Antifungal effect of poly(lactic acid) films containing thymol and R-(-)-carvone against anthracnose pathogens isolated from avocado and citrus

- Poly(lactic acid) films were incorporated with thymol and R-(-)-carvone.
- The antifungal activity against anthracnose was studied at 12 and 25 °C.
- Thymol was generally more effective than R-(-)-carvone.
- Headspace vapor concentration was correlated to the reduction in mycelial growth.

Biodegradable antifungal films were developed to be used for controlling postharvest anthracnose pathogens. Two antifungal compounds, thymol and R-(-)-carvone, were incorporated into poly(lactic acid) (PLA)-based polymer at 10, 15 and 20% (w/w). Antifungal activity of the pure compounds and the antifungal films against Colletotrichum gloeosporioides isolated from avocado and citrus was evaluated at 12 and 25 °C using vapor diffusion assays. The results indicated that the colony diameter was affected by the vapor concentration of the antifungal compounds in the headspace. At 12 °C, 20% thymol showed complete growth reduction of avocado isolate, while at 25 °C, 15 and 20% thymol showed complete growth reduction of both avocado and citrus isolates. The PLA films incorporated with 15% R-(-)-carvone and 20% thymol were the most effective at 12 °C in suppressing the mycelial growth of the avocado and citrus C. gloeosporioides isolates, respectively, whereas the film incorporated with 20% thymol had the highest antifungal activity against both anthracnose isolates at 25 °C. The inhibitory effect of the antifungal films against anthracnose isolates was correlated to the vapor concentration of the antifungal compounds remaining in the headspace of the Petri dish. Antifungal packaging films can potentially be used to control postharvest pathogens of fresh produce.