Ferulic acid application to control growth Listeria monocytogenes and Salmonella enterica on fresh-cut apples and melon, and its effect in quality parameters

Abstract

Listeria monocytogenes can grow under conditions at which fresh-cut fruit are stored, whereas Salmonella spp. has been associated with a number of outbreaks related to such products. It is therefore necessary to find products capable of reducing microbial counts while maintaining quality of the product. In this regard, ferulic acid (FA) has shown antimicrobial, antioxidant and many physiological functions in humans. This study aimed to test the efficacy of FA in fresh-cut apple and melon in two ways: (a) to prevent pathogenic growth and (b) to maintain fruit quality during storage, maintaining color and preventing enzymatic browning. For this purpose, L. monocytogenes (3 strains) and S. enterica (4 strains) were inoculated in both fruits. FA at concentrations ranging from 2.5–15 g L−1 were tested against individual strains and the results showed that FA did not have any bactericidal effect after application. FA effect was observed at the end of the storage (7 d, 10 °C) with higher effect against L. monocytogenes (averaging 4.2 ± 0.7 log CFU g−1) than against S. enterica (averaging 1.9 ± 1.3 log CFU g−1). The reductions were significantly different from the samples without FA, but significant differences were not found among the 3 tested concentrations. Comparison between immersion and spray applications of FA revealed that immersion was the best method. When the effect of the selected FA dose on quality was evaluated, we found that FA did not prevent the increase of browning index in apples. However, melon treated samples did not overcome significant color changes during storage at 4 °C. FA did not inhibit the growth of total aerobic mesophylls and yeasts and molds, but maintained overall quality of the fruits, including pH, total soluble solids and titratable acidity. Overall, FA could be used in fresh-cut apple and melon to prevent growth of L. monocytogenes without affecting physicochemical quality, delivering a product with increased antioxidant activity and providing a new source of FA (0.25 ± 0.04 g kg-1 of apple, and 1.22 ± 0.07 g kg−1 of melon, dry weight basis).