The statistical properties of a stepwise procedure for testing the purity of fruit juice

In many cases no fixed standards are available and a sample from a target population is used to provide the necessary quality-control norms. Furthermore, many products possess several correlated attributes that are relevant to the authenticity question. This article addresses some issues related to statistical tests used in such cases, focussing in particular on a procedure that has been lately proposed for differentiating between pure and adulterated fruit juice. The quality control of fruit juice is usually performed by comparing the values of several characteristics in the tested sample against some prespecified standards. In many cases those standards are based on the values found in a sample of a presumably pure juice, which is used as a "reference sample" or a "base sample". Several detection methods were recently proposed that use universal "base samples" and are supposed to be valid when applied to juices from different sources or different varieties. We compare the results yielded by the use of various "base samples" and show that the application of such a method to Israeli citrus juice leads to too many rejections of pure juices. We suggest that the main drawbacks of the method is the use of improper "base sample" that is not specific to the sample being tested.     

Unsuitability of data acquired from blended samples for testing orange juice purity

Non-blended juices (83) obtained directly from Spanish oranges and several computer-simulated blends of these juices were used as reference samples for the detection of orange juice dilution. Amino acids (16), absorbances at different wavelengths (3), minerals (3), ash and isocitric acid were determined in each non-blended juice. The values of these characteristics in blended samples were calculated from the proportions of juices used in simulating each blend. When using non-blended juices for reference, no significant erroneous rejection (less than 1% working at the 99% confidence level) of pure juices and quite good detection of diluted samples were observed. By contrast, the use of reference sets of blended samples led to the erroneous rejection of many pure juices (74% of non-blended juices when the reference set was constituted by binary blends).     

啤特果果汁流变学特性研究

为掌握啤特果果汁的流变学特性,试验对啤特果果汁的流体类型、模量以及温度和可溶性固形物对黏度的影响进行了研究.结果表明,在25、35、45、55、65℃条件下,啤特果果汁的流变曲线方程拟合参数n值<1,属于假塑性流体,其储能模量G′大于损耗模量G″;Arrhenius方程 η=Ke-Ea/RT对温度与黏度的拟合参数R2>...     

龙眼果汁的澄清方法

使用自然澄清法、明胶-单宁法、海藻酸钠-碳酸钙法、聚乙烯聚吡咯烷酮(PVPP)法、甘草浸提液澄清法、甲壳素澄清法、冷冻澄清法等常用的澄清方法对龙眼果汁进行澄清实验。结果表明,PVPP法和海藻酸钠-碳酸钙法对龙眼果汁的澄清效果较好,透光率均迭到80%以上;PVPP法对龙眼果汁的澄清效果最好,在龙眼果汁(50mL)中加入1mL1‰PVPP,于6℃静置24h后,透光率达到87.9%,为各种澄清方法中透光率最高的一种。     

果汁牛奶的流变性质测评

对自制果汁牛奶和市售类似产品进行了流变学研究。结果表明,与市售类似产品相比,自制产品的初始黏度及剪切稳定后的黏度均较高,具有明显的“假塑性”,黏度对温度的变化较敏感,感官特征良好。     

番石榴原汁制番石榴果汁饮料的研究

探讨了以台湾珍珠番石榴这一优良品种作为原料，经打浆、护色、调配、均质等工序加工成番石榴果汁饮料的工艺流程。通过试验确定了产品的配方和最佳工艺参数。     

Contribution to the determination of the fruit juice content of fruit juice beverages and syrups

Summary No insurmountable problems now face the food chemist in determining the fruit juice content of fruit juice beverages and syrups made from one species of fruit, since calculations can be based on relevant and reliable authenticity criteria and standards established in European countries. However, if the beverage contains more than one juice, or juice has been added to acidify or give additional colour, the problem is more complex. As a function of the juice exposition specific parameters are needed to calculate the juice content of the main component. Stepwise regression analysis, based on the relative content of the eight amino acids present in all juices, appears to be a useful method to determine the juice composition. This theoretical matter is illustrated here by examples of calculations of the fruit juice content of a syrup, a nectar and four lemonades.

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Beitrag zur Ermittlung des Fruchtsaftgehaltes in fruchtsafthaltigen Erfrischungsgetränken und Sirupen

Zusammenfassung Heutzutage bestehen für Chemiker keine unüberwindlichen Probleme den Fruchtsaftgehalt von Erfrischungsgetränken und Sirupen, die aus einer Fruchtsorte hergestellt sind, festzustellen, da die Kalkulationen auf entsprechenden und zuverlässigen Kriterien basiert werden können, die in den verschiedenen europäischen Ländern gelten. Jedoch müssen Beeinflussungen durch Leitungswasser oder Zusatz von Zucker und auch organischen Säuren in Betracht gezogen werden. Sollte jedoch mehr als ein Saft in unbekannten Proportionen vorhanden sein oder sollten andere Säfte, die zusätzlich Säure oder Farbe bringen, zugegeben werden, wird das Problem komplizierter. Um die Saftzusammensetzung feststellen zu können, muß man spezifische Parameter verwenden, um den Saftgehalt der Hauptkomponente kalkulieren zu können. Eine gute Hilfe die Saftzusammensetzung festzustellen, scheint die schrittweise Regressions-Analyse zu sein, die auf den Aminosäurewerten der acht Hauptaminosäuren basiert, welche in allen Säften vorhanden sind. Dieses recht theoretische Thema wird durch Kalkulationsbeispiele von Sirupen, Nektaren und Limonaden illustriert.

     

桶装果浆快速冷却设备的设计

研究设计的果浆无菌大桶装冷却设备采用偏心轮、动轨和静轨组成摇摆与行进机构，喷淋水冷却与桶的摇摆、前进相结合，强化桶内果浆的换热，缩短了冷却时间，保证了果浆的自然色泽和纯正口味。     

发展我国果汁工业的对策

<正> 我国幅员辽阔,水果资源丰富,为我国果汁工业的发展,提供了良好的基础。目前,果汁市场竞争激烈,品牌众多,许多加工企业都陷入困境,如何发展果汁工业,已成为一个值得重视的课题。 发展概况 我国的果汁加工业起步晚,发展慢,从建国初期到现在近50年间,果汁的产量从无到1995年的115万吨,其发展过程大致可分为三个阶段:     

果蔬汁产品危害分析关键控制点

对保证食品安全的预防性技术管理体系HACCP作了介绍,并对果蔬汁产品的关键点作了说明.     

我国果蔬汁加工现状及改进措施

<正> 随着人类社会的不断发展,人们对高热量食物的需求已大大下降,而对一些具有营养保健意义的重要成份,如矿物质、维生素、微量元素等的需求则不断增加。消费者追求高营养、低热最的食品,果蔬及其加工制品止好满足了人们这方面的需求。因此,果蔬汁作为一种天然饮料得到了迅猛发展。     

果汁中胭脂红、柠檬黄和日落黄含量检测能力验证研究

目的通过分析、评定实验室的检测结果,了解国内实验室对果汁中胭脂红、柠檬黄和日落黄的检测能力。方法采用果汁添加标准品的方式制备样品,通过F检验、Ss≤0.3?和|x-y|≤0.3?法对所制备的样品进行均匀性和稳定性检验。以稳健分析算法A得出的稳健平均值和稳健标准差,作为本次能力验证计划的指定值和能力评定标准差,利用z比分数进行参加实验室的能力评定。结果参加实验室检测胭脂红、柠檬黄和日落黄能力评定的满意率分别为79%、87%和77%。结论大部分参加实验室对胭脂红、柠檬黄和日落黄具备较好的检测能力。     

常见果汁掺假检测技术的研究进展

对常见果汁掺假进行理化检测技术进行了综述。     

吸附技术在果汁行业中的应用

介绍了吸附技术在果汁行业的应用 ,对其工艺、原理、价格做以简要描述 ,并对几种果汁澄清技术进行了对比。     

分层果汁酸奶的研究

以产品的黏度、持水力、流变特性和感官评定为主要指标,使果汁与酸奶形成明显的两层。结果表明:果汁添加量为质量分数20%,果汁中添加CMC∶明胶=3︰1～2︰1(1.8%),变性淀粉︰卡拉胶=10︰1～7︰1(2.5%),卡拉胶︰黄原胶=4︰1～3︰1(1.0%)复配效果较好,其中以变性淀粉和卡拉胶复配效果最好。     

果汁求斯糖的研制

从现有的瑞士果汁糖实样分析,同时参考德国糖果中央学院Juan Falsy教授提供的求斯糖基本配方,结合本单位实际,经数十次试验,确定了配方及工艺,取得了成功.     

南瓜菠萝复合汁制造工艺研究

研究了由南瓜、菠萝、苹果和西瓜复合的果汁制造工艺,采用D-最优设计确定了复合配方,并对其稳定性进行了研究。结果表明,由40%南瓜汁、30%菠萝汁、17%苹果汁和13%西瓜汁复合时,口感最好;添加0.02%黄原胶和0.06%果胶的果蔬汁保温至40℃时,在40MPa的压力下均质2次后,悬浮稳定性好。     

果胶酶在猕猴桃果汁处理中的应用

研究了采用果胶酶HC澄清猕猴桃果汁时的工艺条件和在猕猴桃果浆榨汗中的应用，并通过实验得出结论，澄清时，酶HC加量40mg/L,pH3-4，温度40－50℃，处理150min，用此处理工艺所得猕猴桃汁的Vc损失较小，透光率较高，果胶基本分解完全在果浆榨汁中，也只需采用相同的用量就能使果汁的粘度下降71％，出汁率提高10％以上，而营养物质基本无损耗。     

Effect of high pressure homogenization (HPH) on the rheological properties of a fruit juice serum model

High pressure homogenization (HPH) is a non-thermal technology that has been widely studied as a partial or total substitute for thermal food processing. The present work evaluated the effect of HPH on the rheological properties of a fruit juice serum model, designed to be similar to tomato juice serum. Product viscosity decreased due to the increase in homogenization pressure, and could be modelled well using two functions (power-sigmoidal and exponential; R² > 0.98). The serum model processed at 200 MPa showed a viscosity decrease of 20% when compared to the original. Since fruit juice rheology is defined by the interactions occurring between the dispersed phase (suspended particles) and the solution (serum), the expected fruit juice behaviour was then discussed.     

Ultraviolet radiation as a non-thermal treatment for the inactivation of microorganisms in fruit juice

Fruit juices can be processed using ultraviolet (UV-C) light to reduce the number of microorganisms. The UV-C wavelength of 254 nm is used for the disinfection and has a germicidal effect against microorganisms. A novel turbulent flow system was used for the treatment of apple juice, guava-and-pineapple juice, mango nectar, strawberry nectar and two different orange and tropical juices. In comparison to heat pasteurization, juices treated with UV did not change taste and color profiles. Ultraviolet dosage levels (J L^− 1) of 0, 230, 459, 689, 918, 1 148, 1 377, 1 607 and 2 066 were applied to the different juice products in order to reduce the microbial load to acceptable levels. UV-C radiation was successfully applied to reduce the microbial load in the different single strength fruit juices and nectars but optimization is essential for each juice treated. This novel UV technology could be an alternative technology, instead of thermal treatment or application of antimicrobial compounds.

Industrial relevance

This novel UV-C system can be applied successfully to the Food Industry. UV-C can be effectively used to reduce the number of spoilage and pathogenic bacteria, as well as yeasts and moulds in different kinds of fruit juices.