Protenction Of Volatile Compounds In Post-harvest Red Fragrant Pear By CAP

Red fragrant pear(Pyrus spp ‘Red fragrant pear’)is famous for its special aroma.The aroma of red fragrant pear is easy to loss even deterioration under unsuitable conditions. This study focused on the volatile compounds of Red fragrant pear during storage. The prediction model of soluble solid content(SSC) and pulp firmness was established by electronic nose(EN). The condition of controlled atmosphere package(CAP) was optimized. The protection of CAP to volatile compounds was analyzed.This study provides support for detecting the quality and extending the shelf life of Red fragrant pear rapidly. The main findings were as follows:(1) In order to evaluate the property index of Red fragrant pear rapidly, the volatile compounds of Red fragrant pear were detected by electronic nose during storage. In order to achieve non-destructivedetection rapidly, partial least-squares regression(PLS), back-propagation(BP) network and multiple linear regression(MLR) were applied to predict the pulp hardness and SSC of Red fragrant pear by mathematical model. The results of EN showed that No. 2, 7 sensors varies significantly during storage and primary sensors were No. 2, 7, 9 sensors for analyzing the volatile aromatic compounds. Flavor changes can be distinguished between different storage of Red fragrant pear by LDA but PCA can not. The prediction results showed that the model of BP network was the best in three prediction model. In SSC model, R2=0.91,RMSEC=0.43. In pulp hardness model, R2=0.89,RMSEC=2.42. The results between prediction and measurements of SSC and pulp hardness existed good fitting degree in test set. The response signal of EN can predict the SSC and pulp hardness of Red fragrant pear effectively.(2) Seven kinds of common plastics materials as controlled atmospherepackaging(CAP) were preliminarily studied. These packages were filled with N2, air,vacuum, and the pears which exposed to ambient air were as the control. The results showed that there were quite different among the species and thickness of materials.Materials of PO, LDPE and CPP were more suitable for CAP of Red fragrant pear, and the effects of N2 were significantly better than that of air and vacuum.(3) Box-Benhnken principle was used to optimize of condition on CAP of Red fragrant pear by response surface methodology. The results were as follows:Y=78.17-3.75X1-3.17X2+1.25X3+1.50X4-3.50X1X2+2.75X1X3-3.50X1X4+1.50X2X3+0.50X2X4-2.50X3X4. The optimal conditions for CAP were that Material PO, temperature1.8 ℃, 4.6% O2 and 5.9% CO2. The equation coefficient of determination R2=0.9126.This equation can be used to optimize the condition on CAP. Validation results indicated that optimized condition was suitable for presentation inferring from the sensory evaluation score and quality index. Reliability of Box-Benhnken experimental design and response surface methodology was validated.(4) The content of aroma compounds in unbroken fruit was higher than fruit puree. The optimal extraction condition for GC-MS was that extraction temperature60 ℃, extraction time 45 min and Na Cl concentration 0.36 g/m L. The content of esters was mainly affected by hexyl acetate, ethyl butyrate and ethyl acetate. Alcohols increased slowly at initial storage time and then fell. Aldehydes decreased during the storage. Hexanal contributed to aldehydes mainly. 2-furan-carboxylic acid contributed to acids mainly. Compared with CK, the content of active volatiles was higher in CAP,which was contributed to the content of hexyl acetate, ethyl butyrate, ethyl acetate and hexanal. CAP can inhibit the undesirable flavor, including acid during the storage.