Evaluation of Technological Properties of Lactococci Isolated from Fermented Foods of Cold Desert Region of India

Abstract

Lactic acid bacteria, particularly lactococci, play an important role in fermented dairy products because of their contribution to acidification, flavour development, proteolysis, texture, and product stability. Indigenous fermented foods from cold desert regions may harbour technologically useful lactococcal strains; however, their techno-functional characteristics remain insufficiently characterised for potential starter-culture applications. This study evaluated the technological properties of lactococcal cultures isolated from fermented foods of the cold desert region, focusing on acidification, diacetyl production, proteolytic activity, exopolysaccharide (EPS) production, and antimicrobial activity. Acidification was assessed in skim milk through pH, titratable acidity, and the Horrall-Elliker activity test, while diacetyl production was evaluated using the creatine test. Proteolytic activity was measured by the o-phthaldialdehyde method, and EPS formation and antimicrobial activity were examined using capsule staining and an agar well diffusion assay, respectively. In Table 1, pH values after 6 h ranged from 4.60 to 5.43 and titratable acidity from 0.32 to 0.76% lactic acid, indicating marked strain-level variation in acid-producing ability. Four cultures were strongly positive and four were moderately positive for diacetyl production. In Table 2, protein content expressed as leucine equivalent at the curd-set point ranged from 0.077 to 0.131 mg/mL among the reported isolates, with CDM107 showing the highest value. None of the Lactococcus cultures showed detectable EPS production or antimicrobial activity against the tested indicator organisms under the experimental conditions. Overall, the isolates displayed substantial variability in technologically relevant traits, particularly acidification, flavour-forming ability, and proteolytic activity, supporting strain-level evaluation when selecting cultures for potential starter-culture applications.