Characterisation, physicochemical kinetics, and assay studies of an innovative Moringa-oleifera chitosan edible biopreservative for tomato self-life extension

Abstract

The work focused on explicating the potency of Moringa oleifera leaf extracts (MOLE) and chitosan edible bio-preservative (MOCEB) in shelf-life of tomato fruits. MOLE was extracted using 95% food grade ethanol at a dosage ratio of 5% (w/v) and $$\:{50}^{\:\text{o}}\text{C}$$ for 12 h, while MOCEB was formed by mixing different concentrations of chitosan solution (0.5% 1%, 1.5%, 2%, 2.5%) at $$\:{40}^{\:\text{o}}\text{C}$$ under constant stirring (500 rpm) for 2 h. FTIR of MOCEB revealed the presence of imines (C = N, 1661.8 $$\:{\text{c}\text{m}}^{\:-1}$$), authenticating cross-linking reaction between -NH2 of chitosan and carbonyl groups of MOLE. Hydrocarbon and phytochemical characterization indicated that MOLE contained significant amounts of antimicrobial hydrocarbons (Pentadecane, 18.46%; Tridecane, 12.386%; Heptacosane, 12.013%). MOCEB was found to contain notable antioxidants including quercetin (10.265%). After 20 days of non-refrigerated storage (1% chitosan conc. and MOCEB ratio of 40:60), tomato fruit maintained 2.33 g/kg titratable acidity (TA), and, weight loss of 9.86%. Zero-order (0.9797 ≤ R2≤0.9815) and first order (0.8941 ≤ R2 ≤ 0.9417) models were superior in describing the bio-preservation process at optimum chitosan conc. and MOCEB mixing ratio, respectively. Assay studies showed the efficacy of MOCEB biofilm in antagonizing the growth of gram-positive (rA = 7.93 mm) and gram-negative (rA = 7.73 mm) bacteria, and authenticating the anti-oxidant activity (DPPH = 71% and FRAP = 0.62). The effectiveness of MOCEB was further demonstrated by sensory assessment, which tracked changes in texture, flavor, color, smell, and appearance. Our results demonstrated that MOCEB biofilm can be employed to significantly reduce post-harvest losses of tomato fruits.