Impacts of ohmic-heating on the surface characteristics, membrane integrity, morphology, and chemical compounds of Bifidobacterium animalis paraprobiotic

Abstract

The aim of this paper was to obtain paraprobiotic from Bifidobacterium animalis subsp. lactis Bb-12 (BB) with a promising ohmic-heating (OH) condition through response surface modeling, based on the flow cytometry and spectrophotometry analyses. Some properties of the obtained BB paraprobiotic (BBP) were studied, including the cell surface hydrophobicity (CSH), cell auto- and co-aggregation (CAA and CCA), and membrane integrity (MI). Among fitted models, the linear model was more accurate for co-aggregation (R2-pred 85.77%), and the quadratic model for CSH (R2-pred: 84.17%), auto-aggregation (R2-pred=87.25%), MI (R2-pred: 83.65%). The electric field (EF) had the most destructive effect on the MI of BBP. However, OH temperature had the most enhancing effect on the surface characteristics. The surface characteristics of BBP (CSH: 44.82, CAA: 38.05, and CCA: 40.79) obtained by the OH process at optimum condition was remarkably more than BB without OH treatment (CSH: 34.21, CAA: 27.18, and CCA: 28.5). The confirming analysis regarding the MI changes was performed successfully by scanning electron microscopy analysis. Lactic and acetic acids were the most amounts of characterized metabolites in BBP and BB. The OH condition, including EF of 8 V/cm, OH temperature of 88˚C, BB population of 8 (log CFU/mL), and OH time of 3 min, were considered optimum condition. At this optimum OH condition, the responses for CSH, CAA, CCA, and MI were observed 44.82, 38.05, 40.79, and 94.82 %, respectively.