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Apple blue mold is a significant postharvest disease caused by Penicillium expansum. pH modification in colonized tissues leads to the production of organic substances, the modulation of enzymes, and then increases fungal pathogenicity. This study evaluated Penicillium expansum-inoculated apple fruits’ quality responding to pH treatments ranging from 2.5 to 8.5 and analyzed the reactive oxygen species (ROS) metabolism modulation in inoculated apple fruits at the same pH. The results showed that the fruit quality of the firmness, total soluble solids, and titratable acid displayed a quick loss at pHs 5.0 and 7.0, compared with 2.5 and 8.5. Similarly, higher disease incidence was observed at pHs 5.0 and 7.0. Apple fruits infected with P. expansum at pHs 2.5 and 8.5 had less content of O2•−, H2O2, and malondialdehyde (MDA); lower enzymatic activity of NADPH oxidase (NOX); and greater cell membrane integrity than those at pHs 5.0 and 7.0. The analysis of the antioxidant enzymatic activities showed upregulation of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), ascorbate peroxidase (APX), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), and glutathione reductase (GR) at pHs 2.5 and 8.5 compared with those at pHs 5.0 and 7.0. Similar trends were shown in ascorbic acid and glutathione. These results support the hypothesis that inoculated apple fruits at pHs 2.5 and 8.5 improve resistance to P. expansum by modulating ROS metabolism, compared with pHs 5.0 and 7.0.

Fusarium rot of muskmelon fruit is a common postharvest disease, which not only causes quantity deterioration but also leads to trichothecene accumulation in decay fruits. Neosolaniol (NEO) is one of main trichothecene, which poses a severe threat to human health. In this study, UPLC-MS/MS method was developed to determine NEO in muskmelon inoculated with Fusarium sulphureum. Diatomite was used to remove NEO in muskmelon and the adsorption kinetics, adsorption thermodynamics were analyzed in this adsorption process, and the changes of muskmelon juice quality before and after adsorption were investigated. The results showed that diatomite was a good adsorbent to remove NEO from muskmelon juice. The reaction process fits the Langmuir model and it was spontaneous exothermic reaction and not easy to be desorbed; the kinetic results showed that the maximum adsorption capacity was 12.35 μg/g, and this process fits the Pseudo-second-order model; diatomite had no significant effect on juice quality. [ABSTRACT FROM AUTHOR]