Abstract
ABSTRACTThe effects of thermal treatment on the ultrastructure and quality of Chilgoza pine nuts stored at near-freezing temperature were investigated. The moisture content of pine nuts was adjusted to 13.3%, compared to the initial 17.3% moisture content. Thermal treatment improved the storage stability. The hydrolysis of lipids was delayed in low-moisture pine nuts, resulting in a significant inhibition of free fatty acid accumulation in pine nuts. Low-moisture pine nuts also showed lower peroxide and thiobarbituric acid (TBA) values compared with the control. Ultrastructure characterization revealed that thermal treatment maintained the cell integrity, deferred the degradation of the plasmalemma and protected the internal lipid droplet. Thermal treatment better retained the antioxidant components, including total phenolics and vitamin E, and reduced the activities of lipase and lipoxygenase in pine nuts. These results indicated that thermal treatment could retard the senescence and deterioration of quality in pine nuts stored at a near-freezing temperature.
Highlights
The Chilgoza pine nut (Pinus gerardiana) is the edible seed of the Chilgoza pine, which belongs to the Pinaceae family, mainly distributed in the natural regions of Afghanistan, Pakistan, India and China (Hoon, Choo, Watawana, Jayawardena, & Waisundara, 2015)
The quality deterioration of pine nuts in storage is caused by the metabolism of nuts and microorganisms, which depends on storage conditions including temperature, moisture content and gas composition
The objective of this study was to examine the changes in lipid content, free fatty acids (FFAs), peroxide value (PV), thiobarbituric acid (TBA) value, ultrastructure, total phenolics, vitamin E and activities of lipid metabolism-related enzymes, including lipase and lipoxygenase (LOX), of low-moisture pine nuts during nearfreezing temperature storage
Summary
The Chilgoza pine nut (Pinus gerardiana) is the edible seed of the Chilgoza pine, which belongs to the Pinaceae family, mainly distributed in the natural regions of Afghanistan, Pakistan, India and China (Hoon, Choo, Watawana, Jayawardena, & Waisundara, 2015). It is an important international trade commodity worldwide and is used as a food ingredient in desserts, sauces and salads. As pine nuts contain high amounts of fats and unsaturated fatty acids, they are prone to hydrolytic and oxidative rancidity, which leads to quality loss during storage (Kaijser, Dutta, & Savage, 2000; Xie, Miles, & Calder, 2016). Near-freezing temperature storage is regarded as an effective system that offers the possibility of storing grain for the long term
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