Melatonin maintains the storage quality of fresh-cut Chinese water chestnuts by regulating phenolic and reactive oxygen species metabolism

Fresh-cut Chinese water chestnuts(CWCs)are prone to quality deterioration during storage,which does not meet consumer demand.In this study,the effect of exogenous melatonin(5 mmol·L^(-1))on the quality and potential mechanisms in fresh-cut CWC was investigated.The results showed that melatonin treatment alleviated the cut-surface discoloration of CWCs.Not only did this treatment significantly slow down the in-crease in browning degree and yellowness(b*)as well as the decrease in lightness(L*),but it also significantly delayed the loss of weight and total soluble solids.Further investigations indicated that melatonin-treated fresh-cut CWCs exhibited significantly lower total phenolics and soluble quinones and suppressed the activities of phenylalanine ammonia-lyase,polyphenol oxidase,and peroxidase.Meanwhile,when fresh-cut CWCs were treated with melatonin,the total flavonoid concentration was significantly decreased compared to the control.Ad ditionally,melatonin significantly inhibited the accumulation of H_(2)O_(2)and malondialdehyde as well as enhanced the activities of superoxide dismutase and catalase by promoting the production of O_(2)^(-·).In summary,melatonin treatment may delay the surface discoloration of fresh-cut CWCs by inhibiting phenolic compound metabolism and improving antioxidant capacity,thereby effectively maintaining the quality and prolonging the shelf life of fresh-cut CWCs.

Research on Genetic Diversities between Xiaogan Water Chestnut and Wild Chestnut by Randomly Amplified Polymorphic DNA Technology

[Objective] The aim was to study the genetic diversities between Xiaogan water chestnut and wild chestnut with randomly amplified polymorphic DNA （RAPD） technology. [Method] Genetic diversities of the local cultivated water chestnut,wild chestnut,Lepironia articulata and Scirpus planiculmis Fr. Schmidt were analyzed by RAPD technology. [Result] Among the screened random primers 841,842,807 and 840,the polymorphism of amplification product of 841 was evident,and the obtained bands in electrophoresis were clear and showed good repeatability. Cluster analysis result showed that the affinity of cultivated water chestnut and wild water chestnut was nearer than that between Lepironia articulata and Scirpus planiculmis. [Conclusion] The research provides theoretical basis for cultivating high-quality new varieties of water chestnut.

Flowering Habits and Seed Setting Traits under Artificial Pollination in Chinese Water Chestnut(Eleocharis dulcis)

[Objective] This study was conducted to investigate the crossbreeding method for Chinese water chestnut. [Method] The growth of Chinese water chestnut stalk and inflorescence was observed. Chinese water chestnut flowering law and stamen and pistil growth were investigated in an artificial pollination experiment. [Result] Stamens and pistils reached their full bloom stages when the flower stalk lengths were approximate 37.0 and 46.9 cm, respectively, with a height difference of 9.84 cm and time difference of 28.5 h; and 9：00-11：00 a.m. was the optimal period for artificial pollination. Seven hours after artificial pollination, pistils wilted rapidly. The seed setting rates under artificial pollination and a natural condition was 43% and 15.5%, respectively. [Conclusion} The time difference between the full bloom stages of stamens and pistils is crucial to the success of artificial pollination of Chinese water chestnut. The seed setting rate under artificial pollination is much higher than that under a natural condition.

Optimization of Microwave Extraction of Flavonoids from Water Chestnut Skin Dregs with Response Surface Method

[Objective] In order to take full advantage of processing by-product of water chestnut, the microwave extraction method of flavonoids from water chestnut skin dregs was optimized. The extracted flavonoids had a relatively high yield. [Method] The Box-Behnken design-based response surface method was adopted to optimize the microwave extraction of flavonoids from water chestnut skin dregs, a by-product of water chestnut starch. The mathematical relationships between various influencing factors and flavonoids yield were established. [Result] The optimum extraction conditions of flavonoids from water chestnut skin dregs were as follows： ethanol concentration of 55.4%, solid/liquid ratio of 1：30 g/ml, microwave power of 320 W, microwave time of 3 min and microwave time of 2 times. Under the optimum extraction conditions, the theoretical flavonoids yield was 2.376%. However, the actual flavonoids yield under the optimum extraction conditions was 2.365%. The relative error between actual values and theoretically predicted values was 0.461%. [Conclusion] The results showed the optimized extraction method is reliable, and it can provide a reference for the comprehensive and highly efficient utilization of water chestnut processing wastes.

Development of Tuanfeng Fermented Water Chestnut Beverage

With Tuanfeng water chestnut as a raw material, the optimal fermentation conditions for Tuanfeng fermented water chestnut beverage were obtained as follows ： pulp-to-water ratio at 1：2, inoculation amount of 2.00%, fermentation temperature at 41℃, and fermentation time of 8 h.

Effect of Water Chestnut Powder on Gel Properties of Silver Carp Surimi

[Objectives]The effects of water chestnut powder on the gel properties and quality of silver carp surimi were investigated.[Methods]The surimi gel was prepared by adding 0%,1%,2%,3%,4%and 5%of water chestnut powder to the surimi of silver carp.The gel properties,water-holding capacity,cooking loss,whiteness value,puncture and texture profile analysis(TPA)indexes of surimi products were determined to assess the effects of adding different amounts of water chestnut powder on surimi gel.[Results]The results showed that the gel strength,breaking force and depression distance of surimi products increased first and then decreased with the increase of the addition of water chestnut powder.Compared with the control group,the hardness and chewiness of surimi gel in TPA could be significantly improved by adding water chestnut powder.When the addition of water chestnut powder was 2%,the maximum water-holding capacity was 83.68%;the cooking loss rate was the lowest;and the whiteness value was the highest.Adding 2%of water chestnut powder could significantly improve the gel properties of silver carp surimi and obtain a good gel product.[Conclusions]This study provides a scientific basis for the effective utilization of water chestnut resources and the development of new fish surimi products.

Fermentation Conditions on the Production of Single Cell Protein Feed by Water Chestnut Peel

In order to improve the comprehensive utilization value of water chestnut peel and the income of farmers. Contents of crude protein （ CP）, total sugar and reducing sugar were taken as indicators. Effects of initial pH, ratio of yeast to fungi species, incubation time and liquid volume on production of single cell pro- tein （SCP） feed was studied, and technological conditions on production of SCP feed by water chestnut peel were optimized by orthogonal test. Results showed that the production of SCP feed by water chestnut peel was optimal when pH was 5.0, ratio of yeast to fungi species was 2： 1, fermentation time was 2 d and the liquid volume was 70 mL / 250 mL. Under the optimum conditions, content of fermentation CP was 64.25%, content of total sugar was 19.8%, content of reducing sugar was 5.0%, content of coarse fibre was 0.0% and content of ash was 8.04%.