Journal Articles

Permanent URI for this collectionhttps://mro.massey.ac.nz/handle/10179/7915

Browse

Filters

2012 - 201912020 - 20242

Settings

Author: search.filters.author.Loveday SMSubject: search.filters.subject.Milk

Search Results

Now showing 1 - 3 of 3
  • Thumbnail Image
    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 NC
    This 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.
  • Thumbnail Image
    Item
    Genome-wide association studies for citric and lactic acids in dairy sheep milk in a New Zealand flock
    (Taylor and Francis Group, 2024-08-05) Zongqi A; Marshall AC; Jayawardana JMDR; Weeks M; Loveday SM; McNabb W; Lopez-Villalobos N
    The objectives of this study were to estimate genetic parameters for citric acid content (CA) and lactic acid content (LA) in sheep milk and to identify the associated candidate genes in a New Zealand dairy sheep flock. Records from 165 ewes were used. Heritability estimates based on pedigree records for CA and LA were 0.65 and 0.33, respectively. The genetic and phenotypic correlations between CA and LA were strong-moderate and negative. Estimates of genomic heritability for CA and LA were also high (0.85, 0.51) and the genomic correlation between CA and LA was strongly negative (-0.96 ± 0.11). No significant associations were found at the Bonferroni level. However, one intragenic SNP in C1QTNF1 (chromosome 11) was associated with CA, at the chromosomal significance threshold. Another SNP associated with CA was intergenic (chromosome 15). For LA, the most notable SNP was intragenic in CYTH1 (chromosome 11), the other two SNPs were intragenic in MGAT5B and TIMP2 (chromosome 11), and four SNPs were intergenic (chromosomes 1 and 24). The functions of candidate genes indicate that CA and LA could potentially be used as biomarkers for energy balance and clinical mastitis. Further research is recommended to validate the present results.
  • Thumbnail Image
    Item
    β-Lactoglobulin nanofibrils: Effect of temperature on fibril formation kinetics, fibril morphology and the rheological properties of fibril dispersions
    (Elsevier Ltd, 2012-05) Loveday SM; Wang XL; Rao MA; Anema SG; Singh H
    Almost all published studies of heat-induced b-lactoglobulin self-assembly into amyloid-like fibrils at low pH and low ionic strength have involved heating at 80 C, and the effect of heating temperature on self-assembly has received little attention. Here we heated b-lactoglobulin at pH 2 and 75 C, 80 C, 90 C, 100 C, 110 C or 120 C and investigated the kinetics of self-assembly (using Thioflavin T fluorescence), the morphology of fibrils, and the rheological properties of fibril dispersions. Self-assembly occurred at all temperatures tested. Thioflavin T fluorescence increased sigmoidally at all temperatures, however it decreased sharply with >3.3 h heating at 110 C and with >5 h heating at 120 C. The sharp decreases were attributed partly to local gelation, but destruction of fibrils may have occurred at 120 C. Thioflavin T fluorescence results indicated that maximal rates of fibril formation increased with increasing temperature, especially above 100 C, but fibril yield (maximum Thioflavin T fluorescence) was not affected by temperature. At 100 C and 110 C, fibrils were slightly shorter than at 80 C, but otherwise they looked very similar. Fibrils made by heating at 120 C for 1 h were also similar, but heating at 120 C for 8 h gave predominantly short fibrils, apparently the products of larger fibrils fragmenting. Heating at 100 C gave consistently higher viscosity than at 80 C, and heating for >2 h at 120 C decreased viscosity, which may have been linked with fibril fragmentation seen in micrographs.