（節(jié)選）外文翻譯--從檸檬副產(chǎn)品中通過響應(yīng)曲面法酸化棗汁提取果膠的優(yōu)化程序（節(jié)選）

1、<p>　　中文2480字,1450單詞</p><p>　　本科生畢業(yè)設(shè)計（論文）外文資料譯文</p><p>　　畢業(yè)設(shè)計（論文）題目： 檸檬中果膠提取工藝的優(yōu)化探討 </p><p>　　學(xué)生姓名： 學(xué)號： </p>

2、<p>　　分 院： 班級： </p><p>　　指導(dǎo)教師： 職稱： </p><p>　　填表日期： 2014 年 12 月 29 日</p><p>　　Carboh

3、ydrate Polymers 74 (2008) 185–192</p><p>　　Optimization of pectin extraction from lemon by-product with acidi?ed date juice using response surface methodology</p><p>　　Manel Masmoudi a, Souhail

4、Besbes , Moncef Chaabouni , Christelle Robert ,</p><p>　　Michel Paquot , Christophe Blecker , Hamadi Attia</p><p><b>　　Abstract</b></p><p>　　Response surface methodology

5、 was used to optimize pectin recovery from lemon by-product using an acidi?ed date juice as extraction solution. When enriched in pectin, this latter can be useful for preparation of date-lemon jelly. The e?ects of three

6、 parameters namely temperature, pH and extraction time, on pectin extraction were studied. The ?tted mathematical model allowed us to plot response sur- faces as well as isoresponse curves and to determine optimal extrac

7、tion conditions. Results clearly</p><p>　　© 2008 Elsevier Ltd. All rights reserved.</p><p>　　Keywords: Pectin extraction; Lemon by-product; Acidi?ed date juice; Response surface methodology

8、</p><p>　　Introduction</p><p>　　Lemon (Citrus limon L.) and date (Phoenix dactylifera L.) have always played an important part in the economic and social lives in Tunisia. In fact, the productio

9、n of lemon and limes reached nearly 27,000 metric tons and that of the dates was about 125,000 tons in 2005 (FAOSTAT, 2006).</p><p>　　A large quantity of dates (about 30% of the total pro-</p><p&g

10、t;　　duction) is lost during picking, manufacture of some date products, or storage of second category dates which are generally discarded or partially integrated in animal feed (Besbes et al., 2006). Studies concerning t

11、he use of these by-products to develop new products are scarce and con- cern metabolites or biomass production (Abou Zeid,Abderrahman, & Baghlef, 1991; Besbes et al., 2006). Owing to their high content in sugar,

12、 dates were also used for the preparation of some food products, suc</p><p>　　Likewise, during citrus juice processing, a considerable quantity of wastes or by-products is generated. Though some portion of t

13、hese by-products is consumed as animal feed, the majority of the processing wastes are thrown out, and consequently pollutes the environment. Therefore, citrus-processing industries have been searching for appli- cati

14、ons for these by-products which have been revealed to be a source of many important natural compounds such as citric acid, ?avono¨?ds and especially pe</p><p>　　Pectins are complex polysaccharides from

15、higher plants, composed mainly of a-1,4-linked D-galacturonic acid (GalA) chains (so called homogalacturonan or smooth regions) in which the carboxyl groups of the Gal A can be free or methyl-esteri?ed. Pectins are also

16、constituted of hairy regions (also called rhamnogalacturonan I) with Gal A- rhamnose regions, where the rhamnose moieties can be substituted with neutral sugars (Voragen, Pilnik, Thibault, Axelos, & Renard, 1995). Pe

17、ctins are widely used i</p><p>　　Pectins may be obtained by extractions of the cell-wall material by hot dilute acid, by cold dilute sodium hydroxide or by solutions of chelating agents (Levigne, Ralet, &a

18、mp; Thibault, 2002). Commercial pectins are extracted at high temperatures by hydrolyzing protopec- tin using acids such as sulfuric, phosphoric, nitric, hydro- chloric or citric acid (May, 1990; Minkov, Minchev, & P

19、aev 1996). After concentration, the pectin is precipitated by addition of alcohol, dried, ground and ?nally sieved</p><p>　　& Pouillaude, 1985; Pagan & Ibarz, 1999; Yapo, Robert, Etienne, Wathelet, &

20、amp; Paquot, 2007). Pagan and Ibarz (1999) extracted pectin from fresh peach pomace at dif- ferent experimental conditions and found that the highest yields were obtained at the highest temperatures and at the lowest as

21、sayed pH. El-Nawawi and Shehata (1987) who studied the e?ect of experimental conditions on the yield of pectin extracted from Egyptian orange, found an optimum yield at 90 °C, a pH of 1.7 and 2 h of extrac</p

22、><p>　　The aim of this study was to look for the experimental</p><p>　　conditions leading to the maximum pectin extraction from lemon by-product using an acidi?ed date juice as extraction solution.

23、 This latter, enriched with lemon pectin and ?a- vour, has been selected as it will be used in a subsequent study for the formulation of date-lemon jelly. As many fac- tors can in?uence the extraction yield, response sur

24、face methodology (RSM) was applied to ?t and exploit a math- ematical model representing the relationship between the response (extraction yield) and vari</p><p>　　Material and methods</p><p>　　

25、Experimental section</p><p>　　Lemon by-product</p><p>　　One batch of 25 kg of lemon by-product (Citrus limonL.) was supplied by a fruit beverage industry (Zina, Sfax,Tunisia) using mixed lemon v

26、arieties from Nabeul region (Tunisia). This by-product consists of the peel, the pulp and the pips. Upon its arrival, the pips were discarded and the remaining matter was lyophilised and milled. The obtained powder was

27、sieved (60-mesh size screen) and stored at —20 °C until use.</p><p><b>　　Dates</b></p><p>　　Dates (Phoenix dactylifera L.) of ‘‘Deglet Nour” variety were provided by the Nationa

28、l Institute of arid zone (Deg- ach, Tunisia). We used a batch of 50 kg of dates of second category (hard texture) collected at the ‘‘Tamr” stage (full ripeness). Dates were directly pitted, washed in running tap water an

29、d dried 12 h in a drying oven at 45 °C. Then, the collected pulp was milled to obtain date paste.</p><p>　　Date juice preparation</p><p>　　Date juice was prepared by adding water to date pa

30、ste at a ratio of 3:1 (v/w) as described by Youssif, Alshaawan, Mininah, and Eltaisan (1987) and Youssif, Abou Ali, and Abou Idreese (1990). The date paste–water mixture was boiled gently with continuous stirring for 5 m

31、in. The extract was ?ltered through ?ne-mesh cheesecloth. The obtained date juice was stored at —20 °C until analysis and use.</p><p>　　Physico-chemical analysis of the lemon by-product, dates and date

32、juice</p><p>　　Dry matter was determined by drying samples at 106 °C to constant weights (AOAC, 1995). Ash content was deter- mined at 550 °C using a mu?e furnace (NABER, Ger- many) for 8 h. The to

33、tal ash was expressed as percent of dry weight (AOAC, 1995).</p><p>　　Protein (N × 6.25) was analysed according to the Kjeld- hal procedure (AOAC, 1995). The determination of the cel- lulosic content wa

34、s performed according to the Weende method (AOAC, 1995). Total carbohydrate was deter- mined with the phenol-sulfuric acid colorimetric method (Dubois, Gilles, Hamilton, Rebers, & Smith, 1956) using glucose as a stan

35、dard. Pectin content (galacturonic acids) was determined by the colorimetric method described by Englyst, Quigley, and Hudson (1994). The pH of the date</p><p>　　Pectin extraction</p><p>　　A pre

36、liminary study showed that pH, temperature and time were the main parameters a?ecting the yield of pectin extraction (unpublished results). Extractions at di?erent conditions were carried out in a glass ?ask immersed in

37、a water bath as follows: 12 g of lyophilised lemon by-product were stirred at 250 rpm (Stirrer Heidolph RZR 20051 elec- tronic, Germany) in 300 ml of the prepared date juice (solid–liquid ratio; 1:25; w/v). The pH of the

38、 mixtures (lemon by-product/date juice) was adjusted wi</p><p>　　The resulting slurries were allowed to cool to room tem-perature (25 °C) and ?ltered through a cheesecloth. The ?l-trate was centrifuged

39、at 20 °C for 30 min at 7000 rpm to remove solid particles. The supernatant was ?ltered again through Whatman ?lter paper N. 1 (Kim et al., 2004).</p><p>　　For pectin precipitation, two volumes of 96% w/

40、w etha- nol were added to one volume of pectin extracts, while gently stirring to break up the gelatinous lumps. The obtained mixture was kept for 1 h at 4 °C. Then, pectin gels were centrifuged at 5000 rpm, for 20

41、min at 10 °C. To remove the mono and disaccharides, the pectin precipitate was washed three times with 50%, 75% and 100% ethanol and centrifuged at 5000 rpm for 10 min at 10 °C. Finally, the obtained pectin was

42、 dried at 50 °C to a constan</p><p>　　The pectin extraction yield, subject of this study, was calculated as follows:</p><p>　　Yield (%) = (weight of the total soluble pectin — weight of dat