Optimization of Mixed Lactic Acid Bacteria Fermentation and Its Effects on Quality of Fresh-Cut Shredded Potatoes

Mechanical damage readily induces browning and flavor deterioration in fresh-cut shredded potatoes (FCSPs). This study applied mixed lactic acid bacteria (LAB) fermentation to improve the comprehensive quality of FCSP. A mixed fermentation system was established using Lactiplantibacillus plantarum ZYN-09 and Lacticaseibacillus rhamnosus ZYN-08, two strains isolated from naturally fermented shredded potatoes. Single-factor tests, Plackett–Burman screening, and central composite design (CCD) response surface methodology were combined to optimize the fermentation process. Under optimized conditions, antioxidant activity, key browning-related enzyme activities, and flavor components were determined to evaluate the quality changes induced by fermentation. The results showed that the optimal fermentation parameters were fermentation time of 42 h, temperature of 36 °C, inoculum size of 3.6% (v/v), strain ratio of 2:1 (v/v), and salt added amount of 2% (w/v). Under these conditions, the hardness of FCSP reached 4901.77 N with a sensory evaluation score of 92.08. Mixed LAB fermentation significantly enhanced the scavenging capacities against DPPH, ABTS+, and ·OH free radicals as well as Fe2+ chelating activity. It retarded browning by inhibiting polyphenol oxidase (PPO) and peroxidase (POD) activities and malondialdehyde (MDA) accumulation while increasing phenylalanine ammonialyase (PAL) activity. Meanwhile, it reconstructed the volatile flavor system and optimized flavor composition. In conclusion, this controlled mixed LAB fermentation technique can simultaneously improve texture, sensory attributes, antioxidant capacity, anti-browning performance and flavor quality of FCSP. This work provides technical support and theoretical basis for green preservation and quality regulation of fresh-cut potatoes.