Research On The Influence Factors Of Guizhou Dried Radish Quality And Its Control

Guizhou Dried radish,characterized with abundant nutritions and high nutritive value,tastes spicy and delicious and is deeply recepted by consumers,which shows great promise.However the lack standard of production technology of drid radish results uneven quality,thusing seriously hindering its further development.Based on the reason,Guizhou Dried radish was involved in this study.Taking radishes growing in Guizhou as raw materials,harvest maturity,hot-air drying process,preservation methods and the profile of volatile compounds in different process were evaluated to study the key techniques for Guizhou Dried radish's production and provide the technical support of high-quality products for the enterprise.The main research contents and results show as follows:1.Research on the impacts of different maturity stage on changes of main nutrients of fresh radish and product quality after drying.Radish harvested in different time reprensented different maturity.Change trends of main nutrients(protein,soluble sugar,starch,Vc,crude fibre,mineralls)in radish at different maturity stage were summarized and effects of maturity on rehydration rate,volumetric shrinkage,produce rate,dried radish output per mu via heat air drying and dried radish texture after rehydration were explored.Comprehensive comparison was made on the quality of fresh radish after drying.The results showed that the dried radish made from the sixth maturity stage gained highest rehydration rate and product output rate,of 5.03 and 12.36% respectively.At the same time,it featured with low volumetric shrinkage,moderate hardness and suitable chewing degree.Hence,fresh radish at the sixth maturity stage is the candidate of raw materials.2.Research on characteristics of hot air drying on radish,its impacts on quality of dried radish and mathematical modeling.It's identified that the drying process is mainly in a decelerated stage.Four factors including hot air temperature,hot air velocity,cutting thickness and drying spread density were taken into consideration.After single factor experiments,comprehensive evaluation on volumetric shrinkage of radish,rehydration rate,drying time,color aberration and sensory score were investigated by degree of membership.According to the comprehensive scores,orthogonal design was experimented.The results spotted that hot air temperature and cutting thickness had significant influences on quality comprehensive scores of dried radish,analyzed with SPSS software.The factors mostly affecting the scores consecutively were hot air temperature,cutting thickness,drying spread density and hot air velocity.The optimal is 70 ? of hot air temperature,0.7 m/s of hot air velocity,7 mm of cutting thickness,6 kg/m2 of drying spread density.In optimal condition,dried radish obtained a highest comprehensive score of 0.7456 on average,with a uniform slight yellow color,characteristic flavor of the dried radish,regular shape,moderate shrinkage,and desirable rehydration rate.The experiment data were studied by fitting anslysis using three classical thin layer drying models.It was indicated that Page models reflects well the process of hot air drying.3.The processing of Guizhou dried radish,its quality changes during storage and the predictive modeling of shelf lifeUnder optimal drying conditions,water content in dried radish was studied to investigate its influence in product quality of dried radish.It has found that water content has a negatively significant impact on hardness,cohesiveness and chewiness.The dried radish with water content of 35% earned the highest sensory scores of 85.36,hardness of 659 g and chewiness of 35.2 m J,exhibiting desirable chewiness and hardness.The optimal sterilization conditions of Guizhou Dried Radish were evaluated based on bacterial mortality and sensory scores.It was demonstrated that at sterilization temperature of 100 ?and time with 18 min,highest bacterial amount were killed and there was negligible effect of sterilization on the taste and flavors of dried radish.The influences of storage temperature on sterilized dried radish were probed,in terms of texture,color aberration,total number of colonies,sensory quality and browning degree.By correlation analysis,the important indicators that influenced sensory scores during storage were figured out.Change trends of hardness and colonies of dried radish during storage were fitted by chemical dynamics-the first order equation.The correlation coefficient of the models were both greater than 0.95.Integrated with Arrhenius,predictive model concerning shelf life of dried radish was built,which could effectively predict the rest shelf life of dried radish at different storage temperature.4.Research on the profile of volatile compounds from dried radish in different processing.The volatile compounds from dried radish and its products were isolated by using SPME and analysed by GC-MS.137 different substances were identified.Identified volatile compunds belonged to several classes of chemical: 26 alcohols,26 aldehydes,13 alkanes,18 olefins,15 esters,8 ethers,8 isothiocyanates,8 ketones,3furans,3 phenols,3 pyrazines and 3 others,which were characterized by the largest number of alcohols,aldehydes and olefins.Dried radish and spices-mixed dried radish showed more kinds of volatiles,characterized with 85 and 77 respectively.While the least kinds of volatile substances were determined in in fresh radish,only 40.Drying and spice-mixing processing technology greatly enriched the variety of volatile compounds and kept pungent substances originated from fresh radish--isothiocyanates to a minimum,whose pungency could not be distinguished in taste.