Effects Of The Processing Technology Of Concentrated Apple Juice On Aroma Components And Process Optimization

China is the largest producer of concentrated apple juice in the world. However, it has been technical difficulties because of the dissipation and loss of aromatic substance. In this study, using response surface methodology, we took apple as raw material to study the effect of unit operation, such as enzymatic hydrolysis, ultrafiltration, and aroma recovery parameters, on sensory quality and aroma component of apple juice during production process. Moreover, we constructed regression models between the main aroma components of apple juice, esters, alcohols, acids, aldehydes and ketones, and processing parameters by headspace solid-phase micro-extraction (SPME-GC-MS) method and multiple regression analysis. The main results are as follow:(1) The effect of pectinase processing parameters on sensory quality and aroma component of apple juice showed that the enzyme hydrolysis time and enzyme dosage had a remarked significant influence on sensory quality (p<0.01). The order of factors is as follows: enzyme hydrolysis time> enzyme dosage> enzyme hydrolysis temperature. In conclusion, we recommended that the optimum pectinase processing parameter for apple juice is0.04g/L pectinase at47.50℃for2.77h. The influencing sequence for esters are as follows:enzyme dosage> enzyme hydrolysis time> enzyme hydrolysis temperature. The influencing sequence for alcohols are as follows:enzyme hydrolysis time> enzyme hydrolysis temperature> enzyme dosage. The influencing sequence for acids are as follows:enzyme hydrolysis temperature> enzyme dosage> enzyme hydrolysis time. The influencing sequence for aldehydes and ketones are as follows:enzyme hydrolysis time> enzyme hydrolysis temperature> enzyme dosage.(2) The effect of ultrafiltration processing parameters on sensory quality and aroma component of apple juice showed that the treatment temperature, treatment pressure and treatment frequency all had a remarked significant effect on sensory quality (p<0.01). The order of factors is as follows:pressure> frequency> temperature. In conclusion, we recommended that the optimum ultrafiltration processing parameter for apple juice is in9.75Hz frequency,0.51MPa pressure at43.59℃. The influencing sequence from high to low for esters are as follows:temperature> frequency> pressure. The influencing sequence for alcohols is as follows:temperature> frequency> pressure. The influencing sequence for acids is as follows:temperature> pressure> frequency. The influencing sequence for aldehydes and ketones are as follows:pressure> temperature> frequency.(3) The effect of aroma recovery processing parameters on sensory quality and aroma component of apple juice showed that both treatment temperature and addition of aroma extracting solution had a remarked significant effect on sensory quality (p<0.01) while proportion of recycled liquids affected sensory quality significantly (0.0(p<0.05). The order of factors is as follows:addition of aroma extracting solution> treatment temperature> proportion of recycled liquids. In conclusion, we recommended that the optimum pectinase processing parameter for apple juice is1.9proportions of recycled liquids at47.50℃for4.56mL. The influencing sequence for esters is as follows:addition of aroma extracting solution> proportion of recycled liquids> treatment temperature. The influencing sequence for alcohols is as follows:treatment temperature> addition of aroma extracting solution> proportion of recycled liquids. The influencing sequence for acids is as follows:proportion of recycled liquids> addition of aroma extracting solution> treatment temperature. The influencing sequence for aldehydes and ketones are as follows:treatment temperature> addition of aroma extracting solution> proportion of recycled liquids.(4) The further study showed that the eater content was decreased during the hydrolysis process, while ultrafiltration process increased original easter matter and produced lots of new easter. Easters were decreased during aroma recovery processing and pasteurization could increase easter matter. This was mainly because of producing new easters rather than the increase of original easters.(5) After the long heating at lower than70℃, including enzyme hydrolysis and aroma recovery processing, both types and contents of alcohols were increased. At the pasteurization more than90℃, alcohols content was decreased while ultrafiltration process partly decreased alcohols content and produced less new alcohols matter.(6) Changes of acids were similar to alcohols. After the long heating at lower than70℃, including enzyme hydrolysis and aroma recovery processing, both types and contents of acids were increased. At the pasteurization more than90℃, acids content was decreased while ultrafiltration process partly decreased acids content and produced less new acids matter.(7) The increase of aldehydes and ketones in the process of enzymatic hydrolyzing is the result of joint action both of the old substance increase and of the new substance formation. In the original UF process, the total content of aldehydes and ketones was decreased by the degradation of6kinds of substance. The increase of the total content of aldehydes and ketones in concentrating process is largely due to the formation of new substance and not to the increase of old substance. Original pasteurization decreased or even eliminated part of the aldehydes and ketones, and produced few new aldehydes and ketones at the same time.(8) In the concentrated apple juice processing, the total contents of aromatic substances show a downward trend. Esters and alcohols were decreased lower acids and aldehydes and ketones were increased.