Controlled release of Michelia alba oil vapour from plastic sachets to control the growth of Aspergillus flavus on brown rice and its possible mode of action

This study aimed to create antifungal volatile-releasing sachets, from various commercially available synthetics (Tyvek®; high density polyethylene; HDPE, polypropylene/polyethylene; PP/PE and polyamide/polyethylene; PA/PE) and bio-based plastic sachet materials (Polylactic acid; PLA and cellophane), containing Michelia alba (MA) essential oil to be used against A. flavus on malt extract agar (MEA) and brown rice. In addition, the bioactive compounds (total phenolic content and total flavonoid content) and antioxidant activity (DPPH, ABTS, and FRAP) of brown rice after treatment by the active sachets were examined. Results indicated that different sachet materials affected the release of the linalool and caryophyllene as antifungal volatiles. Tyvek® and PP/PE had a suitable permeability for controlling the release of the volatiles, which could be matched with the maximum concentration within 48 h, whereas PA/PE, PLA and cellophane had lower permeability. The antifungal volatiles released from Tyvek® and PP/PE sachets containing MA essential oil at 300 μl could completely inhibit the growth of A. flavus on MEA and brown rice for at least 20 days using accelerated conditions at 25 °C and 80%RH. No spore germination or deformed hyphae of A. flavus could be observed in the treated brown rice when compared to the control which showed swelling spores and regular structure with uniformity. In addition, the bioactive compounds and antioxidant activity of brown rice treated with MA essential oil in the Tyvek® and PP/PE sachets were higher than in the control. Therefore, this study demonstrates a good opportunity to implement antifungal volatile-releasing sachets containing MA for shelf-life extension and improving the antioxidant activity of brown rice.