Physical and antimicrobial properties of grape seed extract, nisin, and EDTA incorporated soy protein edible films

The physical and antimicrobial properties of soy protein isolate (SPI) films containing grape seed extract (GSE 1% w/w), nisin (10,000 IU/g). ethylenediaminetetraacetic acid (EDTA 0.16% w/w), and their combinations were evaluated. The incorporation of GSE significantly increased the thickness, puncture, and tensile strengths compared to the control film. The SPI film containing combinations of GSE, nisin, and EDTA had a thickness of 61.8 mu m and demonstrated 3.3 N puncture strength while the control film had 33.0 mu m thickness and 2.5 N puncture strength. Furthermore, the darkness of the film was increased in the presence of GSE as indicated by the lower L* (Lightness) values. The SPI film incorporated with the combined GSE, nisin, and EDTA demonstrated the greatest inhibitory activity against Listeria monocytogenes. Furthermore, the results showed that the SPI film containing GSE 1%. nisin 10,000 IU/g, and EDTA 0.16% was able to reduce Listeria monocytogenes populations by 2.9 log CFU/ml, while the population of Escherichia coli O157:H7 and Salmonella typhimurium were reduced by 1.8 and 0.6 log CFU/ml, respectively. This finding has potential applications to maintain shelf life, and improve safety of ready-to-eat food products. (C) 2008 Elsevier Ltd. All rights reserved.