The Microstructure and Physicochemical Properties of Probiotic Buffalo Yoghurt During Fermentation and Storage: a Comparison with Bovine Yoghurt

Abstract

The physicochemical and rheological properties of yoghurt made from unstandardised unhomogenised buffalo milk were investigated during fermentation and 28 days of storage and compared to the properties of yoghurt made from homogenised fortified bovine milk. A number of differences observed in the gel network can be linked to differences in milk composition. The microstructure of buffalo yoghurt, as assessed by confocal laser scanning microscopy (CLSM) and cryo scanning electron microscopy (cryo-SEM), was interrupted by large fat globules and featured more serum pores. These fat globules have a lower surface area and bind less protein than the homogenised fat globules in bovine milk. These microstructural differences likely lead to the higher syneresis observed for buffalo yoghurt with an increase from 17.4 % (w/w) to 19.7 % (w/w) in the weight of whey generated at day 1 and day 28 of the storage. The higher concentration of total calcium in buffalo milk resulted in the release of more ionic calcium during fermentation. Gelation was also slower but the strength of the two gels was similar due to similar protein and total solids concentrations. Buffalo yoghurt was more viscous, less able to recover from deformation and less Newtonian than bovine yoghurt with a thixotropy of 3035 Pa.s -1 measured for buffalo yoghurt at the end of the storage, at least four times higher than the thixotropy of bovine yoghurt. While the titratable acidity, lactose consumption and changes in organic acid concentrations were similar, differences were recorded in the viability of probiotic bacteria with a lower viability of Lactobacillus acidophilus of 5.17 log (CFU/g) recorded for buffalo yoghurt at day 28 of the storage. Our results show that factors other than the total solids content and protein concentration of milk affect the structural properties of yoghurt. They also illustrate the physicochemical reasons why buffalo and bovine yoghurt are reported to have different sensory properties and provide insight into how compositional changes can be used to alter the microstructure and properties of dairy products.

Rheological, textural, colour and sensorial properties of kefir produced with buffalo milk using kefir grains and starter culture: A comparison with cows’ milk kefir

“…This is a major visible defect that develops during storage of fermented dairy products that directly affects consumer acceptance (Nguyen et al . ). In the present study, the WHC values of the kefir samples ranged from 42.61 to 77.35% and the highest value was determined for the BS samples (Table ).…”

“…Additionally, the surface area of the fat globules is another parameter that affects the WHC of fermented dairy products as protein can be absorbed to the surface of fat globules leading to a network that can hold water (Nguyen et al . ). Nguyen et al .…”

“…Nguyen et al . () reported that a decrease in yoghurt WHC depended on the increase in the surface area of the fat globules of cows' milk. However, Menard et al .…”

“…Comparative analysis of kefir produced with buffalo and cows’ milk is important for understanding the differences between milk type effects on the composition and physical properties of kefir (Nguyen et al . ). Kefir manufacture with different milk types can also offer more diverse products with regard to flavour, taste and quality.…”

Effects of Pleurotus eryngii polysaccharides on bacterial growth, texture properties, proteolytic capacity, and angiotensin-I-converting enzyme–inhibitory activities of fermented milk

“…Nile red-stained fat globules appeared red, and FITC-stained homogeneous matrix of protein appeared green. Denser protein aggregates appeared light green or light yellow, and the black areas were serum pores (Cruz et al, 2009;Nguyen et al, 2014). Values are expressed as mean ± SD, n = 3.…”