Abstract: To analyze the patterns of variation in Chinese chestnut quality under different processing methods, this study constructed a model for describing the sweetness (D value) as a function of starch and soluble sugar contents using principal component analysis and membership function analysis for systematic evaluation of the suitability of 20 major cultivars for raw consumption, steaming, roasting and sand-frying. Eight traits including starch and soluble sugar contents of raw, steamed, roasted and sand-fried chestnuts at 40 days postharvest were determined by high performance liquid chromatography (HPLC) and a dual-wavelength method. Correlation analysis, principal component analysis, membership function analysis, and cluster analysis were conducted using the software SPSS 20.0 and Mega 7.0. The results showed that there were significant differences between raw and processed chestnuts in the eight traits, confirming their usefulness for comprehensive evaluation of chestnuts. Thermal processing significantly altered sugar metabolism balance in chestnuts and reduced the variation in sugar contents among varieties, thereby narrowing the differences in quality. The changes in chestnut quality indicators after thermal processing were based on the targeted adjustment of its inherent characteristics. In fresh chestnuts, there was a metabolic antagonism between starch synthesis and sugar accumulation, which was significantly changed after thermal processing. Steaming increased maltose content compared with fresh fruits and resulted in a positive correlation between amylose and maltose. On the other hand, roasting reduced sucrose and fructose contents and maintained the negative correlation between starch and sucrose. Principal component analysis indicated that processing methods reshaped the weight distribution of quality indicators. The quality indicators of fresh chestnuts were dominated by sucrose and amylose, the major quality factor of steamed chestnuts was maltose, roasted chestnuts showed a competition between sucrose and maltose, and sand frying had an equal influence on both sugars. Cluster analysis identified chestnut varieties suitable for different processing methods; Yanshan Duanzhi and Daban hong were found to be suitable for raw consumption, roasting, and sand-frying, while Zipo was suitable for raw consumption, steaming, and roasting. This study confirmed that a “processing method-variety-quality” matching system could be established for the thermal processing of chestnuts, providing a basis for quality control and targeted breeding in chestnut processing.

Key words: Chinese chestnut; variety; processing; quality; evaluation