Impact of Cold Storage on Physicochemical, Microbiological, Sensory and Biofunctional Properties of a Peptide-rich Functional Fermented Dairy Beverage

Abstract

Background: Functional fermented dairy beverages require adequate storage stability to retain product quality, viable cultures, sensory acceptability, and biofunctional properties. Aim: The present study investigated the effect of cold storage on the physicochemical, microbiological, sensory, and biofunctional properties of a bioactive peptide-rich functional fermented dairy beverage, namely dipeptidyl peptidase (DPP)-IV inhibitory activity, α-glucosidase inhibitory activity, and antioxidant activity. Place and Duration of Study: The study was conducted at the Dairy Microbiology Division, National Dairy Research Institute, Karnal, Haryana, India, during 2020-2021. Methodology: A fermented dairy beverage prepared under optimised conditions was stored at a refrigerated temperature and evaluated at weekly intervals for various quality and functional parameters. Results: Coliforms, yeasts, and moulds were not detected in the beverage throughout the 42-day storage period, indicating satisfactory microbiological quality. The beverage retained more than 7.0 log CFU/mL viable cells of the functional strain Lacticaseibacillus rhamnosus NCDC 24 at the end of storage. A significant increase in titratable acidity (0.75±0.035 to 0.88±0.042% LA), accompanied by a reduction in pH (4.58±0.054 to 4.37±0.067), was observed after 14 days of storage. The peptide concentration increased significantly between days 14 and 28 of storage and subsequently remained stable until the end of the storage period (1.261±0.123 mg/mL eq. of leucine). Correspondingly, DPP-IV inhibitory and ABTS radical-scavenging activities increased significantly from days 14 to 28, whereas α-glucosidase inhibitory and DPPH radical-scavenging activities improved significantly from day 21. Furthermore, the peptide-rich fermented dairy beverage remained sensorially acceptable for up to 35 days, with an overall acceptability score of 7.0±0.29 on a nine-point hedonic scale. Conclusion: The findings indicate that the peptide-rich fermented dairy beverage developed with the proteolytic strain L. rhamnosus NCDC 24 retained its biofunctional properties during cold storage without adversely affecting the measured quality parameters.