浓缩柑橘汁流变特性研究

采用AR500流变仪对不同浓度的浓缩柑橘汁在不同温度下的流变学特性进行了研究。通过回归分析发现,在研究的温度和浓度的范围内,浓缩柑橘汁表现为假塑性流体,温度对粘度的影响可用阿累尼乌斯方程来表示,浓度对粘度的影响可用指数方程来表示,推导出了温度和浓度对浓缩柑橘汁粘度综合影响的方程式。     

浓缩蓝莓汁的流变特性研究

以浓缩蓝莓汁为原料,采用BROOKFEILD R/S+CC流变仪测量不同浓度(15%、45%、75%)与不同温度(20℃、30℃、40℃、50℃、60℃、70℃)下浓缩蓝莓汁的流变特性并进行研究。结果表明,在所研究的温度范围内,浓缩蓝莓汁属于牛顿流体;回归分析结果显示,温度变化对粘度表观影响的关系式符合阿累尼乌斯方程η=K0exp(Ea/RT),浓度对粘度表观影响的关系式符合指数方程η=Kexp(AC);推导出温度和浓度对粘度综合影响的方程式,该方程可用来预测实际加工过程中一定温度和浓度范围内浓缩蓝莓汁的粘度,为其加工生产提供理论依据。     

慈姑浓缩汁流变学特性研究

以慈姑酶解汁为原料,采用减压浓缩技术,研究了不同温度和时间对慈姑浓缩汁可溶性固形物含量、褐变度和浊度的影响。在此基础上,考察在不同温度和浓度条件下,慈姑浓缩汁的流变学性质。结果显示,浓缩慈姑汁在一定的温度和浓度范围内属于假塑性流体,具有触变性。温度对粘度的影响符合阿累尼乌斯(Arrhenius)方程,浓度对粘度的影响可用指数方程准确表示,并由此推导出慈姑浓缩汁粘度中温度和浓度综合影响的方程式,通过该方程能很好描述浓缩汁粘度的变化。     

蓝莓浓缩汁流变特性及化学组成的变化

流体的流变学可为工艺设计提供有关数据,并有助于找出产品组成及加工工艺对流变性质的影响。本研究采用AR1000型流变仪研究了浓缩蓝莓汁(60°Brix)在(20～60℃)范围内的流变特性。通过回归分析发现,在研究的温度和浓度范围内,浓缩蓝莓汁表现为牛顿型流体,温度对粘度的影响可用阿雷尼乌斯(Arrhenius)方程来表示,浓度对粘度的影响可用指数方程来表示。推导出了温度和浓度对浓缩蓝莓汁粘度综合影响的方程式并比较了浓缩前后蓝莓汁化学组成的变化。     

浓缩红葡萄汁的粘度与酒石析出

采用浓缩与低温处理相结合的方法可更好地去除葡萄汁中的酒石。它是利用酒石的溶解度随温度的降低而减小的原理 ,通过降低葡萄汁贮存温度使葡萄汁中的酒石酸氢钾和酒石酸钙(统称酒石 )结晶沉淀于容器底部 ,分离后达到除酒石的目的。实验中发现 ,70°Bx的葡萄汁在 2 5℃贮存时反而比在 4℃更容易使酒石结晶析出。经分析 ,导致这种现象的关键因素在于低温下高浓度葡萄汁的粘度抑制了酒石结晶的生成。试验中测定了不同糖度的葡萄汁在不同温度下的粘度变化 ,并找出了浓缩葡萄汁的粘度与酒石析出的关系。     

马齿苋饮料主剂浓缩工艺及其流变特性研究

采用真空浓缩的方法,确定马齿苋饮料主剂的浓缩工艺为浓缩倍数为3倍,即可溶性固形物含量15°Brix,浓缩温度为70℃,浓缩时间为15min.采用CV-Ⅲ+型数字流变仪对不同浓度(5、10、15、20、25、30°Brix)的马齿苋饮料主剂分别在20、40、60℃条件时的流变学性质进行了研究,结果表明:在研究的温度和浓度的范围内,马齿苋饮料主剂为胀塑性流体;回归分析表明,温度对粘度的影响符合Arrhenius方程,浓度对粘度的影响可以用指数方程η=Kexp(AC)更好地表示,并推导出温度和粘度对马齿苋饮料主剂综合影响的方程.     

结冷胶水溶液的流变特性及其影响因素研究

研究了结冷胶水溶液的流变特性及浓度、温度、pH、钙离子对溶液粘度的影响。结果表明,结冷胶水溶液在0.01%～0.04%的范围时呈假塑性流体特性;不同浓度、不同温度、不同钙离子浓度的结冷胶水溶液粘度也呈相应变化;在pH为4～10的范围内,溶液粘度几乎不受影响。     

浓缩和酸化对番茄汁质量的影响

本文研究了不同热破碎温度和时间对番茄汁粘度的影响，及浓缩过程中番茄汁色泽和粘度的变化，给出了浓缩时间、浓缩番茄汁的可溶性固形物含量和浓缩番茄汁的ａ／ｂ值间的回归方程；并探讨了酸化保存番茄汁的可能性。     

复合食用菌浓缩液的流变特性研究

采用CV-Ⅲ 型数字流变仪对不同浓度的复合食用菌浓缩液在不同温度下的流变学特性进行了研究.通过分析发现,在研究的温度和浓度的范围内,复合食用菌浓缩液表现为非牛顿流体,温度对粘度的影响可用阿累尼乌斯方程来表示,浓度对粘度的影响可用指数方程来表示,推导出了温度和浓度对复合食用菌浓缩液粘度综合影响的方程式.     

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。     

EFFECT OF TEMPERATURE ON VISCOSITY OF FRUIT JUICES AND PUREES

SUMMARY: The viscosities of selected fruit juices and purees were measured with a coaxial-cylinder viscometer in the temperature range 20–70°C. Depectinized apple juice and Concord grape juice were Newtonian fluids at all concentrations and their viscosity decreased considerably at higher temperatures. Cloudy apple and orange juices changed from Newtonian to pseudoplastic at concentrations higher than 50 and 20° Brix. respectively. Temperature had a smaller effect on viscosity of cloudy juices than of clear juices. The apparent viscosity of fruit purees (pseudoplastic fluids) decreased slightly at higher temperatures. The activation energy for flow increased with the juice concentration and decreased with the presence of suspended particles in the fruit product. The data and conclusions are useful in the design and operation of efficient food-processing equipment.     

浓缩石榴汁流变特性研究

研究了不同浓度的石榴汁在不同温度下的流变特性。结果表明:在实验范围内,石榴汁表现为胀塑性流体,通过回归分析,温度对表观粘度的影响可以用Arrhenius方程表示,浓度对表观粘度的影响可以用指数方程更好地表示,并推导出温度和浓度对表观粘度综合影响的方程式。该方程的建立可以用来预测实际加工过程中一定温度和浓度时石榴汁的表观粘度。     

芒果浓缩汁的流变学特性

研究了不同质量分数的芒果浓缩汁在不同温度下的流变学特性.回归分析发现,在研究的温度和质量分数范围内,芒果浓缩汁表现为Herschel-Bulkley流体,温度对黏度的影响可用阿伦尼鸟兹方程表示,质量分数对黏度的影响可用幂函数表示,推导出了温度和质量分数对浓缩芒果汁黏度综合影响的方程.随着芒果浓缩汁质量分数的提高,体系的静态屈服应力值也增大.     

Simultaneous estimation of the thermophysical properties of three kinds of fruit juices based on the measured result by a transient heat flow probe method

The thermophysical properties of three kinds of fruit juices (grape juice, orange juice, and pineapple juice) were measured at various temperatures (10–50 °C) and concentrations (10–50%). A new method for the simultaneous determination of thermophysical properties using a modified version of current probe theory method was proposed. The temperature changes of the probe upon insertion in the sample were fitted to an approximate solution of the heat conduction equation, and the values of two parameters in that solution were determined. Using the values of these parameters, the thermal conductivity and thermal diffusivity of each sample were determined. The specific heat of each sample was estimated from the definition of thermal diffusivity. These thermophysical properties were expressed as a function of concentration and temperature.     

澄清水蜜桃汁的流变学特性研究

对澄清水蜜桃汁和脱果胶水蜜桃汁的流变学特性进行了研究。实验发现无果胶和悬浮果肉的水蜜桃汁表现为牛顿型流体。实验研究了不同温度对不同浓度水蜜桃汁粘度的影响,最后给出了描述温度和浓度对水蜜桃汁粘度影响的综合性方程。     

Viscosity of tangerine and lemon juices as a function of temperature and concentration

Viscosities of two fruit (lemon and tangerine) juices have been measured with a capillary flow technique. Measurements were made in the temperature range from 303 to 393 K. The range of concentration was between 15 and 40 °Brix for tangerine juice and between 17 and 45 °Brix for the lemon juice. The total uncertainty of viscosity and temperature measurements was estimated to be <0.5% at low concentrations and up to 1.5% at high concentrations and 0.025 K, respectively. The effect of temperature and concentration on viscosity of tangerine and lemon juices was study. The measured values of the viscosity were used to calculate the temperature, (? ln η/?T)_x, and concentration, (? ln η/?x)_T, coefficients for each juice. The Arrhenius type correlation equations for viscosity were used to represent the temperature dependence of viscosity. The values of the Arrhenius equation parameters (flow activation energy, E_a, and η_∞) were calculated for the measured viscosities of tangerine and lemon juices as a function of concentration. Different theoretical models for the viscosity of fruit juices were stringently tested with new accurate measurements on tangerine and lemon juices. The predictive capability of the various models was studied. The concentration and temperature dependence behavior of the viscosity of tangerine and lemon juices are discussed in light of the various theoretical models for viscosity of fruit juices. The applicability and predictive capability of the models used previously for aqueous solutions to represent the effect of temperature and concentration on viscosity of fruit juices was also studied. New model was developed to represent the combined effect of temperature and concentration on the viscosity of the juices. The average absolute deviation between measured and calculated values from this correlation equation for the viscosity was 0.8% and 2.1% for tangerine and lemon juices, respectively.     

Rheological behaviour of blueberry cloudy juice (Vaccinium corymbosum L.)

The rheological behaviour of blueberry cloudy juice ( Vaccinium corymbosum L.), prepared from fresh berries, was studied as a function of solids concentration, in the range 25–61 °Brix, at different temperatures (5–50 °C), with a control rate (CR) rheometer. Cloudy juice was concentrated by vacuum evaporation, and solutions at other concentrations were prepared from the concentrate by adding the liquid collected as distillate. The juices were slightly thixotropic between 45 and 61°Brix. For lower concentrations, the thixotropy was low and could be easily eliminated by shearing. The power law model was applied to fit the pseudoplastic behaviour. The activation energy for flow, evaluated with the Arrhenius–Guzman equation, increased with solids concentration and ranged from 4.6 to 24 kJ gmol^–1. A non-linear correlation, accounting for temperature and concentration effects on the consistency coefficient, was identified.     

Phytochemical Polyphenol Extraction and Elemental Composition of Vitis labrusca L. Grape Juices Through Optimization of Pectinolytic Activity

Grape juice is a natural source of polyphenols with potential health benefits. The aim of this study was to assess the optimized basis of the pectinolytic activity through a multivariate design for the bioactive enrichment of polyphenols in grape juices and to evaluate the effect of pectinases on the extraction of minerals by ICP-MS and FAAS. Grape juices were treated with pectinases Everzym® Color and Rapidase® Smart at different conditions of enzyme concentration (0.16–1.84 g L^?1), temperature (14.8–83.6?ºC), and incubation time (9.6–110.5 min), and the effect on total phenolics, anthocyanin content, and antioxidant activity of juices were determined by employing a second-order central composite design in combination with response surface methodology. The different conditions showed significant variations in polyphenol levels of grape juices. For both of the enzymes, the increase of temperature and enzyme concentration led to a higher extraction of polyphenols, with a significant effect. Estimated effects depict a good correlation among dependent variables. For Rapidase, the optimized extraction of polyphenols was determined at an enzyme concentration of 1.57 g L^?1 and at a temperature of 54.8?ºC. For Everzym, higher concentrations of polyphenols were obtained at the enzyme concentration of 1.30 g L^?1 at 46.8?ºC. The extraction using the Rapidase enzyme significantly increased the levels of Na, K, Mg, and Fe in grape juices (p?<?0.05). The pectinolytic activity increased the polyphenol and mineral concentrations in grape juices. In addition, the optimal conditions of the pectinolytic treatment comprise a feasible alternative to improve the bioactive potential of grape juices.