Microbial Features and Qualitative Detection of Adulteration along with Physicochemical Characteristics of Sweetened Yoghurt

Background and Objective: Food adulteration is of major public health concern worldwide. The food safety situation in Bangladesh is at an alarming stage due to food adulteration, microbiological contamination and fraudulence. Consumption of milk and milk product are increasing because of their health benefit effect. However, milk and milk products are being currently adulterated by substituting ingredients with cheaper materials. The aim of this study was the qualitative detection of adulterants along with physico-chemical and microbial features of sweetened yoghurt.

Methodology: Sixteen sweetened yoghurt samples (Ten locally available and six commercial brands) were collected from different area in Bangladesh. All the sweetened yoghurt samples were subjected to urea, starch, ammonium sulphate, hydrogen peroxide analyses. Physico-chemical analysis of sweetened yoghurt was also done. Moreover, yoghurt samples were also microbiologically assessed.

Results: Acidity content of all sweetened yoghurt was found to be ranges from 0.66 ±.05% to 0.77±0.05 which was lower than the standard level of (0.8 to1.2). In both cases (Commercial) branded and (Local) unbranded yoghurt had lower moisture content and higher total solid content compared to standard level (13.5%). Those measurements indicated that sweetened yoghurt samples were adulterated with starch. Meanwhile, both branded and unbranded sweetened yoghurt samples had fat contents ranging between 1.56 ±0.09% to 2.63 ±0.2% which were below the standard level (3%). On the other hand, protein content ranged between 3.71±0.02% to 4.33±0.15%, which was higher than standard level of 3.2%. These results revealed that all sweetened yoghurt samples were highly adulterated with urea, starch and ammonium sulphate. From the microbiological point of view, all sweetened yoghurt samples had good quality. For instance, L. bulgaricus and S. thermophilus were found to be under acceptable range, and there were no pathogenic coliform bacteria were found in any of the samples.

Conclusion: Results obtained from this study might help the consumers to be more aware when they purchase yoghurt from local market.