Postharvest Spoilage Incidence and Prestorage Treatment in Chinese Chestnut and Complex Hybrid Cultivars

Abstract

U.S. chestnut (Castanea sp.) production is expanding as knowledge of seedling cultivation and germplasm advances. Chestnuts have high starch and water content, making them highly perishable; therefore, they require cold storage immediately following harvest. Postharvest spoilage remains a significant area for improvement. Several postharvest fungi (including Fusarium sp. and Penicillium sp.) can infect chestnuts during storage, leading to spoilage and nonsellable nuts. The annual crop losses can reach up to 10%, thereby affecting trees differently. Our research objectives were to 1) evaluate spoilage incidence on the interior (i.e., pellicle, kernel) and exterior (i.e., nutshell) of the nut over the course of 200 days of cold storage on eight cultivars and 2) assess the impact of food contact-approved chlorine solution and 2% peracetic acid (PAA) with 27% hydrogen peroxide prestorage treatments for spoilage suppression on ‘Qing’ nuts. Fourteen timepoints were observed during the study period, each with four replications of 16 nuts. An additional four replicates of 16 ‘Qing’ nuts were treated prestorage and observed over seven time points. The incidence of spoilage was reported as the percentage of nonsellable nuts for each treatment and cultivar at four timepoints. The nut interior showed the highest spoilage incidence after 200 days, with four cultivars having >30% nonsellable nuts. Overall, the cultivars had an average of 10% nonsellable nuts from interior spoilage after 60 days in storage. ‘Hong Kong’ had the highest percentage of nonsellable nuts by the end of the study at 60%, whereas ‘Qing’ and ‘Mossbarger’ had the lowest rates, with only 14% nonsellable nuts. Spoilage of the exterior, although less frequent, is visible to buyers and impacts nut marketability. ‘Kohr’ had the highest percentage of nonsellable nuts because of exterior spoilage (35.9%). ‘Mossbarger’ had the lowest percentage of nonsellable nuts because of exterior spoilage (3.1%). ‘Qing’ nuts treated with 500 ppm chlorine and 100/200 ppm PAA demonstrated reduced exterior spoilage with longer storage times. Prestorage treatment did not show efficacy for reducing interior spoilage. This study provides a preliminary report of evidence that cultivar differences influence the spoilage incidence and supports taking nuts to market within 60 days of harvesting. These preliminary data also inform breeding parent combinations and studies of inheritance for postharvest spoilage tolerance at the University of Missouri Center for Agroforestry breeding program.