Comparative Analysis of Quality Attributes and Flavor Profiles of Broccoli (Brassica oleracea var. italica) Stalk and Floret Juices Fermented by Limosilactobacillus reuteri

This study compared the physicochemical properties, nutritional composition, and flavor characteristics of broccoli stalk and floret juices fermented with Limosilactobacillus reuteri 18 (Lr18) to enhance the valorization of broccoli processing by-products. Four sample groups were analyzed: non-fermented stalks, fermented stalks, non-fermented florets, and fermented florets. After 48 h of fermentation, total viable counts and total phenolic content were slightly higher in florets than in stalks. Total titratable acids, total sugars, total soluble solids (TSS), total flavonoids, and vitamin C were initially higher in florets but decreased after fermentation in both groups. Organic acid analysis revealed that fermentation increased citric acid, reduced oxalic acid, and promoted the conversion of malic acid to lactic acid. Stalks contained higher levels of lactic and malic acids but lower citric acid than florets. Tryptophan content was higher in florets and was partially converted to indole derivatives after fermentation. Volatile compound analysis and sensory evaluation indicated that fermentation reduced fruity notes in florets while increasing acidic and sulfurous notes. In contrast, fermentation enhanced fruity and rounded notes in stalks while reducing pungency. These findings provide a scientific basis for developing fermented vegetable products with improved functional and sensory properties, particularly using broccoli stalks as a valuable by-product.