单体速冻荔枝生产工艺的研究

通过对单体速冻荔枝生产工艺的研究与实践,探索出单体速冻荔枝较佳的生产工艺,并制定了单体速冻荔枝产品标准。同时对原料成熟度的选择、荔枝的热烫处理与浸酸护色、荔枝的预冷、荔枝的速冻等关键生产工艺进行了研究。     

Improved energy efficiency of farmers' cooperative litchi drying operation in Northern Thailand

In 2007, Hmong farmers growing litchi in the mountainous region of Northern Thailand started to dry the fruit in response to its declining market price. However, the locally available dryer, although affordable and of a size appropriate for smallholder farmers' cooperatives, showed excessive gas consumption, and this, along with rising fuel costs, imposed a threat to the drying operation. The objective of this study was to test low‐cost, easy‐to‐implement modifications to a locally available convection dryer, to improve its energy efficiency. Experiments were conducted in cooperation with a Hmong farmers' cooperative in Northern Thailand. Insulation of the air ducts and control of the air recirculation rate led to energy cost savings of US$2.45 per dryer‐load. With the modifications required being simple, the investment needed was recovered after only approximately 20 loads, while the energy efficiency of the dryer increased from 33% to 39%.     

A comparative analysis of property of lychee polyphenoloxidase using endogenous and exogenous substrates

Lychee polyphenoloxidase (PPO) was extracted and partially purified using ammonium sulphate precipitation and dialysis. The comparative analysis of PPO property was performed using its endogenous substrate (–)-epicatechin and exogenous substrate catechol. The pH optima for activity and activation temperature profiles of lychee PPO were very different when the enzyme reacted with endogenous and exogenous substrates. The addition of ethylenediaminetetraacetic acid disodium salt into the endogenous or exogenous substrate–enzyme system exhibited the same lowest inhibition of the PPO activity. However, l-cysteine was most effective in inhibiting enzymatic activity in the endogenous substrate–enzyme system while ascorbic acid was the best inhibitor in the exogenous substrate–enzyme system. Fe²⁺ greatly accelerated the enzymatic reaction between endogenous substrate and PPO, but Cu²⁺ exerted the same effect on the reaction between exogenous substrate and PPO. Based on the kinetic analysis, lychee PPO could strongly bind endogenous substrate but it possessed a higher catalytic efficiency to exogenous substrate.     

Visible light-induced photodegradation of methylene blue and reduction of 4-nitrophenol to 4-aminophenol over bio-synthesized silver nanoparticles

Silver nanoparticles are synthesized by an eco-friendly protocol using Litchi chinensis fruit juice as a reducing and capping agent. UV-vis spectroscopy (SPR band around 447 nm), XRD (crystallinity), HRTEM (size and morphology), EDS (elemental composition) and FTIR (surface functionalities) were used to characterize silver nanoparticles. They are highly dispersed, mostly spherical with an average size of 10 nm. The prepared nanoparticles exhibited rapid reduction of 4-nitro phenol to 4-amino phenol (K = 0.09/min) and photodegradation of methylene blue (K = 0.0335/min) under visible light. The prepared nanoparticles could be an excellent candidate for the separation of hazardous materials.     

Effect of Ozone Treatment on the Reduction of Chlorpyrifos Residues in Fresh Lychee Fruits

The effect of ozone on the reduction of chlorpyrifos residue in lychee cv. Chakapat (Litchi chinensis Sonn.) was studied. Lychee fruits were dipped in the solution of chlorpyrifos at a concentration of 10 mg L^?1 for 10 min. Then, they were exposed to ozone gas (O₃) at concentrations of 80, 160, 200, 240 mg L^?1 and dipped in ozone-containing water, at concentrations of 2.2, 2.4, 3.4 and 3.2 mg. L^?1 for 10, 20, 30 and 60 min, respectively. Both ozone gas and ozone-containing water reduced pesticide residue in lychee, but exposure to ozone gas for 60 min was most effective. When lychee fruits were stored at 25 °C for 6 days, both processes did not show significant differences in weight loss, total soluble solids (TSS) and titratable acidity (TA). However, ozone-containing water decreased the eating quality of lychees after storage, compared with the ozone-fumigated groups.     

荔枝品种的酿酒适性

为充分利用荔枝资源,提高荔枝酒品质,研究了广东省主栽荔枝品种的加工性质、酶解性质和酿酒性能,结果表明:对酿酒品质影响较大的因素是荔枝的香气和糖酸含量,如“仙婆果”、“糯米糍”、“淮枝”和“妃子笑”荔枝清甜香浓,发酵时可赋予果酒典型的荔枝香味;经果胶酶酶解后,榨汁容易,出汁率高,且稳定性好。通过对不同品种荔枝成品酒的品质分析比较,得出“仙婆果”为酿造荔枝酒的最佳品种,“糯米糍”、“淮枝”和“妃子笑”为酿造荔枝酒的优良品种。     

基于城市更新视角的旧城中心区水系整治——以广州荔枝湾涌、东濠涌为例

以广州市荔枝湾涌、东濠涌整治工程为例,从城市更新的角度探讨大事件促成的旧城中心区水系整治所面临的种种问题及措施.先简要分析当前中国城市更新和旧城中心区水系整治的关系和主要特点,继而介绍广州市2项重点工程的主要内容.在此基础上从更新目标与效果差异、利益格局多元博弈、管理机制内在失谐、更新发展难以持续4个方面分析其中的冲突,并思考整治方法的不足.最后提出旧城中心区水系整治是历史文化生态综合廊道的建设,另外也需注意社会经济和管理制度2个方面的重要作用.