大豆蛋白超滤中的膜污染与清洗方法的研究

阐述了超滤膜污染机理及其影响因素,针对中空纤维超滤膜处理大豆蛋白所引起的膜污染问题,提出了预防措施,对不同清洗方法和清洗剂的清洗效果进行了研究,试验证明物理清洗和化学清洗相结合可有效地提高超滤膜的再生效果,不同清洗剂的清洗效果有显著差别,其中使用复合清洗剂（高锰酸钾和蛋白酶）的清洗效果最佳,其超滤膜的透水恢复率可达新膜透水率的96%以上。     

EFFECTS OF PROCESSING ON ADSORPTION OF OFF-FLAVORS ONTO SOY PROTEIN1

Heats of adsorption and adsorption coefficients for the reversible adsorption of several aliphatic alcohols, aldehydes, and ketones on soy protein were measured using gas chromatography. The physical state of protein samples was changed by heating at 100°C and 121°C at moisture contents of 29%and 40%. A comparison was made with values for untreated soy isolate and sheared soy isolate, and the effects of moisture, temperature, and their interaction were examined by analysis of variance. Heats of adsorption were unchanged, but changes in adsorption coefficients of the treated samples demonstrated a significant decrease in binding that can be attributed to protein denaturation. The response depended on the interaction of moisture and temperature effects.     

ASSESSMENT OF AN EXPONENTIAL MODEL FOR ULTRAFILTRATION OF APPLE JUICE

The clarification of apple juice by ultrafiltration has been commercially used for many years. A common phenomenon in membrane processes is the decline of permeate flux (J) with time (t), called “membrane fouling.” The phenomenon of membrane fouling is very complex and difficult to describe theoretically, and model studies are limited. A number of semiempirical and empirical models have been proposed to explain flux behavior during membrane filtration processes. Using these models, typical t versus J curve observed in membrane filtration applications was examined in two or three periods. However, the boundaries between each period could not be accurately determined and were specific to the system under investigation. Thus, these semiempirical and empirical models are valid only for the system investigated. In this article, the applicability of an exponential model to ultrafiltration of apple juice was studied. The results showed that the exponential model can be successfully applied to analyze the raw filtrate volume V versus t data of ultrafiltration of apple juice, and initial flux J₀, membrane resistance R_m and exponential fouling coefficient k values can easily be determined from the raw data.     

芹菜汁醋酸保健饮料的生产工艺

以芹菜为原料,经酒精发酵、醋酸发酵制成芹菜醋,再加入芹菜汁、蜂蜜、白砂糖调配成芹菜汁醋酸保健饮料．最佳调配比例为芹菜醋25％、芹菜汁25％、蜂蜜6％、白砂糖3％。酒精发酵最适宜pH值为3．5,当酒精度达8％时停止发酵,醋酸发酵产酸量达6．1％时停止发酵。     

ALTERNATIVE PRETREATMENT METHODS TO ENZYMATIC TREATMENT FOR CLARIFICATION OF MOSAMBI JUICE USING ULTRAFILTRATION

A series of pretreatment methods to mosambi juice were undertaken and results were compared to pectinase treatment for clarification of the treated juice using ultrafiltration. The pretreatment methods attempted were centrifugation, centrifugation followed by addition of gelatin, centrifugation followed by addition of bentonite, centrifugation followed by fining using both bentonite and gelatin and enzymatic treatment, using pectinase as the enzyme. A systematic study was undertaken to select the operating centrifugation speed and time. The permeate flux and quality of the permeate were comparable to the enzyme‐treated juice.     

FOULING MODELS FOR HEAT EXCHANGERS IN DAIRY PROCESSING: A REVIEW

Fouling is a common food industry‐wide issue during thermal treatment using heat exchangers. It directly contributes toward increased energy costs in operation and maintenance, production losses and energy and water losses because of the repetitive cleaning operation, i.e., every 5–10 h in fluid food industry. There has been a considerable amount of work on modeling of the fouling process as well as the hydrodynamic and thermodynamic performances of heat exchangers. A variety of different fouling kinetics exists depending upon food components, types of heat exchangers and operating conditions. The available information on existing fouling models is summarized in terms of fouling mechanisms, dynamic performances of heat exchangers and integrated fouling dynamics. This review provides the basis for developing a vision of further research for understanding, quantifying and minimizing fouling of food materials in heat exchangers.     

采用烘烤酶解方法生产枣汁饮料

以山西大枣为主要原料，采用烘烤预处理结合果胶酶酶解技术对枣中的营养及生理活性成分进行浸提，通过正交试验筛选出理想取汁工艺，确定出最佳工艺参数为：加酶量0．2％，浸提时间4h，浸提温度50℃，料水比1：3。     

EFFECT of pH and ENZYMATIC TREATMENT ON MICROFILTRATION and ULTRAFILTRATION of TANGERINE JUICE

Tangerine (Citrus reticulata blanco) juice clarification by crossflow microfiltration and ultrafiltration using polysulphone flat sheet membranes with nominal molecular weight cut off of 25,000, 50,000, 100,000 and 0.1 μm, 0.2 μm pore sizes was studied. the juice was pretreated by polygalacturonase and pH adjustment. the treated juice was clarified with a laboratory scale filtration unit with effective filtration area of 14 cm². Filtration conditions were transmembrane pressure of 93 to 194 kPa, crossflow velocity of 0.96 to 3.5 m/s and 25°C. Membrane performance was evaluated in terms of volume flux and clarity (% transmittance) of the permeate. Pretreatment of the juice by polygalacturonase and adjustment to pH 2 with HCl resulted in a clearer supernatant than enzyme treatment alone. Maximum flux was obtained with the 0.1 μm microfiltration membrane. Flux increased with transmembrane pressure and crossflow velocity. Flux at 194 kPa and 3.5 m/s was 69 L per square meter per hour. Permeate clarity was better at higher transmembrane pressure and lower velocity, due to the effect of the polarized/fouling layer of solute on the membrane surface, which acted as a secondary “dynamic” filter.     

REVERSE OSMOSIS TRANSPORT and MODULE ANALYSIS FOR GREEN TEA JUICE CONCENTRATION

Reverse osmosis experiments were performed to concentrate the green tea juice, and the experimental data was analyzed by using a set of transport equations together with osmotic pressure and density data of the green tea juice. the transport parameters obtained numerically by the above analytical procedure were then used to calculate several dimensionless quantities that can characterize a reverse osmosis module. an example of module design calculation was attempted using the dimensionless parameters so obtained. It has been found that an increase in operating pressure reduces the module length significantly when the feed tea juice concentration is high. an increase of the mass transfer coefficient on the high pressure side of the membrane has the same effect.     

EFFECTS of pH ON the ULTRAFILTRATION of BOVINE SERUM ALBUMIN AT HIGH IONIC STRENGTH USING A MACROPOROUS TITANIA MEMBRANE

The ultrafiltration of bovine serum albumin (BSA) buffered at pH 3.8, 4.8 and 6.8 in solutions with ionic strengths greater than 0.05 mol dm⁻³ was investigated at pressures of 0.20 and 0.70 MPa using a macroporous titania membrane. Protein rejections as high as 0.94 were obtained. Both pH and pressure affected the permeability and rejection. the relative amount of irreversible fouling was estimated by evaluating parameters of a resistance model. Conditions providing the lowest fouling index and the least irreversible fouling while retaining high BSA rejection were obtained at the highest pH, 6.8, and lowest pressure, 0.20 MPa.     

AIR DRYING BEHAVIOR of FRESH and OSMOTICALLY DEHYDRATED PINEAPPLE

Fick's Law of diffusion was used in the analysis of the air drying behavior of fresh (non-osmosed) and osmosed pineapple. the drying rates of osmosed pineapples were significantly decreased due to the presence of infused solute. the effective diffusion coefficient decreased with the increasing solid gain during osmosis.     

ENZYMES IMMOBILIZED ON FORMED-IN-PLACE MEMBRANES FOR FOOD PROCESSING: PROCEDURES and PROPERTIES

The formation and properties of Formed-In-Place (FIP) membranes upon which enzymes had been immobilized were investigated to examine the potential of these reactive membranes in food processing applications. Enzymes were immobilized on two types of FIP membranes and their activities in appropriate fluids investigated. Flux was increased in the microfiltration of pectin solutions by immobilizing pectinase on titanium dioxide microfiltration membranes. A flux increase of 15% was obtained without permeate recycle and 112% with permeate recycle using a 0.1% solution of citrus pectin. Glucose production from dextrin was performed using glucoamylase (GA) immobilized on a zirconium hydrous oxide-polyacrylate nanofiltration membrane. Optimum activity occurred at pH 4.0 and 50C for the immobilized GA. the dextrose equivalent (DE) value of the membrane permeate was approximately ten times higher than the product obtained with free GA during the same time interval.