Xuehui Cao,Ge Bai,Jianrong Zheng,Danshi Zhu,Jianrong Li
Freezing is a way to preserve the quality of fruit for a long time. Nanguo pear stored at low temperature is prone to browning and lignification. In this study, freeze–thaw cycles were used to simulate the temperature fluctuation in the process, storage, and transportation. The texture properties were taken as the research focus to analyze the lignification phenomenon of Nanguo pear under freeze–thaw cycles. The results showed that freeze–thaw treatment significantly reduced the firmness and propectin content of Nanguo pear, increased the content of stone cells in the fruit, but also destroyed the size of stone cells in the fruit. However, with the increase of freezing–thawing cycles, the content of lignin, stone cell content, and PAL activity increased significantly, while the content of chlorogenic acid increased first and then decreased. These results are helpful to further understand the correlation between texture change with fruit firmness and formation mechanism of stone cells during freeze–thaw cycles of Nanguo pear.
Cold storage can effectively delay the ripening of ‘Nanguo’ pears ( Pyrus ussuriensis Maxim.). However, the aroma-related esters of ‘Nanguo’ pears decreased after cold storage. In this study, we aimed to investigate the effect of intermittent warming (IW) treatment on the formation of aroma-related esters and unsaturated fatty acid synthesis from cold stored pears. IW-treated pears were exposed to 20 ± 1 °C for 1 day every 20 days during storage at 0 ± 0.5 °C, every 21 days was a cycle and a total of 90 days. The pears in control group were stored at 0 ± 0.5 °C for 90 days. After this 90-day storage, both groups of pears (control and IW-treated) were transferred to a shelf life of 12 days at room temperature. The results showed that, compared with the pears in control group, the productions of aroma-related esters and the expression levels of PuLOX1 , PuADH3 , and PuAAT1 in IW-treated pears were significantly higher during the shelf life ( P < 0.05). At the same time, IW-treated pears maintained significantly higher contents of linoleic acid and linolenic acid ( P < 0.05), which were precursors of aroma compounds. We also found that the expression of PuFAD2 and PuFAD3 had significant positive correlation with the contents of unsaturated fatty acids ( P < 0.05). The significantly higher expression levels of PuFAD2 and PuFAD3 in IW-treated pears may have played an important role in the improvement of ester contents ( P < 0.05). It could be inferred that IW treatment had an impact on the aroma-related esters of cold-stored ‘Nanguo’ pears through regulation of unsaturated fatty acid synthesis.
Hui Jiang,Fei Wu,Xi Jiang,Yun-Feng Pu,Li-Rong Shen,Cui-Yun Wu,Hong-Jin Bai
Pear is one of the most popular fruits in the world. With the fruit ripening, a series of physiological changes have taken place in fragrant pear, but up to now, the research on the metabolism and biological activity of phenolic compounds in different growth stages of fragrant pear is still lacking. In this study, four kinds of Xinjiang pears were selected as research objects, and the changes of phenolic content, antioxidant capacity, cell protection and whitening activity during fruit development were analyzed. The results showed that the phenolic content and antioxidant capacity of four pear varieties presented a decreasing trend throughout the developmental stages. The phenolic content and antioxidant activity of the four pears in the young fruit stage were the highest, and the active ingredients of the Nanguo pear were higher than the other three pear fruits. Pear extract could protect cells by eliminating excessive ROS in cells, especially in young fruit stage. The western blot results showed that the extract of fragrant pear in the young fruit stage could inhibit the expression of TYR, TYR1 and MITF in B16 cells, and it was speculated that the extract of fragrant pear in the young fruit stage might have good whitening activity. Therefore, the findings suggest that young pear display a good antioxidant potential and could have a good application prospect in food preservation and health product industry.
危险品化学品经营许可证（带存储）