Inactivation mechanisms of lactic acid starter cultures preserved by drying processes

Abstract

Summary The preservation of lactic acid starter cultures by drying are of increased interest. A further improvement of cell viability is, however, still needed, and the insight into inactivation mechanisms of the cells is a prerequisite. In this present work, we review the inactivation mechanisms of lactic acid starter cultures during drying which are not yet completely understood. Inactivation is not only induced by dehydration inactivation but also by thermal‐ and cryo‐injuries depending on the drying processes employed. The cell membrane has been reported as a major site of damage during drying or rehydration where transitions of membrane phases occur. Some drying processes, such as freeze drying or spray drying, involve subzero or very high temperatures. These physical conditions pose additional stresses to cells during the drying processes. Injuries of cells subjected to freezing temperatures may be due to the high electrolyte concentration (solution effect) or intracellular ice formation, depending on the cooling rate. High temperatures affect most essential cellular components. It is difficult to identify a critical component, although ribosomal functionality is speculated as the primary reason. The activation during storage is mainly due to membrane lipid oxidation, while the storage conditions such as temperature moisture content of the dried starter cultures are important factors.

Microencapsulation of Lactobacillus plantarum MTCC 5422 in fructooligosaccharide and whey protein wall systems and its impact on noodle quality

“…This reduction in the viability may be attributed to higher temperature application during drying at 55°C. Heat stress during dehydration leads to viability loss due to the cell wall and cell membrane damage (Santivarangkna et al 2008). On comparison encapsulated probiotic cell viability in fresh noodles had relatively high than dried noodles.…”

“…After cooking, complete viability loss was observed in the dried noodles. This can be attributed to thermal inactivation occurred during rehydration of dried cells due to leakage of essential cellular components (Santivarangkna et al 2008). However, fresh noodles retained 62.42 % encapsulated cell viability after cooking due to the presence of initial moisture (36 %) in the fresh noodles that protected the cell membrane from osmotic shock and thermal injury during rehydration.…”

Influence of Two-Component Signal Transduction Systems of Lactobacillus casei BL23 on Tolerance to Stress Conditions

“…Probiotic microorganisms must survive the industrial production processes (3,23) and transit through the gastrointestinal tract (3). Bacteria have evolved sophisticated mechanisms to detect and adapt to environmental changes, and among them, two-component systems (TCS) play a central role (25).…”

Comparative Genomic Analysis of Two-Component Signal Transduction Systems in Probiotic Lactobacillus casei

“…have achieved popularity in the manufacturing of probiotic products because of their convincing beneficial effects on human health. However, before providing benefit to human health, probiotic bacteria must survive the industrial production processes and transit through the gastrointestinal tract [1,2]. Bacterial twocomponent signal transduction systems (TCSs) play important roles for many bacteria by enabling them to detect and respond to diverse changes/stresses in the environment [3].…”