Treatment of Grape Juice by Osmotic Evaporation

ABSTRACT: Osmotic evaporation (OE) was applied to grape juice to increase the sugar content and thus to improve the quality of wine obtained after fermentation. The use of aqueous solutions of glycerol as extractant avoids corrosion and scaling, which are the main problems in OE with brines. Preliminary experiments were performed on lab scale using water or glucose solutions as feed, and NaCl or glycerol as extractant. The runs with NaCl allowed measurement of the membrane transport properties, whereas glycerol was used to quantify the concentration polarization phenomena involved. The extract side concentration polarization severely limited the flux achievable for glycerol concentration above 50% wt, while the extract side concentration was negligible in the OE with NaCl. The feed side concentration polarization played a minor role for glucose content up to 40% wt. Experiments with grape juice were performed on pilot scale equipped with plate and frame modules. The performance were in good agreement with lab results on glucose model solutions, the lower flux observed was due only to the low temperature of operation. The process was tested on 3 types of grape juice (white, rosé, and red). Treated and control juices were fermented, and corresponding wines were analyzed for selected parameters and evaluated by sensory analysis. The OE treatment removed water from grape juice and increased both the total soluble solids and sugar content of juice, thus ethanol content and dry extract in wine always increased. The osmotic evaporation significantly improved sensory quality of red wine that was judged as having a full body, more structure, and persistence.     

含糖量对山葡萄酒苹果酸-乳酸发酵的影响

以东北高寒地区产的山葡萄酿造的山葡萄酒为研究对象,探究山葡萄酒苹果酸-乳酸发酵过程中含糖量对其pH值、总酸、苹果酸-乳酸转化程度、总糖的影响。山葡萄酒中的葡萄糖含量对其pH值的升高、总酸的降低及苹果酸乳酸转化程度均有影响。在4个梯度葡萄糖含量的山葡萄酒中,含糖量为10.67 g/L的山葡萄酒其pH升高值（0.18）、总酸度降低值（6.05 g/L）最大,苹果酸乳酸转化程度最高。     

葡萄酒酿造过程中酸的添加

在葡萄汁或葡萄醪(酒)中加入酸。会引起pH值的降低和滴定酸的增加，优化pH环境，有利于增加SO2的作用效果；抑制与氧化和微生物败坏的有关反应；增加色密度和红葡萄酒的色调；增加酶和皂土作用的效果和提高陈酿潜力。添加的酸有酒石酸、苹果酸、柠檬酸；添加时间为破碎后和分离后。     

Ascorbic acid improves the antioxidant activity of European grape juices by improving the juices' ability to inhibit lipid peroxidation of human LDL in vitro

Antioxidant activities of red and white European grape juices towards copper induced lipid oxidation of human low-density lipoproteins (LDL) were examined in vitro . LDL lipid peroxidation was assessed spectrophotometrically by monitoring the development of conjugated lipid hydroperoxides at 234 nm. Red grape juice concentrate inhibited lipid peroxidation of LDL by prolonging the lag phase by 2.7 times relative to a control when evaluated at a total phenolic concentration of 10 μM gallic acid equivalents (GAE). Both red grape juices tested blocked lipid peroxidation of LDL at 20 μM GAE. White grape juice exerted prooxidant activity at 5–20 μM GAE. The antioxidant activity, inhibition of lipid peroxidation of LDL in vitro , was correlated with the juices' levels of total phenols ( r  > 0.98, P  < 0.01), anthocyanins ( r  > 0.99, P  < 0.01), flavan-3-ols ( r  > 0.97, P  < 0.05), and hydroxybenzoates ( r  > 0.96, P  < 0.05) when the phenolic composition of each grape juices was analysed by HPLC. 5 μM ascorbic acid alone did not exert antioxidant activity towards LDL, but combinations of 5 μM ascorbic acid with 5 μM GAE juice phenols eliminated the prooxidant activity of white grape juice, and significantly improved the antioxidant activities of red grape juices.     

黄金梨汁和柑橘汁混合发酵干型酒的初步研究

利用柑橘汁和梨汁混合发酵酿制果酒,柑橘汁起到调酸和原料的双重作用。实验结果表明,利用果汁混合发酵,柑橘汁的量小于20％时,能增加原酒的果香味和风味,使酒体更加饱满;果酒的香气来源于原料中的香气物质和发酵过程中产生的香气;利用柑橘汁调节发酵初始酸度应控制柑橘汁在20％以下,发酵原液的pH值调节在4．0左右,此时酒精产率高。     

EFFECTS OF PROCESSING TIME AND TEMPERATURE ON THE QUALITY COMPONENTS OF CAMPBELL GRAPE JUICE

Campbell grape juice was processed at different temperatures (60, 70, 80 and 90C) and different times (30, 45 and 60 min), and evaluated for quality components and sensorial properties. The grapes were crushed, added with enzyme, heated, and pressed; then the juice was cold stabilized, filtered and pasteurized. The samples showed an increase in pH and a decrease in titratable acidity. Sugar/acid ratio and total soluble solids increased until 80C then decreased when 90C was reached. A slight increase in L* and b* values and a decrease in a* color values were also shown. Significant differences were mostly observed between processing temperatures than between processing times. Increasing processing temperature enhances the total phenolics, total anthocyanin and total flavonoid contents, and % radical scavenging activity of the juice until 80C but declined when the temperature reached 90C. Sensory evaluation showed that the preferred time–temperature combination for processing Campbell juice is between 70 and 80C for 30–45 min.

PRACTICAL APPLICATIONS

Campbell Early ( V. labrusca B.) is one of the major table grapes in Korea and overproduction of this grape variety in Korean market calls for an alternative product in which excess grapes can be utilized. This study is focused on the determination of the effects of processing time and temperature on the quality components of Campbell grape juice. The results can be a guide to have a processing method that can be used in producing Campbell grape juice with good sensory properties and high bioactive compounds     

Variation of Microwave Dielectric Properties in the Glucose Biosensor System

Glucose biosensor is generally based on the reaction between glucose and glucose oxidase, which produces gluconic acid and hydrogen peroxide. The gluconic acid is a conductive material, while hydrogen peroxide has polar molecules. This article examines the changes of dielectric properties due to the conductive loss below 2 GHz and dipole orientation of above that frequency of this reaction. The difference between the dielectric loss of glucose solution and the dielectric loss of glucose-enzyme reaction can be related to the glucose concentration in the samples, such as orange juice, black grape juice, sugarcane juice, and sapodilla juice. A good sensitivity to these differences due to the effect of ionic conductivity and dipole orientation was found at 1 and 16.44 GHz, respectively. The minimum detection limit of glucose concentration in the proposed technique was about 0.01 M (0.20 g/100 ml) with an optimum reaction ratio of about 1:1 between the enzyme solution and the glucose solution. This technique could benefit the future development of microwave biosensor by which both ionic conductivity and dipole effects can be considered simultaneously.     

Antibacterial Effect of Glucose Oxidase on Growth of Pseudomonas fragi as Related to pH

The effect of glucose oxidase (GOX) catalyzed reaction with glucose on Pseudomonas fragi was analyzed in nutrient broth and fish extract media. Growth of P. fiugi in nutrient broth was clearly suppressed by 1.0, 2.0 and 4.0 mg/mL glucose when combined with 0.5–2.0 U/mL GOX. The same GOX/glucose combinations inhibited P. frasi growth in fish extract media. Viable cell numbers in fish media showed clear growth inhibition with combinations of l.0–2.0 U/mL GOX and 8.0–16.0 mg/mL glucose. Higher GOX and glucose rapidly produced 2.0–2.5 unit decreases in pH, but produced enough gluconic acid to precipitate fish proteins. Use of 0.5 U/mL GOX in fish extract media resulted in slow, sustained activity with potential for inhibition of microbial growth in foods without excessive acidity.     

Evaluation of potential side activities of commercial enzyme preparations used in winemaking

Twenty‐one commercial enzyme preparations used in winemaking were characterised for the α‐L‐rhamnosidase, α‐L‐arabinosidase, β‐D‐xylosidase, ?β‐D‐galactosidase, β‐D‐glucosidase, esterase, protease, cinnamoyl esterase and laccase activities. A new rapid fluorimetric method to assay esterase activity was developed. Enzyme preparations differed for the level of each enzyme activity assayed rather than for the type of enzymatic activity detected. High levels of protease, glycosidase, esterase and cinnamoyl esterase activity were found among enzyme preparations for different technological applications. A drastic reduction in the level of cinnamoyl esterase was observed in commercial grape juice, pH 3.6, total acidity 5.3 g L^?1_, sugar 170 g L^?1. Protease activity was only weakly reduced, from 10 to 20%, in commercial grape juice. β‐glucosidase activity levels are reduced in the presence of increasing concentration of glucose but are still present at the higher glucose concentration (100 g L^?1). The extent of the reduction observed was dependent on the enzymatic preparations tested.     

酿酒条件对两株商业酿酒酵母β-葡萄糖苷酶的影响

研究酿酒条件（氧气、pH值、温度、糖和乙醇等）对两株商业酿酒酵母β-葡萄糖苷酶的影响。结果显示：氧气促进酵母β-葡萄糖苷酶的合成,两株商业酿酒酵母完整细胞的β-葡萄糖苷酶最适pH值为5.0,最适温度为60 ℃,果糖、葡萄糖和蔗糖对两株酿酒酵母完整细胞的β-葡萄糖苷酶活性具有轻微抑制作用,乙醇（体积分数2%～20%）促进β-葡萄糖苷酶的酶活力。在葡萄酒发酵过程中,β-葡萄糖苷酶主要存在于完整细胞和透性化细胞中,上清液中酶较少。     

Effects of noble rot on must composition and aroma profile of Amarone wine produced by the traditional grape withering protocol

The effects of noble rot on the overall quality of Amarone wine, a “Passito” dry red wine, produced by a traditional withering grape process are poorly understood. Wines obtained from healthy and selected grapes infected by noble rot were compared. Validation of the experimental plan was carried out by determining glycerol and gluconic acid content, laccase activity and microbial analysis of the musts. Botrytis cinerea infection produced significant variation in esterase and β-glucosidase activity of grape must. Aroma analysis in healthy and botrytised wines was carried out by SPE extraction followed by GC–MS quantification. A decrease of several fermentative esters was observed in botrytised wine, while wine produced from healthy grapes showed a higher fatty acid content. Molecules such as 1-octen-3-ol, phenylacetaldehyde and furaneol were positively linked to the noble-rotten grapes. Interestingly, γ-nonalactone and 4-carbethoxy-γ-butyrolactone increased, while sherry lactones decreased in botrytised wine. The strong increase of N-(3-methylbutyl)acetamide was related to B. cinerea grape infection.     

超过滤膜在葡萄酒酿造中的应用

论述了应用超过滤膜处理葡萄汁、超过滤果汁发酵葡萄酒及葡萄酒的超过滤。通过对试验结果的分析得出,在葡萄酒酿造中应用超过滤膜,能除去果汁中杂菌,减少氧化褐变物质,苦涩味成分;使发酵醪澄清并除菌;使葡萄酒酒质稳定。     

Comparison of Commercial Enzymes for the Processing of Marula Pulp, Wine, and Spirits

ABSTRACT: Commercial enzymes were compared in this study to improve the yield and clarification of marula fruit ( Sclerocarya berria sub. caffra ) juice. An increase in yield of up to 12% in juice treated with the enzyme Rapidase Filtration was recorded. A 15-fold improvement in juice clarity and an increase in total terpenes were observed after treatment with prefermentation processing enzymes. Post-fermented marula wine was treated with enzymes to hydrolyze bound monoterpenes. An increase in the free monoterpenes of at least 92% was observed in enzyme-treated juice. The different enzymes had both positive and negative effects on the flavor of the juice, wine, and distillate. Trenolin Bukett increased the aroma profile of the wine, while it remained closely related to the unaltered marula profile of the control. AR2000 had an overwhelming effect on the flavor profile, but the risk of deviating from the typical marula flavor was high.     

生物传感器法检测葡萄汁中葡萄糖含量

采用葡萄糖氧化酶与过氧化氢电极,在0.2 mol/L的磷酸盐缓冲液（pH 7.2）和1‰的葡萄糖标准溶液反应体系中,建立葡萄汁中葡萄糖含量检测的生物传感器分析方法。结果表明,在葡萄糖质量浓度为0～1 000 mg/L的范围内生物传感器法测定葡萄糖含量的线性良好;线性回归方程为y=0.994 8x-3.081,相关系数R2=0.999 9;稳定性好,相对标准偏差（RSD）=1.63%;加标回收率为96.0%～102.4%;专一性强,只对葡萄糖进行专一性测定。     

果胶酶对红葡萄酒主要成分的影响

以赤霞珠和蛇龙珠葡萄为原料，在葡萄破碎除梗后加入不同浓度的葡萄酒专用果胶酶，分析其对葡萄汁成分、葡萄酒发酵参数及原酒主要成分的影响。结果表明，加入果胶酶对葡萄汁的糖酸含量几乎无影响，但可降低汁液的粘度，利于色素的溶出，颜色较深；加入果胶酶的样品比未加果胶酶的样品发酵剧烈迅速，可降低挥发酸的生成量；可使原酒干浸出物含量和总酚含量增加，提高葡萄酒质量；残糖略有上升，但均在4g／L以下，不影响葡萄酒质量。     

A review of potassium nutrition in grapevines with special emphasis on berry accumulation

Potassium (K) is essential for vine growth and yield. Grape berries are a strong sink for K, particularly during ripening. Excess K levels in grape berries may have a negative impact on wine quality, mainly because it decreases free tartaric acid resulting in an increase in the pH of grape juice, must and wine. In Australia, high K status is common in most vineyards, which reflects the high K and high pH values of most Australian grape juice. This necessitates pH adjustment during the vinification process, and tartaric acid addition is a common practice in most Australian wineries. High K concentration may also lead to excessive loss of the additional tartaric acid by precipitation as potassium bitartrate and, as a consequence, pH adjustment becomes more difficult and expensive. Ensuring naturally low K levels in the berry will help reduce costs of input and waste management at the winery. Potential vineyard management options to manipulate berry K accumulation include selective use of rootstock/scion combination, canopy management and irrigation strategies. However, the impact of these practices on determining the optimum K concentration requires careful calibration of production parameters and the desirable grape juice and wine quality in relation to tissue K concentration. This paper reviews and discusses the possible functions of K in grape berries, translocation of K into the berry, and genetic and cultural factors that may affect the accumulation of K in the berry. This will help to identify the key research and management strategies needed for controlling K concentrations in grape berries.     

微波预处理对苹果汁褐变及品质的影响

以新鲜苹果为原料,以传统热灭酶工艺为对照,测定苹果汁褐变指数、总酚、多酚氧化酶活性、可溶性醌、pH、抗坏血酸含量以及抗氧化性等指标,采用高效液相色谱测定果汁中酚类化合物的含量,并用扫描电子显微镜和透射电子显微镜观察果肉微观结构,研究微波预处理对果汁褐变及品质的影响。研究结果表明,在微波功率800 W,处理时间140 s条件下显著抑制果汁褐变,降低多酚氧化酶酶活,提高苹果汁的总酚含量、抗氧化能力以及稳定性(P<0.05),这是一种有潜力的苹果汁加工方式。     

酶处理促进龙眼果汁中蔗糖的转化和低聚果糖的生成

为了降低龙眼果汁中的蔗糖含量和制备一种富含低聚果糖的龙眼果汁,本研究以龙眼果汁为原料,探讨底物浓度、底物pH、果糖基转移酶添加量、酶处理温度和时间等单因素对果汁中蔗糖的转化和生成低聚果糖的影响。采用液相色谱法(HPLC)分析酶转化前后果汁中蔗糖、果糖、葡萄糖、低聚果糖含量的变化。结果表明,底物浓度、pH、酶用量、温度和处理时间等因素对龙眼果汁蔗糖转化和低聚果糖的生成有显著影响(p0.05)。在底物浓度30 oBrix、pH 6.0、酶用量9 U/g、55℃下转化7 h的龙眼果汁,蔗糖含量从164.36 mg/m L减少至22.34 mg/m L,生成的低聚果糖含量为97.88 mg/mL,占果汁中总糖的38.21%。利用果糖基转移酶处理龙眼果汁,能有效降低果汁中的蔗糖含量,获得一种低热量且富含低聚果糖的功能性果汁。     

花青素葡萄复合饮料的工艺研究

以葡萄为主要原料,黑米花青素、白砂糖、柠檬酸和水晶葡萄香精为辅料,研发一款复合型功能饮料。通过单因素实验确定了果胶酶处理葡萄汁的最佳工艺参数,并在此基础上,通过单因素实验和正交试验,得出复合果汁的最佳工艺配方。结果表明,果胶酶提取的最佳提取工艺条件为pH4、温度45℃、果胶酶用量为1.35g/L,处理时间为40min;复合果汁的最佳工艺配方为葡萄汁15%、黑米花青素0.003%、白砂糖7%、柠檬酸0.1%、水晶葡萄香精0.015%。本实验结果将为系列花青素饮料的工业化生产提供理论依据。     

浓缩与低温处理去除葡萄汁中酒石的研究

本试验选用巨峰葡萄为试材，通过对不同榨汁处理的葡萄汁进行真空浓缩，分析和研究不同浓度的葡萄汁在低温下贮放时，其中化学成分的变化规律。葡萄汁的稳定性取决于其中酒石酸及其盐类和色素等物质的含量。葡萄汁经浓缩后，其中糖类、总酸、酒石酸、花色素等物质含量提高，而ｐＨ值则降低。浓缩葡萄汁在低温下处理，酒石酸、花色素、总酸等物质含量降低，其中酒石酸含量下降程度高于其它物质，－５℃处理比０℃处理效果更显著。浓缩后的葡萄汁，其浓缩倍数越高，对酒石析出的促进效果越明显。浓缩葡萄汁在低温下处理，可加速其中酒石的沉淀，使其沉淀更彻底，达到提高葡萄汁质量稳定性的目的。