Higher CO2 during controlled atmosphere storage of unshelled 'Barton' pecans or carnauba wax coating: Effect on the quality after long-term storage at two temperatures.

Pecan nuts, a healthy food, have shown an increased demand for consumption. Therefore, there must be a certain level of care to avoid quality losses, which are primarily influenced by storage conditions and time. This study evaluates the effects of long-term controlled atmosphere (CA) storage with low O2 partial pressure (pO2 - 2 kPa), combined or not with high CO2 (pCO2 - 40 or 80 kPa), carnauba wax coating (CW), and ambient atmosphere (AMB; control) at 10 and 20 °C, on unshelled 'Barton' pecan nut quality. Color, water activity (Aw), moisture content (MC), and oxidation markers, such as peroxide value (PV), acidity value (AV), TBARS, and volatile compounds (VC) were evaluated. Storage up to twelve months at 10 °C and with CA (regardless of the temperature) ensured higher luminosity and color parameter b* ("golden") and a lower a* parameter ("reddish"). The MC ranged from 2.8 to 3.6%, irrespective of storage conditions, for up to twelve months, which is suitable. The AMB at 10 °C ensured lower AV, TBARS, and PV compared to the CW treatment. Furthermore, CA with low pO2 and high pCO2, even at 20 °C, guaranteed lower AV, TBARS, and PV. Storage at 20 °C increased characteristic VCs of lipid oxidation (aldehydes, acids, alcohols, ketones, lactones, and esters, especially with CW coating). However, all conditions at 10 °C and with pCO2 (even associated at 20 °C) reduced the presence of these VCs. The CW used as a coating on the pecans did not show satisfactory results and should not be recommended for pecan storage at these applied conditions. Our findings showed that low pO2 and high pCO2 maintain better pecan quality than O2 ambient (20 kPa), even at temperatures above refrigeration (20 °C). Nevertheless, there were no significant differences between 40 and 80 kPa CO2.

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

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.