PRODUCTION AND USE OF YEAST PECTOLYTIC ENZYMES TO AID PINEAPPLE JUICE EXTRACTION

A crude preparation of pectolytic enzyme was obtained by culturing Saccharomyces cerevisiae (ATCC512712) in pineapple juice. Maximum cell growth was obtained on the 6th day after inoculation. Correspondingly, optimum protein concentration and enzyme activity were also observed on the 6th day old culture. Although not purified, the addition of this crude enzyme extract to crushed pineapple mash at 0.02% resulted in a significant increase in juice yield (P≥0.05). The overall processing time was also significantly reduced (P≤0.05) with the enzyme treatment compared to controls. A combination of 0.02% enzyme treatment of mash for 30 min, was found to be the most effective dosage in reducing the processing time significantly.     

EFFECT OF BREAK TEMPERATURE AND HOLDING TIME ON PECTIN AND PECTIC ENZYMES IN TOMATO PULP

SUMMARY –The effect of break temperature and holding time on chemical and physical properties of canned tomato pulp and on the activity of polygalacturonase (PG) and pectin esterase (PE) was investigated. Samples preheated above 200°F were slightly higher in pH value and lower in titratable acidity than those preheated at 160°F and 140°F. The gross viscosity and serum viscosity of the canned tomato pulp increased as break temperature increased. A slight increase in serum viscosity was also observed when holding time was lengthened. The effect of break temperature on serum viscosity was much greater than that of holding time. The total pectin content of the tomato pulp as well as that of the serum increased as the break temperature increased. The same observation holds true for the effect of holding time on the total pectin content of the tomato pulp and tomato serum. This was explained by the inactivation of pectic enzymes at higher break temperature and longer holding periods. The level of PE and PG activity in the frozen tomato pulp decreased as break temperature and holding time increased. No PE activity was detected in samples preheated at 180°F for 15 sec. Samples preheated at 220°F for 15 sec showed no PG activity, while those preheated at 200°F for 15–87 sec still show some PG activity with a retention of about 3.54–5.68%. PG in tomatoes may be inactivated by giving the macerated fruits a hot break temperature higher than 200°F. The critical conditions for inactivation of PE (180°F for 15 sec) and of PG (220°F for 15 sec) found in the course of this investigation are supported by the data obtained on pectin analysis and serum viscosity.     

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     

THE EFFECT OF CRAWFISH PROTEASES ON INACTIVATION AND THE HYDROLYTIC CLEAVAGE OF PECTIC ENZYMES1

Four proteases (CP‐I, ‐II, ‐111 and ‐IV) were isolated and purified from hepatopancreas of crawfish. Based upon their activities with known inhibitors, they resembled trypsin. All were cross‐reactive with polyclonal antibodies raised against CP‐II, indicating they shared structural components. Each of these was able to inactivate orange peel pectinesterase, tomato pectinesterase and pectate lyase C at room temperature under nondenaturing conditions. Using matrix‐assisted‐laser‐desorption time of flight mass spectrometry (MALDl‐TOF MS), an analysis of peptides generated during proteolysis of pectate lyase C from Erwinia chrysenthemi showed similar peptide patterns for the four crawfish proteases, indicating a common specificity for each isozyme. However, the cleavage patterns were different from those obtained by the action of bovine trypsin on pectate lyase C. These studies indicate the four proteases from the hepatopancreas of crawfish are isozymes which may be used for the inactivation of pectinolytic enzymes.     

不同酶种及助剂对酶活影响的研究

几种生物酶应用于棉织物前处理．采用DNS法和紫外分光光度法研究了生物酶的专一性和不同酶种及助剂对酶活的影响．结果表明，淀粉酶、纤维素酶及果胶酶均具有良好的专一性，不同种类酶之间及与所选用的非离子助剂均有较好的相容性，为混合酶前处理的一浴法研究提供了理论基础．     

酶法提取人工养殖鲟鱼皮中胶原蛋白的工艺研究

胶原蛋白是一种具有生物功能的结构蛋白质,广泛应用于医药、化妆品和食品工业中.研究人工养殖鲟鱼皮胶原蛋白的提取工艺.采用酶法提取胶原蛋白,对提取胶原蛋白过程中酶的选择,酶的浓度,提取温度和提取时间对胶原蛋白提取率的影响进行详细的研究.正交试验表明.酶提鲟鱼皮中胶原蛋白的最佳工艺为:以胃蛋白酶-0.5 mol/L乙酸作为提取剂,酶量4000U/g,提取温度37℃,提取时间为6 h,固液比为1:4;在此条件下得胶原蛋白的提取率为70.15%.同时,测定人工养殖的鲟鱼皮胶原蛋白的最大紫外吸收波长为235 nm.     

胶原蛋白复合果汁饮料的生产工艺及稳定性研究

采用单因素试验和正交试验,对胶原蛋白复合果汁饮料配方、生产工艺及其稳定性进行研究.结果表明:饮料的原料优化配比(质量比)为:有机酸(柠檬酸与苹果酸的质量比为2:1)O.4%,蔗糖6%,复合果汁25%,胶原蛋白3%;复合稳定荆的最佳组合为:黄原胶0.04%,耐酸CMC0.10%,海藻酸钠0.15%,阿拉伯胶0.10%;均质压力为25MPa,杀茵温度及时问为80℃.时间为20min.     

EFFECTS OF COMBINED WATER COOKING–VACUUM COOLING WITH WATER ON PROCESSING TIME, MASS LOSS AND QUALITY OF LARGE PORK HAM

The catering system of pork ham is normally a cook–chill system, which is based on the full cooking of pork ham followed by chilling. In order to obtain large pork ham with high quality and safety, a novel method was developed in this work, i.e., combined water cooking–vacuum cooling with water (immersion vacuum cooling) (WC+VW). The effects of WC+VW on processing time, mass loss and quality of large pork ham were evaluated by comparing them with those of four traditional pork ham processing methods, i.e., dry air cooking combined with air blast cooling (DAC+AB), dry air cooking combined with cold room cooling (DAC+CR), wet air cooking combined with air blast cooling (WAC+AB) and wet air cooking combined with cold room cooling (WAC+CR). WC+VW achieved the shortest processing time, resulting from the shortest time of vacuum cooling with water (308.0 min). Furthermore, present results showed that WC+VW could produce mass loss and quality of large pork ham comparable to those of the four traditional processing methods.     

复合酶法提取茶多酚工艺条件研究

实验采用复合酶解法在低温下提取茶叶中的活性物质——茶多酚。采用单因素和正交实验确定了最佳提取条件。结果表明，采用复合酶法提取茶多酚，提取率高达98％以上，茶多酚中的活性成分儿茶素相对含量较传统沸水提取法高出9％～10％。     

胡萝卜木瓜南瓜复合保健饮料的研制

以胡萝卜、木瓜、南瓜为主要原料,采用正交试验设计方法、单因素试验设计及感官评定研究胡萝卜、木瓜、南瓜复合果蔬饮料的最佳配方.试验结果表明,最佳配方为:胡萝卜木瓜南瓜体积比为10:30:20,白糖12%,柠檬酸0.26%,琼脂0.1%.     

EFFECTS OF RAW MATERIALS AND PROCESS VARIABLES ON THE HEAT PENETRATION TIMES, FIRMNESS, AND PECTIC ENZYME ACTIVITY OF DICED TOMATOES (HALLEY BOS 3155 CV)

The effects of raw materials and process variables on the heat penetration times into diced tomatoes (Halley Bos 3155 cv) were evaluated. Variables included dice size (1.27 and 2.54 cm), maturity at harvest (red and red+2 weeks), and processing temperature (88 and 92C). Heat penetration times between dice sizes were significantly different, but not between maturities or processing temperatures. Tomatoes were also evaluated for firmness, pectin-methylesterase (PME) and polygalacturonase (PG) activities. Half-inch size diced tomatoes were processed at 88 and 92C, and evaluated for firmness using the shear-compression method. Firmness decreased to 60% of the initial raw firmness from 8.8 × 10⁵ to 5.3 × 10⁵ g-mm after 15 s at 88C, and to 50% from 8.8 × 10⁵ to 4.4 × 10⁵ g-mm after 15 s at 92C. Diced tomato firmness showed a slight firming trend after 150 s at both temperatures. PME was inactivated after 45 s, while 5% residual PG activity remained after 3 min.     

大蒜汁脱臭工艺的筛选

对大蒜分别采用加热法、加添加剂法、包埋法、掩蔽法等不同方法进行脱臭处理，结果表明：采用海带汁3．3％，半胱氨酸0．1％，β-环糊精0．008％，蜂蜜0．008％，作为复合脱臭液，在10℃的温度条件下处理72h，对大蒜汁脱臭效果显著。     

乙酸-微波预处理法提取辣椒素的研究

采用微波辅助提取方法,以乙酸为提取剂从辣椒粉中提取辣椒素.对影响提取效率的因素进行了优化,获得了最佳提取条件:每g辣椒粉以1 mL,10%乙酸为气化剂,浸润15 min,微波功率480 W,处理90 s,用 8 mL,50%乙酸在50℃下浸取50 min.