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Title: Rheology and microstructure of mozzarella-type curd made from buffalo or cows' milk
Author: Hussain, Imtiaz
Awarding Body: University of Reading
Current Institution: University of Reading
Date of Award: 2012
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Abstract:
The physicochemical properties of buffalo and cows' milk and factors affecting the rheological and microstructural properties of Mozzarella type curd made from buffalo and cows' milk were investigated. Although there have been many studies on the rheological and microstructural properties of rennet curd made from cows' milk. There is no detailed information available in the scientific literature on Mozzarella type curd made from buffalo milk, and the effect of factors such as pH, acidification, gelation temperature and freezing thereon. Cheese and yoghurt are made from buffalo and cows' on a commercial scale without considering differences in their chemical composition, physical, mechanical and microstructural properties. Buffalo milk contains 40-60% more fat, protein and calcium than cows' milk. Due to the higher total solids content of buffalo milk, it would be expected to have greater curd strength (G'), curd yield, curd moisture and fat retention than cows' milk. Mozzarella curd had a better texture and overall quality made from buffalo milk than cows' milk. The factors affecting the overall quality of Mozzarella type curd made from cows' milk were more pronounced than those made from buffalo milk. In frozen buffalo milk, pH, ionic calcium and dynamic moduli (G', G") of resulting curds were reduced when compared to unfrozen milk. This may be due to precipitation of calcium phosphate during freezing. Hence, the concentration of ionic calcium would decrease giving a final reduction in pH. For both species, the effects of acidification on the physicochemical and rheological properties were qualitatively similar but quantitatively different. Buffalo milk displayed a curd structure and rheology different from that of cows' milk, and the casein-bound calcium, as well as the contents of fat, protein and calcium, was also higher. Due to these higher amounts of casein-bound calcium, the overall curd strength of buffalo milk (as indicated by the dynamic moduli) was higher, at similar pH values, than those of equivalent gels produced from cows' milk. The degree of solubilization of calcium in buffalo milk during acidification was quite different from that observed in cows' milk with a lower proportion of the calcium being solubilized in the former. The effects of gelation temperature were found to be more pronounced in cows' curd than buffalo curd. The maximum curd strength i (G') was obtained at a gelation temperature of 34°C in both types of milk. The maximum yield stress was obtained at the gelation temperatures of 34°C and 28°C in buffalo and cows' curd, respectively. The cryo-SEM and CLSM micrographs showed that minimum porosity was observed at the gelation temperature of 34°C in both types of milk. Buffalo curd showed minimum porosity at similar gelation temperature when compared to cows' curd. The curd yield 50% was higher in buffalo milk as compared to cows' milk. This was due to differences in chemical composition of both milks. The fat (50%) and protein (30%) were higher in buffalo milk than cows' milk. The minimum losses of fat and protein in rennet whey occurred at a gelation temperature of 34°C in both milk samples. The different cutting times had a small effect on the yield and overall quality of curds made from both milk types. The curd rheology and microstructure of cows' curd was found to be different, even at equivalent protein/total solids to buffalo milk using ultrafiltration. This may have been due differences in fat globule or casein micelles size or different proportions of casein fractions. The curd yield on both dry & wet basis, curd moisture and curd fat retention were found to be higher in UF cows' milk than for buffalo and cows' milk.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.558766  DOI: Not available
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