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Apple post-harvest infection by Paecilomyces niveus causes spoilage of thermally processed products
Megan Daniels: Cornell University; Abigail Synder: Cornell University; Randy Worobo: Cornell University; Kathie Hodge: Cornell University
<div><i>Paecilomyces niveus</i> is known in the food industry as an important mycotoxigenic mold that spoils heat-processed fruit products. Though regarded as a soil-borne contaminant, our research shows it can be an apple pathogen like its relative <i>Penicillium expansum</i>. Both fungi synthesize patulin, which acts as a virulence factor in apple infection. Our goals were to assess the ability of <i>P. niveus </i>to infect apples and test whether infected apples<i> </i>can be a source of<i> </i>spoilage fungi in the finished apple juice concentrate, a heat-processed product often made from low quality apples. Two varieties of apples were inoculated with <i>P. niveus </i>to study pathogenicity and complete Koch’s postulates. To determine whether <i>P</i>. <i>niveus</i> can survive heat-processing, juice concentrate was made from infected apples. We confirmed <i>P</i>.<i> niveus</i> can infect apples through wounds, causing lesions similar to Bull’s-Eye Fruit Rot. Apple varieties differed significantly in lesion size (p=0.003). Juice concentrate made from infected apples contained viable <i>P</i>.<i> niveus</i> propagules, which were reduced by 4-log CFU/L but not eliminated across five stages of processing. We conclude <i>P</i>.<i> niveus</i> is an overlooked post-harvest apple pathogen that can survive thermal processing and produce patulin, a mycotoxin limited to < 50 ppb in apple products. The link between post-harvest apple disease and food spoilage is novel and may explain the episodic nature of <i>P</i>.<i> niveus </i>food spoilage.</div>

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