果胶酶和壳聚糖对菠萝汁澄清作用的比较研究

本文研究比较了果胶酶和壳聚糖对菠萝汁的澄清方法，并确定了各自的最佳工艺参数，果胶酶法：果胶酶100mg／kg，pH3，温度40℃；壳聚糖法：0．6g／L，pH3，温度40℃。从澄清效果和贮存稳定性看，两种方法都能很好的澄清菠萝汁；从总体成本看，壳聚糖法明显优于果胶酶法，其贮藏时间长，成本低，易控制，是较好的澄清剂。     

壳聚糖澄清菠萝汁工艺研究

研究壳聚糖澄清菠萝汁的最佳工艺.在单因素实验的基础上,设计了以壳聚糖用量、澄清温度、pH和时间4个主要因素的正交试验,确定了最佳澄清条件为壳聚糖添加量0.03 g/100 mL,澄清pH值3.5,温度30℃,澄清45 min,澄清后菠萝汁透光率大于95%,较彻底地清除了影响菠萝汁澄清度的蛋白质和果胶,使得菠萝清汁的贮存稳定性大大提高.     

壳聚糖对菠萝汁澄清作用的影响

果汁加工的关键技术是果汁的澄清技术,因此应用壳聚糖对菠萝汁进行了澄清,研究结果表明在最佳pH、温度、澄清时间的条件下,0.1 g/L~1.0 g/L壳聚糖澄清菠萝汁,其透光率可达80%以上,且岀汁率有明显提高,较彻底地清除了影响菠萝汁澄清度的蛋白质和果胶,使得菠萝清汁的贮存稳定性大大提高。     

壳聚糖在菠萝汁澄清中的应用研究

通过实验研究了壳聚糖澄清菠萝压榨果汁的最优条件为:用脱乙酰度90%的壳聚糖,加入量0.6g/L,然后原果汁于40℃保温30分钟,果汁pH为自然pH值,制得的清汁透光率达到98%;贮藏实验结果表明低温有利于清汁的贮藏稳定,常温下整个实验贮藏期间果汁透光率都大于90%;实验还表明壳聚糖对菠萝果汁的澄清不影响果汁的营养价值。     

壳聚糖与黄原胶对菠萝汁澄清效果的研究

以浊度、色差和透光率为指标,壳聚糖和黄原胶为澄清剂,研究了壳聚糖/黄原胶对菠萝汁的澄清效果,确定了最佳的工艺参数,并在单因素实验的基础上,通过正交实验,得出澄清菠萝汁的最适工艺为:温度35℃,时间70min,壳聚糖(10g/L)与黄原胶(10g/L)的比例1∶1,果汁pH3.4,验证实验结果表明,此时浊度为0.93NTU,透光率高达98.5%,菠萝汁的色差b*=14.47,在此工艺条件不但能得到满意的澄清效果,还能呈现菠萝原汁的亮黄色。      

壳聚糖与黄原胶对菠萝汁澄清效果的研究

以浊度、色差和透光率为指标,壳聚糖和黄原胶为澄清剂,研究了壳聚糖/黄原胶对菠萝汁的澄清效果,确定了最佳的工艺参数,并在单因素实验的基础上,通过正交实验,得出澄清菠萝汁的最适工艺为:温度35℃,时间70min,壳聚糖(10g/L)与黄原胶(10g/L)的比例1∶1,果汁pH3.4,验证实验结果表明,此时浊度为0.93NTU,透光率高达98.5%,菠萝汁的色差b*=14.47,在此工艺条件不但能得到满意的澄清效果,还能呈现菠萝原汁的亮黄色。     

果胶酶和壳聚糖对菠萝汁澄清作用的比较研究

本文研究比较了果胶酶和壳聚糖对菠萝汁的澄清方法,并确定了各自的最佳工艺参数,果胶酶法:果胶酶100mg/kg,pH3,温度40;壳聚糖法:0.6g/L,pH3,温度40。从澄清效果和贮存稳定性看,两种方法都能很好的澄清菠萝汁;从总体成本看,壳聚糖法明显优于果胶酶法,其贮藏时间长,成本低,易控制,是较好的澄清剂。     

壳聚糖对杨梅果汁的澄清作用

研究了壳聚糖对杨梅果汁的澄清作用。结果表明壳聚糖是一种有效的果汁澄清剂，当壳聚糖用量为0.4g／L时对杨梅果汁的澄清效果最好，且不影响其营养成分，经处理后的杨梅果汁具有较好的稳定性。     

壳聚糖对菠萝汁澄清效果的研究

果汁加工的关键技术是果汁的澄清技术。本实验研究了壳聚糖澄清菠萝汁的工艺参数及条件:通过单因素实验研究壳聚糖用量、澄清时间、果汁温度等对菠萝汁澄清效果的影响,选出较合适的工艺参数;然后又通过正交实验对壳聚糖澄清菠萝汁的工艺条件进行优化。实验结果表明:在壳聚糖添加量为0.7g/L、温度35℃、澄清60min的条件下,菠萝汁澄清透明、色泽自然、香气浓郁。     

壳聚糖澄清沙棘果汁工艺条件的研究

用壳聚糖对沙棘果汁进行澄清试验，研究了壳聚糖用量、pH、温度等工艺条件对果汁澄清效果的影响，并通过正交试验确定壳聚糖澄清沙棘果汁的最适工艺条件为：壳聚糖用量0．05％、温度45℃、pH3．5、反应时间1．5h，澄清后，果汁透光率达98．9％，果汁中的营养及活性成分损失较小。     

壳聚糖在绿茶汁澄清中的应用研究

本研究了壳聚糖对绿茶汁的澄清作用，表明壳聚糖是一种良好的澄清剂，能提高绿茶汁的透光度与稳定性，而不影响绿茶汁的主要风味物质。     

Clarification of apple juice by electroflotation

Apple Juice industry is in search of a simplified technology which enables a quick clarification and stabilisation of apple juice. This study aimed to evaluate the potential of electroflotation as an alternative for the clarification of apple juice. Clarification of apple juice by electroflotation was first done at various current densities (10, 20 and 40 mA/cm²) with and without addition of gelatin (200 mg/l). Afterwards, the electroflotation treatments were done at a current density of 20 mA/cm² with various concentrations of added gelatin (0, 50, 100 and 200 mg/l). It was shown that electroflotation treatments alone was efficient to reduce the tannin and protein contents of apple juice. However, the decrease in the protein content was in large part due to the use of pectinases prior to the electroflotation treatments. The use of gelatin in combination with the electroflotation aided in the clarification process. The highest gelatin concentration used in this study (200 mg/l) resulted in a better reduction of tannin and protein levels, while a current density of 20 mA/cm² was found to be optimal. Turbidity observed in the juices clarified with electroflotation treatments was in average lower than 10 NTU but higher than 2 NTU which is generally required to produce a stable clarified juice. Brix degree and pH of the apple juice was not affected by the electroflotation treatments while the color was improved.

Industrial relevance

The production of clarified and stable apple juice is a subject of interest for the beverages industries. The clarification step which remained long and discontinuous implied the addition of a large quantity of pectolytic enzyme and of clarifying agents (such as gelatin) to the freshly pressed juice to induce the precipitation of proteins and other suspended matter in 15–20 h. Fining treatments were followed by a separation step usually consisting of decantation and classical filtration on filter-press, or flotation by dispersed gas. The development of membrane separation processes to replace the traditional approach has enabled the automation of the whole production resulting in lower labor requirement and a considerably shorter process time than the traditional process.However, the performance of membrane separation processes is influenced by the declining permeate flux with time, which is due to membrane fouling. In some instances, permeate flux decline makes membrane separation processes unattractive for the clarification of apple juice. To our knowledge, we are the first research group to use electroflotation (EF) for clarification of apple juice. It was shown that EF treatments alone were efficient to reduce the tannin and protein contents of apple juice. In addition, the use of gelatin in combination with the EF aided in the clarification process. Turbidity observed in the juices clarified with EF treatments for 30 min was in average lower than 10 NTU. Brix degree and pH of the apple juice were not affected by the EF treatments while the color was improved.When compared to the values reported in the literature for flotation by dispersed gas, it seems that EF shows better efficiency than flotation in decreasing the juice turbidity (99% decrease for EF as compared to 90% decrease for flotation). In addition, for experiments carried out by conventional flotation larger amount of fining agent are used (70–150 mg of gelatin/l, 400–800 mg/l of silica sol and 200–500 mg/l of bentonite). For these reasons, the new process we propose is advantageous when compared to the traditional flotation approach and it should have a measurable impact on the advancements in the production of clarified apple juice. If used as a pre-treatment to ultrafiltration clarification, it is expected that it would reduce membrane fouling resulting in higher productivity.     

菠萝汁蒸发浓缩过程传热性能研究

以菠萝汁试验为介质,重点研究酒窝状波纹竖板降膜蒸发器的传热性能,并分析单位板宽上流量I,蒸发温度TV,传热温差ΔT,糖度BX对蒸发器总传热系数K的影响,分别得出总传热系K与I,TV,ΔT,BX回归曲线.试验结果表明:酒窝状波纹竖板降膜蒸发器具有传热系数高、蒸发强度大、不易结垢,尤其适合于热敏性物料的浓缩等优点,能够较好地完成对菠萝汁的浓缩.     

壳聚糖铁的制备及其在蔗汁澄清中的应用研究

本文以脱乙酰度为85%的壳聚糖与FeCl3反应制备壳聚糖铁,并对其用于红糖粉生产的蔗汁澄清工艺进行了研究。将壳聚糖铁用于蔗汁澄清实验,得出澄清蔗汁的最佳工艺是:壳聚糖铁用量为100mg/L,pH值约为7.5,澄清温度为90℃。结果表明壳聚糖经过改性后,其絮凝性能有了较大提升。     

Storage quality of pineapple juice non-thermally pasteurized and clarified by microfiltration

Microfiltration (MF) is classified as a non-thermal process for the fruit juice industry. It could provide a better preservation of the phytochemical property and flavor of the juice. This work aimed to study the stability of phytochemical properties including vitamin C, total phenolic content, antioxidant capacity (2-Diphenly-1-picrylhydrazyl: DPPH, free radical scavenging capacity and Oxygen Radical Absorbance Capacity: ORAC assays), microbial and chemical–physical (color, browning index, pH and total soluble solid) properties of MF-clarified pineapple juice during storage at various temperatures (i.e. 4, 27, and 37 °C). The juices were clarified by microfiltration using hollow fiber module. The results showed that most of the phytochemical properties and soluble components were retained in the juice after microfiltration. No microbial growth was detected after 6 months of storage. The storage time and temperature did not affect total soluble solids and pH (P > 0.05). The color (L^*) of clarified juice stored at 4 °C was lighter than the juices stored at higher temperature levels (P < 0.05). The phytochemical properties and total phenol content of the juice significantly decreased as storage time and temperature increased (P < 0.05). Vitamin C content was the attribute that affected storage time and temperature most as indicated by reaction rate constant and activated energy. Storage of non-thermally pasteurized and clarified pineapple juice at 4 °C was the most suitable since it allowed the best quality preservation.     

Clarification of tomato juice by cross‐flow microfiltration

Clarification of fruit and vegetable juice is one of the integrated parts of modern industrial juice processing. This paper describes the clarification of tomato juice through microfiltration process. In this regard, the influence of transmembrane pressure (1, 2 and 3 bar), cross‐flow velocity which corresponds with Reynolds number (300, 1500 and 2500) and temperature (30, 40 and 50 °C) on permeate flux and some properties of clarified juice such as colour, turbidity, density, viscosity, pH and total soluble solid have been studied. The results revealed that the investigated parameters had an increasing effect on the permeate flux and colour and the greatest effect on the permeate flux and colour was supplied by cross‐flow velocity. The other permeate properties did not significantly change with variations of the operating parameters. Eventually, the statistical analysis indicated that the interactional effect of cross‐flow velocity and TMP on the permeate flux was significant.     

Influence of gas sparging on clarification of pineapple wine by microfiltration

A microfiltration process with a tubular ceramic membrane was applied for clarification of pineapple wine. The process was operated with the membrane pore size of 0.2 μm at transmembrane pressure of 2 bar and crossflow velocity of 2.0 m/s. The effects of gas sparging on permeate flux, fouling and quality of clarified wine were studied. It was found that a relatively low gas sparging rate could increase permeate flux up to 138%. Further increase of the gas sparging rate did not improve permeate flux compared with that without gas sparging. Gas sparging affected the density of cake layer. Increasing gas sparging rate led to an increase in specific cake resistance. It was observed that increasing gas sparging rate could reduce reversible fouling rather than irreversible fouling. The turbidity of pineapple wine was reduced and a clear product with bright yellow color was obtained after microfiltration. The negative effect of gas sparging which caused a loss of alcohol content in the wine was also observed.