Optimization of Blanching Time, Sodium Metabisulphite (Na 2 S2O5 ) Concentration and Processing Time on Vitamin C Content, Microbial Quality and Sensory Characteristics during Canning of Green Pepper (Capsicum sinensis) Using Response Surface Methodology

Abstract

Response surface methodology and central composite rotatable design (CCRD) for K = 3 were used to investigate the combined effect of blanching time (0-1 min), processing time (10-30 min) and sodium metabisulphite (Na 2S2O5) salt concentration (0%-2%) on vitamin C content, hardness (texture), microbial count and color intensity of green pepper (Capsicum sinensis) during canning. Blanching, processing time and sodium metabisulphite (Na 2S2O5) salt concentration all had variable effects on the vitamin C, microbial quality and sensory characteristics of the canned green peppers. Significant (P < 0.05) interactions were noted between all the factors with high regression coefficients (78.7%-97.0%). Increasing processing time caused significant decreases in vitamin C and microbial load of the product. However, salt concentration had only marginal and insignificant effect on the vitamin C content of the canned product. Sensory evaluation on the product showed that both the pre-processing conditions and of blanching and salt concentrations, and the processing time had varied effects on the color and hardness of the products. Hardness of the canned products generally decreased with increasing processing time and blanching time, while only minimal and insignificant effects were noted with blanching time. Increasing blanching time caused significant increasing retention of the dark green color of the peppers with only slight but insignificant increases noted with processing time, while increases in salt concentration consistently reduced the dark green color of the products. The optimum pre-processing and processing conditions that yielded products with high preference and consumer-acceptability were: blanching time of 0 min, processing time of 10 min and sodium metabisulphite concentration of 0.2%.