Survival of Lactobacillus salivarius CECT 4063 and Stability of Antioxidant Compounds in Dried Apple Snacks as Affected by the Water Activity, the Addition of Trehalose and High Pressure Homogenization.

Cristina Gabriela Burca-Busaga,Noelia Betoret,Lucía Seguí,Ester Betoret,Cristina Barrera

doi:10.3390/microorganisms8081095

Abstract

Survival of probiotic microorganisms in dried foods is optimal for water activity (aw) values between 0.1 and 0.3. Encapsulating and adding low-molecular weight additives can enhance probiotic viability in intermediate aw food products, but the effectiveness of sub-lethal homogenization is still not proven. This study evaluates the effect of 10% (w/w) trehalose addition and/or 100 MPa homogenization on Lactobacillus salivarius CECT 4063 counts and antioxidant properties of apple slices dried to different water activity values (freeze-drying to a aw of 0.25 and air-drying at 40 °C to a aw of 0.35 and 0.45) during four-week storage. Optical and mechanical properties of dried samples were also analyzed. Freeze-drying had the least effect on the microbial counts and air drying at 40 °C to a aw of 0.35 had the greatest effect. Antioxidant properties improved with drying, especially with convective drying. Decreases in both microbial and antioxidant content during storage were favored in samples with higher water activity values. Adding trehalose improved cell survival during storage in samples with a water activity of 0.35, but 100 MPa homogenization increased the loss of viability in all cases. Air-dried samples became more translucent and reddish, rather rubbery and less crispy than freeze-dried ones.

Highlights

Functional foods are those that, beyond their nutritional value, benefit human health by improving it, and even reducing the incidence of certain diseases
According to everything discussed above, this study aims to evaluate the effect that the drying technique and the water activity reached by the dried product has on the survival of Lactobacillus salivarius spp. salivarius and the stability of antioxidant properties of apple-based probiotic snacks during four-week storage under controlled conditions
Lactobacillus salivarius spp. salivarius supplied by the Spanish Culture Type Collection was selected as a probiotic microorganism in this study due to its potential effect against the infection caused by Helicobacter pylori and its ability to adaptat to the apple solid matrix [8]

Summary

Introduction

Functional foods are those that, beyond their nutritional value, benefit human health by improving it, and even reducing the incidence of certain diseases. They indicate optimal water activity values to be between 0.1 and 0.3, at which water might interact with functional groups and block reaction sites, avoiding interaction with oxygen and oxidation reactions that cause degradation of lipids and proteins of the probiotic cell Reaching such low water activity values is not an easy task in the case of fruits, due to their relatively high soluble solids content. In such cases, encapsulation [16,18] or the addition of various low-molecular weight additives (inulin, gum arabic, trehalose, sucrose, maltodextrin, etc.) [12,14,17,19,20,21] have been reported to significantly enhance the probiotic viability in intermediate water activity food products. Other techniques, such as the application of sub-lethal homogenization pressures (20–100 MPa) were observed to increase the survival of probiotic strains in adverse conditions by inducing changes in the hydrophobicity of the cell membrane or in the availability of nutrients [22,23]

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