Detection of lytic phage infecting flavour-producing strain of Lacticaseibacillus paracasei in the dairy effluents of Kerala.

The performance of the starter culture is a critical factor that decides the quality of fermented milk. Dahi is a fermented milk product popular in India made using a mixed starter culture of lactic acid bacteria comprising acid and flavour producers. The prevalence of bacteriophages in the dairy environment can critically affect the activity of these starter cultures resulting in starter failure. As there is little information available on the occurrence of bacteriophages in the dairy environment of Kerala, this research communication examines the presence of lytic bacteriophages acting against three potential flavour-producing strains of Lacticaseibacillus paracasei (Lc. paracasei). Dairy effluent samples were screened for the presence of phages against the strains of Lc. paracasei by the multiple host enrichment method. Plates showing clearance zone in spot assay were confirmed for the presence of phages by double-layer agar assay. The plaques obtained in the double-layer agar assay were purified for further identification by next-generation sequencing. A bacteriophage infecting one of the three strains of Lc. paracasei was detected by the plaque assay and the blast annotation of the bacteriophage sequence found 86.05% similarity of the phage to Siphoviridae family. The study endorses the need for monitoring phages in the dairy environment to control phage-related starter failure in the state of Kerala.

Optimization of calcium gluconate and Bacopa monniera extract levels in calcium enriched herbal ice cream by response surface methodology.

Calcium enriched herbal ice cream was developed using calcium gluconate (CG) as calcium source, Bacopa monniera whole plant extract (BME) is an herb containing saponins. Ice cream was prepared by incorporating CG and BME together. Preliminarily the range of CG and BME levels were fixed as 50-250 mg/100 mL and 10-50 mg/100 mL of ice cream mix respectively. Response surface methodology (RSM) was used to optimize the levels of two ingredients (CG and BME). Central Composite Rotatable Design using two variables and five responses comprising of sensory attributes was used for computation of optimized solution. All the responses fitted well into quadratic equation with R2 > 0.60. The optimum levels of CG and BME are 217.34 mg/100 mL and 10 mg/100 mL for preparation of experimental ice cream. RSM recommended with 87% acceptability for the optimum levels of CG and BME. Product is prepared with optimized solution and subjected to sensory evaluation.