Microbial Diversity and Nutritional Properties of Persian "Yellow Curd" (Kashk Zard), a Promising Functional Fermented Food.

"Yellow curd" (YC) is one of the most popular homemade Persian fermented foods and is consumed by many people. Notwithstanding, no studies are available to date on its nutritional and microbiological composition. In this study, we examined YC samples obtained from different local markets of Sistan and Baluchestan province, Iran. The results of the chemical analyses revealed a homogenous content of protein (13.71% ± 1.07), lipids (4.09% ± 0.73), and carbohydrates (61% ± 2.13) among the samples. By comparing the average mineral content of YC with yogurt, many relevant differences were detected. Apart from the calcium content, which was similar on average to that of YC, all other minerals tested are present in higher amounts in YC than in yogurt. The analysis of the main sugars present (i.e., lactose, galactose and glucose) highlighted relevant differences among samples, indicating that different YC samples contain natural strains with different capabilities to metabolize sugars. The concentration of galactose in YC samples should be taken into consideration by galactose intolerant people. From the microbiological perspective, the metagenomics analysis revealed that lactic acid bacteria, and particularly the genera Lactobacillus, Pediococcus, and Streptococcus, were dominant in YC. The information provided shows that YC is an interesting base for the preparation of novel functional foods with a good content of beneficial bacteria.