Effects of melatonin treatment on browning alleviation of fresh-cut foods.

Enzymatic browning is the main quality issue of fresh-cut foods. This study investigated the effects of different concentrations (0.05, 0.1, and 0.2 mM) of melatonin (MT) treatment on the enzymatic browning of four fresh-cut foods, including apples (Malus domestica), pears (Pyrus spp.), potatoes (Solanum tuberosum), and taros (Colocasia esculenta), and found that only 0.05 mM MT was most significant at enhancing the L* values and reducing the browning index (BI) in all four foods. This suggests that 0.05 mM MT might be a universal concentration for the browning alleviation of fresh-cut foods. MT treatment increased the total phenolic contents and PAL activities but reduced the activities of POD, PPO, and LOX in fresh-cut taros. Furthermore, MT significantly affected the expression of sixteen browning-related genes in fresh-cut taros during storage. These results suggest that MT reduced fresh-cut food browning by regulating the activities of browning-related enzymes. However, MT did not significantly influence the browning degree or PPO activity of the taro mash in vitro, suggesting that MT might regulate enzyme activity in an indirect manner. Overall, these results indicate that MT might be a promising anti-browning agent to alleviate the browning of fresh-cut foods. PRACTICAL APPLICATIONS: Melatonin (MT) is an endogenously produced indoleamine. Previous studies have reported that MT displays protective activities in many agricultural products. However, the reported protective MT concentrations vary between different products. To extend this agent to the fresh-cut industry, it is necessary to determine the universal dosage of MT needed for application efficiency. In this study, the effects of three concentrations (0.05, 0.1, and 0.2 mM) of MT on four fresh-cut foods, including apples, pears, potatoes, and taros, were investigated. The results showed that MT treatment alleviated browning development in the slices of these four foods and that 0.05 mM MT was the most effective treatment. Moreover, 0.05 mM MT significantly affected the activities of browning-related enzymes. These results suggest that 0.05 mM MT is a universal dosage for reducing surface browning in fresh-cut foods. This study provides a foundation for the application of MT in the processing of fresh-cut foods, especially fresh-cut taros.

Synergistic improvement of crop physiological status by combination of cadmium immobilization and micronutrient fertilization.

Wollastonite application in cadmium-contaminated soils can reduce cadmium concentrations in plant, while the side effect is the synchronous immobilization of micronutrients, which reduces micronutrient uptake in plant, inducing micronutrient deficient symptoms. Accordingly, we investigated whether the supplement of Zn and Mn fertilizers after the wollastonite addition could promote the growth and photosynthesis in amaranth (Amaranthus tricolor L.). In this study, plants were cultivated in cadmium-contaminated soil under micronutrient fertilization alone, wollastonite addition, and combination of wollastonite and micronutrient fertilization treatments. Then, plant biomass; photosynthesis parameters; and total Cd, Zn, and Mn concentrations were investigated. Moreover, chemical extractions were performed on soil samples. The results show that application of wollastonite decreased Cd, Zn, and Mn concentrations in plant and availability in soil and it increased the gas exchange ability of plants. But, it reduced the chlorophyll content in leaves and had no positive influence on plant biomass. In comparison, Zn and Mn fertilization after wollastonite application greatly increased plant biomass and photosynthetic ability. It also reduced Cd phytoavailability more efficiently. Therefore, synergistic improvement of physiological status of farmland crop by sequential treatment with first wollastonite for cadmium immobilization, and then micronutrient fertilization to avoid micronutrient deficiency, was demonstrated.