Temperatura de secagem e condições de armazenamento para manutenção da qualidade de pecãs com ou sem casca e diferentes umidades da amêndoa

Abstract

The drying and storage of pecans are fundamental processes during the postharvest and require additional research to expand the possibilities for producers. Pecan moisture content reduction by drying process is necessary to reduce the risk of oxidation, and storage under adequate conditions provides good quality pecans to the producer and consumer in the off-season period. In this sense, this dissertation is composed of three chapters (articles). In the first manuscript [1], we sought to evaluate the effect of static (40 °C and 60 °C) and dynamic (ambient and 40↔60 °C) temperature conditions. In the second article [2], the effect of 1-MCP (1μL L-¹) on shelled and unshelled pecans for 6 months at room temperature (17 ± 3.9 °C). In the third article [3], the interaction between of pecan moisture content (MC) (4 and 6%) and atmosphere conditions (AC) with 20.9 and 2 kPa of oxygen was investigated, for 'Barton' and 'Jackson' pecans stored for 8 and 12 months, at 20 °C. In the three articles/chapters analysis were carried out on the physical-chemical quality, color parameters and the volatile compounds profile (VC). Regarding the first manuscript, the best yellow color of the kernel was observed in the dried pecans at ambient temperature, but it did not differ from the dried pecans at 60 °C and drying at 40↔60 °C did not differ from the 60 °C condition. Drying with static temperature at 60 °C and dynamic at 40↔60 °C resulted in pecans with 4.5% kernel MC after 18 and 36 h, resulting in a significant time savings, because at ambient condition the kernel reached this MC only after 800 h. Pecan drying at dynamic temperatures (ambient and 40↔60 °C) showed the lowest total aldehydes abundance compared to drying at static temperature (40 and 60 °C). In the second chapter, the unshelled pecans + 1-MCP resulted in pecans with higher Luminosity (L). A lower incidence and severity of internal browning was found in unshelled pecans, being even lower with the application of 1-MCP. In pecans with and without shell, it was observed lower acidity and peroxide value with 1-MCP treatment before storage. The abundance of aldehydes, alcohols and ketones was drastically reduced by maintaining the shell, and in shelled and unshelled pecans the application of 1-MCP reduced the abundance of pentanol, hexanal, hexanol, octanal, nonanal and total aldehydes and alcohols. In the third chapter, the lower concentration of O2 (2 kPa) in the storage atmosphere was effective in reducing the abundance of oxidation-related volatiles compounds (hexanal, hexanol, heptanol and nonanal) and also in the maintenance of the yellow color (hue° and L) of pecans with 6% and 4% of MC after 8 and 12 months. From the results of the present research, it may be possible to made recommendation to the pecan producers in order to expand the possibilities both for drying (temperature, time and final MC of the kernel) and during storage, depending on the structure available and drying strategies.