This study determined the favourable fermentation conditions for the production of antifungal peptides from kenaf seeds and their effectiveness in extending the shelf-life of tomato puree. The optimum fermentation conditions for the maximum activity of the antifungal peptides were 8.4% (w/v), 7 days and 3.7% for substrate/water ratio, fermentation time and glucose concentration, respectively. Eight cationic peptides of low molecular weight ranging from 840 to 1876 Da were identified in kenaf seed peptides mixture (KSPM). The minimum inhibitory concentration and minimum fungicidal concentration of KSPM against Fusarium sp. were 0.18 mg/mL and 0.70 mg/mL, respectively, while those for Aspergillus niger were 1.41 mg/mL and 2.81 mg/mL respectively. KSPM exhibited a fungicidal effect and a prolonged lag phase, with increased fungal membrane permeability as the concentration of KSPM increased, as evidenced by the release of intracellular constituents. The treatment of tomato puree with 1000 mg/kg KSPM delayed fungal growth for up to 14 and 23 days at 25 °C and 4 °C respectively, significantly reducing Aspergillus niger and Fusarium sp. counts. In conclusion, kenaf seed peptides prepared by lacto-fermentation possess antifungal activity, hence can be applied as natural bio preservatives to extend the shelf-life of food products such as tomato puree.
Rice bran protein concentrates (RBPC) were extracted using mild alkaline solvents (pH: 8, 9, 10). The physicochemical, thermal, functional, and structural aspects of freeze-drying (FD) and spray-drying (SD) were compared. FD and SD of RBPC had porous and grooved surfaces, with FD having non-collapsed plates and SD being spherical. Alkaline extraction increases FD's protein concentration and browning, whereas SD inhibits browning. According to amino acid profiling, RBPC-FD9's extraction optimizes and preserves amino acids. A tremendous particle size difference was prominent in FD, thermally stable at a minimal maximum of 92 °C. Increased pH extraction gives FD greater exposal surface hydrophobicity and positively relates to denaturation enthalpy. Mild pH extraction and drying significantly impacted solubility, improved emulsion properties, and foaming properties of RBPC as observed in acidic, neutral, and alkaline environments. RBPC-FD9 and RBPC-SD10 extracts exhibit outstanding foaming and emulsion activity in all pH conditions, respectively. Appropriate drying selection, RBPC-FD or SD potentially employed as foaming/emulsifier agent or meat analog.