Enzymic peeling of Indian grapefruit (Citrus paradisi)

The tough nature of grapefruit (Citrus paradisi) peel and its close adherence to the inner fruit sections limit the industrial processing of grapefruit. Two commercial peeling enzymes coded as ‘Brand A’ and ‘Brand B’ were studied for enzymic peeling of Indian grapefruit by vacuum infusion. The peeling process was optimised with respect to process parameters such as scalding time, enzyme concentration, vacuum infusion time and incubation time. © 2001 Society of Chemical Industry     

柑桔类果汁中柠碱的脱苦方法

就柑桔中苦味物质的分布及其主要成分进行了论述，并介绍了几种柑桔类果汁中柠碱的脱苦方法。     

胡柚中3种主要黄酮类物质的含量测定

目的：建立常山胡柚3种主要黄酮类物质含量的测定方法,并比较常山胡柚中皮、肉、籽中该3种黄酮类物质含量的差异。方法：采用反相高效液相色谱法分离检测胡柚中柚皮苷、橙皮苷、新橙皮苷的含量;流动相为乙腈-水(23:77,V/V),柱温25℃,流速1.0mL/min,检测波长283nm。结果：柚皮苷在3.22～1030μg/mL、橙皮苷在0.59～380μg/mL、新橙皮苷在0.077～990μg/mL范围内,黄酮类物质的质量浓度与峰面积呈良好的线性关系;柚皮苷、橙皮苷、新橙皮苷的平均回收率分别为98.43%(RSD＝4.07%)、98.70%(RSD＝4.30%)、99.90%(RSD＝3.47%);并以柚皮苷、橙皮苷和新橙皮苷为标准比较胡柚副产物皮、籽与胡柚肉含量的差异,初步得出皮＞肉＞籽。结论：该方法简便、准确、可靠、重复性好,可用于常山胡柚的质量控制。     

Volatile flavour components of grapefruit juice (Citrus paradisi Macfadyen)

The qualitative analysis of volatile flavour components in grapefruit juice (Citrus paradisi Macfadyen) was performed using a gas chromatography/mass spectro-metry/computer system which allowed the identification of 58 components, 25 of them being reported for the first time. The aroma concentrates were obtained by an efficient simultaneous steam distillation/solvent extraction method which made it possible to identify many trace aroma components. Only quantitative differences were found in the aroma composition of fresh grapefruit juice extracted from different fruit batches of the same geographic origin during one season.     

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。     

MCM-41固定化柚苷酶脱苦葡萄柚汁

以介孔分子筛MCM-41为载体,戊二醛为交联剂,采用吸附-交联法进行了柚苷酶的固定化。研究了酶液浓度、戊二醛浓度、吸附交联时间和固定化pH对固定化效果的影响,对影响固定化效果的因素进行了分析。确定最佳的固定化条件为:酶液浓度为0.4mg/mL,戊二醛浓度2.0%,吸附交联时间为6h,固定化pH为4.0(醋酸缓冲液)。采用海藻酸钠和聚乙烯醇对制备的固定化酶进行二次包埋处理,并应用于葡萄柚汁的脱苦。结果显示,游离酶和MCM-41固定化酶对果汁的脱苦率分别为96.65%和92.90%,海藻酸钠和聚乙烯醇二次固定化的柚苷酶脱苦率分别为72.64%和70.90%。脱苦后的果汁营养成分与理化指标均有一定程度降低。为柚苷酶的固定化提供了一种新型的载体材料,为固定化柚苷酶在果汁脱苦中的工业化应用提供了理论基础。     

A review of limonin in grapefruit (Citrus paradisi) juice,its relationship to flavour,and efforts to reduce it

Ever since limonin was first discovered in grapefruit (Citrus paradisi Macf) juice in 1965 and found responsible for significantly contributing to bitterness in the juice, a great deal of research has been directed towards understanding its role therein. Information is presented relative to limonin's chemical determination, taste threshold and content in grapefruit juice, and to relevant legislation. Also considered are (1) several factors affecting the limonin content of grapefruit juice (2) the effect of limonin content on sensory flavour in grapefruit juice (3) the interaction between the Brix: acid ratio and limonin content in affecting grapefruit juice flavour and (4) methods for reducing limonin in citrus juices generally. Finally, recommendations for future studies on limonin in grapefruit juice are reviewed.     

Variation in Furanocoumarin Content and New Furanocoumarin Dimers in Commercial Grapefruit (Citrus paradisi Macf.) Juices

ABSTRACT: Grapefruit ( Citrus paradisi Macf.) sales and crop value have declined during the last decade. One reason is consumer concerns about possible drug interactions. Coadministered grapefruit increases the bioavailability of some medicines because it contains furanocoumarins that inhibit an intestinal enzyme (cytochrome P450-3A4 or CYP3A4) that normally metabolizes these drugs. Only drugs metabolized by intestinal CYP3A4 are significantly affected when taken with grapefruit juice, but the magnitude of the effect varies considerably between studies, indicating that there are differences in the amount of components responsible for CYP3A4 inhibition in commercial grapefruit juices. Content variation of 6,7-dihydroxybergamottin, bergamottin, and 6 furanocoumarin dimers were determined for 58 commercial grapefruit juices collected over 2 seasons. The content of 6,7-dihydroxybergamottin ranged from 0.2 to 7.7 ppm in all juices tested, and averaged 1.8 ± 0.85 ppm in the red compared with 2.9 ± 2.07 ppm for white grapefruit juices. Bergamottin content ranged from 1.6 to 7.3 ppm for all juices and averaged 3.4 ± 0.98 and 4.2 ± 1.23 ppm and in red and white grapefruit juices, respectively. Only 1 dimer varied significantly between the red and white juice types. Dihydroxybergamottin and 2 dimer compounds were significantly lower in shelf-stable or nonrefrigerated products compared with refrigerated products whereas bergamottin and 1 dimer compound occurred at higher levels in the shelf-stable products. Individual measured dimer compounds varied up to 60-fold in all juices, but the sum of all 6 dimers varied only 14-fold. The clinical significance in terms of CYP3A4 inhibition is uncertain. The presence of 3 new furanocoumarin dimers are also reported.     

Characterization and preparation of Aspergillus niger naringinase for debittering citrus juice

Naringinase from Aspergillus niger was prepared and characterized to evaluate its effectiveness in debittering citrus juice. The enzyme was purified to homogeneity by sulfate fractionation and chromatographies on Q-Sepharose, Sephacryl S-200, and S-100 HR columns, and estimated by gel filtration chromatography (GFC) to have a molecular weight (MW) of 131 kDa, of which its subunit was measured by sodium dodecyl sulfate-polyacrylamide gel electrophoresis to be around 65.5 kDa. The enzyme showed active and stable pH ranges both within 4.5 to 5.0. Its optimal temperature was in the range of 45 to 55 °C. Freeze drying provided an estimated enzymatic recovery of 95.9%, greater than spray drying with the recovery at 55.6%. The freeze-drying powder could retain its enzymatic activity stably at 4 °C for 6 mo. Also, the enzyme in 0.220 U/mL citrus juice could sufficiently remove the naringin for the bitterness. Oral acute toxicity study revealed the maximum tolerated dose (MTD) of the naringinase powder was >10 g/kg in mice. The contents of arsenic (As), lead (Pb), mercury (Hg), the aerobic plate count, and coliform number in the enzyme powder all met the criteria for food use. These characteristics suggest that the naringinase from A. niger is efficient and suitable for debittering the citrus juice, and the process consisting of fermentation, salt precipitation, ion exchange, ultrafiltration, and freeze drying is a promising means to prepare the naringinase for food industry, setting up a strong base to enzymatically debitter citrus juice. PRACTICAL APPLICATION: This study focused on characterization, preparation, and validation of naringinase from A. niger, which provided useful information on how to prepare, store, and use the naringinase. In addition, this naringinase met the safety standards for food use and showed strong ability to remove the bitter taste from citrus juice, which provided useful information for interested readers, and the food industry.     

柚苷酶高产菌株选育及其产酶在蜜橘果汁脱苦中的应用

为了得到1株高产柚苷酶菌株并探究其工业应用价值,从发霉的柚子皮上筛选出1株塔宾曲霉(Asper-gillus tubingensis)MN589840,采用紫外与常压室温等离子体(atmospheric room temperature plasma,ARTP)复合诱变技术,获得突变株UA13,其柚苷酶活力可达41.5...     

柑桔汁微生物脱苦的研究

以ＡＳ１．１４菌种,采用Ｋ－角叉胶进行包埋,研究固定化醋酸杆菌在柑桔汁苦味脱除中的应用。重点研究了选择性培养条件的确定、固定化细胞生物反应器的设计及应用。表明：ＡＳ１．４１在柑桔法中脱苦中可行的。另外,把ＡＳ１．４１菌种用于柑桔汁脱苦的国内外尚属首次。     

柑橘类果汁的脱苦

介绍了柑橘类果汁的几种主要脱苦方法,并对今后柑橘类果汁的脱苦方法进行了展望。     

Degreening and postharvest storage influences 'Star Ruby' grapefruit (Citrus paradisi Macf.) bioactive compounds

Ethylene is commercially used for artificial degreening of early season grapefruits. The present study investigated the effect of degreening and storage period on Star Ruby grapefruit (Citrus paradisi Macf.) bioactive compounds. Freshly harvested grapefruits were degreened in commercial packing shed for 60h using 2ppm of ethylene at a constant temperature of 20°C. Both degreened and non-degreened (control) fruits were stored at 10°C for 21days and later transferred to 20°C for a period of 14days to simulate shipment and retail store market conditions. Bioactive compounds including carotenoids, limonoids, flavonoids and furocoumarins were analyzed using high performance liquid chromatography. Nomilin was significantly higher (P<0.05) in degreened fruits at 35days after storage. In contrast, flavonoids such as narirutin, naringin and poncirin were significantly (P<0.05) lower in degreened fruits at 35days after storage. Degreening treatment reduced the levels of deacetyl nomilinic acid glucoside and bergamottin after 35days of storage; however, it had no significant effect on total soluble solids, decay, fruit softening, taste, odour, ascorbic acid, β-carotene, lycopene, limonin, neohesperidin, didymin, 6,7-dihydroxybergamottin, 5-geranyloxy-7-methoxycoumarin and radical scavenging activity. Therefore, degreening could be utilized to enhance the grapefruit aesthetic quality, with minimal effect on nutritional quality.     

Antibacterial activity of grapefruit (Citrus paradisi) peel extracts

Citrus paradisi peels were successively extracted with hexane, chloroform, acetone and methanol using a Soxhlet extractor for 8 h each. Thin layer chromatography (TLC) of hexane and chloroform extracts showed three spots with different concentrations; hence both the extracts were mixed and fractionated into alcohol soluble and insoluble fractions. Naringin was isolated from acetone and methanol extracts by column chromatography and its structure was confirmed by ¹H and ¹³C NMR spectroscopic studies. Antibacterial activity of these fractions was evaluated against different bacteria. The alcohol soluble fraction was found to possess maximum activity followed by hexane extract. Extracts were more effective against Gram-positive than Gram-negative bacteria.     

超声波辅助碱液-酶解法对柚皮脱苦效果的研究

在柚皮产品深加工中,为了使柚皮达到更好的脱苦效果,以柚皮脱苦率为指标,采用超声波辅助碱液-酶解法对柚皮进行脱苦。经单因素和正交实验得出超声波辅助碱液法优化工艺条件为:料液比1∶30（g/m L）,超声时间20 min,超声温度55℃,超声功率120 W,所得脱苦率为75.31%。在超声波优化基础上,通过响应面优化实验对柚皮进行柚苷酶酶解处理,其优化条件为:酶添加量0.15%,酶解温度52℃,酶解p H4.1,酶解时间36 min,所得柚皮脱苦率为90.14%。此方法与传统柚苷酶酶解法相比,具有更高的脱苦效率。      

柚皮苷酶在蜜柚酒中的脱苦效果研究

通过单因素试验和正交试验考察酶制剂的处理时间、处理pH值、处理温度等对蜜柚酒的脱苦效果,通过对比而选出最优脱苦方法。结果表明,柚皮苷酶对蜜柚酒脱苦的最佳工艺条件为,酶制剂在发酵后添加效果较好;当添加量为0.5 g/L时,pH值6、温度50℃、作用时间30 min,果酒的脱苦率可达48.89%。     

吸附树脂在柑桔汁脱苦中的应用

柑桔汁中主要的苦味成分足柚皮苷和柠碱，采用吸附的方法可以将它们除去。综述了吸附树脂及吸附技术在柑桔汁中脱苦脱酸中的应用。     

亲水胶体对胡柚饮料稳定性的影响

以胡柚饮料为研究对象,以离心沉淀率和混浊稳定性为考察指标,探讨了添加黄原胶、羧甲基纤维素（CMC）、瓜尔豆胶和果胶4种亲水胶体对胡柚饮料稳定性的影响。结果表明：随着亲水胶体添加量的增加,胡柚饮料的稳定性呈上升趋势,其适宜的添加量为0.15%～0.2%,亲水胶体的稳定性顺序为：果胶〉CMC〉瓜尔豆胶〉黄原胶;黄原胶与果胶复配比为1∶2～3,添加量为0.15%～0.2%时,胡柚饮料稳定性最好,口感最佳。     

Treatment of Grapefruit Juice for Bitterness Removal by Amberlite IR 120 and Amberlite IR 400 and Alginate Entrapped Naringinase Enzyme

ABSTRACT: Treatment of grapefruit ( Citrus aurantium ) juice with Amberlite IR 400 resulted in 69.23% naringin removal after 5 min exposure with significant clarification and 89.41% tartness (acidity) reduction. Amberlite IR 120 removed only 9% naringin in 1 min with increased shelf life of the juice without any change in clarity, quality, and naringin content. Alginate entrapped naringinase treatment of the juice resulted in 83.84% naringin hydrolysis at 55°C and 220 rpm in 180 min with 1.98 enzyme units/mL of juice. The soluble enzyme hydrolyzed only 65.53% naringin under similar conditions. Kinetic constant values of the immobilized and soluble enzymes were found to be 9.75 mM and 20 mM, respectively.     

Grapefruit (Citrus paradisi Macfad) Phytochemicals Composition Is Modulated by Household Processing Techniques

Grapefruits (Citrus paradisi Macfad) contain several phytochemicals known to have health maintaining properties. Due to the consumer's interest in obtaining high levels of these phytochemicals, it is important to understand the changes in their levels by common household processing techniques. Therefore, mature Texas "Rio Red" grapefruits were processed by some of the common household processing practices such as blending, juicing, and hand squeezing techniques and analyzed for their phytochemical content by high performance liquid chromatography (HPLC). Results suggest that grapefruit juice processed by blending had significantly (P < 0.05) higher levels of flavonoids (narirutin, naringin, hesperidin, neohesperidin, didymin, and poncirin) and limonin compared to juicing and hand squeezing. No significant variation in their content was noticed in the juice processed by juicing and hand squeezing. Ascorbic acid and citric acid were significantly (P < 0.05) higher in juice processed by juicing and blending, respectively. Furthermore, hand squeezed fruit juice had significantly higher contents of dihydroxybergamottin (DHB) than juice processed by juicing and blending. Bergamottin and 5-methoxy-7 gernoxycoumarin (5-M-7-GC) were significantly higher in blended juice compared to juicing and hand squeezing. Therefore, consuming grapefruit juice processed by blending may provide higher levels of health beneficial phytochemicals such as naringin, narirutin, and poncirin. In contrast, juice processed by hand squeezing and juicing provides lower levels of limonin, bergamottin, and 5-M-7-GC. These results suggest that, processing techniques significantly influence the levels of phytochemicals and blending is a better technique for obtaining higher levels of health beneficial phytochemicals from grapefruits. Practical Application: Blending, squeezing, and juicing are common household processing techniques used for obtaining fresh grapefruit juice. Understanding the levels of health beneficial phytochemicals present in the juice processed by these techniques would enable the consumers to make a better choice to obtain high level of these compounds.