Effects of volatile compounds in apple juices on fungal growth and patulin production of Penicillium expansum

Penicillium expansum was cultured in apple juice media prepared from six different commercial apple juices. The patulin production was profoundly affected by the differences in apple juices, whereas fungal growth was generally not. The maximum concentration of patulin was 7 .3-fold of that in the media containing minimum concentration of patulin. The six apple juices were concentrated by evaporation and reconstructed to the original volumes by adding Milli-Q water. P. expansum was cultured in the media prepared from reconstructed apple juices, and the patulin concentration and fungal growth were determined. Evaporation of apple juice tended to decrease patulin production and to increase fungal growth, suggesting that the volatile compounds promote patulin production and inhibit fungal growth. The volatile compounds in the apple juice were then analyzed by GC-MS. The 13 compounds of which concentrations were largely decreased by evaporation were selected for evaluation of their stimulation of patulin production. Seven out of the 13 compounds, 2-methylpropyl acetate, ethyl butyrate, ethyl 2-methylbutanoate, 3-methyl-1-butanol, hexyl acetate, 1-hexanol, and 2-methylbutanoic acid, increased the patulin production of P. expansum concentration-dependently; 2-methylbutanoic acid and its ethyl ester were highly effective. Our results indicated that the composition of volatile compounds in apple juice media largely affects the patulin production and the growth of P. expansum.