Effect of Fluidized Bed Drying, Matrix Constituents and Structure on the Viability of Probiotic Lactobacillus paracasei ATCC 55544 during Storage at 4 °C, 25 °C and 37 °C.

Manju Gaare,Harjinder Singh,Arup Nag,Jon Palmer,Devastotra Poddar,Shantanu Das

doi:10.3390/microorganisms10010074

Abstract

The stabilization of probiotics for application in non-refrigerated food products is a challenging task. In the present study, probiotic Lactobacillus paracasei (Lacticaseibacillus paracasei) ATCC 55544 cells were immobilized in a dairy matrix comprising of whole milk powder, skim milk powder, or milk protein isolate using fluidized bed drying technology. The samples were taken out at different drying stages, with an apparent water activity (aw) of aw 0.5, aw 0.4, and aw 0.3, respectively, and vacuum-packed to maintain the aw and stored at three different temperatures of 4 °C, 25 °C, and 37 °C. The study evaluated the impact of matrix constituents, milk fat, protein, and carbohydrate on the viability of encapsulated probiotic L . paracasei ATCC 55544 during storage for 1 month. The whole milk powder matrix provided superior protection to the bacteria. Confocal Laser Scanning Microscopy (CLSM) was used to investigate the structure of the immobilizing matrix and the location of the probiotic L. paracasei cells embedded within the matrix. The CLSM study revealed that the probiotic bacterial cells are mostly embedded as clusters beneath the top layer. We hypothesize that the biofilm-like structure, together with the protective whole milk powder matrix, helps to retain the superior viability of probiotic cells during storage at non-refrigerated storage conditions of 25 °C and 37 °C.

Highlights

IntroductionProbiotics are live microorganisms that provide a health benefit to the host upon consumption [1]
Introduction published maps and institutional affilProbiotics are live microorganisms that provide a health benefit to the host upon consumption [1]
During a storage period of 4 weeks, a considerable loss in bacterial viability was observed; the sample stored at 37 ◦ C showed the most considerable loss, where an initial decline to 7.33 ± 0.09 log colony forming units (CFU)/g was observed during the 14 days

Summary

Introduction

Probiotics are live microorganisms that provide a health benefit to the host upon consumption [1]. Immunomodulation is one way by which a probiotic microorganism provides a health benefit to the host [2]. Consumers in post-COVID 19 pandemics are more interested in procuring immune-boosting food products due to commentaries from medical communities and World Health Organization (WHO), which has received widespread media coverage. Delivery of probiotics through non-refrigerated dry food products, for example, infant formula, malted beverage, or snack bars, may bridge this gap (consumer demand). The challenge lies in the loss of viability of probiotics during the shelf life of the food products [3,4], as to claim that food is a “probiotic”, there must be proof of delivery of viable strain(s) at an efficacious dose at the end of shelf-life [5].

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Discussion

Conclusion