title: Physiochemical properties, microstructure, and probiotic survivability of nonfat goats' milk yogurt using heat-treated whey protein concentrate as fat replacer.
abstract: There is a market demand for nonfat fermented goats' milk products. A nonfat goats' milk yogurt containing probiotics (Lactobacillus acidophilus, and Bifidobacterium spp.) was developed using heat-treated whey protein concentrate (HWPC) as a fat replacer and pectin as a thickening agent. Yogurts containing untreated whey protein concentrate (WPC) and pectin, and the one with only pectin were also prepared. Skim cows' milk yogurt with pectin was also made as a control. The yogurts were analyzed for chemical composition, water holding capacity (syneresis), microstructure, changes in pH and viscosity, mold, yeast and coliform counts, and probiotic survivability during storage at 4 °C for 10 wk. The results showed that the nonfat goats' milk yogurt made with 1.2% HWPC (WPC solution heated at 85 °C for 30 min at pH 8.5) and 0.35% pectin had significantly higher viscosity (P < 0.01) than any of the other yogurts and lower syneresis than the goats' yogurt with only pectin (P < 0.01). Viscosity and pH of all the yogurt samples did not change much throughout storage. Bifidobacterium spp. remained stable and was above 10(6) CFU g(-1) during the 10-wk storage. However, the population of Lactobacillus acidophilus dropped to below 10(6) CFU g(-1) after 2 wk of storage. Microstructure analysis of the nonfat goats' milk yogurt by scanning electron microscopy revealed that HWPC interacted with casein micelles to form a relatively compact network in the yogurt gel. The results indicated that HWPC could be used as a fat replacer for improving the consistency of nonfat goats' milk yogurt and other similar products.
authors: Dept. of Food Sciences and Engineering, Jilin Univ, Changchun, Jilin, 130062, China.
authors: Tiehua
authors: T
authors: Zhang
authors: James
authors: J
authors: McCarthy
authors: Guorong
authors: G
authors: Wang
authors: Yanyan
authors: Y
authors: Liu
authors: Mingruo
authors: M
authors: Guo
mesh_terms: D000818:Animals; D001419:Bacteria / Q000254:growth & development*; D001644:Bifidobacterium / Q000254:growth & development; D002417:Cattle; D018752:Diet, Fat-Restricted; D004041:Dietary Fats / Q000008:administration & dosage; D005260:Female; D005511:Food Handling / Q000379:methods*; D006041:Goats; D006358:Hot Temperature; D006801:Humans; D007779:Lactobacillus acidophilus / Q000254:growth & development; D050296:Microbial Viability; D008892:Milk / Q000382:microbiology; D008894:Milk Proteins / Q000737:chemistry; D010368:Pectins; D019936:Probiotics; D014783:Viscosity; D014867:Water; D000067816:Whey Proteins; D015014:Yogurt / Q000032:analysis* / Q000382:microbiology
chemical_list: D004041:Dietary Fats; D008894:Milk Proteins; D000067816:Whey Proteins; D014867:Water; D010368:Pectins
keywords: goats’ milk; nonfat yogurt; probiotic; whey protein concentrate