Impact of bioactive packaging systems based on EVOH films and essential oils in the control of aflatoxigenic fungi and aflatoxin production in maize

Aspergillus flavus and A. parasiticus are the most common fungal species associated with aflatoxin (AF) contamination of cereals, especially maize, and other agricultural commodities. AFB1, the most frequent and toxic metabolite, is a powerful hepatotoxic, teratogenic and mutagenic compound. Effective strategies to control these fungal species and AFs in food and feed are required. Active packaging film containing essential oils (EO) is one of the most innovative food packaging concepts. In this study, ethylene-vinyl alcohol (EVOH) copolymer films incorporating EO from Origanum vulgare (ORE), Cinnamomum zeylanicum (CIN) or their major active constituents, carvacrol (CAR) and cinnamaldehyde (CINHO), respectively, were developed and assayed to control growth of A. flavus and A. parasiticus and AF production in maize grains under different aw and temperature regimens. EO doses assayed in cultures were in the range 0.25–4.0 mg/Petri dish. The factors aw, temperature, type of EVOH-EO film and fungal species significantly influenced the ED50 values of all assayed films. Growth rate (GR) of both species was usually higher at 0.99 than at 0.96 aw and at 37 °C than at 25 °C. However, the contrary was found with regard to AF production. The order of efficacy of EVOH-EO films to control growth of both species and AF production was EVOH-CINHO > EVOH-CAR > EVOH-ORE > EVOH-CIN. The effective dose (ED50) (mg EO/plate) for EVOH-CINHO and EVOH-CIN films against A. flavus were in the ranges of 0.125 and 2.475–3.500 and against A. parasiticus in the ranges of 0.121–0.133 and 2.275–3.625, respectively. Under the assayed conditions, the ED90 for EVOH-CINHO film were 0.22–0.23 mg/plate for both species. It was the most effective bioactive film to control fungal growth (vapour phase) and AF production, regardless of aw and temperature. This is the first study about the impact that interacting environmental conditions and bioactive EVOH-CINHO, EVOH-ORE, EVOH-CIN EVOH-CAR films have on the growth of aflatoxigenic fungi and on AF production in maize grains.
The authors acknowledge financial support from FEDER and Ministry of Economy and Competitiveness (MINECO, Spanish Government) (Project AGL2014-53928-C2-1-R). E.M. Mateo is grateful to “Generalitat Valenciana” for financial support (APOSTD/2016/102) and J.V. Gómez is grateful to FEDER and MINECO for a PhD contract (BES-2015-071242).