藥物化學外文翻譯--黃酮類化合物和酚類化合物在水中和乙醇蜂膠中通過納濾膜的提取率（節(jié)選）

1、<p><b>　　中文6900字</b></p><p>　　出處： Journal of Food Engineering, 2010, 96(4): 533-539.</p><p><b>　　原 文</b></p><p>　　題目： Concentration of ?avonoids an

2、d phenolic compounds in aqueous and ethanolicpropolis extracts through nano?ltration</p><p>　　Abstract </p><p>　　Propolis has a variable and complex chemical composition with high concentration

3、 of ?avonoids andphenolic compounds present in the extract. The extract varies with the solvent used in extraction. Ethanol extracts more phenolic acid and polar compounds than water. Before their use in industry, extrac

4、ts must be concentrated but the use of high temperatures can degrade some compounds. Membrane pro-cesses is an option that allows concentration at low temperatures. Nano?ltration was carried out witha</p><p>

5、;　　1 Introduction</p><p>　　Over the last few decades, interest in functional foods has beengrowing fast, leading to the discovery of new functional components or processes that can improve food processing, a

6、s well as products that may help to retard aging or avoid diseases. In this context, bee products have gained the attention of consumers and researchers, due to their chemical compositions and functional properties. Prop

7、olis is one of the bee products with functional properties, but it cannot be consumed as a food beca</p><p>　　The most common propolis extracting process uses ethanol as the solvent. However, this has some d

8、isadvantages such as the strong residual ?avor, adverse reactions and intolerance to alcohol of some people (Konishi et al., 2004). Researchers and industry are</p><p>　　interested in producing a new type of

9、 extract with the same compounds extracted by the ethanolic method, but without the disadvantages. Water has been tested as the solvent, but resulted in a product containing less extracted compounds (Park et al., 1998).

10、Konishi et al. (2004) tested water with a combination of some tensoactive compounds to replace part of the alcohol used in propolis extraction and all the tests were ef?cient in extracting it, and the product showed good

11、 anti-microbial activit</p><p>　　Depending on the application, the solvent in propolis extracts must be reduced or eliminated. The processes that are used today, as lyophilization, vacuum distillation and ev

12、aporation, have some disadvantages like the use of high temperatures and high energy consumption. Lyophilization requires large amounts of energy, since the sample needs to be maintained at À20 °C for at least

13、24 h, and energy is also required for the sublimation of the solvent used during preparation of the extract. Moreove</p><p>　　Vacuum distillation requires great amounts of energy to generate the vacuum, and

14、can lead to loss of compounds of low molecular weight, which can be removed together with the solvent evaporated in the system. Evaporation maintains the extract underheating at 70 °C, until all the solvent is remov

15、ed. This process, in addition to the high demand for energy, can degrade the ?avonoid and phenolic compounds in propolis, due to the temperature used. However, it is the process that gives greater ease of</p><

16、p>　　wine concentration (Banvolgyi et al., 2006), as well as in juice concentration (Vincze et al., 2006) in the food industry.</p><p>　　The objective of this study was to investigate the membrane concentr

17、ation of propolis extracts using water and ethanol as the solvents, exclusively, verifying the quality of the concentrated products in terms of the retention of ?avonoids and phenolic compounds during processing. The pro

18、cess was evaluated according to the permeate ?ux, in?uence of temperature and pressure and concentration factor. The results obtained for each solution were compared to verify the viability of developing a new pr</p&g

19、t;<p>　　2. Materials and methods</p><p>　　2.1. Propolis</p><p>　　Raw propolis was obtained from Apis mellifera beehives in the State of São Paulo, Brazil, and was acquired in a singl

20、e batch, in order to minimize the variability associated with the vegetation used for its production and the weather conditions. It was stored under refrigeration (4 °C) until use in the preparation of extracts.<

21、/p><p>　　The propolis produced in this region is characterized as group 12 (Brazil has 12 different groups of propolis, with distinct characteristics) and presents a great amount of soluble substances, antimicr

22、obial activity against Staphylococcus aureus and Streptococcus</p><p>　　mutans and greater anti-in?ammatory activity than samples from other parts of the country, which can be associated with the higher conc

23、entrations of ?avonoids and phenolic compounds found in this group (Park et al., 2002).</p><p>　　The ethanolic propolis solution was prepared from crude propolis previously comminuted in a bench blender with

24、 a 500 W motor, homogenized, weighed on a semi-analytical balance and mixed with 80% ethanol. The mixture was kept at room temperature for 7 days and manually stirred once a day. After this period, the sample was centrif

25、uged (Beckman – Allegra 25-R, Beckman Coulter, German) at 8800 g for 20 min. The supernatant was ?ltered and refrigerated for 3 h at 4 °C and then ?ltered again for wax r</p><p>　　Preparation of the aqu

26、eous solutions followed the same procedures, using deionized water. Each solution was prepared in a proportion of 20% propolis and 80% solvent. Both extracts were evaluated with respect to their ?avonoid and phenolic com

27、pounds contents, to be compared with the concentrated products.</p><p>　　2.2. Determination of total ?avonoids</p><p>　　The total ?avonoid content of the propolis solutions was determined by the

28、 aluminum complexation method (Marcucci et al., 1998). In this procedure, the extracted solutions were diluted in the proportion of 1:10 (0.5 mL) and mixed with 0.1 mL of 10% aluminum nitrate, 0.1 mL of 1 mol/L potassium

29、 acetate and 4.3 mL of 80% ethyl alcohol. The samples were kept at room temperature for 40 min and the absorbance read at 415 nm. Quercetin was used as the standard to produce the calibration curve. The mea</p>&l

30、t;p>　　2.3. Determination of the phenolic compounds</p><p>　　The polyphenols in the propolis solutions were determined by the Folin–Ciocalteau colorimetric method (Kumazawa et al., 2004). According to this

31、 procedure, the extracted solution was previously diluted in the proportion of 1:10 (0.5 mL) and then mixed with 0.5 mL of the Folin–Ciocalteau reagent and 0.5 mL of 10% Na2CO3. The absorbance was read at 760 nm after 1

32、h of incubation at room temperature. Gallic acid was used as the standard to produce the calibration curve. The mean of three readings w</p><p>　　2.4. HPLC determination</p><p>　　The compounds p

33、resent in the initial extract, permeate and concentrated products, were determined by HPLC as described by Parket al. (1998). Three hundred microliters of each solution were injected into a liquid chromatograph (Shimadzu

34、, Tokyo, Japan) connected to a diode-array detector at 260 nm. The mobile phase was water/acetic acid (19:1, v/v) (solvent A) and methanol (solvent B), with a constant ?ow rate of 1 mL/min. The gradient started at</p&

35、gt;<p>　　30% solvent B, passing to 60% at 45 min, 75% at 85 min, 90% at 95 min and back to 30% at 105 min. The column was maintained at a constant temperature of 30 °C and the chromatograms processed using th

36、e computer software Chromatography Workstation</p><p>　　(Shimatzu Corporation, Tokyo, Japan). The initial and concentrated samples were diluted in 1.5 mL of distilled water and the permeate sample was inject

37、ed without dilution. The following authentic standards of phenolic acids and ?avonoids (Extrasynthese, Genay, France) were examined: q-cumaric acid, ferulic acid, cinnamicacid, gallic acid, quercetin, kaempferol, kaempfe

38、ride, apigenin, isorhamnetin, rhamnetin, sakuranetin, isosakuranetin, hesperidin, hesperetin, pinocembrin, chrysin, acacetin, gal</p><p>　　2.5. Membrane concentration</p><p>　　In this study, the

39、 propolis extracts were concentrated using a tangential ?ltration system on a pilot scale, with a nano?ltration membrane as seen in the schematic diagram shown in Fig. 1. The experiments were performed on pilot equipment

40、 that permits the batch circulation mode, which means that both permeate and concentrate could be carried back to the feed tank. The permeate was totally removed just in a single experiment, where it was necessaryto obta

41、in the concentrated product of the process</p><p>　　Fig. 1. Schematic diagram of the nano?ltration unit</p><p>　　where Vf is the total volume used in the feed, Vc is the volume collected in the

42、concentrate fraction and Fc is the concentration factor. Other experiments were carried out at different temperatures (20–45 °C) and pressures (2.0–5.0 bar), in order to evaluate the in?uence of these parameters on

43、the permeate ?ux and the concentrated product quality. In these experiments, both the permeate and retentate were maintained under re-circulation in closed systems. The permeate ?ux was calculated accordi</p><

44、p>　　J=Vp/t*Ap (2)</p><p>　　where Vp is the permeate volume collected during the time intervalt and Ap is the membrane surface area of permeation. The quality of the ?ltration pro

45、cess was measured according to the quantity of ?avonoids and phenolic compounds present in permeate, evaluated as described in Sections 2.2–2.4, and the ef?ciency was measured according to the ?ux permeate rate and reten

46、tion index. This index measures the relation between the amounts of the compound of interest in permeate and in the concentrated </p><p>　　R=1-Cp/Cr (3)</p><p>　　It is important to kno

47、w the rate of fouling that occurs in the membrane process, and one way of measuring this is to compare the permeate ?ux of the solution under study with the permeate ?ux when water is used as feed solution, under differe

48、nt pressures. Usually a variation in system pressure will cause a change directly proportional to the permeate ?ux. The fouling in?uence was measured by comparison of the permeate ?ux of the aqueous propolis extract with

49、 the ?ux of distilled water only, incr</p><p>　　from 1.0 to 5.0 bar.</p><p>　　3. Results and discussion </p><p>　　The membrane process was carried out with the aqueous and ethanolic

50、 solutions in a closed system, in which the retentate and permeate streams being conducted back and mixed in a feed tank isolated from the environment, to evaluate the variation in permeate ?ux with time. The temperature

51、 was maintained at 20 °C and the pressure at 5.0 bar. The results are shown in Fig. 2.</p><p>　　After stabilization of the process, the permeate ?ux began to decrease, after around 15 min of processing.

52、 The rate of decrease was higher for the alcoholic extract than for the aqueous extract, evidencing a greater rate of fouling with the alcohol solution. After 20 min of processing, the permeate ?ux tended to stabilize, t

53、hat is, concentration polarization already occurred and fouling did not increase with time. The permeate ?ux in the stable region was about 12.0 L/h m2 and 25.0 L/h m2 for al</p><p>　　Tsui and Cheryan (2007)

54、 used nano?ltration to purify alcoholic corn extracts in the production of xanthophylls, and obtained a permeate ?ux of around 10.0 L/h m2 when working at 27 bar and 50 °C. Hossain (2003) studied the membrane concen

55、tration of anthocyanins from blackcurrant pomace extracts using ultra?ltration, obtaining a maximum permeate ?ux of 17.3 L/h m2 at 1.4 bar and 18 °C. Using nano?ltration a permeate ?ux of 20 L/h m2 was obtained at 2

56、0 bar and 50 °C in the concentration of red win</p><p>　　Fig. 3 shows the difference between the curve of the permeate ?ux for the aqueous propolis extract and the curve of the permeate ?ux for distille

57、d water to measure the degree of fouling in the process with the aqueous propolis solution.The difference between the permeate ?uxes of water and the propolis solution shows the amount of fouling in the process, under th

58、e same conditions of temperature and pressure. This parameter increased, reaching 32% at 5.0 bar. The procedure also provided informati</p><p>　　By increasing the temperature from 20 to 45 °C and mainta

59、ining the pressure at 6.0 bar it was possible to determine the relation ship between the temperature and the permeability of the membrane. Permeate ?ux increased proportionally, by around 8% per degree of temperature, as

60、 shown in Fig. 4. This result may be attributed to the effect of temperature on the viscosity of the solution. Also, the composition of the concentrated products obtained at different temperatures showed no signi?cant di

61、ffe</p><p>　　The initial solutions, permeates and concentrates obtained by nano?ltration in open system were all subjected to a spectrophotometric analysis as described in Sections 2.2 and 2.3. The results f

62、or the aqueous solution indicated that this permeate only contained small amounts of phenolic compounds and ?avonoids, while the permeate from the ethanolic solution showed greater amounts, mostly of low molar weight phe

63、nolic compounds. Considering the losses in the compounds of interest in the resulting </p><p>　　The results for the determination of ?avonoids and phenolic compounds carried out by spectrophotometric methods

64、 were veri?ed by HPLC analysis, as described in Section 2.4. The substances were identi?ed by a comparison of their retention times and ultraviolet spectra with those of standards in the literature. Chromato grams were o

65、btained from the initial aqueous extract, and from the concentrated and permeated products, which are represented in Fig. 5a–c, where the numbers 1–3 indicate the peaks </p><p>　　Table 2 shows the results of

66、 the quantitative analysis for all samples from the aqueous propolis solution. Comparing these data, it can be seen that there were no losses of ferulic acid to the permeate and only 20% of the caffeic acid present in th

67、e initial solution was lost to the permeate, this compound thus being the most abundant in the concentrated extract, of the compounds identi?ed. All the aqueous solutions showed peaks located in the region that</p>

68、<p>　　represents a retention time of up to 20 min. This occurred since the water, being a polar material, only extracts polar compounds. The last peak identi?ed in the permeated solution, probably does not represe

69、nt an isolated compound but interference in the system, since this compound was not present in the other chromatograms. Ferulic acid was not identi?ed in the permeated solution, indicating that no losses to the permeate

70、occurred. The other peaks in the chromatograms represented compounds that</p><p>　　Park et al. (1998) analyzed an aqueous propolis solution prepared in the laboratory, using HPLC, and obtained similar result

71、s to those presented in Fig. 5a, reporting peaks with low retention times that represent polar substances, and identifying the compounds quercetin and pinocembrin. In their experiment, the proportions of water and alcoho

72、l in the solvents for propolis extraction were varied. Initial solutions contained 0–90% of alcohol, through which it was demonstrated that increasing the p</p><p>　　In the present study, the values obtained

73、 for the retention indexes were very similar to those cited in the literature for similar processes.</p><p>　　.4 Conclusions</p><p>　　The results showed that nano?ltration can be considered as a

74、 good alternative for concentrating propolis extracts, since the membrane retained most of the ?avonoids and phenolic compounds, which are of major importance to propolis quality. Particularly in the case of the aqueous

75、extract, it could be considered that there was no loss of compounds to the permeate solution, since almost 100% of the major compounds were retained. In the experiments with alcoholic propolis, the losses were considerab

76、</p><p><b>　　譯 文</b></p><p>　　題目：黃酮類化合物和酚類化合物在水中和乙醇蜂膠中通過納濾膜的提取率</p><p>　　關(guān)鍵詞:蜂膠 膜濃度 黃酮類化合物 酚類化合物 納濾</p><p>　　摘要：蜂膠具有可變的、復雜的化學成分，且蜂膠中黃酮類化合物的濃度較高，酚類化合物存在于蜂膠萃取

77、物。提取溶劑不同，提取物也有所變化。乙醇胺比水更容易提取酚酸和極性化合物。在他們應用于工業(yè)之前，提取物應被濃縮，與此同時高溫會降解一些化合物。膜處理是一個能允許低溫濃縮的一個選擇。納濾膜應用于水和乙醇的提取，但是每一種都會產(chǎn)生不同的結(jié)果：滲透、滯留物。用膜來保留化合物能力用分光光度法進行了驗證：水溶法,膜保持94%左右的酚類化合物和99%的黃酮類化合物,而對乙醇溶解這些數(shù)值分別為53%和90%。水和乙醇的相比酸的保留值為1.00和0.8

78、8。 因此,納濾過程對蜂膠提取物濃度有明顯的較高的提取率。</p><p><b>　　1導語</b></p><p>　　在過去的幾十年，對于功能食品的興趣快速增長，使得改進食品加工新功能成分或工藝有所發(fā)展，也產(chǎn)生了可能幫助延緩衰老或避免疾病的產(chǎn)品。在此背景下，蜂產(chǎn)品由于其化學成分和功能特性吸引了消費者和研究人員的注意。蜂膠是一種擁有功能特性的蜂產(chǎn)品，但它不能作為食

79、品食用，因其是一種樹脂質(zhì)物質(zhì)。它由花蕾和某些植物的滲出物制成。這些物質(zhì)通過添加蜂蠟和蜜蜂唾液中存在的酶葡萄糖苷酶轉(zhuǎn)化為蜂膠，得到的產(chǎn)物被蜜蜂用來保護蜂巢免遭入侵者和污染物的侵害，用來封孔和保持溫度。這種物質(zhì)的一些重要特性已被報告，例如抗微生物和抗氧化作用，麻醉特性及其他。由于這些能帶來健康益處的特性，蜂膠被認為是一種功能成分，應用于食品、飲料、化妝品和藥物以改善健康及預防疾病。蜂膠中有超過150種成分，包括多酚類、萜類、類固醇和氨基酸。

80、類黃酮是最重要的基團之一，能夠代表大約50%的蜂膠成分，這根據(jù)收集蜂蜜的地區(qū)而有所不同，因為其性質(zhì)受植物和氣候的影響。Kumazawa等人(2004)檢測了來自不同地理區(qū)域的蜂膠的抗氧化活性，并展示了每個樣本的不同活性。其他研究表明，來自歐洲和中國的蜂膠含有多種類黃酮和酚酸，而來自巴西的樣本含有更多的萜類和磷香豆</p><p>　　最常見的蜂膠提取工藝使用乙醇作為溶劑。然而，這種方法有一些缺點，例如強烈的殘留味

81、道，不良反應和某些人群的乙醇不耐受 (Konishi等, 2004)。研究者和企業(yè)對生產(chǎn)一種新型的提取物很感興趣，它要有用乙醇方法提取出來的相同化合物，但沒有其缺點。將水作為溶劑測試，得到的產(chǎn)品中提取出的化合物較少(Park等, 1998)。Konishi等人用含有某些化合物的組合測試水取代蜂膠提取中使用的部分乙醇，所有試驗在提取蜂膠上都有效，產(chǎn)品也顯示出很好的抗微生物活性。</p><p>　　根據(jù)應用，蜂膠提

82、取中的溶劑必須被分解或剔除。現(xiàn)在使用的工藝，如凍干法、真空蒸餾和蒸發(fā)，都有一些像高溫的使用和高能源消耗的缺點。凍干法需要大量的能量，因為樣本需要在零下20℃下，保持至少24小時，提取準備過程中溶劑升華時也需要能量。此外，此方法經(jīng)常需要一個濃縮的前期階段，將產(chǎn)品保持在70℃直到溶劑部分蒸發(fā)。</p><p>　　真空蒸餾需要大量能量造成真空，導致低分子化合物的損失，此化合物可以與系統(tǒng)中蒸發(fā)的溶劑一起被移除。蒸發(fā)將提

83、取物保持在70℃加熱，直到所有溶劑都被移除。這種工藝，除了高能源需求外，由于使用的高溫，還會分解蜂膠中的類黃酮和酚類化合物。然而，正是這種工藝給企業(yè)中的實施帶來了極大便利，因其與以往案例相比在所需設(shè)備上花費較小。</p><p>　　膜濃縮工藝的使用由于某些優(yōu)點而變得越來越多，優(yōu)點有：低溫、無需相變和低能耗 (Matta等,2004)。此過程基于溶質(zhì)分子通過半滲透、聚合或無機膜時的選擇性滲透原則。在大多數(shù)膜工藝中

84、，例如微濾、超濾、納濾和反滲透，物質(zhì)穿過膜的驅(qū)動力是機械壓力(Maroulis and Saravacos, 2003)。納濾是一種允許多種應用的單元操作，例如從過濾油中回收溶劑、化工企業(yè)中的溶劑交換(Geens等, 2006)，對乙醇提取葉黃素的濃縮和純化，這對制藥和食品工業(yè)都很重要(Tsui and Cheryan, 2007)，還有在酒類濃縮(Banvolgyi等, 2006)，以及食品工業(yè)的果汁濃縮上(Vincze等, 2006

85、)。</p><p>　　此研究的目的是研究蜂膠提取物用水和乙醇作為溶劑進行的膜濃縮，且只檢驗過程中濃縮產(chǎn)物關(guān)于類黃酮和酚類化合物保留方面的質(zhì)量。此工藝根據(jù)滲透熔劑及溫度、壓力和濃縮因素的影響而評價。每種溶液得出的結(jié)果相比較，以此檢驗用水做溶劑生產(chǎn)新的蜂膠產(chǎn)品的耐久性。</p><p><b>　　2. 材料和方法</b></p><p>&l

86、t;b>　　2.1. 蜂膠</b></p><p>　　蜂膠原料從巴西圣保羅州的蜜蜂蜂巢中獲得，并以單個批量的形式取得，目的是最小化與用來生產(chǎn)的植物和氣候條件有關(guān)的可變性。它儲存在冷藏條件下(4 °C)，直到在提取制備中被使用。</p><p>　　在此地區(qū)生產(chǎn)的蜂膠被描述為第12組（巴西有12組擁有區(qū)別特征的蜂膠）并呈現(xiàn)出大量的可溶性物質(zhì)，抗金黃色葡萄球菌和變

87、形鏈球菌的抗微生物活性，及比來自其他地區(qū)的樣本更大的抗炎活性，而這可能與在此組中發(fā)現(xiàn)的高濃度類黃酮和酚類化合物有關(guān)(Park等, 2002)。</p><p>　　乙醇蜂膠溶液是由使用500瓦馬達的臺架攪拌機粉碎、勻化、在半分析天平上稱量過并混合了80%乙醇的天然蜂膠制成的?；旌衔镌谑覝貤l件下存放7天并每天人工攪拌一次。此階段后，樣本以8800轉(zhuǎn)離心分離20分鐘)。過濾上層清液并將其在4°C條件下冷藏3

88、小時，然后再次過濾以清蠟。最后，得到的提取物儲存于室溫條件下的黑暗中。</p><p>　　水溶劑的配制使用去離子水依照相同工序進行。每種溶液都以20%蜂膠和80%溶劑的比例配制成。兩種提取物都以它們的類黃酮和酚類化合物含量來評價，用來與濃縮產(chǎn)品比較。</p><p>　　2.2. 類黃酮總量測定</p><p>　　蜂膠溶液中的類黃酮總量由鋁絡合方法測定(Marc

89、ucci等,1998)。在此過程中，提取出的溶液以1:10(0.5 mL)的比例稀釋并混入0.1mL濃度為10%的硝酸鋁，0.1mL濃度為1 mol/L的乙酸鉀和4.3 mL濃度為80%的乙醇。樣本在室溫條件下放置40分鐘，吸收率為415nm。槲皮素作為標準產(chǎn)生校準曲線。三個讀數(shù)的平均值以毫克槲皮素當量為單位使用，類黃酮總量也用同樣的單位表述(mg/g)。</p><p>　　2.3. 酚類化合物測定</p

90、><p>　　蜂膠溶液中的多酚由比色法測定(Kumazawa等,2004)。按照此過程，提取出的溶液先以1:10 (0.5 mL)的比例稀釋，然后混入0.5mL 試劑和0.5 mL濃度為10%的Na2CO3。在室溫條件下培養(yǎng)1小時候吸收率為760nm。沒食子酸作為標準產(chǎn)生校準曲線。三個讀數(shù)的平均值以毫克沒食子酸當量為單位使用，酚類化合物總量也用同樣的單位表述(mg/g)。</p><p>　　

91、2.4. 高效液相色譜法測定</p><p>　　存在于最初提取物、滲透物和濃縮產(chǎn)品的化合物是由Park等人(1998)描述的高效液相色譜法測定的。每種溶液取三百微升注入一臺連接著二極管陣列檢測器的波長260 nm的液相色譜儀。流動相為水/乙酸(19:1, v/v) (溶劑A)和甲醇(溶劑B)，恒定流動速率為1 mL/min。梯度在開始時為30%濃度的溶劑B，45分鐘后變成60%，85分鐘后變成75%，95分鐘后

92、變成90%，105分鐘后回到30%。列保持恒溫30 °C，色譜使用計算機軟件色譜工作站進行處理。初始和濃縮樣本在1.5 mL蒸餾水中稀釋，滲透樣本不經(jīng)稀釋直接注入。以下酚酸和類黃酮的真實性標準受到檢驗： Q鍵香豆酸, 阿魏酸、肉桂酸、沒食子酸、槲皮素、山柰酚、山柰素、芹菜素、 異鼠李素、鼠李素、野櫻素、異野櫻素、橙皮苷、橙皮素、松屬素、白楊素、刺槐素、 高良姜素、楊梅黃素、楊芽黃素和阿替匹林C，因為它們與蜂膠中存在的最常見化合

93、物對應。</p><p><b>　　2.5. 膜濃縮</b></p><p>　　在此研究中，蜂膠提取物使用中試切向過濾系統(tǒng)濃縮，使用示意圖1所示的納濾膜。試驗在適用批循環(huán)模式的中試設(shè)備上進行，這種模式意味著滲透物和濃縮物都能夠被送回給水箱。滲透物在一次試驗中就被完全移除了，在此試驗中需要獲取濃縮產(chǎn)物。納濾模塊配備的是NF90膜，這種膜由聚砜和聚酰胺組成，過濾面積為

94、0.6m2，在一次在條件為20 °C和6.0巴使用螺旋模塊進行的試驗中硫酸鎂的截留率為98%。</p><p>　　大約5.0 L每種溶液用了超過30分鐘時間滲透過膜，這段時間正是在開放系統(tǒng)中完成濃縮過程所需的時間，也就意味著滲透物都在過程中被移除。試驗中，滲透物被移除，滲余物重新循環(huán)直到一個濃縮因素達到4左右。這個濃縮因素根據(jù)方程(1)計算：</p><p>　　式中Vf為給水

95、箱的總?cè)莘e，Vc為濃縮餾分的體積，F(xiàn)c為濃縮因素。</p><p>　　其他試驗在不同溫度(20–45 °C)和壓力(2.0–5.0巴)下進行，目的是評估這些參數(shù)對滲透量和濃縮產(chǎn)物質(zhì)量的影響。在這些試驗中，滲透物和滲余物都維持在封閉系統(tǒng)的再循環(huán)下。滲透量根據(jù)以下公式計算：J</p><p>　　J=Vp/t*Ap (2)<

96、/p><p>　　式中Vp為在間隔時間t里收集的滲透物體積，Ap為滲透膜表面積。</p><p>　　過濾過程的質(zhì)量根據(jù)滲透物中存在的類黃酮和酚類化合物的數(shù)量而衡量，如2.2–2.4節(jié)中所描述的那樣評估，效率根據(jù)通量滲透速率和截留指數(shù)衡量。該指數(shù)衡量滲透物和濃縮液中化合物數(shù)量之間的關(guān)系，這展示了膜在實驗條件下</p><p>　　圖1 納濾膜單元的原理圖</p&g

97、t;<p>　　截留該化合物的能力。該指數(shù)根據(jù)公式(3)計算，式中R為截留指數(shù)，Cp為滲透物中化合物的濃度，Cr為滲余物中相同化合物的濃度：</p><p>　　R=1-Cp/Cr (3)</p><p>　　了解出現(xiàn)在膜過程中的污染速率是很重要的，測量改速率的一種方法是比較在此研究下的溶液的滲透量和用水作為液料、在不同壓力下的滲透量。通常，系統(tǒng)壓力的變化

98、會導致滲透量的正比例變化。污染影響根據(jù)水溶蜂膠提取物的滲透量和僅用蒸餾水、壓力從1.0巴增加到5.0巴的流量之間的比較而進行衡量。</p><p><b>　　3. 結(jié)果與討論</b></p><p>　　膜過程用水溶液和乙醇溶液在封閉系統(tǒng)中進行。在此系統(tǒng)中，滲余物和滲透流被導回并混入一個與環(huán)境隔絕的給水箱，用來評估滲透量隨時間的變化。溫度保持在20 °C，

99、壓力保持在5.0巴。結(jié)果如圖2所示：</p><p>　　工藝穩(wěn)定化后，進行約15分鐘后，滲透量開始下降。乙醇提取物的下降率高于水溶提取物，證明了乙醇溶液的污染率更高。進行20分鐘后，滲透量趨于穩(wěn)定，即，濃差極化已經(jīng)發(fā)生且污染并未隨時間增加。乙醇和水溶液在穩(wěn)定區(qū)域的滲透量分別為12.0 L/h m2和25.0 L/h m2。溶液間不同的滲透量可根據(jù)它們的不同成分解釋：乙醇提取物包含更多的低分子化合物，因此更難濃縮