Enzymatic catalytic dynamics of lactic-acetic acid co-fermentation: Effect of cellulase on the physicochemical, phytochemicals, volatiles, and antioxidant activity of jujube puree extracts

Abstract

The processing of jujube (Ziziphus jujuba) is imperative due to its esteemed status and rich pharmacological properties despite its sensory challenges and short shelf-life. Traditional drying methods preserve jujube quality but complicate bioactive compound extraction due to the conjugated polysaccharide matrix. This study addresses the gap in research on enzymatic pretreatment by investigating the use of cellulases to break down the rigid cellulose structure, thus enhancing the efficiency of subsequent fermentation processes. Besides, this research explored the catalytic dynamics of cellulase pretreatment in lactic-acetic acid co-fermentation to improve jujube puree's functional and quality properties. Methodologies involved applying cellulase at concentrations of 1 %, 3 %, and 5 % (v/v) at 40 °C for 4 hours, followed by fermentation with Lactobacillus plantarum CGMCC 3346 and Acetobacter pasteurianus (Ap CICC 20001, CGMCC 1.41). Results indicated that fermentation and enzyme hydrolysis significantly influenced jujube puree's physicochemical and sensory attributes. Fermentation increased densities and moisture content, while unfermented and enzyme-treated samples had higher total soluble solids (TSS) values (11.00–11.50 °Brix). Enzyme concentration affected the reducing sugar and protein content, with higher enzyme concentrations (5 %EF) producing lighter products (L* = 52.00). Total phenolic content increased with fermentation, particularly in the 3 %EF treatment (351.89 mg GAE/100 g FW), while flavonoid and flavonol contents peaked in the 5 %EF (426.33 mg RE/100 g FW) and 3 %EF (25.80 mg QE/100 g FW) treatments, respectively. Proanthocyanidin content was highest at moderate enzyme concentrations, notably in the 3 %EF treatment (715.95 mg CE/100 g FW). Fermentation also enhanced antioxidant properties and altered flavor profiles by decreasing acetoin levels and increasing acid and ester production. This study highlights the significance of the combinative effect of enzyme concentration and fermentation processes in augmenting jujube puree extracts' nutritional and sensory qualities.