Optimization of spray‐dried probiotic buttermilk powder using response surface methodology and evaluation of its shelf stability

In the present study, double-toned milk was inoculated with Streptococcus thermophilus, Lactobacillus delbrueckii subsp. bulgaricus, and Bifidobacterium bifidum, to result in a curd which was further subjected to homogenization and spray drying. Various process parameters like inlet temperature (140–160°C), the flow rate of feed (10–20 ml/min), and compressed air (2–4 kg/cm2) were varied to obtain the best-operating conditions for the maximum viable count in the probiotic cultured buttermilk powder. The yields of the powder ranged between 58.4% and 71.5%. An inlet temperature of 150°C, feed flow rate of 15 ml/min and compressed air of 3 kg/cm2 were the optimum process parameters obtained by response surface methodology for maximum survival of starter culture and probiotic bacteria Bifidobacterium bifidum. The powder stored at 4 ± 1°C showed superior qualities to that stored at 27 ± 1°C. While moisture content, aw, solubility and density showed an increase, hygroscopicity exhibited a decline during storage. The final moisture content, hygroscopicity, aw, solubility index, and bulk density of buttermilk powder stored at 4 ± 1°C and 27 ± 1°C were 5.93, 13.73, 0.293, 59.78, 0.71, and 6.27, 12.31, 0.301, 60.12, 0.93 respectively. The viable counts of Streptococcus thermophilus, Lactobacillus delbrueckii subsp. bulgaricus and Bifidobacterium bifidum in BMP were 8.07 ± 0.21, 7.68 ± 0.17, 6.01 ± 0.18 at 4 ± 1°C and 5.73 ± 0.17, 5.57 ± 0.14, 4.14 ± 0.20 at 27 ± 1°C after 4 weeks of storage. Practical applications Probiotics have gained tremendous attention in recent times. However, the viability of probiotics during rigorous food processing and handling steps remains a matter of concern. Spray drying results in a powder that can be easily handled, stored, and reconstituted in beverages. A probiotic cultured buttermilk powder was obtained by optimizing the inlet temperature, feed flow rate, and compressed air while spray drying. Buttermilk is a valuable by-product usually lost in waste streams during the manufacturing of butter. This study attempts to valorize buttermilk by developing a spray dried probiotic buttermilk powder and evaluate its shelf-life under refrigerated storage and ambient conditions, which would be of great help to the industry.