Optimization of Technology for Preparation of Mulberry Leaf Protein by Fermentation and Determination of in Vitro Digestibility of the Prepared Product
In order to develop and utilize the resources of mulberry leaf protein, protein product was prepared by using Bacillus subtilis fermentation method. Taking yield of mulberry leaf protein as response value, the conditions for mulberry leaf fermentation were optimized through Plackett-Burman, steepest ascent experiment and Box-Behnken experimental design, and in vitro digestibility of mulberry leaf protein after fermentation was evaluated. The results showed that mulberry leaf powder mass concentration, loading volume, sucrose mass concentration and fermentation time had significant influence on yield of mulberry leaf protein (P <0. 05). The influence of each factor on yield of mulberry leaf protein was in the order of mulberry leaf powder mass concentration > loading volume >sucrose mass concentration >fermentation time.The optimized fermentation conditions were as follows: mass concentration of mul- berry leaf powder 2.64 mg/mL, loading volume 105 mt_, mass concentration of sucrose 22 mg/mL, and fermentation time 45. 1 h. Under these optimal conditions, the yield of mulberry leaf protein was 16.43% in theory, and the actual value was 16. 29%. The result was reproducible and the established mathematical regression model for yield of mulberry leaf protein and major factors of fermentation condition werereliable. Digestion experiment showed that the in vitro digestibility of mulberry leaf protein after fermentation was significantly increased (P<0. 05), being 4. 29 percentage points higher than that before fermentation.
Mulberry leafProteinFermentationTechnological conditionPlackett-Burman experimentBox-Behnken experimentDigestion in vitro
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