Reduction in Activity/Gene Expression of Anthocyanin Degradation Enzymes in Lychee Pericarp is Responsible for the Color Protection of the Fruit by Heat and Acid Treatment

Heat and acid treatments were reported to be a promising substitute for SO2 fumigation in color protection of postharvest lychee （Litchi chinensis） fruits, but the mechanism was not clear. In the present study, hot water （70℃） dipping followed by immersion in 2% HC1 （heat-acid） substantially protected the red color of the fruit during storage at 25℃ and inhibited anthocyanin degradation while hot water dipping alone （heat） led to rapidly browning and about 90% loss in anthocyanin content. The pH values in the pericarp of the heat-acid treated fruit dropped to 3.2, while the values maintained around 5.0 in the heat-treated and control fruit. No significantly different pH values were detected among the arils of heat-acid, heat treated and control fruit. Heat-acid treatment dramatically reduced the activities of anthocyanin degradation enzyme （ADE）, peroxidase （POD） and polyphenol oxidase in the pericarp. A marked reduction in LcPOD gene expression was also detected in heat-acid treated fruit, in contrast, induction was found in heat treated fruit. The pericarp of heat-acid treated fruit exhibited significantly lower respiration rate but faster water loss than that of the untreated or heat treated fruit. Taken together, heat treatment triggered quick browning and anthocyanin loss in lychee fruit, while heat-acid treatment protected the fruit color by a great reduction in the activities/gene expression of anthocyanin degradation enzymes and acidification of lychee pericarp.

Lychee seed saponins improve cognitive function and ameliorate hippocampal neuronal injury in Alzheimer disease rat model induced by Aβ_(25-35) through AKT/GSK3β pathway

OBJECTIVE Lychee seed,a famous traditional Chinese medicine,recently were reported to improve the learning and memory abilities in mice.However,it is still unclear whether lychee seed saponins(LSS)can improve the cognitive function and associated mechanisms.METHODS In present studies,we established the Alzheimer disease(AD)model by injecting Aβ25-35 into the lateral ventricle of rats.Then the spatial learning and memory abilities of LSS-treated rats were evaluated with the Morris water maze,meanwhile the protein expressions of AKT,GSK3β and Tau in the hippocampal neuron were analyzed by immunohistochemistry and Western blotting.RESULTS The results showed LSS can improve the cognitive functions of AD rats through shortening the escape latency,increasing the number across the platform,platform quadrant dwell time and the percentage of the total distance run platform quadrant.The protein expression of AKT was significantly up-regulated and that of GSK3β and Tau were decreased remarkably in the hippocampal CA1 area.CONCLUSION Our study is the first to show that LSS significantly improve the cognitive function and prevent hippocampal neuronal injury of the rats with AD by activation of the PI3K/AKT/GSK3βsignaling pathway,suggesting LSS may be developed into the nutrient supplement for the treatment of AD.

A Study on the Ultrasonic Extraction and Antioxidant Activity of Lychee Pericarp Polysaccharides

The aim was to optimize ultrasonic extraction conditions and study antioxidant activities of lychee pericarp polysaccharides. The effects of extraction temperature,time,ultrasonic power,solid-liquid ratio on polysaccharides yield were investigated by single-factor experiment and orthogonal experiment to obtain optimum extraction conditions; the antioxidant activities of lychee pericarp polysaccharides were evaluated by the total antioxidant activity. Optimum extraction process was under extraction temperature of 80 ℃,extraction time of 2. 5 h,ultrasonic power of 180 W,solid-liquid ratio of 1∶ 25 g / m L; the total antioxidant activity was increased with the increasing concentration of polysaccharides. The extraction process is simple and efficient. The extraction rate of lychee pericarp polysaccharides with antioxidant activities is high.

Effect of Long-term Drip Fertigation on Root Growth of Lychee and Soil pH

Through field experiment,we explore the impact of long-term drip fertigation on growth and distribution of lychee root and changes of soil pH in different layers of soil in lychee garden.The results show that drip fertigation can significantly promote the growth of lychee roots,and increase the contact area of root and soil;if it experiences six years of drip fertigation successively,the dry weight of root,root length and surface area of root in soil in drip fertigation area,will be 2.29 times,2.17 times and 2.25 times that in non-drip fertigation area,respectively.The lychee root is mainly distributed in 0-40 cm layer of soil,but there is conspicuous difference between drip fertigation area and non-drip fertigation area in terms of root distribution in 0-20 cm and 20-40 cm layer of soil.Drip fertigation is more favorable for the root to go deep inside the soil.Under long-term drip fertigation,the soil acidification in lychee garden is prominent,and in comparison with non-drip fertigation area,there is the greatest decline in soil pH in 10-20 cm layer of soil in drip fertigation area,reaching 1.47 units.

Linear Regression Relationship between Lychee Juice Content and Buffering Capacity

Juice drinks are an important commercialization alternative for lychee, a tropical and subtropical fruit. Although the lychee juice content is important when assessing the quality of a drink, there are no published methods to determine it, particularly simple ones for the routine inspection of juice drinks. Lychee juice drinks contain ingredients with buffering capacity including proteins and ions such as phosphate, citrate, lactate, carbonate, acetate and propionate. The relationship between their buffering capacity and lychee juice content was studied. Citric acid was added to pure lychee dilutions in distilled water containing 100%, 90%, 80%, 70%, 60%, 50%, 40%, 30%, 20% and 10% lychee juice. The pH of the dilutions was measured to obtain a linear model for the molar H+ concentration as a function of the added citric acid (g/L) amount LC = (BC-494.2)/12,031, where LC was the lychee juice content and BC was defined as the juice buffering coefficient.

STUDIES ON DESICCATION-SENSITIVITY AND PEROXIDATION OF MEMBRANE LIPIDS IN LYCHEE(Litchi chinensis Sonn. ) SEEDS

Roberts has divided seeds into orthodox seeds and recalcitrant seeds according to their storage behaviours. The former can tolerate desiccation and freezing temperatures, whereas the latter are susceptible to the two factors. When their water contents are lower than cer-

Microstructure changing and moisture removing of lychee during microwave vacuum drying

Micrographs of lychee pericarp and pulp during microwave vacuum drying were tested and analyzed in order to illuminate the microstructure change of lychee and effect of the change on moisture removing in lychee.The results showed that the pericarp consisted of three parts:outer layer with cuticle,inter layer and inner layer.Outer layer and inter layer cells are easily destroyed than inner layer because of small and intact inner layer cells.Furthermore,micrographs showed that the moisture content of pulp keep constant with the temperature increasing at first 40 min due to the inner layer cells prevent the moisture removing from pulp.The long tubular structure of pulp cell would become break and lost over time,because the intercellular spaces reduced and the moisture removing was slow down in pulp.Meanwhile,the microstructure of lychee dried with temperature control was better than that without temperature control.

Germination of lychee seeds after maturation and their ultrastructure observation

Lychee is one of the famous fruits in the subtropical regions. However, lychee seedsdo not undergo maturation desiccation during development, and cannot tolerate drying andchilling in storage. Under natural conditions, lychee seeds can only maintain viability forseveral days, and their germplasm conservation is rather difficult using conventional meth-ods. So they are called recalcitrant seeds.

Optimization of lychee wine fermentation process using response surface methodology to reduce acetic acid content

Acetic acid is the main component of the volatile acid in the wine.However,excessive amounts of acetic acid negatively affect wine quality.The study aimed to decrease acetic acid content produced by Saccharomyces cerevisiae fermentation after adding metal ion at different temperatures.Response surface methodology(RSM)was used to predict the optimum conditions for acetic acid removal.A central composite design was employed for the experiments and results were analyzed to obtain the best possible combination of fermentation temperature(X1:16℃-24℃)and concentrations of potassium(X2:0-12.0 mM),magnesium(X3:0-8.0 mM),and calcium ions(X4:0-0.2 mM)that would generate the minimum acetic acid in lychee wine at an initial acetic acid concentration of 1.5 g/L.Experimental data were fitted to a second-order polynomial equation using multiple regression analysis and analyzed using analysis of variance(ANOVA).During fermentation under pre-established conditions,the correlation coefficients R2 and Adj-R2 of the models for acetic acid removal were 0.9487 and 0.9007,respectively.After testing,the optimum conditions for acetic acid removal were determined as follows:fermentation temperature of 20℃;potassium,magnesium,and calcium ion concentrations of 10.1 mM,6.1 mM,and 0.2 mM,respectively.The experimental acetic acid content of lychee wine under optimal conditions was found to be 0.309 g/L,which agreed well with the model-predicted value of 0.314 g/L.

荔枝、蜜蜂及蜂蜜中7种农药残留的分析方法

【目的】针对目前荔枝上农药使用量的增加、使用种类的扩大，建立荔枝叶、荔枝花、荔枝蜜及蜜蜂上的7种农药的残留检测分析方法。【方法】样品用乙酸乙酯或乙腈提取，氨基固相萃取小柱净化，气相色谱法-电子捕获检测器（GO-ECD）检测7种农药的残留量。【结果】荔枝叶、荔枝花、荔枝蜜及蜜蜂在添加水平为0．01、0．1、1mg／kg时的平均添加回收率分别为79．9％-88．5％、80．5％-90．0％、80．0％～90．1％和79．9％-90．4％；相对标准偏差分别为0．86％-5．73％、1．58％，6．69％、1．79％～6．77％和1．75％。6．32％。【结论】该方法能够较准确的检测荔枝叶、荔枝花、荔枝蜜和蜜蜂中的农药残留量，符合农药残留的检测要求，对于研究农药在荔枝上的传导特性具有重要意义。

Optimal physicochemical properties of dried litchis for Thai consumers

The litchi is a fruit essential for the economies of several Southeast Asian countries,but markets regularly reject it,mainly due to spoilage.Drying extends the shelf-life of litchis,but in Thailand the optimal characteristics of the dried product have not yet been determined.The purpose of this study was to determine the optimum physicochemical properties of dried litchis-those suitable for Thai consumers.The dried fruits were submitted to physicochemical measurement and consumer evaluation,with datasets subsequently integrated using circular ideal-point regression analysis.Response surface methodology was then used to predict the optimum physicochemical properties of the fruits.It was found that Thai consumer preferences with regard to dried litchis are for the fruits to be of golden-yellow color(L*ranging around 54;H ranging around 79°),to have a soft flesh(SMF ranging between 13 and 14 kN/100 g)and to have a sweet taste(TSS:TA ranging between 25 and 28).The results may be used in the future to prescribe pretreatments and drying conditions.