Purpose: To evaluate the effect of sodium alginate coatings with or without cinnamon essential oil (EO) on Aspergillus carbonarius growth and OTA production on apples and pears.
Methods: Fresh apples and pears were intentionally wounded (0.5 cm) on the skin. Additional fruits were cut in slices (1 cm). Aliquots of A. carbonarius spore suspensions were added in the wounds (102 spores/g) or deposit on slices. Fruits were coated with sodium alginate (3% w/v) without (EF) or with EO of cinnamon at 0.3% (0.3 EFC) and 0.9% v/v (0.9 EFC) or left uncoated (C). Samples were stored at 15, 20 and 25 °C. Fungal growth was estimated by colony diameter measurements (n=20) and spores density (log spores/g) on MEA. Total viable counts (n=4) were enumerated on PCA. OTA production was determined by HPLC.
Results: EO was more effective in delaying growth of A. carbonarius at lower temperatures. 0.9% of cinnamon was more effective against fungus on slices than on skin, causing 100% inhibition of growth and OTA production on both fruits. However this treatment caused flesh browning. On pears, 0.3 EFC also prevented appearance of visible mycelium and OTA production. EF did not significantly influence A. carbonarius growth on skin and slices. However, slices with EF showed ca 3-fold higher OTA compared to controls at 20 and 25 °C. At 15 °C, OTA production followed the order C> EF> 0.3 EFC> 0.9 EFC. Higher amounts of OTA were observed on slices than on skin; for instance, at 20 °C average OTA amounts of 3 ppm was produced on pears slices, while 1.5 ppm on skin. Fungal growth was more extensive and OTA concentration was higher on pears compared to apples.
Significance: Edible coatings containing cinnamon may assist to control fungal growth and OTA production on fresh fruits.