Microbial Contamination in Peeled Chestnuts and the Efficacy of Postprocessing Treatments for Microbial Spoilage Management

Abstract

High undesirable spoilage of peeled chestnuts after thawing prompted a 2006–2007 survey in which chestnuts were quantitatively examined for microbial contaminants after harvest and peeling. Chestnuts (C. sativa × C. crenata cv. “Colossal”) were collected after harvest from seven Michigan farms, and peeled using a commercial‐brulage‐peeler. Average mesophilic aerobic bacteria (MAB), yeast and molds populations in peeled chestnuts were 2.70, 2.74 and 2.51 after harvest; 3.46, 3.27 and 2.40 during peeling; and 5.39, 3.09 and <1.70 log CFU/g after peeling, respectively. Two bacteria Rahnella sp., and Curtobacterium sp. and the yeast Candida sp. were the primary causes of spoilage. With the objective of reducing microbial contamination, six postprocessing sanitizer treatments, as well as X‐ray irradiation and warm water (65C) were evaluated (18 days of storage at 4C). X‐ray irradiation, 3 min immersion in 92 ppm hydrogen dioxide and 65C water were most effective in reducing MAB and yeast. Practical Applications High undesirable spoilage of peeled chestnuts after thawing prompted a 2006–2007 survey in which chestnuts were quantitatively examined for microbial contaminants after harvest and peeling. Two bacteria Rahnella sp., and Curtobacterium sp. and the yeast Candida sp. were the primary causes of spoilage. With the objective of reducing microbial contamination, six postprocessing sanitizer treatments, as well as X‐ray irradiation and warm water (65C) were evaluated (18 days of storage at 4C). X‐ray irradiation, 3 min immersion in 92 ppm hydrogen dioxide and 65C water were most effective in reducing MAB and yeast. This treatments can be practically used to reduce microbial decay and enhance peeled chestnut quality.

Microbial Decontamination of Peeled Chestnuts by Electrolyzed Water and Its Effect on Biochemical and Sensory Properties

“…As chestnuts possess a relatively higher moisture content (moisture level ~12%) (Beuchat 1978), there is a greater possibility for survival of spoilage and pathogenic microorganisms in peeled chestnuts once contamination occurs. Increased levels of spoilage microorganisms in chestnuts during peeling and post-peeling stages have been reported (Donis-Gonzalez et al 2017). This clearly indicates the crosscontamination during peeling process and further survival of contaminants in peeled chestnuts.…”

“…However, the removal of the shell and pellicle (which act as natural physical barrier that protects the kernel) can cause the loss of water and contamination of the kernel with opportunistic microorganisms and pathogens (Cantwell 1995;Mencarelli 2001), which negatively affect final quality and safety (Field et al 2006). In an earlier study, average contamination levels of mesophilic aerobic bacteria (MAB), yeast and molds in freshly harvested and unpeeled chestnuts were shown to be 2.70, 2.74 and 2.51 log CFU/g, respectively (Donis-Gonzalez et al 2017). However, the levels of these contaminants were reported to be significantly altered during peeling (3.46, 3.27 and 2.40 log CFU/g) and post-peeling (5.39, 3.09 and <1.70 log CFU/g), respectively.…”

“…and Candida sp., were shown to be the predominant cause of spoilage. Hence, post-processing sanitizer treatments have been recommended to prevent undesirable spoilage of peeled chestnuts (Donis-Gonzalez et al 2017).…”

“…Chlorine in the chemical form of hypochlorous acid and hypochlorite has been extensively used in the food industry, especially the fresh-cut industry, as a disinfectant (Meireles et al 2016). However, treating with chlorine does not always yield meaningful microbial reduction (including foodborne pathogens) and can also lead to the formation of carcinogenic by-products (Donis-Gonzalez et al 2017;Vitro et al 2005). In a study, eco-friendly techniques including warm water (65°C) immersion, 2,700 ppm hydrogen peroxide (H 2 O 2 ) + 200 ppm peracetic acid (CH 3 CO 3 H) and X-ray irradiation (0.5, 1.0, 1.5 and 2.0 kGy) were found to be most effective for aerobic bacteria and yeast reduction in peeled chestnuts (Donis-Gonzalez et al 2017).…”

Brown Rot Caused by Gnomoniopsis smithogilvyi (syn. Gnomoniopsis castaneae) at the Level of the Chestnut Tree (Castanea sativa Mill.)

“…-Post-processing treatments applied to inoculated peeled chestnuts 3 : X-ray irradiation (70 kV/57 mA, doses 0.5, 1, 1.5, 2 kGy); StorOx (2700 ppm hydrogen dioxide + 200 ppm peracetic acid); Agri-cide (1 ppm); 10 ppm chlorine dioxide solution; 0.70 ppm ozone solution; 80 ppm peracetic acid; 100 ppm chlorine solution; 0.2 M sodium chloride; warm water at 65 • C) [77] -Gaseous ozone [66] -Hot-water treatment + enzymes able to degrade the fungal cell wall [63] Applying good management practices in the orchards is essential for reducing the spread and inoculum density of G. smithogilvyi. Dobry and Campbell [18] suggest removing the litter after harvesting to reduce the inoculum.…”