Thermal Reaction Optimization for Production of Edible Spice from Enzymatic Hydrolysate of Ziziphus jujuba
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Abstract:
The thermal reaction between the enzymatic hydrolysate of Ziziphus jujuba and caramelized glucose liquid was used for spice production. The enzymatic hydrolysis conditions for Z. jujuba were optimized through single-factor experiments. The concentrated enzymatic hydrolysate of Z. jujuba was then mixed with caramelized glucose liquid for thermal reactions. The optimal process was determined through single-factor experiments and response surface experiments, using sensory evaluation scores as indicators. The effects of factors including reaction time, temperature, initial pH, and solidto-liquid ratio (concentrated hydrolysate to caramelized glucose) on the quality of the spice were evaluated. The product’s browning index, volatile composition, and antibacterial and antioxidant properties were measured. The optimal enzymatic hydrolysis conditions for Z. jujuba were as follows: mass fraction of enzyme mixture 0.28%, hydrolysis time 4.0 h, and temperature 45 ℃. The browning index increased as the reaction time, temperature, and initial pH value increased. However, the browning index first decreased and then slightly rose with increasing solid-to-liquid ratio. Notably, the browning index did not directly correlate with the sensory evaluation results. The optimal preparation process for Z. jujuba spice was: solidto-liquid ratio 3.1:1, reaction time 58 min, reaction temperature 139 ℃, and initial pH 6.0. The Z. jujuba spice contained 54 volatile components with a total content of 1 122.54 μg/mL. In particular, furfural, furfuryl alcohol, and 5-methylfuranal contributed to caramel, sweet, and other aromas. The DPPH radical scavenging rate of Z. jujuba spice at a concentration of 10 mg/mL was 74.70%. Moreover, the Z. jujuba spice exhibited antibacterial effects against Pseudomonas aeruginosa; however, these were weaker than those of streptomycin. These results provide scientific evidence to support the development, application, and high-value utilization of Z. jujuba spice.
