Optimization of acetylated starch films from purple sweet potato: effect of glycerol, carboxymethylcellulose, and stearic acid

Abstract

The objective of this study was to ascertain the optimal additive conditions to develop a film from an alternative source of modified starch, using the response surface methodology. The central composite design + points used factors to evaluate the effect of the independent variables (glycerol concentration: 0.3, 0.35, and 0.40 g g ^−1 starch; carboxymethylcellulose: 0.5, 0.75 and 1 g/5 g starch; stearic acid 0.025, 0.05, and 0.075 g/5 g starch) on the response variables (solubility, swelling, opacity, luminosity, tensile strength, elongation, water vapor permeability, and water activity). A simultaneous optimization was achieved using concentrations of glycerol 0.30 g g ^−1 starch, CMC 0.32 g/5 g starch, and stearic acid 0.007 g/5 g starch, which generated interesting properties validated through experimentation. Therefore, an ecological film was obtained that can be considered for food coating because it presented a low permeability to water vapor (0.0055 g ms ^−1 MPa ^−1 ), a high percentage of elongation (91%), and a decrease in solubility (23%). This will also allow the incorporation of other compounds such as antioxidants, reinforcements, and sensors with favorable results, and with a positive perspective on the use of alternative sources of starch.

Keywords

• sweet purple potato
• starch
• acetylation
• films