Ultrastructure characteristics and quality changes of low-moisture Chilgoza pine nut ( Pinus gerardiana ) during the near-freezing-temperature storage

摘要

ABSTRACT The 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.