Reduction of Bitterness and Tartness in Grapefruit Juice with Florisil

Treatment of commercial grapefruit juice with Florisil (activated magnesium silicate) simultaneously reduced the content of citric acid and the bitter compounds limonin and naringin. Ascorbic acid concentration and °Brix (total soluble solids) were not altered by the Florisil treatment. Experienced taste panelists were able to differentiate between the nontreated and Florisil-treated juice on the basis of bitterness and tartness (acidity). The panelists indicated a preference for the Florisil-treated juice.     

Influence of Limonin on Consumer Preference of Processed Grapefruit Juice

A batch of Florida frozen concentrated grapefruit juice (GJ) was reconstituted with limonin addition to produce 5 juices containing from 2.3 (control) to 11.0 ppm limonin, 10° Brix, and 8.5 Brix: percent acid. Consumers from 4 large U.S. cities evaluated the juices for flavor and 5 additional quality attributes, and juice preference. Flavor means varied within an acceptable range and were affected negatively by limonin concentration. GJ users rated products significantly higher than did nonusers. Preference by users and nonusers was least for the highest limonin content juice. Bitterness and tartness perception increased with increasing limonin content whereas sweetness perception decreased. All samples were judged somewhat too bitter and tart, and not quite sweet enough.     

Seasonal and Storage Effects on Color of Red-Fleshed Grapefruit Juice

Seasonal and storage characteristics of the juice from four red-fleshed grapefruit (citrus paradisi macf.) cultivars; Ruby Red, Henderson, Ray, and Star Ruby were determined and compared in a search for cultivars having juice with less tendency to fade as the fruit matures and on juice storage. Analyses of the single strength processed juice showed the cultivars to be similar except for lycopene and carotene values. Lycopene, the major pigment in pink and red grapefruit, declined 0.75–0.68 mg/100g, 0.36–0.25 mg/100g, 0.36–0.30 mg/100g and 0.14–0.08 mg/100g for Star Ruby, Henderson, Ray, and Ruby Red, respectively, as the season progressed. Storage of processed juice for 12 months revealed no major decrease in lycopene.     

Influence of the Ratio of Degrees Brix to Percent Acid on Consumer Acceptance of Processed Modified Grapefruit Juice

A batch of frozen concentrated grapefruit juice (GJ) was reconstituted to 10° Brix with water and adjusted with sucrose, citric acid and/or deacidified GJ to produce five experimental samples with Brix:acid ratios from 7–15. Consumers from four large U.S. cities evaluated the samples for flavor, preference and five other quality attributes. Flavor means varied within an acceptable range. Preference was for samples in the 8.4 to 11.1 ratio range. Nonusers preferred 11.1 ratio juice and rated the three lowest ratio juices lower than users. As ratio increased, consumer perception of sweetness increased and decreased for tartness, bitterness, and aroma. All samples were judged somewhat too tart and bitter (except at 15 ratio) and not quite sweet enough.     

Evaluation of Ultrafiltration and Adsorption to Debitter Grapefruit Juice and Grapefruit Pulp Wash

Grapefruit juice and grapefruit pulp wash were ultrafiltered and debittered with a pilot system. The flow rate through the membrane increased with the transmembrane pressure up to 137.8 kPa. Limonin in grapefruit juice and grapefruit pulp wash was completely removed. The debittering process was tested at 13, 27 and 48°C. Limonin removal efficiency was independent of temperature between 13 and 48°C. However the resin column was exhausted more rapidly for na-ringin, narirutin, hesperidin, and neohesperidin particularly at 13°C. Taste panel results suggested that debittering of grapefruit pulp wash appreciably increased its flavor acceptability.     

不同处理方式对纯菠萝汁品质的影响研究

以纯天然菠萝汁为主要研究对象,探讨高压、加热、冷冻等处理方式对菠萝汁感官指标以及保藏特性的影响.结果表明:高压、冷冻和加热对纯天然菠萝汁的色泽和外观无显著影响;经过冷冻处理和加热处理的样品在滋味、香味和总体评分几个方面均与未经任何处理的样品无显著差异,而经高压处理的样品则有显著差异.加热和高压处理都能非常有效地降低菠萝汁中的活菌数.冷冻处理在刚开始对菠萝汁中的活菌数没有太大的影响,经过为期7d的存放,菌落总数有较大程度的降低.冷冻对于纯菠萝汁的品质和贮藏都有相对积极的影响.是较为合适的加工方式.     

不同热烫条件对胡萝卜榨汁效果的影响

本研究通过试验获取了热水、柠檬酸、醋酸、混合酸、蒸汽和微波六种热烫方式对胡萝卜榨汁效果的影响的数据资料。其中榨汁效果主要从出汁率、可溶性固形物、pH值、颜色及稳定性五个方面进行评价     

Effects of Chitosan Treatments on the Clarity and Color of Apple Juice

Acid-soluble and water-soluble chitosans as fining agents for apple juice were compared to conventional silica sol/gelatin/bentonite treatment. Both chitosans proved equally effective in reducing juice turbidity as compared to control treatments and slightly lighter juices resulted from chitosan treatments. Use of the one step chitosan treatment appeares an attractive alternative to conventional fining processes.     

壳聚糖在柚子汁澄清中的应用

研究壳聚糖澄清柚子汁的最优条件为:用脱乙酰度90%的壳聚糖,以0.6 g/L加入量于柚子原果汁中,40℃保温30 min,果汁p H为自然p H,制得的清汁透光率达到98%;贮藏试验结果表明低温有利于清汁的贮藏稳定,常温下整个试验贮藏期间果汁透光率都大于90%,试验还表明壳聚糖对柚子汁的澄清不影响果汁的营养价值。     

超高压和热处理对胡柚汁理化品质的影响

研究了高压(200～600 MPa)、20～60℃处理15 min和热处理(90℃处理2 min及80℃处理30 min)对胡柚汁理化品质的影响.试验结果表明:经超高压和热处理后胡柚汁的平均粒径增大,而超高压处理对胡柚汁色泽的影响较小,对pH值和可溶性固形物含量无显著影响.经超高压处理的胡柚汁的L-抗坏血酸保留率在91.97%～98.29%之间,其中以200MPa压力下处理的保留率较高.超高压和热处理后胡柚汁的柚皮苷和新橙皮苷含量略有降低,果汁的抗氧化性略有提高.     

Effects of Dense Phase Carbon Dioxide Pasteurization on the Physical and Quality Attributes of a Red Grapefruit Juice

ABSTRACT:  Red grapefruit juice was treated with continuous dense phase carbon dioxide (DPCD) equipment to inactivate yeasts and molds and total aerobic microorganisms. A central composite design was used with pressure (13.8, 24.1, and 34.5 MPa) and residence time (5, 7, and 9 min) as variables at constant temperature (40 °C), and CO₂ level (5.7%) after experimentally measuring CO₂ solubility in the juice. Five log reduction for yeasts and molds and total aerobic microorganisms occurred at 34.5 MPa and 7 min of treatment. A storage study was performed on the fresh juice DPCD treated at these conditions. °Brix, pH, titratable acidity (TA), pectinesterase (PE) inactivation, cloud, color, hue tint and color density, total phenolics, antioxidant capacity, and ascorbic acid were measured after the treatment and during 6 wk storage at 4 °C. During storage, the DPCD-treated juice showed no growth of total aerobic microorganisms and yeasts and molds. Cloud increased (91%) while percent PE inactivation was partial (69.17%). No significant (α= 0.05) differences were detected between treated and untreated samples for °Brix, pH, and TA. Treated juice had higher lightness and redness and lower yellowness. No significant differences (α= 0.05) were detected for the hue tint values while the color density value was higher for the treated samples compared to the untreated. The treatment and the storage did not affect the total phenolic content of the juice. Slight differences were detected for the ascorbic acid content and the antioxidant capacity. The experimental results showed evidence that the treatment can maintain the physical and quality attributes of the juice, extending its shelf life and safety.     

Effects of pH, Storage Time and Temperature on the Tin Content of Single Strength Canned Grapefruit Juice

Grapefruit juice modified to pH 3.0, 3.5 and 4.0 and stored at 4, 21, 27, 32 and 38°C manifested a consistent two-stage pattern for tin uptake. The first stage consisted of a rapid (3 wk) uptake of tin (from 12 to approximately 100 ppm) and was relatively independent of juice pH or storage temperature. In the second stage, the increase in tin concentrations was extremely temperature dependent and only slightly pH dependent. Canned grapefruit juice should be stored below 27°C to insure tin contents do not exceed the Codex maximum of 250 ppm. In a survey of 55 commercially canned grapefruit juice samples stored 1-8 months under commercial conditions, tin concentrations ranged from 34-180 ppm.     

A Comparison of the Effects of Pulsed Electric Field and Thermal Treatments on Grape Juice

The work was aimed at comparing the effect of pulsed electric field (PEF) and thermal technologies on physical, chemical, microbiological, and nutritional properties of freshly squeezed grape juice of different varieties when they are applied using continuous flow systems. It has been evidenced that grape variety is a factor to be taken into account when comparing the processing effects of PEF and heat treatments. Nevertheless, results of general and specific microbial populations were not affected by it and followed a very similar trend with each processing treatment. Soluble solids, pH, acidity, and the electrical conductivity of grape juice were not affected by PEF processing. On average, PEF treatment reduced the radical scavenging activity a 9% in front of the 13% of the heat treatment whereas both treatments halved the protein content. Data of vitamin C, total polyphenol, cinnamic acid, free catechin and non-flavonoid content were not enough to show differences between both treatments. However, all these nutritionally related properties share the same behaviour, PEF processing yielded milder values than heat processed samples. Information comparing PEF and thermal processes on food products help to clarify the advantages and disadvantages of each technology even though the disparity in development and use of each one.     

不同澄清剂对紫甘薯汁色泽及抗氧化活性的影响

研究了明胶、皂土、壳聚糖等澄清剂对紫甘薯汁澄清度、色泽及抗氧化活性的影响。试验结果表明,明胶、皂土和壳聚糖在对紫甘薯汁的澄清过程中伴随着花色苷的损失,总酚含量的减少及其抗氧化活性的降低。其中,壳聚糖引起紫甘薯汁花色苷的损失最大,即对紫甘薯汁色泽的影响最为显著。皂土导致紫甘薯汁总酚含量及其抗氧化能力下降程度最大。明胶对紫甘薯汁色泽和抗氧化活性影响最少,但是其澄清效果不佳。     

胶体处理对多依复原果汁品质及澄清机制的影响

研究旨在建立多依复原果汁澄清与色泽优化的胶体处理条件,借助分光光度、HPLC及UPLC-MS-MS等分析方法,解析胶体处理对复原果汁基本性状(色度、浊度、褐色值、pH值、可溶性固形物含量、维生素C含量)、总酚含量、绿原酸含量、多酚物质组成、体外抗氧化活性及非酶褐变动力学参数的影响。结果表明,添加质量分数为0.4%苹果高甲氧基果胶(AHP)、0.1%罗望子多糖(TSP)或0.2%壳聚糖(CTS)可使多依复原果汁澄清化为清亮的金黄色,澄清效果由优到劣依次是CTS、TSP、AHP;冷沉淀(4℃、24h)结合胶体处理的澄清效果更佳,可将复原果汁在55℃下起始非酶褐变速率常数(k₀)从0.150d-1降低至0.071~0.078d-1。复原果汁的色度、浊度、褐色值及k₀的变化皆与总酚质量浓度呈密切的直线关系。综合考虑澄清性、非酶褐变抑制性(降低k₀)、DPPH自由基清除力、膳食纤维等因素,质量分数为0.1%的TSP为胶体处理得到的多依复原果汁相对最佳。多依复原果汁中的多酚类化合物主要为绿原酸类、黄酮类(包括槲皮素-O-葡萄糖苷、山柰酚-O-葡萄糖苷与二木糖苷、根皮苷以及白杨素)、异黄酮类(包括大豆苷、豌豆香堇苷)等。TSP处理会轻微减少绿原酸及其衍生物、黄酮类及异黄酮类含量。热处理会促使多酚类化合物明显减少或消失,产生大量的羟基化绿原酸衍生物,研究结果表明,绿原酸和羟基化绿原酸衍生物为非酶褐变的关键组成物质。希望研究成果可为多依复原果汁的澄清处理提供一定的理论与技术支持。     

不同热力灭菌条件对锦橙汁品质的影响及其DNA稳定性分析

为探讨不同的热力杀菌条件对锦橙汁品质的影响,采用高温瞬时(93℃、30s),低温长时(70℃、15min)以及目前国内工厂常用的杀菌条件(80℃、10min)对鲜榨锦橙汁进行处理,测定锦橙汁理化性质(色度、pH值、可溶性固形物含量、总酸含量、VC含量、有机酸含量和还原糖含量)的变化及其杀菌效果,并对其DNA的稳定性进行探究。结果表明,温度过高或加热时间过长均对橙汁品质产生不好的影响,VC和有机酸含量大量降解,DNA完整性被破坏。最后得出80℃、10min灭菌的橙汁在品质上表现出较强的优势。     

脉冲电场和热处理对鲜榨苹果汁贮藏期品质的影响

研究高压脉冲电场处理 (PEF)和热处理对鲜榨苹果汁贮藏期的品质影响。研究发现 ,4℃贮藏 3 0d ,PEF( 2 5kV/cm ,1 0 3 5个脉冲 )和热处理 ( 72℃、1 5s和 90℃、60s)可以降低果汁中微生物数量 ,而且对苹果汁的电导率、Brix和 pH值的影响不显著 (P >0 0 5 )。但是热处理对果汁的浊度有显著影响 (P <0 0 5 ) ,而PEF处理差异不显著 (P >0 0 5 )。PEF处理苹果汁的L值和色值均优于热处理 ,感官评价中风味和色泽比热处理的苹果汁更接近对照的风味和色泽。     

Effect of Thermal Treatment and Storage Conditions on the Physical and Sensory Properties of Grapefruit Juice

Physical parameters, such as particle size distribution, flow behavior, density, turbidity, and color, were measured and sensory evaluation was carried out to compare the properties of freshly squeezed grapefruit juice with those of juice that has been pasteurized by microwave or by following a conventional heating method. Samples were either frozen-stored or refrigerated. In general, the physical parameters of grapefruit juice were significantly affected by heat treatment, especially in the case of the conventional process. However, from a sensory point of view, pasteurized samples were similar to fresh ones. When frozen, turbidity, particle size distribution, density, flow behavior, and color were stable throughout the studied period, regardless of the pasteurization treatment. During refrigerated storage, the turbidity, particle size distribution, and consistency index decrease. This occurs in a more pronounced way in the case of juice which has not been submitted to a heating treatment, probably due to residual pectin methyl esterase activity. Furthermore, the association between the carboxyl groups of pectin chains and Ca²⁺ could be responsible for both the subsequent increase in the turbidity of the juice and also the decrease in its density. Throughout the period under study, the smallest color change was experienced by microwave-pasteurized juice. For these reasons, and also due to the reduction in the process time, microwave treatment can be recommended as a method for the pasteurization of grapefruit juice.