Enhancing the quality of blueberry pomace juice through fermentation with high-γ-aminobutyric acid-producing lactic acid bacteria

The blueberry processing industry generates nutrient-rich pomace, a byproduct whose disposal poses environmental concerns and causes loss of valuable bioactive compounds. This study aimed to develop a functional beverage by fermenting blueberry pomace juice with a high gamma-aminobutyric acid (GABA)-producing lactic acid bacteria (LAB) strain and to evaluate the resulting functional and sensory properties. A potent GABA-producing strain, Lactobacillus pentosus LAB-2, was isolated from 92 LAB isolates and selected based on its exceptional GABA synthesis capacity (5.02 ± 0.09 mg/mL), probiotic characteristics, and safety profile. Fermentation of blueberry pomace juice with this strain was carried out at 37 °C for 48 h, which significantly enhanced the nutritional and sensory attributes of the product. Specifically, the GABA content increased to 1.88 ± 0.02 mg/mL. Total phenolic content and antioxidant capacity were elevated, and metabolomic analysis revealed the generation of beneficial amino acids, such as cysteine. Furthermore, volatile compound profiling showed an improved aroma profile characterized by pronounced caramel and fruity notes. These findings demonstrate that targeted fermentation with a selected starter strain can effectively upcycle blueberry pomace, simultaneously improving its functionality and sensory acceptability. This approach supports the valorization of food processing byproducts into a promising commercial functional beverage.