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1.
J Dairy Sci ; 2024 Feb 06.
Artigo em Inglês | MEDLINE | ID: mdl-38331176

RESUMO

Milk coagulation is an important step in the production of fermented dairy products such as yogurt and cheese. Jujube is gaining popularity and acceptance as a food ingredient. In China, jujube yogurt is popular among consumers. However, there is limited information on the effect of jujube on acid- and rennet-induced coagulation properties of milk. The objective of this study was to evaluate the effects of jujube pulp at different concentrations on acid- and rennet-induced coagulation kinetics of milk, and the microstructure of acid- and rennet-induced gels. During acid-induced coagulation, with increasing jujube pulp concentration, the initial pH value decreased; however, the final pH value increased. The initial elasticity index (EI) value increased, and the time point at which the mean square displacement curves lost the linear trend advanced. The sample with 10% jujube pulp had the densest structure and highest EI value. During rennet-induced coagulation, with increasing jujube pulp concentration, the production rate and amount of caseinomacropeptide decreased, and the final EI value increased. Protein aggregates in rennet-induced gels became rough, and the sample with 20% jujube pulp had the highest EI value. This study provides a new perspective and understanding of the application of jujube in fermented dairy products.

2.
Food Res Int ; 172: 113207, 2023 10.
Artigo em Inglês | MEDLINE | ID: mdl-37689953

RESUMO

To understand the properties of differently acidified and renneted gels with different soy milk and skim milk proportions, mixed milks were prepared and treated using sequenced renneting then acidification at 4 °C, and the formation, spontaneous whey separation, and microstructure of the gels were monitored. The results showed that both acidification and renneting promoted gel formation in mixed milk and increased gel strength. In gels, the pH range was narrow (pH ≤ 5.2) at low soy milk proportion (25%) and low renneting degrees (0%, 25% and 50%), and the pH range was extended such that gels were formed with increasing soy milk proportion and renneting degree. When compared with pH, soy milk proportion and renneting degree influenced whey separation percentages more strongly. Soy milk significantly reduced whey separation percentages in gels, and gel strength was highest at 50% soy milk. Protein aggregates sizes increased with increasing soy milk proportion at the 75% renneting degree, and the pore sizes of skim milk-dominated gels was strongly influenced by acidification. These results help us understand mixed gel properties and provide valuable information for the manufacture of mixed fermented dairy products.


Assuntos
Produtos Fermentados do Leite , Leite de Soja , Soro do Leite , Proteínas do Soro do Leite , Géis
3.
J Dairy Sci ; 105(8): 6578-6588, 2022 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-35787320

RESUMO

Heating milk at high temperatures impairs its renneting properties, but rennet-induced curds can be formed from ultra-high temperature (UHT) milk inoculated with Saccharomyces cerevisiae. Herein, we measured physicochemical indices of UHT milk inoculated with S. cerevisiae before rennet addition, monitored the kinetics of gel formation, and investigated the physicochemical properties and microstructure of rennet-induced curds to explore the mechanisms by which S. cerevisiae influenced rennet-induced gelation of UHT milk. Compared with untreated pasteurized cow milk and UHT milk, the ethanol content was increased, the pH was decreased, the particle size and ζ-potential were increased, the time points at which the elasticity index began to increase were advanced, and the maximum elasticity index was increased for UHT milk inoculated with S. cerevisiae. The number of S. cerevisiae cells affected the structure of rennet-induced curds; with few cells added, the protein network of curds was continuous and tight, the mean square displacement curves showed an asymptotic behavior, and the water retention capacity and curd yield were high; with more cells added, the loosely entangled proteins aggregated, the continuity of the network was destroyed, and the curd yield decreased. In summary, a low number of S. cerevisiae cells (<1.0 × 107 cfu/mL) can increase particle size, ζ-potential, and ethanol content, and decrease pH of S. cerevisiae-inoculated UHT milk, thereby accelerating the aggregation reactions after enzymatic reaction and improving the renneting properties.


Assuntos
Leite , Saccharomyces cerevisiae , Animais , Caseínas/química , Bovinos , Quimosina/metabolismo , Etanol/análise , Feminino , Leite/química , Saccharomyces cerevisiae/metabolismo , Temperatura
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