Sodium alginate-cinnamon essential oil coated apples and pears: Variability of Aspergillus carbonarius growth and ochratoxin A production

The scope of the present study was to use selected fruits as model foods (wounded skin or slices of apples and pears), for the in situ assessment of the potential of natural antimicrobials to control fungal growth and OTA production and the investigation of alternative ways of their application, e.g., via edible coatings. Fresh fruits were cut: i) in halves or ii) across in round slices of ca. 1 cm thickness. Wounds were introduced into the skin and the center of the slice (5 mm deep; 4 mm diameter) and inoculated with a range of 2.0-7.5 x 10(3 )spores per wound of Aspergillus carbonarius. Following inoculation, samples were coated with Na - alginate supplemented with 0.3 (0.3% ECC) and 0.9% v/v (0.9% ECC) cinnamon EO. Inoculated samples without edible coating and EO (C) or with edible coating and without EO (EC) were used as negative or positive controls, respectively. All samples were stored under aerobic conditions at 15, 20, and 25 degrees C. Fungal growth was estimated by colony diameter measurements (n = 30), while OTA production was determined by HPLC (n = 4). Antimicrobial treatment with 0.9% EO was more effective on fungal growth when the inoculation took place on slices than in wounded skin (p < .05), regardless of storage temperature and fruit. The variability of pmax increased with EO concentration, except for the coated slices of apples with 0.9% v/v EO (at all temperatures), or pears with 0.3% and 0.9% v/v EO (at 15 and 20 degrees C), where no growth was observed. OTA was below the detection limit (1 ppb) on the majority of 0.9% ECC apples slices and in 0.3% ECC and 0.9% ECC pears slices, stored at 20 and 25 degrees C. However, the sample to sample variation in the produced amounts of OTA was remarkable. Thus, considering that inhibition of growth and toxin production do not always concur, the present study provided quantitative information on the variability in A. carbonarius growth and OTA production in real model foods in response to antimicrobial coating with natural active compounds. Such data could be of relevance to risk assessment and assist in designing effective control strategies for limiting OTA levels in foods and thus, protecting consumer health.