Survival of Freeze-dried Leuconostoc mesenteroides and Lactobacillus plantarum Related to Their Cellular Fatty Acids Composition during Storage

Lactic acid bacteria strains Lactobacillus plantarum CWBI-B534 and Leuconostoc ssp. mesenteroïdes (L. mesenteroïdes) Kenya MRog2 were produced in bioreactor, concentrated, with or without cryoprotectants. In general, viable population did not change significantly after freeze-drying (p > 0.05). In most cases, viable population for cells added with cryoprotectants was significantly lower than those without (p < 0.05). Cellular fatty acids (CFAs) from the two strains in this study were analyzed before and after freeze-drying. Six CFAs were identified, namely, palmitic (C₁₆:₀), palmitoleic (C₁₆:₁), stearic (C₁₈:₀), oleic (C₁₈:₁), linoleic (C₁₈:₂), and linolenic (C₁₈:₃) acids were identified. Four of them, C₁₆:₀, C₁₆:₁, C₁₈:₀, and C₁₈:₁, make up more than 94% or 93% of the fatty acids in L. mesenteroides and L. plantarum, respectively, with another one, namely, C18:3, making a smaller (on average 5-6%, respectively) contribution. The C₁₈:₂ contributed very small percentages (on average <= 1%) to the total in each strain. C₁₆:₀ had the highest proportion at most points relative to other fatty acids. Moisture content and water activity (a w) increased significantly during the storage period. It was observed that C₁₆:₁/C₁₆:₀, C₁₈:₀/C₁₆:₀ and C₁₈:₁/C₁₆:₀ ratios for freeze-dried L. mesenteroides or L. plantarum, with or without cryoprotectants, did not change significantly during the storage period. According to the packaging mode and storage temperatures, C₁₈:₂/C₁₆:₀ and C₁₈:₃/C₁₆:₀ ratios for freeze-dried L. mesenteroides and L. plantarum with or without cryoprotectants decreased as the storage time increased. However, a higher C₁₈:₂/C₁₆:₀ or C₁₈:₃/C₁₆:₀ ratio for L. mesenteroides and L. plantarum was noted in the freeze-dried powder held at 4 °C or under vacuum and in dark than at 20 °C or in the presence of oxygen and light.