No abstract

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.

ABSTRACT:The effects of yeast-derived protein (YP) on growth performance, intestinal health, and oxidative status of weanling piglets were investigated. A total of 80 weaned piglets (PIC 327 × 1050, 26 ± 2 days old, 6.20 ± 0.10 kg) were randomly allocated into 2 groups, 5 pens per each group and 8 piglets per each pen, receiving control diet and diet with inclusion of 4% YP at the expenses of fish meal (YP diet) for a period of 28 days. The diets were formulated to contain similar nutrient levels. Compared with control, piglets fed YP diet had markedly higher overall average daily growth (+14%, P < 0.05) and lower final feed conversion ratio (−8%, P < 0.01). Concentrations of serum serine, cystathionine, histidine, hydroxyproline, and urea were decreased in piglets fed YP diet (P < 0.05), whereas alanine and aspartate were increased (P < 0.01). Moreover, serum antioxidant enzyme activity (glutathione peroxidase) was markedly increased (+19%, P < 0.01) in piglets fed YP diet relative to piglets fed control diet. In addition, feeding YP diet considerably (P < 0.05) increased the copy numbers of lactobacilli and total bacteria in the colon of piglets at the end of the experiment. Furthermore, the mRNA abundance of innate immunity-related genes (TLR4, NF-κB1, and IL-6) was increased (P < 0.06) in the ileum of piglets fed YP diet. Collectively, results of this study indicated that diet with the inclusion of YP improved growth performance and partially enhanced anti-oxidative capability as well as intestinal innate immunity of weaning piglets.