Effects of apple and pear varieties and pH on patulin accumulation by Penicillium expansum

BACKGROUND: Accumulation of patulin in apples and pears and subsequently in their by‐products is caused mostly by Penicillium expansum which causes blue mould. Fruit pH and other parameters are sometimes characteristic of a certain variety and thus the use of particular varieties might affect patulin content in the final products. The aim of this study was to evaluate the influence of fruit variety and pH on patulin accumulation. Patulin accumulation in both apple and pear juices at different pH and also in different apple varieties (Golden, Gala and Fuji) and pear varieties (Blanquilla and Conference) was assessed. RESULTS: The pH of juices significantly influenced patulin accumulation, especially in apple juice in which the highest amounts of patulin were detected at pH 3.5. In fruits, the pH values of the substrate were determinant only under cold storage. Thus, Golden apples, which presented a lower pH, accumulated more patulin at 1 °C. However, this trend was not observed at other temperatures in which varieties with higher amounts of organic acids (Golden and Fuji apples) accumulated most patulin. In the pear varieties, significant differences in pH did not lead to significant differences in patulin accumulation. CONCLUSION: Although pH influences patulin accumulation, other factors such as organic acid content may play an important role. Concerning the apple and pear varieties we studied, it seems that rather than variety, other parameters like pH or acidic content may be more important. These parameters vary significantly depending on the degree of ripeness of the fruit. Gala apple, which is used in Spanish juice production, was the only variety that accumulated dramatically higher amounts of patulin. Copyright © 2008 Society of Chemical Industry