Effects of controlled atmosphere and storage temperature on the quality of shelled 'Barton' pecan nuts during long-term storage

Abstract

This study aimed to evaluate the effects of controlled atmosphere (CA) storage at a low oxygen partial pressure (pO₂; 2 kPa of O₂) and low pO₂ associated with high pCO₂ (2 kPa O₂ + 15 kPa CO₂) in relation to ambient atmospheric conditions (control), at different temperatures, on shelled 'Barton' pecan nuts quality after storage. Color, respiration rates, moisture content (MC), and oxidation markers, such as peroxide value (PV), acidity value (AV), and volatile compounds (VC), were evaluated. During six months of storage, the MC decreased in all CA treatments, and treatments at 10 °C had the lowest AVs and PVs. However, the treatment with high pCO₂ levels also guaranteed lower AVs at 20 °C. The color parameter b* (yellow), which is related to the golden appearance of pecans and is a highly desirable visual attribute in the commercialization of nuts, was maintained high in treatments at 10 °C with CA treatments until six months of storage. The VCs, characteristic of lipid oxidation (aldehydes, acids, alcohols, and ketones), increase in all treatments with prolonging storage. When pCO₂ was associated to 10 °C at six month of storage, it showed a larger area in the acids and unsaturated aldehyde classes, while it was relevant for alcohols, lactones, and esters at 20 °C, with sweet characteristics, including ethyl ethanoate, ethyl hexanoate, and butyrolactone. Thus, this study shows another advance in the storage techniques of shelled pecans, pointing to alternatives for reducing energy costs in the cooling chain.

Keywords: Carbon dioxide; Nut storage; Oxidation; Volatiles compounds; [Carya illinoinensis (Wangenh) K. Koch].