Examining the Effect of Freezing Temperatures on the Survival Rate of Micro-Encapsulated Probiotic Lactobacillus acidophilus LA5 Using the Flash Freeze-Drying (FFD) Strategy

Abstract

This work proposes a novel drying method suitable for probiotic bacteria, called flash freeze-drying (FFD), which consists of a cyclic variation in pressure (up-down) in a very short time and is applied during primary drying. The effects of three FFD temperatures (−25 °C, −15 °C, and −3 °C) on the bacterial survival and water activity of Lactobacillus acidophilus LA5 (LA), previously microencapsulated with calcium alginate and chitosan, were evaluated. The total process time was 900 min, which is 68.75% less than the usual freeze-drying (FD) time of 2880 min. After FFD, LA treated at −25 °C reached a cell viability of 89.94%, which is 2.74% higher than that obtained by FD, as well as a water activity of 0.0522, which is 55% significantly lower than that observed using FD. Likewise, this freezing temperature showed 64.72% cell viability at the end of storage (28 days/20 °C/34% relative humidity). With the experimental data, a useful mathematical model was developed to obtain the optimal FFD operating parameters to achieve the target water content in the final drying.

Editorial for the Special Issue “Food and Microbial Bioprocesses”

“…The results from the revision did not show consistent findings, thus the mechanisms behind the successful production of quality meat are not clear, and are possibly due to the usage of diverse probiotic bacteria, the dosage used, time of application, breed, age, and health conditions of the ruminants. The effect of freezing on the survival rate of encapsulated probiotic Lactobacillus acidophilus LA5 by using a novel flash freeze drying process was also reported [9]. In this work, the use of flash 13 freeze-drying (FFD), a cyclic and rapid increasing and decreasing of pressure during primary drying was studied, obtaining total process times of about a third that of the classical freeze-drying.…”