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 (C(16:0)), palmitoleic (C(16:1)), stearic (C(18:0)), oleic (C(18:1)), linoleic (C(18:2)), and linolenic (C(18:3)) acids were identified. Four of them, C(16:0), C(16:1), C(18:0), and C(18:1), 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 C(18:2) contributed very small percentages (on average <or= 1%) to the total in each strain. C(16:0) 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 C(16:1)/C(16:0), C(18:0)/C(16:0) and C(18:1)/C(16:0) 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, C(18:2)/C(16:0) and C(18:3)/C(16:0) ratios for freeze-dried L. mesenteroides and L. plantarum with or without cryoprotectants decreased as the storage time increased. However, a higher C(18:2)/C(16:0) or C(18:3)/C(16:0) ratio for L. mesenteroides and L. plantarum was noted in the freeze-dried powder held at 4 degrees C or under vacuum and in dark than at 20 degrees C or in the presence of oxygen and light.