Effects of Carbon Dioxide in High-Pressure Processing on Pectinmethylesterase in Single-strength Orange Juice

ABSTRACT: High-pressure processing (HPP) in combination with added CO was examined for efficacy in inactivating Valencia orange juice pectinmethylesterase (PME). Noncarbonated juice and carbonated juice were subjected to a range of conditions from 200 to 600 MPa, 30 to 300 s dwell time at pressure, and 15 to 50 °C at final processing temperature. Processing pressure magnitude, temperature, and dwell time were significant factors (p < 0.001) in the inactivation of PME. At 600 MPa and 25 °C final processing temperature, the addition of 12 psig carbon dioxide resulted in a decrease of pressure processing time from 346 s to 111 s, while achieving an equivalent reduction in PME activity.     

High-Pressure Processing of Orange Juice: Kinetics of Pectinmethylesterase Inactivation

ABSTRACT: A kinetic study of pectinmethylesterase (PME) inactivation in orange juice was conducted. Juice samples were subjected to combinations of high pressure (400, 500, 600 MPa) and thermal (25, 37.5, 50 °C) treatments for various time periods. PME inactivation followed a first-order kinetic model with a residual activity of pressure-resistant enzyme remaining. Calculated D-values ranged from 4.6 min to 117.5 min at 600 MPa/50 °C and 400 MPa/25 °C, respectively. Pressures in excess of 500 MPa resulted in sufficiently fast inactivation rates for economic viability of the process.     

A Continuous High Pressure Carbon Dioxide System for Microbial Reduction in Orange Juice

ABSTRACT: A continuous high-pressure carbon dioxide system, run at ambient conditions, was tested on its performance in reducing both natural and inoculated microbial loads. The prototype system continuously processes orange juice with carbon dioxide (CO₂) at high pressures. A central composite design was originally used to examine the variables of pressure, residence time, and CO₂/juice ratio. For microbial reduction, residence time was the major factor followed by pressure. The CO₂/juice ratio showed no influence on microbial load, and in this equipment, was difficult to control. The unit was able to cause a 5-log reduction of the natural flora in spoiled juice, and could attain a 5-log decrease in numbers of pathogenic Escherichia coli O157:H7, Salmonella typhimurium , and Listeriamonocytogenes . No viable cells of E . coli O157:H7 orS. typhimurium were cultured after the treated juices were stored at room temperature (22 °C) for 14 d. Thus, non-thermal pathogen reduction is possible with this system.     

High-Pressure Processing of Orange Juice: Combination Treatments and a Shelf Life Study

ABSTRACT: Several process alternatives for the stabilization of fresh orange juice at pressures between 500 MPa and 800 MPa and temperatures between 25 and 50 °C were evaluated. Processing at 800 MPa and 25 °C for 1 min and use of thermally pasteurized pulp yielded the lowest level of residual pectinmethylesterase activity (3.9%) and good cloud stability at 4 and 37 °C over a period of more than 2 mo. Ascorbic acid loss was less than 20% after storage for 3 mo at 4 °C or 2 mo at 15 °C. Color values were stable during storage at 4, 15, and 26 °C     

A Continuous High-Pressure Carbon Dioxide System for Cloud and Quality Retention in Orange Juice

ABSTRACT:  Orange juice (OJ) was treated with a continuous high-pressure carbon dioxide (HPCD) system, and the quality parameters pH, Brix, titratable acidity (TA), cloud, pectinesterase (PE) activity, color, and sensory attributes were determined. Treatment pressures were 38, 72, and 107 MPa, and CO₂/juice (w/w) ratios were from 0.40 to 1.18. Residence time was kept at 10 min. Cloud increased between 446% and 846% after treatments. There were no significant changes in pH and Brix (α= 0.05). TA of the treated juice was found to be significantly different from that of control (α= 0.01). PE was not completely inactivated. There was a small, but significant increase in juice L-value (α= 0.01) and a decrease in a-value for color. There was no significant change in b-values (α= 0.05). Statistical analysis for the sensory data showed no difference between fresh, frozen control juice and treated juice after 2 wk of refrigerated storage at 1.7 °C.     

Cloud Stabilization of Orange Juice by High Pressure Processing

High pressure processing (HPP) was investigated as a means to preserve cloud in freshly squeezed orange juice. Cloud loss is a major quality defect in orange juice, and methods of preserving cloud without the extreme temperatures used in commercial pasteurization are desirable. Pressures from 500 to 900 MPa were investigated at dwell times of 1 sec, 1 min and 10 min. Higher pressures and longer processing times were more effective at preserving cloud, while all treatments yielded a microbially stable product. A 90-day shelf life under refrigeration conditions could be achieved using pressures of 700 MPa and higher combined with treatment times of 1 min.     

高压CO_2处理对西瓜汁的影响

以海南麒麟西瓜为原料,榨汁后进行HPCD(高压CO2)杀菌处理,处理温度为25℃,压力为20 MPa和30 MPa,处理时间分别为10、30和60 min,测定HPCD处理后西瓜汁的主要理化指标、细菌总数和PME酶(果胶甲基酯酶)活性变化。结果表明:HPCD处理后西瓜汁pH值降低0.3～0.7、可溶性固形物无明显变化、颜色更红、浊度增加,细菌总数降低可达到2个对数,果胶甲基酯酶活性可降低50%。     

高压二氧化碳对鲜榨西瓜汁杀菌效果和风味的影响

为研究高压二氧化碳对鲜榨西瓜汁的杀菌效果及对风味的影响,采用高压二氧化碳(HPCD)技术对鲜榨西瓜汁进行处理。以95℃、1min热处理西瓜汁作为对照,考察30MPa、60min HPCD处理对西瓜汁中菌落总数、霉菌和酵母菌总数及典型风味化合物含量的影响;并探讨两种处理西瓜汁在4℃、30d贮藏过程中上述指标的变化情况。结果表明:95℃、1min热处理的杀菌效果略好于30MPa、60min HPCD处理,采用两种处理西瓜汁的微生物指标均符合《果、蔬汁饮料卫生标准》的要求;并且保质期满足鲜榨西瓜汁的消费要求。30MPa、60min HPCD处理对西瓜汁的典型风味化合物含量影响较小;贮藏过程中风味变化也较小。总体看来,HPCD处理更适合于鲜榨西瓜汁的加工。     

超高压处理对脐橙汁中香气成分柠檬烯的影响

以脐橙汁为对象,采用Box-behnken 响应曲面设计,研究超高压处理对橙汁中柠檬烯香气成分的影响,实验参数选择压力(100～500MPa)、温度(20～40℃)、处理时间(10～20min),建立超高压处理下柠檬烯含量变化的二次多项数学模型。结果表明：模型的确定系数R2=0.9938,调整确定系数RAdj=0.9858,方差分析表明模型极度显著(P ＜ 0.0001),该模型可用于超高压处理橙汁中柠檬烯含量变化的分析与预测。     

Multiple Forms of Pectinmethylesterase from Citrus Peel and Their Effects on Juice Cloud Stability

Heparin chromatography of a dialysis supernatant fraction from total salt extractable proteins of Citrus sinensis (L.) Osb. var. Valencia fruit peel (flavedo plus albedo) resolved four peaks of pectinmethylesterase activity (PME 1–4). One of these was thermally tolerant (PME 3). Binding to concanavalin A suggested PME 3 was a glycoprotein. At 30°C and 5 U - mL1 PME 1, 2 and 3 destabilized the cloud of pasteurized FCOJ within 10 days. PME 1 caused the most rapid cloud loss (3d), followed by PME 3 and PME 2. PME 4 had no effect on juice cloud during this time period. At 4°C PME 3 caused the most rapid cloud loss (3d), followed by PME 1 (14d) and PME 2 (>14d). PME 4 had no effect on juice cloud stability after 10 days at 30°C or 14 days at 4°C.     

血橙果汁贮藏过程中品质变化研究

通过血橙原汁成分分析,对血橙原汁低温贮藏过程中与品质相关的几项指标的变化进行监测,以探讨低温贮藏对血橙果汁品质的影响。结果表明：血橙汁富含花色苷(68.84mg/L)、黄酮类物质(0.18mg/mL)、抗坏血酸(0.63mg/mL)、氨基酸(43.012mg/mL)、糖类(128.3mg/mL)等物质,还含有Ca、Mg、Zn、Fe、Cu 等丰富的人体必需微量元素;同时HPLC 分析显示血橙汁含有的可溶性糖主要是蔗糖(7.4g/100mL)、果糖(2.2g/100mL)、葡萄糖(2.1g/100mL)。在血橙汁贮藏过程中,随着花色苷含量的下降橙汁鲜艳的红色也逐渐褪色成浅黄褐色,抗坏血酸含量明显下降,贮藏40d 后含量下降约52%;而还原糖含量变化缓慢,总酸含量平缓增加。     

Microbial, Enzymatic, and Chemical Changes During Storage of Fresh and Processed Orange Juice

Microbial, enzymatic, and chemical comparisons were made on orange juice stored at 4°C without pasteurization, with light pasteurization (66°C, 10 sec) directed at vegetative microorganisms, and with full pasteurization (90°C, 60 sec) directed at the heat stable isozyme of pectinesterase. Effects of oxygen-barrier and nonbarrier packaging were also examined. Oxygen-barrier packaging did not benefit unpasteurized juice. However, lightly and fully pasteurized juices in barrier cartons exhibited lower microbial counts, greater ascorbic acid retention, and apparent slowing of cloud loss by the third week of storage. During the first 22 days storage, microbial, cloud, sugar, and ascorbic acid values for lightly pasteurized juice were similar to those of juice receiving full pasteurization.     

桔汁酿酒可行性研究

对以无核桔为原料生产桔子酒的可行性进行了研究。探讨了温度、时间、接种量等因素对酒体品质及风味的影响,并通过感官评定得出桔子酒的最佳生产工艺。结果表明：采用压榨取汁,主酵温度 23℃、酵母接种量 2× 106cfu/mL、主酵时间 5d、后酵温度 10℃、时间为 21d,所酿制的桔子酒果香浓郁、风味独特。     

Influence of High-Pressure Treatment at 25°C and 80°C on Folates in Orange Juice and Model Media

ABSTRACT: The influence of high-pressure treatment on the 3 main folate species present in orange juice was assessed under conditions similar to those used in high-pressure pasteurization and sterilization using freshly squeezed orange juice and different model orange juices. The latter were used also to determine the influence of matrix components, pH, and excess ascorbic acid. Excess ascorbate strongly protected folates against pressure and heat. Pressurization at 600 MPa and 80°C affected model juice folates synergistically, and pressure increased the formation of 5,10-methenylfolate. In fresh orange juice, components other than ascorbate additionally stabilized folates, thus pressure preservation and pressure sterilization appeared very feasible.     

超高压处理对鲜橙汁中果胶酶及过氧化物酶活性的影响

为推进国内非冷冻浓缩橙汁加工业的发展,对新型超高压杀菌技术对橙汁中酶钝化的效果进行研究,采用200～600MPa超高静压处理鲜榨橙汁,使用紫外分光光度法、滴定法分别测定鲜橙汁中过氧化物酶(POD)和果胶酶(PME)的活性,进行两种酶在常温下超高压钝化酶一级动力学拟合研究。结果表明：在常温条件下200MPa处理10min使两种酶轻微激活,在300～600MPa条件下,随压力和处理时间的增大,两种酶钝化反应明显,且符合一级动力学模型,且果胶酶对压力钝化更加敏感。     

Effect of Pectinmethylesterase Infusion Methods and Processing Techniques on Strawberry Firmness

Strawberry halves were pretreated with fungal pectinmethylesterase (PME) and calcium chloride using, respectively, passive osmotic infusion, vacuum‐assisted infusion, and pressure‐assisted infusion with the aim to improve the firmness. The vacuum‐assisted procedure was observed to be the only method able to accomplish an uptake of infusion solution and hence capable of improving the firmness of the strawberries. Significantly less firmness increase was realized when tomato PME was vacuum‐infused instead of fungal PME. Strawberry halves were pretreated by vacuum‐assisted infusion with fungal PME and calcium chloride and were subsequently subjected to thermal treatments at 60 °C and 80 °C and pressure treatments at about 400 MPa and 550 MPa. For all treatments studied, the pretreated sample was significantly firmer compared with the reference sample. For the thermal processes, the residual firmness relative to the initial value before treatment was depending on the temperature of the treatment and not on the pretreatment. However, vacuum‐assisted infusion of PME and calcium could limit the portion of firmness loss due to pressure treatment to 30% compared with 80% for non‐pretreated fruits.     

浓缩蜜橘汁的工业化加工研究

以湘西蜜橘为原料加工成浓缩蜜橘桶汁,研究了浓缩蜜橘汁的加工工艺,结果表明:蜜橘果实榨汁时,用0.4%果胶酶在45℃下酶解处理果浆90min,可提高出汁率15%。通过正交试验,确定了真空浓缩最佳工艺参数为:真空浓缩温度50～55℃、真空度(9.33～10.0)×10~4Pa、果汁流量6000～6500L/h、蒸汽压力7.5～8.0×10~4 MPa;贮存温度≤-18℃下,产品pH值、总酸和Vc无影响,并制定了产品质量标准,为我国浓缩汁加工企业提供了有益的借鉴。     

Commercial-Scale Pulsed Electric Field Processing of Orange Juice

Effects of commercial‐scale pulsed electric field (PEF) processing on the microbial stability, ascorbic acid, flavor compounds, color, Brix, pH, and sensory properties of orange juice were studied and compared with those of thermal processing. Freshly squeezed orange juice was thermally processed at 90 °C for 90 s or processed by PEF at 40 kV/cm for 97 ms. Both thermally processed and PEF‐processed juices showed microbial shelf life at 4 °C for 196 d. PEF‐processed juice retained more ascorbic acid, flavor, and color than thermally processed juice (P<0.05). Sensory evaluation of texture, flavor, and overall acceptability were ranked highest for control juice, followed by PEF‐processed juice and then by thermally processed juice (P<0.01).     

天然防腐剂柠檬烯在橙汁保鲜中的应用

对柠檬烯乳化及其在橙汁保鲜中的应用进行研究。乳化实验结果表明,添加20g/L 的蔗糖酯SE-15,乳化效果最好,离心前后吸光变化率为26.70%。橙汁保鲜实验结果表明,添加0.25g/L 的柠檬烯保鲜效果较差,贮存期间细菌总数变化,只有第4 天明显低于空白对照,pH 值和感官品质与空白对照相比,始终无明显差异;而添加大于等于0.50g/L 的柠檬烯,保鲜效果明显,在整个检测过程中,细菌总数、pH 值变化和感官品质都明显优于空白对照。