| Chestnut(Castanea mollissima)is an important food crop in China and becoming popular worldwide due to its nutritional composition.However,the nutrient contents vary very much in different chestnut varieties.This study aimed to evaluate the difference in nutritional components of chestnuts from different origins in China and effects of different cooking methods on the content of important nutrients and sensory properties of Chinese chestnut fruits.Three varieties of chestnut from northern China(Dabanhong from Hebei Province,Jinfeng from Shandong Province and Hongyouli from Henan Province)and three varieties from southern China(Zaoli from Hubei Province,Jiujiazhong from Jiangsu Province and Guihua from Anhui Province)were chosen,and the nutritional compositions of raw and cooked(boiled,roasted)chestnuts were analyzed,including the nut phenotype,moisture content,ash content,soluble solid content,crude fat content,crude protein content,water-solubility protein content,starch content,amylose content,soluble sugar content,reducing sugar content,free amino acids content,total acids content,total phenolic content,total flavone content and riboflavin content.The texture characteristics and sensory properties of cooked chestnut kernels were also determined.The obtained results were as follows:(1)Among the different varieties of chestnut,the single weight of Jiujiazhong was the heaviest,and that of Guihua was the lightest.The single weight and volume showed a large range of variation,while there was no significant difference in the shape and edible rate of chestnuts from different origins.(2)The moisture content of raw chestnut was between 46.63%-58.14%.Soluble solid content was 19.15%-30.00%and ash content was between 2.11%-3.07%based on dry weight.The range of crude fat content was 2.55%to 3.99%.Protein content was 7.58%to 11.91%while the soluble protein content was about 1/3 of the total protein content.The total starch content of different varieties of chestnut was 58.33%-63.58%and the ratio of amylose in total starch was between 22.20%and 29.81%.Soluble sugar content was 11.81%-14.42%and the contents of reducing sugar in Chinese chestnuts were relatively lower(0.41%-0.57%).A total of 17 free amino acids were detected,among which the contents of asparagine,glutamine and arginine were the highest.The contents of total acids,total phenols,total flavonoids and thiamine in the different chestnut varieties were 2.98-3.67,0.91-1.43,1.05-1.44 and 0.20-0.26 mg/100 g,respectively.(3)The reduction of moisture content in the roasted chestnut was significantly greater than that of boiled chestnut.The content of soluble solid in chestnut was significantly decreased after cooking(P<0.01),and the content of roasted chestnut was higher than that of boiled chestnut(P<0.01).After cooking,the crude fat content significantly decreased in boiled and roasted chestnuts,and the degree of the reduction in roasted chestnut was higher than that of boiled chestnut.The soluble protein content of six varieties of chestnut decreased significantly after heat treatment(P<0.01).The effect of boiling on total starch content was greater than that of roasting.The amylose content of chestnut changed slightly after thermal processing.There was significant difference in free amino acids contents between chestnuts from different origins and cooked by different methods.The total acid content decreased slightly after boiling,while the total acid content of the roasted chestnut was significantly increased.The total phenolics of different varieties were significantly increased after cooking.The contents of flavonoids in chestnuts were significantly increased after roasting.The two-way ANOVA analysis showed that the varieties,cooking methods and the interaction of varieties×cooking methods significantly affected the contents of nutritional compositions in Chinese chestnuts(P<0.01).(4)The hardness,springiness,gumminess and chewiness of fresh kernels of Jiangsu Jiujiazhong were significantly higher than those of the other varieties(P<0.01).After cooking,the hardness of chestnut changed insignificantly,and the cohesiveness of boiled chestnut was significantly lower than that of raw chestnut and roasted chestnut.The springiness and chewiness decreased significantly after cooking.The gumminess of the boiled chestnut was significantly lower than that of raw chestnut and roasted chestnut The correlation analysis showed that the moisture content was positively correlated with the springiness(P<0.05).The amylose content was positively correlated with the cohesiveness,chewiness and gumminess of cooked chestnut kernels(P<0.05).There was a significant positive correlation between soluble protein content and springiness(P<0.01),and the protein content was positively correlated with springiness and chewiness(P<0.05).There was a significant positive correlation between soluble sugar content and sweetness of cooked chestnut kernel(P<0.05)In summary,the nutritional contents vary very much in different chestnut varieties,which showing regional characteristics.The quality of Chinese chestnuts differs significantly between the northern and southern cultivars.In addition,the varieties,cooking methods and the interaction of varieties×cooking methods significantly affected the contents of nutrient composition and texture characteristics of Chinese chestnut.The texture and sensory quality of cooked chestnut kernels had significant correlation with the nutritional content of chestnuts from different origins in China. |
