Evaluation of fast method for aroma profiling of fungal infection of pear fruit (Pyrus communis) by SIFT-MS

Abstract

Botrytis cinerea causing gray mold and Penicillium expansum causing blue mold are the two major pathogens causing postharvest rots in pears. In this study, wounded pears were inoculated with these two pathogens and compared with wounded control and mock infected fruit. Lesion size and pear fruit aroma were monitored for 7 d at 20–22 °C. SIFT-MS and SPME-GC-MS were used to determine the impact of fungal infection on the volatile profiles. Results showed ‘Conference’ pear stored for 11 weeks to be less susceptible to P. expansum but most sensitive to inoculation with B. cinerea. This was reflected by changes in the aroma profile of ‘Conference’ pear as shown by multivariate analyses. Furthermore, ‘Cepuna’ pear stored for 26 weeks prior to the infection were more susceptible to P. expansum as compared to the fruit stored for 15 weeks, most likely due to more advanced ripening. By using SIFT-MS to measure the volatile profile of intact pear fruit, a significant difference could be observed between infected fruit and both types of control fruit 7 d after inoculation. P. expansum-infected ‘Cepuna’ pears were characterized by increased styrene and ethanol levels, while in B. cinerea-infected ‘Conference’ pears elevated ethanol levels were found. B. cinerea-infected ‘Cepuna’ pears stored for 26 weeks had significantly different benzaldehyde levels compared to control and mock infected fruit. The results obtained with the SIFT-MS on intact fruit were confirmed by classical SPME-GC-MS analyses of destructive juice samples. In conclusion, the aroma profile obtained via SIFT-MS can be used to nondestructively predict the progression of infection for both pathogens and tentatively identify compounds that can distinguish infected from sound pears without sample concentration as required in traditional GC-MS methods. Further, calibration models that were built using a wider range of product ions (i.e., fingerprinting approach) were found to better discriminate sound versus infected fruit compared to the limited product ions of identified compounds.