用于苹果汁吸附实验的不溶性壳聚糖制备工艺的研究

研究了用于苹果汁吸附实验的不溶性壳聚糖的制备工艺。不溶性壳聚糖的制备工艺条件为:脱乙酰处理时NaOH的质量分数为35%、50℃、6h。对不溶性壳聚糖的吸附性能、再生性能和质量标准进行了研究,制备的不溶性壳聚糖符合国家标准的要求,可以多次再生使用,不易造成二次污染,且具有良好的机械强度,适合用做苹果汁脱色和澄清的吸附材料。      

不溶性壳聚糖对苹果汁脱色及澄清效果的研究

本论文对不溶性壳聚糖在苹果汁脱色及澄清中的作用进行了研究,初步确定了不溶性壳聚糖用量、温度、pH值对苹果汁色值和透光度的影响从而分别提出不溶性壳聚糖脱色的最佳工艺条件是:不溶性壳聚糖用量3.0g/100ml,温度35℃,pH值4.0不溶性壳聚糖澄清的最佳工艺条件是:不溶性壳聚糖用量2.5g/100ml,温度25℃,pH值4.0对不溶性壳聚糖装柱连续吸附法也进行了研究,结果表明此法可用于苹果汁的工业生产     

用于苹果法吸附实验的不溶性壳聚糖制备工艺的研究

研究了用于苹果汁吸附实验的不溶性壳聚糖的制备工艺.不溶性壳聚糖的制备工艺条件为:脱乙酰处理时NaOH的质量分数为35%、50℃、6h.对不溶性壳聚糖的吸附性能、再生性能和质量标准进行了研究,制备的不溶性壳聚糖符合国家标准的要求,可以多次再生使用,不易造成二次污染,且具有良好的机械强度,适合用做苹果汁脱色和澄清的吸附材料.     

壳聚糖澄清苹果汁工艺的研究

本试验在分析壳聚糖澄清苹果汁机理的基础上,研究了利用自制壳聚糖澄清苹果汁工艺。通过正交试验优选出了壳聚糖澄清苹果汁的最佳工艺参数:壳聚糖剂量0.4g/L,澄清温度50℃,澄清pH值3.5。并对澄清前后苹果汁营养成分变化,澄清果汁稳定性做了初步的探讨。     

活性炭负载壳聚糖对苹果汁的澄清效果研究

以透光率为指标,以壳聚糖澄清和活性炭澄清为对照,探讨活性炭负载壳聚糖澄清剂在不同添加量、温度、时间和pH条件下对苹量汁的澄清效果影响,并采用Box-Behnken中心组合设计法进行澄清工艺条件的响应面优化。试验结果表明：经活性炭负载的壳聚糖澄清剂对苹果汁有较好的澄清效果,且明显优于对照组;建立的响应面模型能较好地预测透光率随澄清条件的变化规律,且在最优澄清条件负载澄清剂用量12 g,澄清时间9.6 min,澄清温度55℃,pH 2.56下的透光率为96.47%。     

苹果汁复合澄清法和壳聚糖澄清法的优化研究

研究了果胶酶复合澄清法和壳聚糖澄清法对苹果汁的澄清效果,确定了最佳工艺条件,采用优化的澄清方法,苹果汁的透光率可达98％以上。论文对不同成熟期的苹果制汁的澄清工艺进行了调整,还探讨了澄清工艺对苹果汁主要成分的影响。     

壳聚糖在苹果汁,山梨汁,山楂汁澄清中的应用研究

介绍了壳聚糖用于苹果汁，山梨汁和山渣汁的澄清实验，澄清后果汁透光率均在９０％以上，实验结果表明，壳聚糖是苹果汁、山梨汁和山楂汁较理想的澄清剂。     

热烫处理对苹果汁理化性质与营养成分的影响

为探究热烫时间对苹果汁品质的影响,分别对削皮后的苹果热烫0、2、4、6、8 min,再加工成果汁,测定果汁的色值、p H值、含糖量、感官品质、营养成分。结果表明,随着热烫时间的延长,苹果汁的色值、感官评分均呈先增大后减小的趋势(P 0. 05),而含糖量、p H值逐渐降低。建议在制备苹果汁前,将苹果热烫2～4 min。     

浓缩苹果汁主要技术指标控制的研究

介绍了浓缩苹果汁的主要技术指标，对各项指标的变化进行了分析，制定了相关的工艺控制措施。     

壳聚糖影响苹果汁澄清条件的探讨

目的 考察壳聚糖澄清苹果汁的效果,探讨影响澄清工艺的因素,确定壳聚糖澄清果汁的最佳条件.方法 以澄清果汁720 nm处的透光度评价各条件,比较各因素的较优水平.结果 温度40℃,壳聚糖用量0.15 g/L,时间1 h,pH3时壳聚糖澄清苹果汁的效果最佳,果汁的营养成分和风味不受影响.结论 壳聚糖可用于果汁澄清工艺.     

The antifungal properties of chitosan in laboratory media and apple juice.

The antimicrobial properties of chitosan glutamate, a derivative of chitin, were investigated in laboratory media and apple juice against 15 yeasts and moulds associated with food spoilage in order to assess the potential for using chitosan as a natural food preservative. Of the seven strains of filamentous fungi studied, chitosan reduced the growth rate of Mucor racemosus at 1 g/l whilst concentrations of 5 g/l were required to completely prevent growth of three strains of Byssochlamys spp. on agar plates incubated at 25 degrees C for 3 weeks. Three strains of filamentous fungi were resistant to the antifungal effects of chitosan at 10 g/l. The presence of chitosan in apple juice (pH 3.4) at levels ranging from 0.1 to 5 g/l inhibited growth at 25 degrees C of all eight spoilage yeasts examined in this study. The initial effect of chitosan in apple juice was biocidal with viable numbers reduced by up to 3 log cycles. Following an extended lag phase, some strains recovered and resumed growth to levels similar to those observed in unsupplemented apple juice. The most sensitive strain was an isolate of Zygosaccharomyces bailii obtained from a spoiled carbonated beverage; this yeast was completely inactivated by chitosan at 0.1 and 0.4 g/l for 32 days of storage at 25 degrees C. The most resistant strain was Saccharomycodes ludwigii, an isolate from spoiled cider: a level of addition of 5 g/l of chitosan was required to inactivate this strain and to maintain yeast-free conditions in apple juice for 14 days at 25 degrees C. Growth inhibition and inactivation of filamentous moulds and yeasts, respectively, was concentration-, pH- and temperature-dependent. It was concluded that chitosan was worthy of further study as a natural preservative for foods prone to fungal spoilage.     

High-pressure treatment of cloudy apple juice

A factorial design with four factors (pressure, holding time, temperature and waiting period between crushing of apple and high-pressure (HP) treatment) was built up to study the effect of HP treatment on pectin methylesterase activity (PME, EC 3.1.1.11) in cloudy apple juice. PME activity was measured by the methanol release during the storage of samples at 4 °C for 1 month. Only the holding time of the treatment and three interactions between factors (holding time×temperature, pressure×waiting and holding time×waiting) had significant effects on the PME level. Increasing the pressure or the holding time at moderate temperatures (15-40 °C) increased the activity. PME purified from apple was pressure stable in the range 100-600 MPa at 25 °C. The soluble pectin content was not changed after HP treatment. The particles size increased with the temperature reached during the treatment, in agreement with a diffusion-limited-aggregation model but were independent of pressure and holding time. In a separate experiment we found a positive correlation between the PME activity and the residual content of the catechins suggesting that polyphenoloxidase (PPO, EC 1.14.18.1) and oxidized polyphenols play a role in the PME activity level after HP treatment.     

Reduction of patulin during apple juice clarification

Patulin is a mycotoxin produced by a number of molds involved in fruit spoilage. This compound is carcinogenic and teratogenic. Various methods are currently used to reduce the levels of patulin in apple juice, namely, charcoal treatment, chemical preservation (sulfur dioxide), gamma irradiation, fermentation, and trimming of fungus-infected apples. Many of these processes are expensive and time-consuming. Therefore, there is a need to find a convenient and economical process to control patulin levels. This study was undertaken to evaluate the effectiveness of several clarification processes for the reduction of patulin. Clarification was carried out on a laboratory scale. Apple pulp was spiked with patulin, pressed, and clarified using four different processes, namely, fining with bentonite, enzyme (pectinase) treatment, paper filtration, and centrifugation. Patulin was recovered from the clarified juice by liquid-liquid extraction, and solid-phase chromatography was used for sample clean-up prior to analysis by high-performance liquid chromatography (HPLC). The minimum detectable limit using HPLC was 20 microg/liter. Pressing followed by centrifugation resulted in an average toxin reduction of 89%. Total toxin reduction using filtration, enzyme treatment, and fining were 70, 73, and 77%, respectively. Patulin reduction was due to the binding of the toxin to solid substrates that was verified by analyzing the clarified juice as well as the filter cake, pellet, and sediment. The combined concentrations correlated to the spiked concentration. These results reveal that clarification was successful in the reduction of patulin levels in apple juice. However, clarification resulted in high levels of patulin in the pressed pulp after filtration and centrifugation, and this could be harmful if they are used as animal feeds.     

Effect of apple cultivar and enzyme treatment on phenolic compounds content during clear apple juice production

The aim of the investigation was evaluation of phenolic compounds content, measured by HPLC method at selected stages of clear apple juice production with pectolytic mash enzymation from ‘Shampion’ and ‘Idared’ apples. Sum of phenolic compounds in ‘Shampion’ mash was significantly higher than in ‘Idared’ mash, 520 and 352 mg kg^?1, respectively. Enzymation of ‘Idared’ mash resulted in a higher phenolic compounds decrease compared to ‘Shampion’, 23% and 14% respectively. Sum of phenolics in juices from ‘Shampion’ for Panzym at 50 °C (366 mg kg^?1) was significantly higher than in juices from ‘Shampion’ for Rohapect at 20 °C and ‘Idared’ for Panzym at 50 °C (256 and 234 mg kg^?1, respectively). The lowest phenolics (95 mg kg^?1) was in juices from ‘Idared’ for Rohapect at 20 °C. There was a positive correlation (R² = 0.933) between phenolics content and antioxidant activity of juices (ABTS^?+). In general, enzymation at 50 °C with Panzym lead to a higher content of the phenolic compounds in juices compared to Rohapect at 20 °C.     

麦苗汁营养酸奶的研制

通过单因素和正交试验对麦苗汁营养酸奶的配方和最佳发酵工艺条件进行优化,并对产品质量作出评价。研究表明,麦苗汁酸奶的最佳配方（在原料乳的基础上）：麦苗汁添加量为5％,蔗糖添加量为8％（均为质量分数）,同时加入质量分数为0、2％的PGA和0．1％CMC—Na：最佳发酵工艺条件为温度42℃,发酵时间4h。在此工艺条件下制备的麦苗汁营养酸奶具有感官品质佳、稳定性好和营养丰富等特点。     

紫果西番莲果汁贮存过程中主要营养成分的变化

通过不同条件保存紫果西番莲果汁，测定主要营养成分，并对果汁进行感官评价。结果表明，贮存半年后，置于０℃以上环境中的果汁，其Ｖｃ和ＳＯＤ含量损失很大，但低温冷冻下（－２０℃）的果汁Ｖｃ和ＳＯＤ含量未减。总酸和可溶性固形物含量未有显著变化。感官评价以冷冻贮存得分最高（１４．７分）。     

胡柚汁热处理过程柚皮苷变化特性

采用高效液相色谱法(HPLC)进行定量分析,研究了加热温度和加热时间对胡柚汁中柚皮苷含量的影响。试验结果表明:加热时间一定,随着加热温度的升高,柚皮苷含量呈总体上升趋势,在75～90℃之间变化明显。时间试验中,加热15min时,胡柚汁中的柚皮苷含量达到最大值。优化试验显示,加热时间是影响胡柚汁热加工中柚皮苷变化的主要因素,加热温度次之,采用高温度短时间的热处理方式有利于控制胡柚汁中柚皮苷的含量。     

The effects of processing technology on the patulin content of juice during commercial apple juice concentrate production

 The effects of different treatments on the patulin content of apple juice during the production of industrial apple juice concentrate were investigated. Conventional clarification using a rotary vacuum precoat filter was found to be more effective than using ultrafiltration for the removal of patulin from apple juice. The average losses of patulin were 39% and 25% for conventional clarification and filtration, and ultrafiltration, respectively. Washing and handling appeared to be the most critical steps in removing patulin from apples since up to 54% could be removed using high-pressure water spraying. Received: 22 January 1998 / Revised version: 21 April 1998     

浓缩苹果汁加工链中棒曲霉素的动态分析研究

研究了浓缩苹果汁加工过程中各工序对棒曲霉素含量的影响。结果表明,喷淋、拣选、清洗是去除棒曲霉素的关键步骤,去除率为60.18％;吸附树脂对棒曲霉素去除效果显著。此外,研究了加工季节中棒曲霉素的变化规律,为果汁加工厂家建立科学完善的HACCP管理体系提供了理论依据。