Effect of milk phospholipids on the growth and cryotolerance of lactic acid bacteria cultured and stored in acid whey-based media

Abstract

Supplementation of a lactic acid bacteria (LAB) culture medium with milk phospholipids (MPL) at low concentration (0.5%) results in a significant increase in viability and metabolic activity after freeze-thawing cycles. We speculate that the nature of the milk phospholipids maintains the integrity of the bacterial membranes and thus their metabolic function. This work demonstrates a feasible and economic way to enhance the cryotolerance of lactic acid bacteria, pointing toward possible means to develop functional foods and valorize acid whey. Highlights • Acidification activity is retained by adding milk phospholipids to acid whey-based medium • Retention of activity (as rate of lactic acid production) is relevant to cryoprotection studies • Acid whey from cottage cheese production is a good medium for preserving frozen cultures Abstract: Increasing interest in foods beyond their nutritional value has promoted the development of various novel functional foods that could convey multiple health benefits to consumers. The application of lactic acid bacteria (LAB) and milk phospholipids (MPL) in combination has shown some amplifying effects on the health benefits provided by both ingredients. Freezing is commonly used in LAB preservation and storage. However, the freezing/thawing process damages cell membranes and leads to a loss in viability and functionality of LAB. This study aimed to investigate the influence of MPL on growth and cryotolerance of LAB using acid whey-based medium (AWM) supplemented with 0.5% MPL. Fourteen LAB strains were initially screened from 124 LAB using acid whey-based medium (AW). We then evaluated the cell viability and acidification ability, using the plate counting method and skim milk fermentation test, respectively, of the 14 strains cultured in AW and AWM before and after 3 cycles of freezing/thawing. The presence of 0.5% MPL in AWM significantly promoted the growth of LAB. Supplementing the culture and storage medium with 0.5% MPL significantly enhanced the resistance of selected LAB to freeze-thaw cycles in terms of cell viability and acidification ability. These results suggest that supplementing with 0.5% MPL might promote the growth of LAB and enhance the cryotolerance of LAB cultures in fermented dairy products. This finding leads to a better understanding of the synergistic effects contributed by the LAB-MPL combination and promotes the development of new LAB-MPL functional products. M ilk phospholipids (MPL) are valuable dairy components of