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  • Author or Editor: William Aldred x
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`Stuart' pecans were harvested as soon as shucks would split in the fall of 1989 and 45 kg inshell samples were placed in 30 × 30 × 105 cm drying bins. The nuts were dried at air volumes of either 0, 1.27, 1.56, 1.84, or 2.12 m3/min down to 4% moisture. Air temperature in the drying bins was maintained at uniform 35°C with the exception of the 0 air volume treatment which was allowed to dry at room temperature. Four random samples of each treatment were held in frozen storage awaiting fatty acid analysis. Palmitic, stearic, oleic, linoleic, and linolinic fatty acids were separated in a 183 cm × 3 mm packed column using a 10% Silar 10C phase on a Gas Chrom QII, 100/120. The samples dried with a air volume of 1.27 m3/min retained a significantly higher oleic acid content than the 0 and 2.12 m3/min drying volumes. The 1.27 m3/min volume retained 64.55 % oleic acid compared with 61.37'% for the 0 velocity sample and 59.61% for 2.12 m3/min treatment. The more desirable oleic/linoleic ratio of 2.24 was found in the 1.27 m3/min sample compared to a 1.78 ratio in the 2.12 m3/min sample. Increased volume of air in the drying bins was thus deleterious to these samples because of the loss of monounsaturated fatty acid.

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Previous work in this lab has shown that drying temperatures above 35°C will cause excessive loss of the kernel's natural light color and less oleic (18:1) oxidation to linoleic (18:2) fatty acid. The former is undesirable because of poor consumer appeal and the latter is desirable because of superiority of oleic acid in reducing low density lipoprotein in the blood plasma of consumers and a longer shelf life. The drying temperature of 35°C and an air volume of 45 CFM was superior in 1989 to 75 CFM at the same temperature and an air dried control. Lower air volumes in 1990 proved to be no better than 45 CFM at 35°C The best compromise drying regime was determined to be 45 CFM at 35°C.

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