Release of volatile compounds and biodegradability of active soy protein lignin blend films with added citronella essential oil

Active biodegradable bilayer films based on soy protein isolate, lignin and formaldehyde were developed. These films showed high water resistance and malleability, making them suitable for use in extreme environmental conditions. The presence of lignin in the formulation provided greater protection against light, especially UV. With the addition of 3% w/w citronella essential oil, the films showed good antifungal activity against Fusarium oxysporum pathogen microorganism in bananas. When the bananas were covered by the films during storage, there was a noticeable reduction in total aerobic mesophiles and moulds and yeasts. As the films aged (1, 3, 6 months), in both controlled and environmental conditions, the main active compounds in the citronella essential oil, citronellal and geraniol, were progressively released from the film matrix, citronellal more than geraniol. Over 30 days of soil degradation, the films lost around 30% of weight irrespective of the conditioning time.