Optimization of Extraction Process of Valonia Tannins and Its Kinetics and Thermodynamics
Using valonia shell powder as raw material,industrial cellulose composite enzymes were used to assist in the extraction of valonia tannins.Based on single factor experiments,the extraction process were optimized by response surface methodology,and the corresponding kinetics and thermodynamic models during the aqueous enzymatic extraction process were further studied.The results showed that the optimal extraction conditions for valonia tannins was pH of 5.0,valonia shell powder of 1.00 g,solid-liquid ratio of 1∶50(g∶mL),extraction time of 27.7 min,extraction temperature of 55℃,the enzyme dosage was 1.9%of the weight of valonia shell powder.Under these conditions,the tannin extraction rate was 97.56%.Under these optimized conditions,when the mass of raw materials was magnified to90 g,the extraction rate of tannin still reached97.3%.The tannin content in the extract was 55.0%,the total polysaccharide mass fraction was 5.16%,and the total flavonoid mass fraction was 2.95%.In addition,the kinetic and thermodynamic studies showed that the tannin extraction process conformed to the Fick'second law.In the range of 293-353 K,the rate constant(k)was0.122 0-0.259 6 min-1,the apparent activation energy(Ea)was 10.683 kJ/mol,and the pre-exponential factor(A)was 9.6.During the extraction process,the enthalpy change(ΔH)was 28.584 kJ/mol,the entropy change(ΔS)was 110.576 J/(mol·K),Gibbs free energy change(ΔG)was-8.652--4.074 kJ/mol,indicating that the extraction process could proceed spontaneously and increasing the temperature was beneficial for the extraction of valonia tannins.
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