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

Abstract

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.