Multiple Response Optimization of Poly(vinyl alcohol)/Starch Based Bioactive Composite Films for Antimicrobial Packaging Applications

In this work, the incorporation of additives i.e. glycerol, citric acid and zinc oxide at four-levels into poly(vinyl alcohol)/starch (PSt) films containing extracted spent coffee ground (ex-SCG) was designed and optimized using Taguchi method combined with Grey relational analysis. Citric acid was the most significant parameter affecting the antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Addition of glycerol in PSt films enhanced water resistance and biodegradability of the samples, but decreased their tensile strength and modulus values. The presence of ZnO increased the tensile strength of PSt films. The Grey relational analysis showed that the optimal mix proportion for PSt film could be achieved at 10 wt% glycerol, 45 wt% citric acid and 1 wt% ZnO. The PSt films based on the optimized mix proportion of additives were used as packaging for fresh cherry tomatoes. The films remarkably inhibited growth of bacteria and maintained freshness of the packaged cherry tomatoes. Based on the finding in this work, experimentally made PSt films could have a potential for food preservation and antimicrobial packaging applications to enhance the quality and to extend the shelf-life of fresh fruits and vegetables.