Antioxidant Capacity and Oxidative Changes in Lipids of Cow and Buffalo Milk Yoghurt in Different Storage Temperatures

Abstract

Yoghurt is normally kept at 34oC but majority of domestic and retail fridges keep at 8-10 
C. The effects of high storage temperature on antioxidant and lipid oxidation of cow and buffalo 
milk yoghurt have not been well investigated. Fermentation of whole cow and buffalo milk used 
Streptococcus thermophilus and Lactobacillus bulgaricus to prepare yoghurt and stored them at 4, 8 
and 12oC in 20 days. Alterations on fatty acid composition, free fatty acids, peroxide value, 
conjugated dienes, vitamins A and E, color, and flavor were assessed on day 0, 10 and 20. Storage 
at 4 and 8oC did not significantly influence the yoghurt composition and antioxidant activity after 
20 days. After 20 days, the total antioxidant capacity in cow and buffalo yoghurt at 12oC reduced to 
28.1 and 48.6 percent, respectively. In buffalo yoghurt kept at 12oC, the unsaturated fatty acids 
decreased up to 25.47%. Peroxide values increased to 0.51 MeqO2 /kg (cow) and 0.42 MeqO2 /kg 
(buffalo) and conversely, conjugated dienes were found to increase significantly during the same 
conditions. Vitamins A and E were found to be stable at 4 and 8oC but reduced dramatically at 12oC. 
The quality of flavors was kept at 4 and 8oC but worsened significantly at 12oC.  Keeping yoghurt 
at a temperature above 8oC promotes oxidation of lipid and loss of antioxidant qualities as well as 
deterioration of flavor. Thus, it is necessary to keep the storage at a temperature not exceeding 8oC 
to retain nutritional and sensory values of cow and buffalo milk yoghurt.