ULTRAFILTRATION OF WHOLE MILK WITH HOLLOW FIBER MEMBRANES

Whole milk was concentrated using Romicon PM50 membranes. Rententate and permeate were analyzed for total solids, protein (TKN) and fat at five concentration levels. The effects of pressure, concentration, fiber length and several milk pretreatments on flux were examined. A 5X concentrate was prepared containing 37.2% solids, 13.3% protein and 17.8% fat. The highest initial and 4X fluxes were obtained using a pressure differential of 1.4 kg/cm² - 2.11/0.7 (20 psig - 30/10). Flux declined slowly with concentration to 3X (20% loss) and decreased more rapidly thereafter. Higher fluid velocities were deemed responsible for 27% higher initial flux and 47% higher 4X flux when a shorter module was employed (63.5 versus 109.2 cm). Clarification, pasteurization and/or homogenization had little effect on flux at either level.     

APPLE JUICE QUALITY AS INFLUENCED BY ULTRAFILTRATION

Objective quality of ultrafiltered (UF) apple juice compared favorably to apple juice filtered by conventional plate and frame filtration (PF). Agtron red and green values were higher for the UF juice, indicating a lighter colored product. Agtron green values were lower after 4 months of storage and compared well to juice from conventional methods over the remaining 8 months of storage. Green color of the UF juice remained steady at storage temperatures of either 1° or 21°C and was equal to the color values of the conventional juice stored at 1°, 21° or 32°. Clarity of the UF juice was excellent and remained stable over the entire storage period at either 1 or 21° with only a slight drop in clarity at 32°. UF juice was rated significantly lower in sensory flavor than PF juice. Sensory color of the UF juice was not rated as high as the PF juice at the start of the study, but as time in storage progressed sensory color improved. Initial panel reaction to UF apple juice was that the UF juice was too light in color and watery in flavor.     

MASS TRANSFER CHARACTERISTICS OF HOLLOW FIBER ULTRAFILTRATION OF SOY PROTEIN SYSTEMS

Mass transfer characteristics and the applicability of theoretical transport models in ultrafilitration were evaluated in a pilot-scale hollow fiber system processing soybean water extracts. Permeate flux was found to increase linearly with transmembrane pressure and then reach an asymptotic value. Substantial deviations from the pure water permeation line and marked hysteresis effects were also observed, indicative of concentration polarization and additional hydrodynamic resistance at the membrane surface. Pressure-independence occurred at lower pressures with lower Reynolds Numbers (Re) and higher Schmidt Numbers (Sc). Flow rate and temperature significantly affected flux in the totally polarized region. The exponent in the flux-Reα relationship varied from 0.6 at 20°C to 0.32 at 50°C. Theoretical laminar flow mass transfer models were found to predict Sherwood Numbers (Sh) and flux lower than experimental values. The correlation that fit the data best was Sh = 0.181 (Re).⁴⁷ (Sc).³³     

INFLUENCE OF CONVENTIONAL CLARIFICATION AND ULTRAFILTRATION ON THE PHENOLIC COMPOSITION OF GOLDEN DELICIOUS APPLE JUICE

Abstract The effects of conventional clarification and ultrafiltration techniques on the phenolic composition of apple juice was studied. Since the health benefit of fruits and fruit juices have been ascribed, in part, to the phenolic antioxidants, it is very important to know what the effects of processing steps are on the level of phenolic compounds in fruit juices. The total losses of phenolic compounds were determined to be 28% and 7% during conventional clarification using gelatin and bentonite, and ultrafiltration, respectively. A total of 14 phenolic compounds were identified in apple juice prepared from Golden Delicious apples. The phenolic compounds were found to be based mainly on hydroxycinnamic acids (∼ 50% of total phenolics) and chlorogenic acid was found to be the major phenolic compound with its concentration as high as 465.45 mg 1⁻¹ in raw apple juice.     

果胶酶提高葡萄出汁率的工艺研究

研究了用果胶酶提高葡萄出汁率的方法。通过单因素与正交试验分析了酶添加量、酶解温度和酶解时间对葡萄出汁率的影响，最佳工艺条件为，果胶酶用量0．08mL／kg，酶解温度55℃，酶解时间120min。     

超滤法澄清西番莲果汁的研究

以寻求提高西番莲原汁超滤时的渗透通量为目的，用国产芳香聚酰胺膜平板超滤器进行试验，对超滤操作条件，果汁预处理，膜的清洗进行研究。结果表明，西番莲原汁超滤时渗透通量最高的操作压力为0．15MPa，最佳进料速度为22mL/s，操作温度为室温；原汁经海藻酸钠—碳酸钠澄清剂预处理后可以明显增大渗透通量；超滤处理后。原汁的西番莲固有滋味和品质得到较好保留。采用超滤澄清法生产高质量的西番莲原汁是可行的。     

采收期对金红苹果贮藏品质的影响

以金红苹果为试材,研究不同采收期对金红苹果贮藏品质的影响,为金红苹果贮藏保鲜提供理论和实践依据.研究结果表明:在吉林地区,金红苹果适宜的采收期为8月末9月初.此期,果实的硬度约为11.00kg/cm2,可溶性固形物含量约为12.40%,可滴定酸含量约为0.76%.果实冷藏100d后,仍能保持硬度达7.90 kg/cm2,可溶性固形物含量约为11.30%,可滴定酸含量达0.50%,失重率4.70%,而且果实外观新鲜,腐烂率仅为0.50%.     

DILUTION AND SOLIDS ADULTERATION OF APPLE JUICE

The adulteration of apple juice with pear juice and corn drived syrups has been practiced in many countries. The sorbitol/sucrose ratios and the sorbitol/total sugar ratios were determined for the juices of 14 apple varieties and 3 pear varieties. A multivariate normal test was applied to develop an equation for the detection of apple juice adulteration with sugar solutions or pear juice. Adulteration of apple juice with more than 10% sugar solution or pear juice were detectable with this method.     

果胶酶和纤维素酶对菠萝汁澄清效果的研究

本文研究比较了果胶酶和纤维素酶对菠萝汁的澄清效果,确定了各自的最佳工艺参数,并在单因素试验的基础上,通过复合酶的多因素正交试验,获得澄清菠萝汁的最适工艺条件为：果胶酶用量为8.48 U/100mL、纤维素酶42.13 U/100g、时间45min、温度30℃,此时菠萝汁的透光率能达到了87%以上.     

STORAGE STABILITY OF A STIMULANT COCONUT WATER-CASHEW APPLE JUICE BEVERAGE

Besides flavor, appearance and overall impression, food consumers seek foods rich in nutrients. Fruits are a rich source of nutrients and minerals, and fruit juices are a popular way of consuming them. Development of new products, where two or more kinds of fruit juices are blended to obtain a product that combines the nutritional value of both fruits, which present a different and pleasant taste, has been encouraged by the food industry and has been well accepted by consumers. In this work, the storage stability of a coconut water‐cashew apple juice (87.5:12.5 v/v) beverage was evaluated. Caffeine addition (100 mg/L) conferred stimulating properties to the blend. The physicochemical, microbiological and sensory stability of this blended beverage was evaluated during 6 months. The results showed that the beverage presented good stability for all parameters that were analyzed except for vitamin C, which presented a loss of 58% from the initial content.     

QUALITY AND STABILITY OF BLUEBERRY JUICE BLENDED WITH APPLE,GRAPE AND CRANBERRY JUICE1

Sensory quality and storage stability of blueberry juice blends were investigated with the goal of maintaining dominant blueberry flavor, aroma and color. Apple juice, Concord and Venus grape juices and cranberry juice cocktail were blended at 75, 50 and 25% with blueberry juice. As the percent of blueberry juice decreased, the intensity of blueberry‐related sensory attributes decreased. The 25% Concord and Venus blends were the only blends that resulted in blueberry flavor similar to the reference. Apple and cranberry juice cocktail blended with blueberry juice produced several blends with good flavor and aroma, but they were not readily characterized as blueberry juice. All blends at the 25% level produced blueberry color equal to or greater than the reference. The juice samples were evaluated initially and after three months of storage at 37C. After storage, all blends had decreased red color.