The Quality Change And The Relationship Of Quality Index Of Winter Jujube Slices During Drying Process

Winter jujube is nutritious,crisp and juicy,loved by consumers.At present,domestic and foreign research on the drying of jujube slices is mainly devoted to the comparison of drying characteristics and quality changes before and after drying,while the research on the relationship between the quality change kinetics and quality indicators of the jujube during the drying process is less involved.This study takes winter jujube slices as the research object,through the pulsed air jet impingement drying of winter jujube slices,the quality change kinetics and the correlation of winter jujube slices quality indicators during the drying process was completed,The prediction models of quality index were established and evaluated.The main conclusions are as follows:(1)The kinetics of the sensory quality changes of jujube slices during the drying process under different wind temperatures and wind speeds conditions were completed.Under different wind temperatures(55℃,60℃,65℃,70℃),different wind speeds(3m/s,6m/s,9m/s),the moisture content and the value of-a* of jujube slices were studied.The research indicates: Under the condition of significant level of 0.05,the effect of wind temperature on the value of-a* and moisture content of jujube slices were extremely significant;The effect of wind speed on the moisture content of jujube slices was extremely significant,but the effect of wind speed on the value of-a* of jujube slices was not significant.The thermal degradation of the-a* of winter jujube slices under different wind temperatures was more consistent with the first-order degradation kinetics reaction.The drying activation energy of winter jujube slices was 44.02kJ/mol under different wind temperature.The thermal degradation activation energy of-a* of winter jujube slices was 63.59kJ/mol.(2)The kinetics of the nutritional quality changes of jujube slices during the drying process under different wind temperatures and wind speeds conditions were completed.Under different wind temperatures(55℃,60℃,65℃,70℃),different wind speeds(3m/s,6m/s,9m/s),the dry base VC content,dry base total acid content,dry base reducing sugar content were studied.The research indicates: Under the condition of significant level of 0.05,the effect of wind temperature on the dry base content of VC,dry base content of reducing sugar were extremely significant,while the effect of wind temperature on the dry base total acid content was not significant.The effect of wind speed on the total acid of winter jujube slices during the drying process was significant,but the effect of wind speed on the dry base content of reduction sugar,dry base content of VC were not significant.The thermal degradation of VC of winter jujube slices under different wind temperatures were more consistent with the first-order degradation kinetics reaction,while the thermal degradation of reducing sugars under different wind temperatures were more consistent with the zero-order degradation kinetics reaction.The thermal degradation activation energy of VC,reducing sugar of winter jujube slices were 47.14.kJ/mol,63.85kJ/mol,respectively.(3)The relationship between quality index of winter jujube slices during drying process under different wind temperatures were studied,and the prediction model were established and evaluated.Under different wind temperature(55℃,60℃,65℃,70℃),The relationship of dry base content of VC,dry base content of reducing sugar,the value of-a*,dry base content of total acid and winter jujube moisture content were studied.the study indicate: The correlation coefficients between the value of-a* of winter jujube slices and the dry base content of VC content were 0.708,0.718,0.733,0.751,respectively.The correlation coefficients between the value of-a* and the dry base content of reducing sugar were 0.767,0.785,0.804,and 0.818,respectively.The correlation between the value of-a* and the dry base content of total acid content,and the correlation between water content and dry base content of VC,dry base content of reduction sugar and dry base content of total acid were not obvious.The PLSR,SMLR and PCR were used to establish the quality prediction model.After analysis and comparison,it was determined that the dry base VC content prediction model was more suitable for PLSR modeling,and the dry base reducing sugar content prediction model was more suitable for PCR modeling.The results show that the Rp of prediction model of dry base VC content was 0.769;the RMSEP was 0.59;the RPD values was 2.1.The Rp of prediction model of dry base reducing sugar content was 0.816,the RMSEP was 0.56,the RPD values was 2.2.The results can provide theoretical and methodological support for real-time prediction of quality index changes during the drying process of winter jujube slices.