Effect of controlled atmosphere, vacuum packaging and different temperatures on the growth of spoilage fungi in shelled pecan nuts during storage

Fungal spoilage significantly affects the quality of pecan nuts in post-harvest. Although several alternatives have been used to avoid this type of food spoilage, studies correlating controlled atmosphere (CA) and its effects on preserving pecan nuts are still scarce in the literature. Therefore, this study aimed to evaluate the use of vacuum and static controlled atmosphere with low oxygen partial pressure (pO2) and high carbon dioxide (pCO2) at different temperatures (1, 10, and 20 degrees C), for up to 6 months of storage, on the fungal contamination of shelled 'Barton' pecan nuts. The samples were mycologically analyzed at the beginning of storage and again at the second, fourth, and sixth month of storage by the direct plating method using dichloran 18% glycerol agar (DG18) with incubation for 7 days at 25 degrees C. Xerophilic Aspergillus was the leading spoilage agent under conventional storage (20 degrees C and normal atmosphere) with nuts becoming moldy in up to four months, while the CA ensured the absence and/or low contamination of Aspergillus sp. and Penicillium sp. after 2 months of storage, and Cladosporium sp. up to 4 months of storage at 10 degrees C. At 20 degrees C, high pCO2 presented lower contamination than the low pO2 condition. Vacuum packaging ensured that nuts stored at 20 degrees C maintained lower contamination levels by Aspergillus in all periods analyzed. Potential aflatoxin-producing species were not detected in any of the evaluated conditions.

Automated summary

This study found that controlled atmosphere conditions can effectively reduce fungal spoilage and preserve the quality of pecan nuts. High levels of carbon dioxide resulted in lower contamination, and vacuum packaging can help reduce Aspergillus contamination levels.