Response Surface Optimization of Lipase‐Catalyzed Surface Esterification for Modification of Cassava Starch with Rosin Acid

Abstract

The rosin acid starch (RAS) is prepared under the catalysis of lipase, by esterification on the starch particles' surface in a two-phase reaction system, using rosin acid and native cassava starch as starting materials. The effects of reaction time, solvent types, substrate ratio, reaction temperature, and lipase dosage on the degree of substitution (DS) of RAS are investigated. Based on the single factor experiments, the reaction conditions are optimized according to the principle of the combination Box-behnken centered design and response surface methodology analysis. The mathematical model of the influence of reaction temperature, material ratio, and enzyme addition amount on DS is established. The optimum synthesis conditions are determined as follows: solvent, trichloromethane; reaction time, 10 h; reaction temperature, 59 °C; substrate ratio (mRosin acid:mstarch), 4.1; and lipase dosage, 264 µL. Under these conditions, it is found that the DS is 0.0608. The analysis of variance and verification experiments show that the mathematical model has good fit degree and high credibility. Compared with the native cassava starch, RAS has improved contact angle, emulsion capacity, and emulsion stability.