; Singh H; Ye APlant proteins have become increasingly desirable due to their sustainability and proposed health benefits. This study initially examined the effects of heat treatment on the solubility of pea protein (PP) in a 3 % (w/w) protein solution, applying heat from 65 °C to 95 °C for varying durations across pH conditions ranging from 5.5 to 7.8. Subsequently, an advanced dynamic gastric digestion model—the Human Gastric Simulator—was employed to examine the in vitro gastric digestion behaviours of heat-treated and untreated PP. Results suggest that heat treatment reduces the protein aggregate size and enhances PP solubility, potentially due to a decrease in α-helix and β-turn structures or an increase in β-sheet content, as determined via Fourier transform infrared spectroscopy. Additionally, heat treatment elevated the surface hydrophobicity and free sulfhydryl group concentration of PP. During in vitro dynamic gastric digestion with pepsin, PP underwent notable structural and physical stability modifications. Unheated and heated PP exhibited small particles in the digesta and remained unaggregated throughout digestion. However, the heat-treated PP showed a smaller particle size during gastric digestion and a greater hydrolysis rate than the unheated protein. This study systematically evaluates the solubility and digestion behaviour of PP subjected to food processing conditions, highlighting its stability and structural changes that may influence the delivery of macronutrients from the stomach to the next phase of digestion.Item Emulsifying properties of hemp and whey protein complexes achieved by microparticulation(Elsevier Ltd, 2026-03-01) Ma S; Ye A; Singh H; Acevedo-Fani AHemp is a sustainable source of protein. However, the utilisation of commercial hemp protein (HP) is limited due to its poor functionality. This study provided a microparticulation method to produce hybrid microparticles by complexing HP and whey protein isolate (WPI), and investigated their emulsifying potential. The emulsions, composed of 10 % oil and 0.25–1.8 % protein (non-microparticulated or microparticulated HP/WPI), were produced and the impact of microparticulation on the emulsifying ability of HP/WPI was explored using static light scattering, CLSM, TEM and SDS electrophoresis analysis. The results showed that non-microparticulated HP/WPI stabilised emulsions exhibited preferential whey protein adsorption at the oil-water interface, leading to sufficient protein coverage at most protein concentrations (0.25–1.8 %) with relatively small droplet size (∼0.5 μm) and minimal flocculation. In contrast, in the 'emulsifier-poor' regime (0.25–1 %), microparticulated HP/WPI stabilised emulsions displayed larger droplet size with clear signs of bridging flocculation. However, when the protein concentration was sufficient (≥1.5 % protein), it reached a similar droplet size as that of non-microparticulated HP/WPI emulsion with minimal flocculation. Microparticulation increased HP loading at the interface, while emulsions stabilised by non-microparticulated HP/WPI showed less HP adsorption. Transmission electron microscopy further confirmed the microparticle coverage. Moreover, the heat stability of microparticulated HP/WPI stabilised emulsions increased, compared with non-microparticulated HP/WPI. These findings highlight the potential of microparticulated HP/WPI systems in the application of emulsification and enhance HP applications in the food industry.Item Physical properties and microstructure of hybrid processed cheeses formulated with plant protein and milk protein ingredients(Elsevier Ltd, 2026-02-01) Lu D; Roy D; Acevedo-Fani A; Singh H; Waterland M; Ye AHybrid processed cheese analogues (HPCAs) containing either mung bean (MPI) or hemp protein (HPI) with rennet casein (RC) at various ratios were prepared and analysed to understand their spatial and microstructural distribution and related physical properties, such as rheological properties, texture profile, meltability, and stretchability. In addition, protein composition and secondary protein structure were studied using SDS–PAGE and FTIR spectroscopy, while CLSM and TEM were employed to visualise the microstructure of the cheese matrix. Results indicated that plant protein types and concentration significantly affected the physical properties and microstructure of HPCAs. The addition of 30 % or more plant protein altered the physical and textural properties as well as the microstructure of the cheese analogues, with a decrease in β-sheet content and an increase in random coil structures. Mung bean protein–based HPCAs exhibit greater stretchability (e.g. 93.8 mm in 30 % MPI vs 41.53 mm in 30 % HPI), rheological, and textural properties, but not meltability (e.g. 1 % in 70 % MPI vs 48 % in 70 % HPI), compared with the hemp protein system at the same mixing ratios. This difference can be attributed to the size of the plant protein aggregation. All data were analysed by one-way ANOVA with Tukey's test (p < 0.05). These findings deepen our understanding of plant protein-based and hybrid cheeses, paving the way for optimised plant-based dairy alternatives.Item Gastric protein digestion of cow, goat, and sheep milk is not reflected in the amino acid appearance in the blood of suckling piglets(Elsevier Inc on behalf of the American Dairy Science Association, 2025-06) Roy D; Montoya CA; Stroebinger N; Hodgkinson SM; Ye A; McNabb WC; Moughan PJ; Singh HStructural changes in milk during gastric digestion are a key driving factor for the rate of digestion of nutrients in the gastrointestinal tract. Thus, the influence of gastric coagulation behavior on the kinetics of protein digestion of raw cow, goat, and sheep whole milk in the stomach was investigated using the 3-wk-old suckled male piglet as an animal model for human infants. Piglets received a single meal of fresh raw milk normalized for protein content, and were slaughtered at 0, 30, 90, 150, or 210 min postprandially. Gastric chyme and cardiac blood samples were collected. Gastric pepsin activity, rate of protein hydrolysis, and gastric emptying of AA were determined along with how these changes influence the appearance of AA in the plasma. The disappearance rates of individual proteins (especially β-LG and αS-CN), total digested proteins entering the small intestine, as well as the gastric emptying of some AA (proline, leucine) were (or tended to be) greater for goat and sheep milk than for cow milk. Differences in plasma concentrations for some AA (e.g., leucine) were observed across milk types, but they did not directly reflect changes in gastric protein digestion and the gastric emptying of AA. In conclusion, a combination of protein (and AA) composition, susceptibility of specific proteins to hydrolysis, and the nature of the curd structure formed influenced the digestion behavior of milk proteins in the stomach and their subsequent release into the small intestine.Item Secretion of inflammatory mediators by human intestinal epithelial cells incubated with gastric digesta of emulsion gels containing capsaicinoids: Implication on gastric irritation(Elsevier B V, 2025-06) Luo N; Wolber FM; Singh H; Ye AAn in vitro method was developed to test gastric irritation by quantifying the secretion of interleukin-8 (IL-8) by human intestinal epithelial cells Caco-2 after incubation with gastric digesta of emulsion gels containing capsaicinoids (CAP) obtained from simulated dynamic gastric digestion. The emulsion gel structure was modified using different emulsifiers: whey proteins versus Tween 80. Results indicate that both the CAP and Tween 80 molecules were proinflammatory to Caco-2 cells and stimulated cells to produce IL-8. Gastric digesta from CAP-loaded Tween 80 emulsion gel stimulated significantly more IL-8 production than CAP-loaded whey protein emulsion gel, possibly because of the presence of Tween 80 and also, because more CAP molecules were released from Tween 80 emulsion gel during gastric digestion. Tween 80 emulsion gel had a loose structure; it was easily broken down into smaller pieces and had large amounts of oil droplet liberation from the protein matrix, which would promote the release of CAP molecules, leading to higher IL-8 production. On the other hand, whey-protein-coated oil droplets had strong connections with surrounding protein matrix and were well protected during gastric digestion; the release of CAP molecules was much less. This study suggests that by modifying the structure of the foods, the gastric digestion behaviour can be modified, which would affect the release behaviour of CAP molecules and influence gastric irritation / inflammation.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 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 Interfacial composition of coenzyme Q10 emulsions impacts coagulation of fortified milk during gastric digestion(Elsevier Ltd, 2025-02-01) Wang X; Zhu P; Ye A; Singh H; Acevedo-Fani AThis study aimed to investigate the gastric digestion behaviour of heat-treated enriched milk containing Coenzyme Q10-loaded emulsions with different interfacial compositions. Four enriched milk types were compared: pasteurized with a Tween 80 stabilised emulsion (PAST-TW80), or with a sodium caseinate-stabilised emulsion (PAST-NaCN), and UHT with a TW80-stabilised emulsion (UHT-TW80), or PAST with a NaCN-stabilised emulsion (UHT-NaCN); all loaded with Coenzyme Q10. An in vitro dynamic gastric digestion model (Human Gastric Simulator) was utilized and the kinetics of milk coagulation and emptying of protein, lipid and Coenzyme Q10 were monitored. Adding NaCN-stabilised emulsion to heated milk led to a largely fragmented curd with signs of extensive droplets coalescence, disintegrating rapidly and accelerating protein and lipid release. Heated milk with TW80-stabilised emulsion produced a compact and closely integrated curd with limited coalescence, slowing nutrient emptying. UHT milk showed more curd fragmentation than PAST milk, regardless of emulsion type. The release profiles of Coenzyme Q10 were similar between UHT-TW80 and PAST-TW80 or between PAST-NaCN and UHT-NaCN, indicating the emulsion's interfacial composition as a key factor in controlling lipophilic bioactive release from the food matrix, regardless of heat treatment. These findings demonstrate that the emulsion's interfacial composition (NaCN vs TW80) and the heat treatment (PAST vs UHT) can be combined as a strategy to modulate milk coagulation kinetics and the rate of nutrient delivery to the small intestinal stage. This study provides insights into the development of functional milk products fortified with lipophilic bioactive compounds, as well as strategies for optimizing the controlled release of these compounds upon consumption.Item Digestion of food proteins: the role of pepsin.(Taylor and Francis Group, 2025-01-21) Yang M; Yang Z; Everett DW; Gilbert EP; Singh H; Ye AThe nutritive value of a protein is determined not only by its amino acid composition, but also by its digestibility in the gastrointestinal tract. The interaction between proteins and pepsin in the gastric stage is the first step and plays an important role in protein hydrolysis. Moreover, it affects the amino acid release rates and the allergenicity of the proteins. The interaction between pepsin and proteins from different food sources is highly dependent on the protein species, composition, processing treatment, and the presence of other food components. Coagulation of milk proteins under gastric conditions to form a coagulum is a unique behavior that affects gastric emptying and further hydrolysis of proteins. The processing treatment of proteins, either from milk or other sources, may change their structure, interactions with pepsin, and allergenicity. For example, the heat treatment of milk proteins results in the formation of a looser curd in the gastric phase and facilitates protein digestion by pepsin. Heated meat proteins undergo denaturation and conformational changes that enhance the rate of pepsin digestion. This review provides new ideas for the design of food products containing high protein concentrations that optimize nutrition while facilitating low allergenicity for consumers.Item Investigation of the gastric digestion behavior of commercial infant formulae using an in vitro dynamic infant digestion model.(Frontiers Media S.A., 2024-12-05) Descallar FB; Roy D; Wang X; Zhu P; Ye A; Liang Y; Pundir S; Singh H; Acevedo-Fani A; Lambers TThe gastric digestion behavior of different commercial Stage 1 infant formulae (for 0-6 months) with different formulation backgrounds was investigated using an in vitro dynamic infant human gastric simulator (iHGS). The microstructural arrangements of the protein and lipid, colloidal stability and protein hydrolysis during digestion were elucidated. During gastric digestion, casein-dominant formulations showed a higher extent of aggregation due to their high proportion of casein micelles that underwent coagulation upon acidification and via the action of pepsin. The extensive protein coagulation/curd formation in casein-dominant infant formulae slowed the rate of protein hydrolysis and resulted in the retention of caseins in the iHGS for longer times. Confocal micrographs showed that oil droplets were entrapped in the curd particles of casein-dominant infant formulae, which consequently slowed the gastric emptying of lipids. Conversely, whey-dominant formulations showed a lower degree of protein aggregation that resulted in faster protein hydrolysis and rapid protein and lipid emptying from the iHGS. It was also revealed that whey-dominant infant formulae in the presence of biopolymers increased the viscosity of gastric chyme and induced the flocculation of oil droplets. This altered the rate of protein hydrolysis and emptying of lipids. Correlation analyses depicted the overall kinetics of gastric emptying of macronutrients during digestion and comprised two stages: (i) driven by the continuous stomach emptying and (ii) influenced by aggregation and coalescence indices. The present study highlights the similarities and differences in the digestion behaviors of commercial infant formulae based on important ingredients such as types of proteins and biopolymers, regardless of the formulation or processing histories.