Study of Probiotics Viability and Attributes Stability in Powdered Milk Prepared by Lyophilization

Abstract

Synthetic infant formulas have served the purpose of nutrition, but they come along with food intolerance and food allergy. To come up with this issue, milk from five different sources i.e. Cow milk, goat milk, sheep milk, soy milk, and skim milk were fermented using characterized Streptococcus thermophilus QAUSTN63, Lactobacillus delbrueckii subsp. bulgaricus QAULDN14, and Lactococcus lactis QAULLNA8, and Geotrichum candidum QAUGC01 (PRJNA523005) followed by lyophilization. The proximate analysis of the milk products was carried out before (per 100ml) and after lyophilization (per 100g) to ensure nutritional intactness. The results showed highest crude protein in soy milk i.e. 6.0% and 27.01%, highest ash content i.e. 1.053% and 5.48%, and fat content i.e. 8.5% and 29.07%, total solids 19.44% and 96.82% in sheep milk in liquid and lyophilized product respectively. Alongside this, the probiotic attributes stability was carried out for bacterial consortium and Geotrichum candidum isolated from each lyophilized milk samples. All the cultures were found to be viable up to 108 CFUs/ml. Lastly, the probiotic attribute stability tests showed that both the bacterial consortium and Geotrichum candidum gave positive Bile salt Hydrolase (BSH) activity, proteolytic activity, lipolytic activity, NaCl tolerance, and bile salts tolerance. Whereas, lactose fermentation, milk fermentation, and antibiotic susceptibility were positive only for bacterial consortium. The antimicrobial activity against Pseudomonas aeruginosa ATCC 27853, Salmonella enterica ATCC 14028, E. coli ATCC 25922, Bacillus subtilis ATCC 5230, and Staphylococcus aureus ATCC 25923 was observed for bacterial consortium, while Geotrichum candidum was antifungal susceptible with positive antimicrobial activity against Pseudomonas aeruginosa ATCC 9027, Candida albicans ATCC 10231, and Staphylococcus aureus ATCC 6538 along with the aforementioned strains. The optimum temperature for bacterial consortium and Geotrichum candidum was 37oC and 25oC, along with 6-8 and 4-6 as optimum pH for both respectively. All these tests proved that the strains were active after lyophilization with all the milk nutrients intact in each product. Hence, the present study was believed to be the most reliable natural fermented alternative to synthetic infant formulas.