Journal Articles
Permanent URI for this collectionhttps://mro.massey.ac.nz/handle/10179/7915
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Item Intragastric restructuring dictates the digestive kinetics of heat-set milk protein gels of contrasting textures(Elsevier, 2024-11) Li S; Mungure T; Ye A; Loveday SM; Ellis A; Weeks M; Singh HThe gelation of milk proteins can be achieved by various means, enabling the development of diverse products. In this study, heat-set milk protein gels (15 % protein) of diverse textures were made by pH modulation and two gels were selected for dynamic in vitro gastric digestion: a spoonable soft gel (SG, pH 6.55' G' of ∼100 Pa) and a sliceable firm gel (FG, pH 5.65; G' of ∼7000 Pa). The two gels displayed markedly different structural changes and digestion kinetics during gastric digestion. The SG underwent substantial structural compaction during the first 120 min of gastric digestion into a denser and firmer gastric chyme (26.3 % crude protein, G* of ∼8500 Pa) than the chyme of the FG (15.7 % crude protein, G* of ∼3000 Pa). These contrasting intragastric structural changes of the gels reversed their original textural differences, which led to slower digestion and gastric emptying of proteins from the SG compared with the FG. The different intragastric pH profiles during the digestion of the two gels likely played a key role by modulating the proteolytic activity and specificity (to κ-casein) of pepsin. Preferential early cleavage of κ-casein in SG stimulated coagulation and compaction of solid chyme, whereas rapid hydrolysis of αS- and β-caseins in the FG weakened coagulation. This study provided new insights into controlling the structural development of dairy-based foods during gastric digestion and modulating digestion kinetics.Item Identifying temporal drivers of product acceptance and rejection across sips during whole product consumption(John Wiley & Sons, Inc, 2023-10) Weerawarna N. R. P. M; Godfrey AJR; Ellis A; Hort JMeasuring emotional response gives insights into consumer product experiences beyond liking. However, existing research rarely considers that emotional and hedonic responses can change during consumption of a whole portion. This research considered how well a combined multiple-sip temporal check-all-that-apply approach captured temporal drivers of product acceptance and rejection. Consumers (n = 104) profiled temporal sensory, liking and emotional responses to three milkshakes. Associations in temporal sensory, liking and emotional response citation pattern across multiple sips were investigated using generalized linear models, analysis of deviance and Pearson's chi-square test. Differences in the temporal dynamics of sensory, liking and emotional responses and associations between temporal sensory and affective responses were identified highlighting liking and emotional experience were related to the evolution of sensory attributes over time. Notably, sensory associations with emotional responses, including “bored,” “relaxed,” and “satisfied,” were better at identifying temporal drivers of acceptance/rejection more than associations to level of liking. Practical Applications: The research demonstrated that a combined multiple-sip temporal check-all-that-apply (TCATA) approach, representing whole product consumption, is an effective approach to gain deeper insights into the sensory drivers of consumer affective response. However, the applicability of analyzing within-sip variations in perception, and potential to use check all that apply by sip as opposed to TCATA needs to be considered on a product category basis.Item Impact of protectant uptake on the shelf-life of dried Lacticaseibacillus rhamnosus(Elsevier, 2022-01) Priour S; Welman A; Singh H; Ellis ATo improve the survival of dried probiotics, it is advised to expose the bacteria to protectants prior to processing, allowing equilibration of internal solutes. However, optimal conditions for this exposure remain unclear. This study examined solute uptake by Lacticaseibacillus rhamnosus HN001 (formally known as Lactobacillus rhamnosus HN001) at 4 °C and 20 °C, over exposure times of 0–240 min. The cells were exposed to hyperosmotic solutions of glucose and sucrose, two potential protective sugars, which are metabolisable and have different molecular weights. Sugar uptake was analysed through HPLC, while the impact on cell viability after freeze-drying was examined at 30 °C and 40 °C. The interactions between cell biomolecules and sugars were examined using Nano DSC. Results showed that the sugars were rapidly taken up by the cells, independent of temperature. At 20 °C, glucose was readily metabolised, eventually resulting in loss of cell viability during storage. Conversely, the Nano DSC study revealed interactions between the cells and sucrose, potentially providing some explanation as to the stability of the cells. In conclusion, sugar type and exposure temperature were shown to exert a significant effect on the viability of Lacticaseibacillus rhamnosus. Nano DSC is a promising technique to understand the protectant and cells’ interactions.Item The Protein Composition of Bovine Milk from Once-a-Day and Twice-a-Day Milking Production Systems in New Zealand(MDPI (Basel, Switzerland), 2023-12) van der Zeijden M; Ellis A; Lopez-Villalobos N; Li S; Roy NC; McNabb W; Antanaitis RAn increasing number of dairy farmers in New Zealand (NZ) have adopted a once-a-day (OAD) milking production system, and little is known about the impact of this production system on milk protein composition. The objective of this study was to evaluate the effect of OAD milking on the protein composition in milk from individual cows. Milk was sampled in early, mid-, and late lactation from cows kept at Massey University farms Dairy No. 1 (OAD milking) and Dairy No. 4 (TAD milking) in Palmerston North, NZ. The yields of total milk and milk solids, the proximate composition, and the protein composition were determined. Results showed that OAD milking yielded less milk and milk solids than TAD milking. However, no significant differences in protein, fat, and lactose contents were found. While the proportions of total casein (CN), total whey proteins, αs1-CN, β-CN, and β-lactoglobulin were not affected by the milking frequency, milk from a OAD milking system contained higher proportions of αs2-CN and κ-CN and lower proportions of α-lactalbumin. These proteins also changed differently throughout the milking season in a OAD milking system than in a TAD milking system. These changes in the protein composition of the milk observed in a OAD milking system could have implications for its processing properties and product quality.Item Modelling Lactation Curves for Dairy Sheep in a New Zealand Flock(MDPI (Basel, Switzerland), 2023-01-19) Marshall AC; Lopez-Villalobos N; Loveday SM; Ellis A; McNabb WLactation curves were modelled for dairy sheep in a New Zealand flock, providing information on the lactation yields of milk, fat, protein, and lactose, corrected for 130 days of milking. From 169 ewes, a total of 622 test-day records were obtained during the milk production season of 2021-2022 (from October to January). The flock produced an average of 86.1 kg of milk, 5.1 kg of fat, 4.5 kg of protein, and 4.1 kg of lactose, and moderate to large coefficients of variation were observed (27-31%) for these traits. The lactation persistency of milk, fat, protein, and lactose yields ranged from 52.3 to 72.7%. Analyses of variance for total yield and persistency were performed with an animal model that included the fixed effects of age (parity number), litter size, coat colour, and milking frequency (days in twice-a-day milking) and random residuals. Age and milking frequency were the only factors that significantly affected the yields of milk, fat, protein, and lactose. Age significantly affected the lactation persistency of milk and lactose yields, whereas litter size affected the persistency of protein, and milking frequency affected the persistency of fat. This study on this single flock provides valuable experience for a larger-scale animal breeding programme in New Zealand.Item Effect of sipping method on sensory response to single and multiple sips of vanilla milkshake using temporal-check-all-that-apply(Wiley Periodicals LLC, 2022-10-05) Weerawarna N.R.P M; Godfrey AJR; Ellis A; Hort JWhether drinking from a cup versus through a straw effects sensory perception is inconclusive, as is whether such differences hold across and within multiple sips. This study aimed to determine if product profiles and product discrimination varied depending on whether a product was sipped from a cup or through a straw. An expert panel (n = 9) investigated differences in temporal profiles of six milkshakes across sipping methods. Temporal discrimination across eight attributes was analyzed on selected time slices, across eight sips using generalized linear model Analysis of Deviance. Sweetness, vanilla, astringency, and liquorice attributes were cited significantly more often sipping through a straw, however sipping from a cup showed more significant attribute discriminations across products. Attribute discrimination was increased across multiple sips compared to sip one. Multiple sip TCATA analysis showed significant effects of sipping method within-sips and over multiple sips emphasizing the effects of sipping method on multiple sip TCATA product discriminations. Practical Applications: Milkshakes are often sold in bottles (enabling consumption either directly from the bottle or from a cup) or as on-the-go packs with a straw. This study showed that the sensory profile of milkshake varied depending on whether sipped from a cup or through a straw. However, often-sensory evaluations of beverages are performed by tasting from a cup. This indicates an important practical consideration in terms of sensory study design regarding evaluating products in the intended consumption format or formats. The findings also highlighted the importance of evaluating product volume (or weight) equivalent to single serving size to capture consumer experience closer to actual consumption occasions, as differences in response to one sip changed across multiple sips.Item Soy Protein Pressed Gels: Gelation Mechanism Affects the In Vitro Proteolysis and Bioaccessibility of Added Phenolic Acids(MDPI (Basel, Switzerland), 13/01/2021) Marinea M; Ellis A; Golding M; Loveday SMIn this study, a model system of firm tofu (pressed gel) was prepared to study how the coagulation mechanism-acidification with glucono δ-lactone (GDL) or coagulation with magnesium sulphate (MgSO4)-affected the physical properties of the gels along with their in vitro proteolysis (or extent of proteolysis). The two types of gels were also fortified with 3.5 mM protocatechuic (PCA) and coumaric acid (CMA) to test whether they can be used as bioactive delivery systems. Texture analysis showed that all MgSO4-induced gels (fortified and control) had a higher hydration capacity and a weaker texture than the GDL-induced gels (p < 0.05). MgSO4 gels had almost double proteolysis percentages throughout the in vitro digestion and showed a significantly higher amino acid bioaccessibility than the GDL gels (essential amino acid bioaccessibility of 56% versus 31%; p < 0.05). Lastly, both gel matrices showed a similar phenolic acid release profile, on a percentage basis (~80% for PCA and ~100% for CMA). However, GDL gels delivered significantly higher masses of bioactives under simulated intestinal conditions because they could retain more of the bioactives in the gel after pressing. It was concluded that the coagulation mechanism affects both the macro- and microstructure of the soy protein pressed gels and as a result their protein digestibility. Both pressed gel matrices are promising delivery systems for bioactive phenolic acids.