Ultrasound-assisted probiotics fermentation suspension treatment under mild heat to improve the storage quality of freshly cut lotus root

Abstract

Ultrasound-assisted probiotic fermentation suspension treatment under mild heat was applied to freshly cut lotus root. Combined treatment significantly (p < 0.05) improved the bactericidal effect: S. aureus, E. coli O157:H7, A. flavus spores, and yeast were completely killed at 55℃ for 6 min, morphological and structural changes of cells were observed. Combined treatment inhibited enzymatic browning via decreasing the activities of PPO, POD, PAL, and decreasing TPC, soluble quinone content. The decrease of external resistance, capacitance and the increase of internal resistance reflected the loss of structural integrity of cells after combined treatment. For combined treatment samples, no obvious color change was observed during 12 days of storage but weight loss rate, total acid increased significantly (p < 0.05) and hardness decreased, the shelf life was extended to 12 d. Ultrasound-assisted probiotic fermentation suspension treatment under mild heat had the dual effects of sterilization and inhibition of browning.

Keywords: Freshly cut lotus root; Mild heat; Probiotics fermentation suspension; Storage quality; Ultrasound.