Spread of bacterial pathogens during preparation of freshly squeezed orange juice

To study the potential of three bacterial pathogens to cross-contaminate orange juice during extraction, normal operation conditions during juice preparation at food service establishments were simulated. The spread of Salmonella enterica serovar Typhimurium, Escherichia coli O157:H7, and Listeria monocytogenes from inoculated oranges to work surfaces and to the final product was determined. The transference of these three bacterial pathogens to orange juice made from uninoculated oranges with the use of contaminated utensils was also studied. Fresh oranges were inoculated with a marker strain of rifampicin-resistant Salmonella Typhimurium, E. coli O157:H7, or L. monocytogenes. Final pathogen levels in juice were compared as a function of the use of electric or mechanical juice extractors to squeeze orange juice from inoculated oranges. Pathogen populations on different contact surfaces during orange juice extraction were determined on sulfite-phenol red-rifampicin plates for Salmonella Typhimurium and E. coli O157:H7 and on tryptic soy agar supplemented with 0.1 g of rifampicin per liter for L. monocytogenes. After inoculation, the average pathogen counts for the orange rind surface were 2.3 log10 CFU/cm2 for Salmonella Typhimurium, 3.6 log10 CFU/cm2 for E. coli O157:H7, and 4.4 log10 CFU/cm2 for L. monocytogenes. This contamination was spread over all utensils used in orange juice squeezing. Mean pathogen counts for the cutting board, the knife, and the extractor ranged from -0.3 to 2.1 log10 CFU/cm2, and the juice contained 1.0 log10 CFU of Salmonella Typhimurium per ml, 2.3 log10 CFU of E. coli O157:H7 per ml, and 2.7 log10 CFU of L. monocytogenes per ml. Contact with contaminated surfaces resulted in the presence of all pathogens in orange juice made from uninoculated oranges. These results give emphasis to the importance of fresh oranges as a source of pathogens in orange juice.     

Studies on non-enzymic browning in orange juice using a model system based on freshly squeezed orange juice

An orange juice based model system was set up wherein variables such as the addition of glucose, lysine, sorbitol and L -ascorbic acid and changes in pH and storage temperature were introduced to study their effects on L -ascorbic acid degradation and on browning. The addition of glucose, lysine and sorbitol did not have a significant effect on L -ascorbic acid degradation, whereas added L -ascorbic acid acted solely as a reserve material. In terms of browning, a change in pH and storage at elevated temperature produced a synergistic effect in the development of brown colour which was enhanced by the introduction of additives. Based on the results obtained, L -ascorbic acid appears to be the precursor in the non-enzymic browning occurring in this type of sample due to the formation of reactive carbonyl compounds produced upon its degradation which tend to polymerise, or to react with nitrogenous compounds, to give brown pigments.     

鲜榨果汁基因组DNA快速提取方法的建立及优化

目的 建立及优化鲜榨果汁基因组DNA快速提取方法。方法 本研究比较了植物 DNA 快速提取试剂盒法、棉签法、纤维素膜片法和滤纸片法 4 种方法提取 15 种鲜榨果汁基因组 DNA 的效果,并筛选不同的提取液和裂解液、优化裂解液中的盐酸胍浓度和果汁基因组提取时间。结果 滤纸片法采用DNA裂解液（6 mol/L盐酸胍、1%聚乙烯吡咯烷酮、50 mmol/L三羟甲基氨基甲烷盐酸盐、20 mmol/L乙二胺四乙酸、21.3 mmol/L曲拉通-X-100;pH 6.4）、DNA漂洗液1（8 mol/L盐酸胍、50 mmol/L三羟甲基氨基甲烷盐酸盐;pH 6.4）和DNA漂洗液2（10 mmol/L 三羟甲基氨基甲烷盐酸盐、100 mmol/L氯化钠;pH 8）即可在 5 min 内从鲜榨果汁中提取得到适用于聚合酶链式反应（polymerase chain reaction,PCR）的基因组 DNA。结论 本研究建立的滤纸片法不需要离心机等昂贵的仪器设备、操作简单、无刺激性气味、无环境条件限制,具有快速、价廉、环保等优点,为果汁基因组 DNA 快速提取与现场鉴定研究提供了参考。     

Fresh squeezed orange juice odor: a review

Fresh orange juice is a highly desirable but unstable product. This review examines analytical findings, odor activity, and variations due to cultivar, sampling methods, manner of juicing, plus possible enzymatic and microbial artifacts. Initial attempts to characterize orange juice odor were based on volatile quantitation and overemphasized the importance of high concentration volatiles. Although over 300 volatiles have been reported from GC-MS analytical studies, this review presents 36 consensus aroma active components from GC-olfactometry studies consisting of 14 aldehydes, 7 esters, 5 terpenes, 6 alcohols, and 4 ketones. Most are trace (microg/L) components. (+)-Limonene is an essential component in orange juice odor although its exact function is still uncertain. Total amounts of volatiles in mechanically squeezed juices are three to 10 times greater than hand-squeezed juices because of elevated peel oil levels. Elevated peel oil changes the relative proportion of several key odorants. Odor active components from solvent extraction studies differ from those collected using headspace techniques as they include volatiles with low vapor pressure such as vanillin. Some reported odorants such as 2,3-butanedione are microbial contamination artifacts. Orange juice odor models confirm that fresh orange aroma is complex as the most successful models contain 23 odorants.     

商业树脂对鲜榨柠檬汁的脱苦效果

以工业生产中鲜榨柠檬原汁为试材,研究了不同商业树脂对鲜榨柠檬汁脱苦效果的影响。结果表明:大孔吸附树脂对柚皮苷和柠檬苦素的吸附率优于离子交换树脂,且对营养成分的影响较小;优选出的大孔吸附树脂R6在达到吸附平衡时对柚皮苷和柠檬苦素的吸附率最大,分别达82.87%和69.13%,且吸附时间较短,其对柚皮苷和柠檬苦素的吸附等温线分别与Langmuir经典方程式和Freundlich经典方程式拟合度最好,具有良好的静态吸附性能。     

Effect of extraction method on quality of orange juice: hand-squeezed, commercial-fresh squeezed and processed

BACKGROUND: Fresh orange juice is perceived to be more wholesome than processed juice. Fresh juice may have flavor and nutrients that differ from pasteurized or processed juice. RESULTS: ‘Hamlin’ and ‘Valencia’ oranges were extracted using a commercial food service juicer, pasteurized or not, resulting in fresh‐commercial juice (FCJ) or pasteurized juice (FCPJ) for comparison with pasteurized processed juice (PPJ) in 2009, and gently hand‐squeezed ‘Valencia’ juice (HSJ) in 2010 for quality attributes. There was higher peel oil, lower pectin content, and less cloud loss in FCJ/FCPJ compared to PPJ and HSJ regardless of pasteurization. Titratable acidity was generally higher and the ratio of solids to acids lower in FCJ/FCPJ or HSJ compared to PPJ. FCJ/FCPJ had generally higher levels of most aroma volatiles than did PPJ and, overall, the highest esters and terpenes, while methanol and ethanol levels were highest in HSJ. For sensory evaluation, FCJ/FCPJ had more peel oil and PPJ more cooked flavor than other samples, while ‘Valencia’ HSJ was preferred over the other juices. CONCLUSION: High peel oil content and thermo‐pasteurization process decreased cloud loss of orange juice. Extraction and finishing processes rather than pasteurization or oil content were major factors in influencing orange juice flavor quality. Copyright © 2012 Society of Chemical Industry     

Characterisation of the key aroma compounds in a freshly reconstituted orange juice from concentrate

Application of an aroma extract dilution analysis on the entire volatile fraction isolated from an orange juice freshly reconstituted from concentrate revealed 40 odour-active constituents in the flavour dilution (FD) factor range of 4–2,048. Among them, ethyl butanoate and linalool showed the highest FD factor of 2,048, followed by octanal with an FD factor of 512. Thirty-six of the 40 odour-active compounds detected could be identified, all of which have previously been reported as volatile constituents of various orange juices. Quantification of 17 key odorants by stable isotope dilution assays followed by a calculation of odour activity values (OAVs) on the basis of odour thresholds in water or citrate buffer (pH 3.8), respectively, revealed the following most important odorants in the overall aroma of the freshly reconstituted juice: (R/S)-linalool, (R)-limonene and (S)-ethyl 2-methylbutanoate with the highest OAVs (>1,000) followed by octanal, (R)-α-pinene, ethyl butanoate, myrcene, acetaldehyde, decanal and (E)-β-damascenone with OAVs > 100. A model mixture containing all 14 aroma compounds with OAVs > 1 in their actual concentrations in the juice showed a good similarity with the aroma of the original orange juice under investigation, thus corroborating that the key odorants of a freshly reconstituted orange juice were characterised for the first time.     

超高压鲜榨哈密瓜汁加工工艺技术的研究

系 统 研 究 了 超 高 压 杀 菌 技 术 对 热 敏 性 哈 密 瓜 汁 加 工 的 工 艺 和 参 数 , 分 别 确 定 了 超 高 压 杀 菌 的 压 力 和 时 间 、 酸 化 pH 的 范围 及施 压的 方 式 。研 究 结 果 表明 ,采用 500M Pa, 20m in 的超 高压 杀 菌强 度, 产品 完全 达 到美 国 FD A 有 关 鲜 榨 果 蔬 汁 饮 料 的 卫 生 安 全 要 求 。500M Pa,20m in 超 高 压 处 理 的 哈 密 瓜 汁 香 气 经 固 相 微 萃 取 分 析 测 定 和 感 官 评 定 其 质 量 与 鲜 哈 密 瓜 汁 相 近 ,产 品 质 量 完 全 可 以 接 受 。     

Mathematical modeling of yeast inactivation of freshly squeezed apple juice under high-pressure carbon dioxide

The number of data sets available in literature regarding inactivation kinetic of microorganisms at low temperature, demonstrate an increasing attention to new technologies for food preservation at ambient temperature. Nevertheless, no reliable modeling, capable to describe complex inactivation curves, such as the ones due to dense gas pasteurization with a log-linear behavior, have been developed thus far. In this respect, the main aim of this work is to analyze and model experimental data of dense carbon dioxide yeast pasteurization of natural apple juice at different condition of temperature (25-36°C) and sample volume (5-10 ml). The Weibull model modified by Albert and Mafart was verified to be an interesting model capable to take into account CO2 inactivation kinetic, with a first phase with a shoulder, a second phase with a log-linear shape, and a final phase with a tailing with either a non-zero or a zero asymptote. Clearly, the results obtained shows that an increase in temperature decreases the time needed for the same inactivation efficiency; the residual yeast concentration of N(RES), a thermodynamic parameter, results volume independent, and temperature dependent; the treatment time required to reach 90% of inactivation results temperature dependent, with a sample volume of 5 ml; at 100 bar - 25°C-10 mL a shoulder effect is evident in the inactivation kinetic. The model can be considered a new useful tool to predict new CO2 pasteurization data at different operative conditions.     

Effect of thermal treatment during processing of orange juice on the enantiomeric distribution of chiral terpenes

Chiral terpenes in orange juices were examined by solid-phase microextraction-gas chromatography-mass spectrometry to study the dependence of their enantiomeric composition on the thermal treatment applied during the industrial manufacture. The experimental conditions used in the isolation and concentration of the compounds of interest produced relative standard deviations ranging from 2.9 to 15.1% when absolute areas were used and from 1.7 to 18.3% when normalized areas were used. Recovery varied between 8.8 and 56.1%, and detection limits ranged from 0.11 to 0.32 microg/ml. The enantiomeric compositions of the majority of the chiral terpenes varied within a reasonably narrow range. Nevertheless, the enantiomeric ratio of two monoterpene alcohols, alpha-terpineol and linalool, exhibited considerable variation according to the thermal treatment used in the manufacture of the juices. Therefore, the knowledge of the enantiomeric composition of alpha-terpineol and linalool might be useful for thermal treatment control purposes.     

Removal of limonin from bitter orange juice

Polyamides are shown to be effective adsorbents for removal of the bitter principle, limonin, from pasteurised Washington Navel orange juice. The extent of limonin removal varies with different juices, but sufficient can be removed by one or two treatments to bring the concentration below the organoleptically detectable level. The commercial use of polyamides to prepare non-bitter juices from Navel oranges is discussed.     

Salmonella and Shigella in freshly squeezed orange juice, fresh oranges, and wiping cloths collected from public markets and street booths in Guadalajara, Mexico: incidence and comparison of analytical routes

A survey of the presence of Salmonella and Shigella in freshly squeezed orange juice and related samples was conducted in Guadalajara, Mexico. One hundred samples of freshly squeezed orange juice were collected from 49 street booths and 51 small food service establishments. In addition, 75 fresh orange samples, each consisting of five orange units, and 75 wiping cloths were collected from the same establishments from which juice had been collected. Salmonella was isolated from 14, 20, and 23% of samples of orange juice, orange surfaces, and wiping cloths collected from street vendors, while Shigella was isolated from 6, 17, and 5% of these samples. In general, the frequency of isolation of these pathogens in samples from juice serving establishments at public markets was significantly lower than that found among street vendors (P < 0.05). Salmonella enterica serotypes Agona, Typhimurium, and Anatum were found in orange juice, fresh oranges, and wiping cloth samples, while serotype Mexico was found on fresh oranges and in wiping cloths and serotypes Muenchen and Panama were found only in wiping cloth samples. Regarding Shigella species, Shigella sonnei was found in all three types of sample tested; Shigella dysenteriae was found in juice and orange samples, Shigella boydii in orange and wiping cloth samples, and Shigella flexneri on oranges only. Thirty-one percent and 39% of the juice samples showed aerobic plate counts of > or = 5.0 log CFU/ml and Escherichia coli counts of > 3.0 log CFU/ml, respectively. These high counts may indicate poor sanitation and potential exposure to fecal contamination either in the raw materials or during the orange-crushing and juice-serving process. These data may be useful for a further risk assessment of Salmonella or Shigella in unpasteurized, freshly squeezed juice.     

柑桔类果汁苦味物质的脱除研究

柠碱和柚苷是柑桔汁和柑桔其他制品中的主要苦味成分,采用吸附脱苦法、酶脱苦法、β-环糊精脱苦法、乙烯利代谢脱苦法及其他脱苦法可将它们除去,文中还提出了采用综合脱苦法应用于生产实际的观点。     

Vitamin C in frozen,fresh squeezed,unpasteurized, polyethylene-bottled orange juice: a storage study

A storage study of frozen, fresh squeezed, unpasteurized, polyethylene-bottled orange juice was conducted to determine vitamin C loss on a monthly basis over a period of 24 months. Vitamin C content declined from an initial value of 40.6 mg/100 ml to 32.8 mg/100 ml in the final analysis for a loss of 19.2% over the storage period. A regression analysis showed a decrease of about 0.34 mg/100 ml of the vitamin C per month at this condition. The estimated shelf-life of this juice to meet the label claim of vitamin C of 130% DV is about 22 months at −23°C.     

Ultraviolet treatment of orange juice

Ultraviolet (UV) with a wavelength of 254 nm tends to inactivate most types of microorganisms. Most juices are opaque to UV due to the high-suspended solids in them and hence the conventional UV treatment, usually used for water treatment, cannot be used for treating juices. In order to make the process efficient, a thin film reactor was designed and constructed from glass with the juice flowing along the inner surface of a vertical glass tube as a thin film. The decimal reduction doses required for the reconstitute orange juices (OJ; 10.5° Brix) were 87±7 and 119±17 mJ/cm² for the standard aerobic plate count (APC) and yeast and moulds, respectively. The shelf life of fresh squeezed orange juice was extended to 5 days with a limited exposure of UV (73.8 mJ/cm²). The effect of UV on the concentration of Vitamin C was investigated using both HPLC and titration methods of measurements. The degradation of Vitamin C was 17% under high UV exposure of 100 mJ/cm², which was similar to that usually found in thermal sterilization. Enzyme pectin methylesterase (PME) activity, which is the major cause of cloud loss of juices, was also measured. In contrast to the heat treatment, UV processing does not inactivate enzyme pectin methylesterase. The energy required for UV treatment of orange juice (2.0 kW h/m³) was much smaller than that required in thermal treatment (82 kW h/m³). The color and pH of the juice were not significantly influenced by the treatment.

Industrial relevance

This paper is of interest since it suggest—despite the low UV transmittance in orange juices—the use of a thin film UV reactor. The data suggest that shelf life extension from 2 to more than 5 days could be achieved with less energy requirements than for thermal processing. However, it seems unlikely that such thin film reactors could provide a real alternative to current conventional or new (e.g. high pressure pulsed electric field) processing.     

超声波提取橘皮中柠檬苦素化合物的工艺研究

研究了超声波法从温州蜜柑果皮中提取柠檬苦素化合物的工艺,探讨溶剂种类及浓度、料液比、超声时间、提取温度对柠檬苦素化合物提取率的影响。通过正交实验确定其最佳提取工艺条件为:65%乙醇溶液、料液比1:30(g/mL)、超声18min、提取温度60℃,提取率为6.25mg/g。     

酶法制取橙皮果胶的研究

纤维素酶酶系组成复杂,不同来源纤维素酶在果胶提取中表现出的作用不同。采取与前人研究不同的纤维素酶对橙皮果胶进行提取,对三种不同来源的纤维素酶比较分析,筛选出一种价格低廉、适合果胶提取的纤维素酶,并采用四元二次通用旋转组合设计方法研究了其提取果胶工艺中缓冲溶液的pH、提取时间、酶添加量、提取温度对果胶得率的影响;建立数学模型,寻求测定条件的最优组合;以DesignExpert软件进行分析,模型经检验差异显著,失拟检验不显著,具有良好的统计学意义,最优组合为:酶添加量3.38mL、时间6.66h、温度47.5℃、pH4.95,预测模型果胶得率为14.43%,验证实验得率为14.79%,大大提高了纤维素酶制取果胶的得率,远远高于文献报道,并且酶的价格低廉,大大降低了生产成本。