Fermentation of Dendrobium officinale juice using lactic acid bacteria and evaluation of its antioxidant and structural properties.

This study investigated the effects of mono- and co-culture lactic acid bacteria (LAB) fermentation on the antioxidant capacity, structural properties and aroma of Dendrobium officinale juice. Fermentation was performed using Lactiplantibacillus plantarum (LP), Lacticaseibacillus paracasei (LPC) and Lactobacillus helveticus (LH) individually and in binary combinations (LP-LPC, LP-LH and LPC-LH). An integrated analytical approach, including total phenolic content (TPC), total flavonoid content (TFC), 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging assays, Headspace solid-phase microextraction coupled to gas chromatography-mass spectrometry HS-SPME-GC/MS, electronic nose (E-nose), ATR-FTIR, X-ray diffraction (XRD) and confocal laser scanning microscopy (CLSM), was applied to evaluate fermentation-induced modifications. LAB fermentation significantly enhanced antioxidant properties in a specie-dependent manner (p < 0.05). LPC-LH co-culture (D6) exhibited the highest TPC (492.38 mg GAE/mL) and TFC (545.78 mg QE/mL), representing nearly five-fold and four-fold increases, respectively, Compared with the control. Furthermore, D6 showed the strongest DPPH (72.58%) and ABTS (84.44%) radical scavenging activities. Gas chromatography-mass spectrometry (GC-MS) analysis revealed substantial volatile reconfiguration, characterized by increased organic acids, glycerol and nitrogen-containing metabolites, particularly in co-culture systems. Electronic Nose PCA explained 94.45% of total variance, clearly distinguishing treatments (p < 0.05). Structural analyses demonstrated significant protein conformational changes and increased semi-crystallinity in mixed cultures, while Confocal Laser Scanning Microscope (CLSM) confirmed extensive matrix disruption and enhanced porosity. The investigation underscores the potential of LAB, particularly in co-culture systems, to optimize the nutritional properties of D. officinale juice, paving the way for its development as a functional fermented beverage.