Pear Pomace Valorization: Development and Comprehensive Quality Evaluation of a Beverage Fermented by Lactic Acid Bacteria

To achieve high-value utilization of pear pomace, this study systematically evaluated the effects of Lacticaseibacillus rhamnosus (Lr), Lactiplantibacillus plantarum (Lp), and Lactobacillus delbrueckii subsp. bulgaricus (Lb) on the comprehensive quality (physicochemical properties, active components, antioxidant activity, organic acids, and volatile flavor compounds) of fermented pear pomace beverages, aiming to select strains with excellent fermentation characteristics. The results demonstrated that fermentation effectively promoted the release and transformation of active substances in pear pomace, and significantly enhanced its antioxidant capacity. Lp demonstrated the best fermentation performance, reaching the stable growth phase at 24 h with a viable count of 5.45 × 10⁸ CFU/mL, significantly higher than Lr (1.16 × 10⁸ CFU/mL) and Lb (5.07 × 10⁸ CFU/mL) at the same time point (P < 0.05). Additionally, Lp exhibited significantly higher lactic acid production capacity compared with Lr and Lb. After 36 hours of fermentation, the superoxide dismutase (SOD) activity of Lp-fermented beverage reached 33.63 U/mL, significantly higher than that of Lr- (20.74 U/mL) and Lb-fermented beverages (25.63 U/mL) (P < 0.05), while no significant differences were observed in total phenolic and total flavonoid contents among the three beverages. A total of 63 volatile flavor compounds were identified during the fermentation process of pear pomace by the three lactic acid bacterial strains, characterized by an increase in the contents of alcohols, acids, and ketones, and a decrease in the content of aldehydes. After 36 hours of fermentation with Lp, the contents of alcohols, acids, and ketones increased 1.50-, 37.23-, and 8.43-fold, respectively, while the content of aldehydes decreased by 93.43%, resulting in enhanced flavor complexity of the product. To address the bottleneck of efficient utilization of insoluble dietary fiber (IDF) in the raw material, a combined pretreatment of high-pressure heat-moisture and multienzymatic hydrolysis (HPHM-CE) was applied, reducing the IDF content by 33.80% and increasing the reducing sugar content by 75.28%. Following this pretreatment, the total phenolics content, total flavonoids content, SOD activity, and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging capacity of the Lp-fermented product increased by 44%, 92%, 46%, and 39%, respectively. This study provides a reliable technical pathway and theoretical support for the high-value utilization of pear pomace and the development of high-quality fermented products.