Reduction of bitterness and acidity in grapefruit juice by adsorptive processes

By choosing an appropriate adsorbent, the bitter principles (naringin and limonin) and titratable acids could be removed from grapefruit juice in varying combinations. For example, Amberlite XAD-7 removed about 63% naringin, 85% limonin and 3% titratable acids and Deacidite-FFIP removed about 20% naringin, 8% limonin and 23% titratable acids when contacted for 1 h with grapefruit juice at the rate of 20 g (dry wt) of adsorbent per litre of juice. Such treatments, applied consecutively, would eliminate excessive bitterness and acidity from juices containing up to 2 g naringin and 36 mg limonin litre^?1 and with a total soluble solids:titratable acid ratio of < 6. The adsorbents are readily available, may be used as supplied and can be reactivated simply and economically; some of them have already been approved for use with foods, and such approval seems possible for the others.     

Pectinase and naringinase help to improve juice production and quality from pummelo (Citrus grandis) fruit

Pectinase and naringinase were investigated for improving the production of pummelo juice by increasing the juice yield and eliminating juice bitterness. Compared to a control, the enzymatic treatment significantly (p<0.05) increased the juice yield, soluble pectin and total soluble solid (TSS) contents, and the clarity, while decreasing the concentrations of the bitter chemicals naringin, limonin, and nomilin. A combined processing treatment of peeling and enzymatic hydrolyses using 5U/g of pectinase and 0.4 U/g of naringinase at 50oC for 60 min resulted in a juice yield of 42.3%, a TSS content of 11.4oBx, a titrable acidity (TA) of 0.96%, a vitamin C concentration of 38.4 mg/100 mL, and concentrations of naringin, limonin, and nomilin of 42.4 μg/mL, 33.5 μg/mL, and 13.3 μg/mL, respectively. The enzymatic method was effective and practical for production of high quantity pummelo juice.     

Effect of maturity and processing on bitter compounds in Thai tangerine juice

Optimum conditions of fruit maturity and processing for improved quality of Thai tangerine fruit juice were evaluated. Limonin and naringin components causing bitterness, acidity, total soluble solids and vitamin C were quantified in specified fruit setting and processing conditions.
Higher limonin contents were observed in tangerine fruits harvested early in the season of 1989, whereas naringin contents gradually decreased with maturity. The optimum harvesting time for Thai tangerine fruit which meets the worldwide quality indicators of extracted juice was nine months after fruit set.
Low temperature storage of tangerine juice was only effective in delaying limonin formation if not pasteurized, which resulted in higher limonin concentrations at the start of the storage period. However, naringin concentrations of tangerine juice were not affected by storage conditions and the pasteurization process. Lower extraction pressure of juice resulted in low limonin and naringin concentrations.     

黑曲霉DB056柚苷酶制剂对琯溪蜜柚果汁的脱苦效果

采用高效液相色谱法测定琯溪蜜柚果汁中柚皮苷及其降解产物的变化,研究黑曲霉DB056柚苷酶制剂脱苦琯溪蜜柚果汁的优化条件;并且在此优化条件下,使用该柚苷酶制剂对琯溪蜜柚鲜柚汁、浑浊浓缩柚汁和澄清浓缩柚汁进行脱苦。结果表明：黑曲霉DB056柚苷酶制剂催化琯溪蜜柚果汁中柚皮苷水解成普鲁宁和柚皮素;该柚苷酶制剂在40～55℃、果汁自然pH值条件下对琯溪蜜柚鲜柚汁进行脱苦,酶用量90U/mL、处理时间80min,柚皮苷脱除率达到89%;处理不同浓缩程度的浑浊浓缩柚汁,脱苦率约为80%左右。结果说明黑曲霉DB056柚苷酶制剂对琯溪蜜柚果汁具有良好的脱苦作用。     

机械挤压对柚子砂囊的损伤特性及苦味物质增加

本研究以柚子砂囊形变程度为参数,考察了不同机械挤压程度对沙田柚、白肉蜜柚和红肉蜜柚砂囊物理破损程度、营养成分、色泽及柚皮苷、柠檬苦素等苦味物质的影响。结果表明,机械挤压对柚子砂囊的色泽、总酸含量影响不大。随着机械挤压程度的增加,3个柚子品种砂囊的汁液流失率、可溶性蛋白含量、柚皮苷含量、总酚含量、可溶性固形物含量上升,抗坏血酸含量、原果胶含量均下降,可溶性果胶和脂肪含量在机械损伤致形变程度为40%时达到最大值。与白肉蜜柚和红肉蜜柚相比,机械损伤导致沙田砂囊总糖含量下降2.89%,柠檬苦素含量增加64.12%;柚皮苷含量增幅较大,增幅为17.48%。本研究表明,机械挤压越大对柚子砂囊损伤越大,而引起的苦味物质累积则因柚子品种而异,其中机械损伤引起沙田柚苦味的增加较为明显。     

Selective adsorption of limonin and naringin from orange juice to natural and synthetic adsorbents

In the majority of citrus juices, bitterness is mainly ascribed to the presence of limonoids (triterpenes) and flavanone glycosides (flavonoids), namely limonin and naringin. In this study, the selective removal of limonin and naringin from citrus juice by batch adsorption to different materials was investigated. Since the removal of reducing sugars, pigments and vitamin C may also occur, the eventual adsorption of these compounds was also investigated. The following adsorbents were tested: activated diatomaceous earths, granulated activated carbon and synthetic neutral resins (Amberlite XAD-4, XAD-7 and XAD-16). Both Freundlich and Langmuir isotherm models showed a good fit to the adsorption of limonin to the resins used. Concerning naringin adsorption, a good fit of these models was only observed when the XAD-7 resin was used. Sigmoidal profiles were obtained for the adsorption of limonin to granular activated carbon. Unfavourable isotherms were also observed for limonin and naringin adsorption to activated earths. These isotherm adsorption profiles can be explained by a multilayer adsorption phenomenon. The highest adsorption efficiency for the bitter compounds was observed when synthetic neutral resin, Amberlite XAD-7 was used. The separation factor limonin/naringin varied from 16 (with earths) to 57 (with XAD-7 resin). The adsorption of sugars and pigments to the resins was low. No adsorption of vitamin C was detected for any of the adsorbents tested. The estimated affinity and separation factors show that the neutral resins tested are adequate for the selective removal of limonin from orange juices. The estimated values of free energy of adsorption, lower than -13.3 kJ mol^-1 K^-1, indicate that a physiosorption process occurred.     

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(Aspergillus 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41.524 U/mL,是原始菌株的3.06倍。对酶解条件进行探究,其酶解最适温度为40~50℃,最适pH值为5.0。利用突变株UA13发酵产酶脱苦宜昌蜜橘果汁并进行理化指标检测,当酶解约50 min时,果汁中柚皮苷含量低于柚皮苷苦阈值;当酶解时间>75 min,果汁中仅剩下少量柚皮苷。使用高效液相色谱对脱苦结果验证检测,结果显示,突变株UA13产酶可有效水解果汁中的柚皮苷,且能提高果汁风味。因此,突变株UA13具有潜在的工业应用价值,为后续实验研究奠定基础。     

THE USE OF PULSED ELECTRIC FIELDS IN PRODUCING JUICE FROM PAPRIKA (CAPSICUM ANNUUM L.)

Investigations were conducted on the impact of pulsed electric field (PEF) treatment on yield and some quality parameters of juice from paprika and results were compared to the results of juice obtained from enzymatically treated or untreated paprika mash. Paprika was comminuted mechanically after which the mash was subjected to either PEF (electric field strength = 1.7 kV/cm, pulse number = 30 and specific energy input per pulse = 0.5 kJ/kg) or a pectolytic enzyme preparation treatment. The extent of cell disintegration after the different pretreatments was monitored through cell disintegration index (Z_p) measurement prior to juice extraction through pressure (10 MPa for 4 min). Some quality parameters (pH, soluble solids (°Brix), total dry matter, color, total carotenoids as β-carotene and vitamin C) of the resultant juice samples were determined. PEF and enzyme treatments resulted in about 10% and 9% increase in juice yield, respectively. Juice from PEF treated paprika compared well in quality with enzyme treated or the untreated. And in some cases such as in color (redness, a value) of the juice, PEF treated had values (+ 18) higher than enzyme treated having + 15.5 and also in the amount of β-carotene extracted into the juice PEF treated juice had more than 60% as compared to about 44% from enzyme treated juice. The pH value for enzyme treated juice was lower than the others.     

Naringinase Immobilization in Packaging Films for Reducing Naringin Concentration in Grapefruit Juice

Naringin, a bitter compound in citrus, may be converted to a nonbitter form by enzymic hydrolysis. Our objective was to determine the feasibility of immobilizing naringinase in a food contact approved packaging film. Naringinase from Penicillium sp. was immobilized in cellulose acetate films with up to 23% efficiency at 7°C. Kinetic studies showed that the free enzyme had an optimum pH=3.5 and the immobilized enzyme pH=4.0. Activation energy decreased upon immobilization (from 14.2 to 11.0 Kcal/mol), thus providing an increased catalytic efficiency for immobilized naringinase. The Michaelis constant for immobilized naringinase (K_m=2.1 mM) was lower than for free enzyme (K_mm=3.6 mM). Keeping films under dry storage for 1 mo at room temperature did not cause decreased enzyme activity. A film area/volume ratio (cm²/mL of 10° Brix grapefruit juice) of 7.2 hydrolyzed 60% of the naringin in 15 days at 7°C.     

柚皮苷酶对琯溪蜜柚果汁脱苦效果工艺优化

以琯溪蜜柚果汁为对象,研究在不同条件下柚皮苷酶对蜜柚果汁的脱苦效果。采用HPLC 测定柚皮苷含量,通过单因素试验分别考察加酶量、温度、酶解时间及pH 值对柚皮苷酶酶解反应的影响,在单因素试验基础上以柚皮苷脱除率为指标进行正交试验,确定最佳工艺条件：酶解温度60℃,酶活7.4U/mL 柚汁,酶解时间100min,pH3.6。在此条件下琯溪蜜柚果汁的柚皮苷脱除率达97% 以上。     

响应面优化酶法提取沾化冬枣汁的工艺研究

为提高沾化冬枣的出汁率,采用酶解法对冬枣进行处理,确定复合酶(果胶酶和纤维素酶)的效果优于单一酶,并确定复合酶的质量比为1∶2时效果最好。同时,在单因素试验基础上,采用Box-Behnken响应面设计优化冬枣汁酶法提取工艺,研究酶用量、酶解时间、酶解温度对冬枣出汁率和可溶性固形物含量的影响。试验结果表明,酶用量为0.1%、酶解时间为68 min、酶解温度为50℃,在此条件下出汁率可达到(72.27±0.3)%、可溶性固形物含量为(8.0±0.2)%,与预测结果基本相符。     

Effects of Chitosan on Yield and Compositional Data of Carrot and Apple Juice

Effects of chitosans on yield, titratable acidity, pH, soluble solids, and color of carrot and apple juice were evaluated. Carrots (Lange Rote Stumpfe) and apples (Golden Delicious) were treated with chitosan solutions (in 2% ascorbic acid) of two different concentrations and viscosities at 25°C between 0 and 120 min. The juices were obtained with a laboratory cage press following a standard program during 20 min. Treatments with chitosan produced no effect on juice yield but pH values and soluble solids were affected. Also chitosan treatment resulted in significant (P < 0.05) reduction of titratable acidity and color index. Reduction of β-carotene in carrot juice was also achieved and correlated with color index.     

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.     

柚皮苷/柠檬苦素微胶囊的制备、结构分析及特性研究

为提高柚皮中柚皮苷和柠檬苦素的生物利用度,降低其苦味,拓展其在食品开发中的应用,本研究以海藻酸钠-壳聚糖-氯化钙体系为壁材,采用锐孔造粒法微胶囊化柚皮苷/柠檬苦素,并以柚皮苷/柠檬苦素包埋率为响应值,通过单因素实验和响应面试验优化柚皮苷/柠檬苦素微胶囊的制备工艺。进一步通过扫描电镜（SEM）、傅里叶变换红外光谱仪（FTIR）、电子舌、热稳定性分析以及体外模拟消化试验对柚皮苷/柠檬苦素微胶囊的微观形态、分子结构、相对苦味强度、热稳定性及胃肠消化特性进行了研究。结果表明,微胶囊化最佳工艺条件为壁芯材比为8:3、壳聚糖质量分数为0.9%,氯化钙质量分数为3%,此时包埋率可达88.2%,与理论值的88.68%相对误差小于5%,说明该工艺准确可靠;扫描电镜证实海藻酸钠-壳聚糖-氯化钙体系组成的微胶囊结构能高效且紧实包裹柚皮苷和柠檬苦素,并且微胶囊表面无裂缝、孔洞和凹陷的现象。热稳定性和电子舌试验表明,柚皮苷和柠檬苦素的微胶囊化可以明显提高柚皮苷和柠檬苦素的稳定性,并且有效降低其苦味强度;体外模拟胃肠道消化缓释试验表明,微胶囊在模拟胃液中消化6 h后总体释放率才达31%左右,在模拟肠液中消化45 min时累计释放率已经超过75%,表明微胶囊化能有效促进柚皮苷/柠檬苦素在肠道内的生物转化与吸收,提高其利用率。本研究结果可为拓展柚皮苷/柠檬苦素在食品和医药领域的高值化利用提供依据。     

Effects of High Pressure and Heat Treatment on Pectic Substances and Related Characteristics in Guava Juice

Effects of high pressure treatment on guava juice pectic substances and related juice characteristics were investigated and compared with heat treatment. The viscosity and turbidity of guava juice pressurized at 600 MPa and 25°C for 10 min increased slightly; whereas the viscosity of juice heated at 95°C for 5 min decreased while turbidity increased. There were no apparent changes in water soluble, oxalate soluble and alkali soluble pectin in pressurized juice. However, heat treatment of juice decreased water and alkali soluble pectins and slightly increased oxalate soluble pectin. High pressure treatment resulted in no marked changes in pectic and cloud substances of guava juice, and maintained the natural viscous of the juice.     

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。     

粒状活性炭固定床用于柑橘汁的脱苦

粒状活性炭用于柑橘汁脱苦具有简化生产工艺的优点 ,研究了用粒状活性炭固定床脱苦的效果 ,在固定床高度为 70cm ,流量为 0 6mL/min逆流操作时 ,柚皮苷和柠檬苦素的脱除率分别为 75 5 8%和 76 0 0 % ,为进一步研究粒粉活性炭的脱苦提供了依据。     

Rapid Extraction of Pawpaw Juice with the Application of Locally Produced Pectic Enzymes from Saccharomyces Cerevisiae ATCC 51712

Pawpaw (Carica papaya) fruit is highly perishable; hence, conversion into a value-added product such as juice concentrate will be useful. Pawpaw fruit is, however, high in pectin; therefore, its juice extraction is difficult without an extraction aid such as the addition of pectic enzymes. Our laboratory has developed a simple enzymatic method that enables the extraction of pawpaw juice with considerable ease. Pectic enzymes were obtained from Saccharomyces cerevisiae (ATCC 52712) cultured in pawpaw juice for 6 days at room temperature (25–28°C) and centrifuged to obtain the enzyme in the supernatant. Addition of this enzyme (32 mg total protein) to 200 g pawpaw mash and incubation for 30 min resulted in significant (P < 0.05) reduction in the viscosity of the mash with corresponding increases in the flow rate of free-run juice (85%). Simultaneously, large increases in the volume of free-run juice (180%) over the controls were obtained. Since the overall increase in total juice volume was only 35% as compared with 180% for volume of free–run juice and 80% increase in flow rate for free–run juice, it was concluded that the major effect of the enzyme treatment on pawpaw juice extraction is on the decrease in processing time as a result of the degradation of the pectin in the fruit flesh.     

黑曲霉TC-01产柚苷酶对柚皮苷酶解作用的研究

柚皮苷是一类主要的类黄酮物质,它是引起柚类和葡萄果实苦味的主要来源,去除柚皮苷会使果汁苦味减轻,而柚皮苷酶能在不影响柑橘果汁品质的前提下较好地去除苦味。但是由于不同来源的柚苷酶的结构不同,其催化特性也不尽相同,本文通过利用前期筛选的黑曲霉(Aspergillus.niger TC-01)产柚苷酶对柚皮苷酶解作用进行研究,实验采用高效液相色谱法测定柚皮苷、普鲁宁和柚皮素的三者之间含量变化,确定酶解最适温度、时间、pH及酶用量,并测定TC-01产柚苷酶的米氏常数以确定酶解反应的最佳条件。结果表明,TC-01产柚苷酶酶解最适温度为60℃、酶解最适时间为30-40min,最适pH4.0,酶最佳用量为24u/mL。米氏方程为Y=0.0018X-3.0×10-6,其中Km值为598.8ug/mL,Vmax=2.06g/(min.mL)。此研究结果为柚苷酶的应用提供了理论依据。     

Removal of limonin bitterness by treatment of ion exchange and adsorbent resins

This study, the selective removal of limonin bitterness from Washington navel orange juice by batch adsorption to the Amberlite XAD-16HP and Dowex Optipore L285 was investigated and the determination of some compositional changes that occurred with orange juices debittering using adsorption resins were the primary focus. Amberlite XAD-16HP and Dowex Optipore L285 have been successfully used to reduce bitterness to acceptable levels in Washington navel orange juices. Amberlite XAD-16HP does not have any important negative effects on the quality characteristics of orange juices. However, Dowex Optipore L285 reduces the titratable acidity (TA) in the orange juices and so increases the content of soluble solids contents (SSC), pH value, and ratio accordingly.