影响荔枝酒发酵过程中挥发酸的因素

挥发酸的控制是荔枝酒的生产过程中的重要技术瓶颈,发酵过程易造成荔枝果酒挥     

Effect of Calcium Lactate, 4-Hexyl Resorcinol and Vacuum Packing on Physico-chemical, Sensory and Microbiological Qualities of Minimally Processed Litchi (Litchi chinensis Sonn.)

Litchi (Litchi chinensis Sonn.) fruits are very susceptible to pericarp browning which adversely affects consumer acceptability even though the aril portion remains in excellent condition. Litchi arils (litchis) were treated with a solution containing 0–2% (w/v) calcium lactate (CL), 0–0.02% (w/v) 4‐hexyl resorcinol (4‐HR) and 1% potassium sorbate. The pH of solution was adjusted to 4.0 with citric acid. Treated litchis were packed in polystyrene trays, over‐wrapped with polypropylene film, vacuum‐packed (0, 47409.3, 94831.9 Pa) and stored at 4 ± 2 °C. Drip losses, pH, total soluble solids (TSS), sensory attributes and microbiological quality of stored samples were estimated. A four‐factor, three‐level experimental design (D₆ Hokes design) with 19 experiments was chosen. Mathematical models were developed to analyse and predict the effect of CL, 4‐HR, in‐package vacuum and storage time on the responses. TSS, pH and sensory scores decreased significantly (P 0.01), whereas drip losses and microbial count increased significantly (P 0.01) with time. Drip loss was significantly (P 0.1) reduced by addition of CL. 4‐HR prevented browning and changes in colour score during storage were significantly less. Vacuum in packages exerted significant (P 0.01) effect over pH, TSS, sensory and microbiological qualities of minimally processed litchis.     

基于人性化理念的荔枝剥皮器设计

目的为解决手剥荔枝不卫生和易弄伤指甲等问题,设计一款供日常食用荔枝使用的剥皮器。方法分析荔枝的物理特性和常用的荔枝剥皮方法,根据人性化设计理念中的人机工程学因素和美学因素综合进行设计:依据人手尺寸确定剥皮器手柄的造型与尺寸,根据荔枝物理特性确定刀刃的尺寸,设计并进行实验确定刀刃的锋利程度及手柄与刀刃的厚度;根据美学因素完善造型,确定3种色彩计划。结论得到了较理想的、能满足日常使用需求的荔枝剥皮器。     

荔枝保鲜的研究

在低温下 ,对不同时期的贮藏荔枝的酸度和含糖量进行了测定 ,对比了不同贮藏方法下 ,荔枝内部发生的变化     

银杏叶粗提物对荔枝的防腐保鲜效果

以银杏为研究对象,利用乙醇浸提法得到银杏叶粗提物,从色泽、VC含量、质量损失率、菌落总数以及感官评定等方面评价银杏叶粗提物对荔枝的防腐保鲜效果。结果表明:随着处理时间的延长,银杏叶粗提物能减少荔枝水分损失,抑制褐变,延缓VC含量的下降,减少微生物对荔枝果肉的侵染以及降低腐烂率,较好地保持了荔枝的感官品质。在试验浓度范围内(0.2%~0.6%),银杏叶粗提物浓度与荔枝防腐保鲜效果呈正相关。银杏叶粗提物对荔枝具有较好的防腐保鲜效果。     

Effects of pretreatments on colour alterations of litchi during drying and storage

The objective of this research was to study the effect of osmotic pretreatment with combined anti-browning agents (acid, glycerol and/or trehalose) on the colour characteristics of dried litchi after drying and during 5 months of storage compared to samples without pretreatment. The pretreated samples showed good inhibition of polyphenol oxidase activity when compared with the control, while the total phenolic contents in the dried products were not reduced. The results demonstrated that water activity, lightness difference, chroma, degree of browning (DB), and 5-hydroxymethylfurfural values of all pretreated samples increased, while hue angle decreased with storage time. Samples pretreated with glycerol showed the best potential for browning retardation, followed by glycerol combined with trehalose, and trehalose, respectively. In addition, the colour parameters were used to calculate the luminescence values, representing the data in grey scale, which were correlated with a non-enzymatic browning index. The results showed grey value could be adequately used to represent the DB of dried litchi with r ² value of 0.92.     

荔枝核淀粉理化特性的研究

利用SEM、X-光射线衍射、Brabender黏度仪、DSC等研究荔枝核淀粉的理化性质。结果表明:荔枝核淀粉颗粒多呈椭圆形或多角形,平均粒径为12.6μm;有明显的黑十字且交叉点在颗粒中心;颗粒晶体结构为C型;起糊温度较高,为85.3℃,热稳定好,有黏度峰值,为177BU;DSC测得T°、Tp、Tc分别为69.04℃、78.79℃、87.08℃,ΔHgel为7.50J/g;支链淀粉、直链淀粉含量分别为88.8%和11.2%。     

荔枝茶多酚保健饮料的研制

以茶提取物茶多酚、澄清荔枝汁等为主要成分研制出具有保健功能的饮料,通过正交试验得到最佳配方,并且对澄清工艺进行研究。实验结果表明:荔枝汁、茶多酚的添加量分别为40%、0.8g/1000mL;澄清工艺中壳聚糖的添加量为0.2～0.3g/L,室温静置4h,即可得到透光率97%以上、清澈透明且对热稳定的荔枝果汁。本品不但具有抗疲劳和抗氧化作用,并具有一定的延缓衰老作用。     

荔枝中多酚含量的测定

为快速准确检测荔枝中的多酚,选择白糖罂、白腊、糯米糍3个品种,分别提取、测定其不同部位多酚含量;测定条件是:C18色谱柱,检测波长280 nm,柱温42℃,进样量10μL,3%乙酸水溶液与乙腈梯度洗脱。结果表明:以丙酮为溶剂提取效果最好;多酚总量为白糖罂(662.51 mg/kg)>白腊(442.20)>糯米糍(264.36 mg/kg);在所测9种多酚中,表儿茶素含量最高,依次为394.07、242.45、168.79 mg/kg。3种荔枝果肉中多酚总量依次为3.41、5.78、3.00 mg/kg,果皮中多酚总量依次为469.89、155.96、137.89 mg/kg,果核中多酚总量依次为189.21、283.24、120.69mg/kg。同一品种不同部位是果肉中多酚含量最低,果皮与果核中多酚含量的高低则因品种而异,选取适宜品种或部位是提取荔枝多酚的关键。     

纤维素酶糖化水解荔枝渣工艺条件的优化研究

采用纤维素酶解的方法对荔枝渣进行糖化水解,以增加料液中还原糖的含量,进而提高生物质发酵的利用率。试验研究了酶添加量、酶解初始pH、酶解温度及时间4个因素对糖化效果的影响,先后采用了单因素试验和正交设计试验对糖化工艺进行优化,并经验证得出最佳工艺条件为:纤维素酶添加量50u/g、初始pH4.8、酶解温度50℃、酶解时间持续2.5h,此条件下荔枝渣料液中的还原糖含量可达12.41mg/mL。