| Waxy property is one of the most important edible quality of Chinese chestnut(Castanea mollissima Blume), and varies greatly according to its varieties and cultivated areas. To date no good method for evaluating the waxy property in chestnut has been set up as while. In this study,24 varieties of Chinese chestnut from 3 cultivar groups collected at 9 different cultivated areas were sampled to deal with the waxy texture. The objectives of this present study were:(1) to study the relationship between the morphological structure and composition substance of chestnut seeds and its waxy property; (2) to analyze the contribution of chestnut starch properties to waxy quality; (3) to use PCA (Principal Component Analysis) to discuss the correlation among factors that influencing waxy texture of chestnut; (4) to establish a PCA-based system that evaluated the waxy quality of chestnut. This study was the first to integrate the external and internal factors that affect the waxy property of chestnut together, and attempted to provide theoretical guide for the breeding and fine processing of chestnut. The following are main results.1. Waxy quality of chestnut depended greatly on its cultivar and cultivated areas. North Cultivar Group (NVG) in chestnut showed high waxy quality, whereas these varieties from Anhui and Hunan areas have poor waxy quality.2. The waxy level of chestnut was affected by its starch granule structure. The curing treatment resulted in chestnut starch granules to gelatinize and then form a cellular texture adhered together. The cellular structures differed between High Waxy Quality (HWQ) chestnut and Low Waxy Quality (LWQ) chestnut after curing due to honeycomb densification. Normally, the chestnuts with HWQ less honeycombed and starch granules adhered strongly. The chestnuts with LWQ produced more honeycomb with three-dimensional net structure. Differences in the structure of starch granules cured cause different varieties to have specific waxy texture.3. Starch properties contributed largely to the waxy texture of chestnut. The swelling power and pasting character of chestnut starch affected the waxy property based on sensory evaluation score. The swelling power of starch negatively correlated with its crystallinity, and positively correlated with Iodine Blue Value (IBV) of amylopectin. Iodine Combining Power (ICP) of Starch and amylopectin/amylase content ratio (AP/AM ratio). The pasting characteristic value of starch correlated with IBV of amylopectin, IBV of starch and AP/AM ratio. Basically, AP/AM ratio and crystallinity, branch chain length of amylopectin and chain length distribution of amylose were factors affecting the waxy quality of chestnut. Unlike the chestnut starch with LWQ, the chestnut starch with HWQ has lower crystallinity and IBV of amylopectin, higher IBV of starch and AP/AM ratio. Higher branching degree of amylopectin, shorter chain length of amylase and lower crystallinity higher waxy property chestnut has.4. Protein and fat were proved to be main substances affecting the waxy quality of chestnut throughout forming starch-protein or starch-fat complex that influenced the swelling and pasting properties of starch.(1) Waxy property significantly related to protein content and starch/protein content ratio stored in nuts. The types and contents of starch-associated-protein were obviously different due to waxy quality among varieties. There was close relationship between Sensory Evaluation Score (SES) of waxy quality and fatty acid (FA) composition, especially for starch-lipid of C16:0 FA, C18:2 FA and the ratio of C16/C18 and AP/AM.(2) The swelling and pasting properties of chestnut powder and nuts greatly changed after de-fate and de-protein treatments. De-fat and de-protein treatments caused chestnut starch to increase its swelling power.'Pasting temperature'decreased and 'Peak time'was shorter. The swelling and pasting of starch was dependant on the presence of protein and lipid. Moreover, the change in swelling and pasting was subjected to chestnut varieties and its cultivated areas. Chestnut powder and starch from NVG had higher swelling power, lower'Pasting temperature'and shorter'Peak time', easily swelling and pasting. In additions, the changes in swelling power and pasting characteristic value was significantly subjected to protein content, starch-lipid content, C16/C18 FA ratio and SFA/UFA ratio in starch-lipid. Thus, the swelling and pasting properties comprehensively were influenced by composition and property of substance. Edible quality and processing character of chestnut might be improved on purpose throughout the adjust of its starch, protein and lipid.5.24 internal and external factors were recognized intergratedly to cause chestnut to have different waxy property among varieties. A PCA-based system was established for evaluating the waxy texture property of chestnut. The waxy quality of 19 chestnut's varieties according to the PCA-based system coincided with that from sensory evaluation method, and the accuracy rate was more than 79%.6. In summary, this study was the first time to prove various internal and external factors to cause Chinese chestnut to have diversity in waxy quality. The diversity in waxy quality suggests that PCA-based system should be promising for the evaluation of chestnut waxy texture.
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