Thermal conditions and active substance stability affect the isomerization and degradation of lycopene.

This study evaluated the effects of thermal treatment conditions (100-120 °C, 0-5 h) and active substance stability on the isomerization and degradation of lycopene in the "Sanhong" pummelo (C. grandis cv. Sanhongmiyou) matrix. The results revealed that the degradation of (all-E)-lycopene and total lycopene in pummelo could be well fit by the first-order kinetic model under thermal treatment. The total Z-lycopene ratio was maintained at nearly 40 % (120 °C, 4 h). The behavior of lycopene was related to the degradation of active substances, such as the degradation of ascorbic acid and polysaccharides. The stability of polysaccharides was temperature-dependent, and with the increasing temperature (100-120 °C), a significant negative correlation was observed between the content of Z-isomers and polysaccharides. The enhancement of lycopene isomerization was attributed to the degradation of polysaccharides under thermal treatment. These findings facilitate the functional development and efficient utilization of lycopene in fruit processing.

Citrus mangshanensis Pollen Confers a Xenia Effect on Linalool Oxide Accumulation in Pummelo Fruit by Enhancing the Expression of a Cytochrome P450 78A7 Gene CitLO1.

The aroma quality of citrus fruit is determined by volatiles that are present at extremely low levels in the citrus fruit juice sacs; it can be greatly improved by increasing volatiles. In this study, we showed that the contents of cis- and trans-linalool oxides were significantly increased in the juice sacs of three pummelos artificially pollinated with the Citrus mangshanensis (MS) pollen. A novel cytochrome P450 78A7 gene (CitLO1) was significantly upregulated in the juice sacs of Huanong Red pummelo pollinated with MS pollen in comparison to that with open pollination. Compared to wild-type tobacco Bright-Yellow2 cells, transgenic cells overexpressing CitLO1 promoted a 3- to 4-fold more conversion of (-)-linalool to cis- and trans-linalool oxides. Overall, our results suggest that MS pollen has a xenia effect on pummelo fruit aroma quality, and CitLO1 is a linalool oxide synthase gene that played an important role in the xenia effect.