Effect Of Thermal Processing On The Colloidal And Functional Properties Of Chestnut Starch

Starch is the main nutrient content of chestnut with content up to 40%-60%(dry weight basis).However,less studies have been focused on the effect of thermal processing on the gel,pasting and functional properties of different kinds of chestnut starches.Three kinds of chestnut from northern China(Jinfeng of Shandong Linyi,Hongyou of Henan Xinyang and Dabanhong of Hebei Kuancheng)and two varieties from southern China(Jiujiazhong of Jiangsu Shuyang,Zaoli of Hubei Luotian)were chosen in the present study.Five different varieties of Chinese chestnut were roasted or steamed respectively,and the effect of thermal processing on the gel,pasting and functional properties of chestnut starch was evaluated.The aim of this study was to give a thorough understanding of processing features of chestnut starch and provide theory basis for the application of chestnut starch in industry.The results were as follows:(1)The total starch contents varied from 55.14%to 78.85%(dry weight basis)in chestnuts of different varieties and cooking degrees.The total starch content of the raw chestnut was high,but that of the cooked chestnut decreased significantly(P<0.01).In addition,the effect of variety on the total starch content of chestnut was significant.The amylose content of different chestnut starch ranged from 16.57%to 30.90%,and that was significantly reduced after thermal processing(P<0.05).The results showed that the content of amylose content in chestnut starch was mainly caused by variety difference,while the thermal process significantly affected the total starch and amylose content in cooked chestnut.(2)The viscosity of starch samples increased with temperature.Different varieties of chestnut starch had different viscosity characteristics,and the influence of thermal treatment was different.Peak viscosity,trough viscosity,final viscosity,breakdown and setback values of cooked starch were significantly lower than those of raw starch,while the gelatinization temperature and the time showed the opposite tendency.Heating process changed the internal structure of starch granules and reduced the combination ability of starch with water,reducing the gelatinization degree.(3)Different varieties of chestnut starch had different gel texture characteristics.The hardness and gumminess of Zaoli were the highest,while those of Hongyou were the lowest.It could be observed that the starch gels of southern varieties were of high strength.The adhesiveness and stringiness of starch gel increased after cooking,however,the hardness,springiness,cohesiveness,chewiness,gumminess and stickiness reduced significantly,showing that heat treatment changed the structure of starch and crystallinity,and reduced the gel intensity.(4)For the five varities of chestnut,the synaeresis of raw starch significantly increased after first few cycles,and that was lower than that of cooked starch(P<0.05).The cooking process significantly reduced the clarity of chestnut starch(P<0.05),of which Jiujiazhong had the highest reduction.Regardless of the cooking degree,starch solubility increased with the increase of temperature.However,the swelling power of raw starch increased along with the temperature more obviously than that of cooked starch.The water absorption character(WAC)and oil absorption character(OAC)of the raw starch were 0.87-1.28 and 0.88-1.11 g/g respectively,and those of the cooked were 2.35-4.56 and 1.03-1.78 g/g respectively.It can be concluded that the cooking process significantly improved the absorption capacity of starch for water and oil(P<0.05).The heating process enhanced the sedimentation capacity of starch paste and lowered its retrogradation stability.In addition,the effect of varieties on the stability of paste was significant.(5)Through the correlation analysis of total starch and amylose content,pasting,functional and gel texture properties,it could be summarized that amylose content and crystallization degree on the functional properties of starch is comprehensive,of which amylose is the key factors influencing the starch properties.Amylose influenced the hardness,gumminess and chewiness of starch gel significantly(r=0.896?0.800?0.847,P<0.01),and it was significantly correlated with the setback value and peak viscosity(r=0.679,P<0.05;r=0.641,P>0.05).