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Biosystems Engineering (2006) 93 (4), 383–391 doi:10.1016/j.biosystemseng.2006.01.008 PH—Postharvest Technology

Molecular for recovering Tocopherol and Fatty Acid Methyl Esters from Rapeseed Oil Deodoriser Distillate

S.T. Jiang1,2; P. Shao1; L.J. Pan1,2; Y.Y. Zhao1,2

1School of Biotechnology and Food Engineering, Hefei University of Technology, Hefei 230009, China; e-mail of corresponding author: [email protected] 2The Key Laboratory of Agricultural Production Biochemistry of the Ministry of Education, Hefei 230069, China

(Received 28 February 2005; accepted in revised form 10 January 2006; published online 9 March 2006)

Tocopherol and fatty acid methyl esters (FAME) were recovered through a process involving acid-catalysed methyl esterification and crystallisation of sterols followed by molecular distillation from rapeseed oil deodoriser distillate (RODD), a by-product of vegetable refining edible oil. The effects of evaporating temperature, feed flow rate and wiper rolling speed on yield of tocopherol were systematically studied by response surface methodology (RSM) based on the separation of fame previously. The first fraction, which was collected at 50 1Cat266 Pa, contains mainly hydrocarbons, ketones and aldehydes. The second fraction, which was collected at 100–110 1Cat532 Pa, contains mainly FAME and the content of FAME in the second distillate was above 90% by analysis of gas –mass spectrometry (GC–MS). The fraction collected at 200–230 1Cat266 Pa was rich in tocopherol (nearly 35%). The overall recovery of tocopherol and FAME were around 50% and 90%, respectively, of the original content in RODD. r 2006 Silsoe Research Institute. All rights reserved Published by Elsevier Ltd

1. Introduction are palm oil for obtaining provitamin A, oils of rice for the oryzanol recovery and natural tocopherols from Molecular distillation is characterised by short vegetable-oil deodoriser distillate, a by-product of the exposure of the distilled liquid to elevated temperatures, vegetable oil-refining process, composed of fatty acids, high vacuum in the distillation space, and a small sterols, tocopherol, sterol esters, hydrocarbons, break- distance between the condenser and (Shima- down products of fatty acids, aldehydes, ketones and da et al., 2000; Ibanez et al., 2002). The short residence acyl glycerol species. Compounds such as tocopherol, of the liquid on the evaporating cylinder, in the order of sterol and fatty acid methyl esters (FAME) are of a few seconds to 1 min, is guaranteed by distributing the interest as high value-added products because of their liquid in the form of a uniform thin film. By reducing the nutraceutical activities (Kusdiana & Saka, 2004). pressure of non-condensable gas in the evaporator to Fatty acids constitute 25–75% of the distillate lower than 01 Pa, a reduction in distillation tempera- depending on the raw material being refined, the type tures can be obtained. Molecular distillation shows of refining process and the conditions employed therein. promise in the separation, purification and concentra- Recently, fatty acids from deodoriser distillate are only tion of natural products, usually composed of complex limited to the use of non-food, low-cost applications and thermally sensitive molecules. Furthermore, this because they are contaminated. Within the past three process has advantages over other techniques that use decades, interest in reducing air pollution and in solvents as the separating agent, avoiding problems with developing domestic energy sources has encouraged toxicity (Lutisan et al., 2002). research in many countries toward developing non- The substitution of conventional materials used in the petroleum fuels for internal combustion engines; it has nutrition, pharmaceutical, and cosmetic areas by natural been shown that the simple alcohol esters of fatty acids products has gained interest and importance. Examples (FA) are acceptable alternatives diesel fuels. Biodiesel is

1537-5110/$32.00 383 r 2006 Silsoe Research Institute. All rights reserved Published by Elsevier Ltd

转载 ARTICLE IN PRESS 中国科技论文在线 http://www.paper.edu.cn 384 S.T. JIANG ET AL. made from agricultural materials, which are produced standard. All other chemicals and reagents were of via photosynthetic carbon fixation; its combustion does analytical grade. Rapeseed oil deodoriser distillate came not contribute to net atmospheric carbon dioxide levels. from Fenda Oil and Fat Ltd (Hefei, China). Its immediate application would be in the blend with diesel, with a value that can reach up to 20%. Initial efforts at producing biodiesel employed refined edible 2.2. Esterification of rapeseed oil deodoriser distillate oil and animal fats as feedstocks for fuel synthesis. More recently, methods have been developed to produce Rapeseed oil deodoriser distillate contained free fatty FAME from cheaper material, such as spent restaurant acids (FFA), neutral glycerides including monoacylgly- grease and waste edible oil (Hass et al., 2003). In this ceride (MAG), diacylglyceride (DAG) and triacylglycer- study, the potentiality of the process for recovering ide (TAG), and unsaponifiable matters. Sulphuric acid catalysed methylation of the FFA in deodoriser distillate biodiesel (FAME) from rapeseed oil deodoriser distillate 1 (RODD) was presented by converting the fatty acids to (methanol/deodoriser distillate in ml g at 100/100) was biodiesel (FAME). conducted in vigorously shaken glass screw-capped containers at 65 1C in the presence of sulphuric acid Some technical information is available pertaining to 1 the recovery of tocopherol, sterols and FAME, invol- (sulphuric acid/deodoriser distillate in ml g at 4/100) ving a series of chemical and physical processing steps with N2 in gas (Shao et al., 2004). (Ibanez et al., 2002; Mendes et al., 2002). These techniques are used alone or in combination with 2.3. Crystallisation of sterols others, including solvent extraction (Iglesias & Lozano, 2004), urea complexation (Udaya & Fereidoon, 1999). The yield and recovery for crystallisation of sterols However, they involved energy consuming, labour- have been studied as follows: the acetone was used as intensive and low recovery of tocopherol. Recently, it solvent, with crystallisation temperature at 5 1Cand was reported that lipase-catalysed methyl esterification crystallisation time of 3 h. A recovery of sterols as high as followed by molecular distillation are very effective for 85% was achieved by using a single-stage batch crystal- enrichment or purification of useful components in lisation of the solvent/material mixture (mass ratio of deodoriser distillate (Ghosh & Bhattacharyya, 1996; 10:1) (Moreira et al., 2004).The products were defined as Kusdiana & Saka, 2004; Ramamurthi & McCurdy. RODD fatty acids and tocopherol concentrate. 1993). However, the large scale of the lipase reaction is difficult because of lipase characteristics and high costs of lipase. Hence, industrial purification of tocopherols 2.4. Distillation of tocopherol and ester fraction often adopts the acid-catalysed esterification to enhance the profit in the developing countries. Few studies on the The FAME and tocopherol, obtained from RODD optimisation of recovering tocopherol and FAME from sample by the combination of methyl esterification and RODD have appeared in the literature. There appears crystallisation of sterols were fractionally distilled in a to be a need for the optimisation of methyl esterification wiped-film molecular distillation (Fig. 1). The first that is more suitable for the guidance of production. fraction, which was collected at 50 1Cat266 Pa, Taking all of these concerns into consideration, in the contains mainly hydrocarbons, ketones and aldehydes. present work, a molecular distillation process for The fraction from 100 to 140 1Cat532 Pa was collected recovery of tocopherol and FAME from RODD has as the second fraction, which was rich in FAME. And been put forward by a combination of acid-catalysed the third fraction was collected at 170–230 1Cat266 Pa methyl esterification and crystallisation, followed by was rich in tocopherol and collected by changing the of the derived product. collecting flask. The evaporating temperature, wiper rolling speed, feed temperature and feed flow rate were investigated systematically on the recovery of FAME 2. Materials and methods and tocopherol. The feed, residue and two fractions were cooled to room temperature, weighed and analysed 2.1. Materials and reagents for FAME, tocopherol, and sterol content according to the methods described below. Palmitic, stearic, oleic, linoleic acid methyl esters, a,g,d-tocopherol, b-sitosterol, stigmasterol, and campes- 2.4.1. Experimental design for the separation of fatty terol were obtained from Sigma Chemical Co.(St Louis, acid methyl ester and tocopherol USA). They were mixed in amounts proportional to The effects of evaporating temperature, feed flow rate, their mass abundance in RODD which served as vacuum and wiper rolling speed were investigated on the ARTICLE IN PRESS 中国科技论文在线 http://www.paper.edu.cn RECOVERING TOCOPHEROL AND FATTY ACID ESTERS 385

Table 1 Independent variables and their levels for central composite b a design

Independent variables Variable levels

10+1

Evaporating temperature X1, 1C 170 200 230 1 Wiper rolling speed X2, min 50 150 250 1 c Feed flow rate X3,ml min 30 90 150

responses, namely Y1 and Y2. The model proposed for d each response of Y was h j Y ¼ A þ A X þ A X þ A X þ A X X þ A X X e i 0 1 1 2 2 3 3 4 1 2 5 1 3 f 2 2 2 k þ A6X 2X 3 þ A7X þ A8X þ A9X ð2Þ g 1 2 3

Fig. 1. Schematic diagram of wiped-film molecular :(a) where: A0 is a constant; A1, A2, and A3 are linear motor drive; (b) feed flask; (c) wiper; (d) residue receiver; (e) coefficients; A4, A5, and A6 are cross-product coeffi- distillate receiver; (f) one-stage condenser inlet; (g) one-stage cients; and A , A and A are quadratic coefficients. condenser outlet; (h) two-stage condenser inlet; (i) two-stage 7 8 9 condenser outlet; (j) cold trap; (k) rotary vane vacuum pump The goodness of fit of the model was evaluated by the coefficient of determination R2 and the analysis of variance (ANOVA). Quadratic polynomial equations were obtained by holding one of the independent separation of FAME by single factor analysis. A central variables at a constant value and changing the level of composite design was employed to study the response, the other variables. namely tocopherol concentration after distillation Y1 in % by wt and recovery of tocopherol Y2 in % by wt [see Eqn (1)]. The independent variables were X1, X2 and X3 2.5. Determination of acid value and saponification value representing evaporating temperature, wiper rolling speed and feed flow rate, respectively. The settings for Acid value and saponification value were determined the independent variables were as follows (low and high by standard method (Ru, 2003). values): evaporating temperature of 170 and 230 1C; wiper rolling speed of 50 and 250 min1; feed flow rate of 30 and 150 ml h1. Each variable to be optimised was 2.6. Gas chromatography—mass spectrometry analysis coded at three levels: 1, 0 and +1. Three replicates at of fatty acid methyl ester the centre (0,0,0) of the design were performed to allow the estimation of the pure error. The central composite The FAME composition of each deodoriser distillate design is shown in Table 1. All experiments were carried was determined by the following procedures. A Hewlett- out in a randomised order to minimise the effect of Packard model HP 6890 gas chromatograph with a mass unexpected variability in the observed response due to spectrometer (GC–MS), detector model (electron impact, extraneous factors. 70eV)andaDB-5(30mby025 mmby025 mm) capillary column was used. Injection was carried out at 250 1C. Y 2 ¼ðT DR=TROÞ100 (1) Helium was the carrier gas. The oven temperature was programmed from 180 1C for 3 min, and then from 180 to 1 1 where TDR and TRO are defined as the tocopherol 210 1Cat251Cmin ,from210to2801Cat251Cmin . content of tocopherol concentrate and RODD fatty The final temperature was maintained for 3 min. Some acids and tocopherol concentrate, respectively. 2ml of extracts obtained by wiped-film molecular distilla- tion and diluted with hexane were injected. The target 2.4.2. Statistical analysis compounds were identified by mass spectrometric in both As for the optimisation for purification of tocopherol SCAN (total number of ions) and selected ion monitoring by molecular distillation, the responses were analysed (SIM) mode. Spectra of the compounds were obtained and using Matlab software. A quadratic polynomial regres- compared with those in the US. National Institute of sion model was assumed for predicting both Y Standards and Technology (NIST) library. ARTICLE IN PRESS 中国科技论文在线 http://www.paper.edu.cn 386 S.T. JIANG ET AL.

2.7. The gas chromatography analysis of fatty acid Table 2 methyl ester Composition of rapeseed oil deodoriser distillate Component Content, % The FAME content was determined with a gas chromatography (Agilent 1790, Agilent, Shanghai, Sterol 1414 China) connected to a DB-wax capillary column (30 m Campesterol 352 b-Sitosterol 642 by 025 mmby025 mm) using a tricaproin as an internal Stigmasterol 420 standard. The column temperature was controlled as Tocopherol 414 follows: 05 min at 190 1C, 4 min to 210 1C, 10 min to a-Tocopherol 098 280 1C, and 2 min at 280 1C. The injector and detector g-Tocopherol 205 temperatures were 245 and 350 1C, respectively. d-Tocopherol 111

2.8. Analysis of tocopherol and sterol of evaporating temperature on the recovery of FAME and loss of tocopherol. The distilled FAME content A Waters series high performance liquid chromoto- increased with increasing temperature and reached graphy (HPLC) equipped with photodiode array detec- nearly steady state (39/100 g ml1) when the temperature tor was used to analyse sterol and tocopherol in the was 110 1Cat532 Pa. The tocopherol content in the RODD and distillate obtained using the molecular residue did not change much over the temperature range distillation technique described above. The separation tested. The effects of feed temperature were investigated column was Atlantis (Waters Co., Ireland) of 15 cm by next [Fig. 2(b)]. The temperature of a liquid entering the 025 mm by 025 mm. Samples were injected into the 20 ml evaporating cylinder of a molecular evaporator was one injection loop of the HPLC system. The mobile phase of the important technological parameters that deter- was methanol and water (96:4, ml ml1) at a flow rate of mined evaporator operation and it was useful to gently 1ml min1. Identification of compounds was achieved pre-heat the feed before it entered the evaporator in by comparing their retention timesd spectra with those appropriate front-end heat exchanger to a temperature of standards. For quantitative analysis, calibration close to the asymptotic temperature. Figure 2(b) shows a curves were prepared by analysing different concentra- typical feed temperature course under these conditions. tions of tocopherol and sterol standards and by Recovery of FAME in the distillate increased to 0385 g representing peak area versus concentration. Detection ml1. When the feed temperature was 80 1C, the loss of for tocopherol and sterols was performed at their tocopherol was about 012%. The effects of rolling adsorption maxima in the ultraviolet, that is, 296 and speed of wiped-film molecular still were investigated in 205 nm, respectively (Abidi & Mounts, 1997). Fig. 2(c). For the rolling speed used, it can be seen that Tocopherol was expressed as a total tocopherol when the rolling speed is 150 min1, the loss of content (sum of a,g, and d-tocopherol) and the sterols tocopherol was very small although FAME could not as a sum of total sterol. The amounts of hydrocarbons eliminated. Based on the analysis above, the reaction and other components were estimated by different of conditions were determined as follows: evaporating total sterols and tocopherol from unsaponifiable matter. temperature 110 1Cat532 Pa, rolling speed of 150 min1 and feed temperature of 80 1C. The esters can be practically removed from the feed stream, 3. Results and discussion thereby concentrating the tocopherol by molecular distillation. The generated biodiesel presented light 3.1. Composition of rapeseed oil deodoriser distillate colour, similar to the refined rapeseed oil, and the colour number was determined according to GB25294 The results of sterols, tocopherols in RODD before of China. Here, the focus was on the tocopherol distillation are shown in Table 2. The acid value and recovery, this one much more thermally sensitive than saponification value of RODD were 8070 and biodiesel. The biodiesel recovery was easier and simpler. 15598 mg [KOH] g1, respectively. Total ion chromatography of FAME was illustrated in Fig. 3 by analysis of GC–MS. The components of 3.2. The recovery of fatty acid methyl ester from rapeseed biodiesel from deodoriser distillate and part properties oil deodoriser distillate were shown in Tables 3 and 4, respectively. The content of biodiesel accorded with the rapeseed oil components. Several factors affecting the FAME treatment of Palmitic methyl ester was the main fatty acid methyl RODD are shown in Fig. 2. Figure 2(a) shows the effect ester (3361%) and erucic methyl ester (739%) was ARTICLE IN PRESS 中国科技论文在线 http://www.paper.edu.cn RECOVERING TOCOPHEROL AND FATTY ACID ESTERS 387

48 4 3.3.1. Model fitting Table 5 showed the responses, i.e. the concentration

1 40 3 of tocopherol Y and recovery of tocopherol Y after

− 1 2 l molecular distillation. The response and variables were 2 32 fitted to each other by multiple regressions. A good fit

g 100 m was obtained. 24 1 in the distillate, % Tocopherol content Recovery of FAME, Y 1 ¼ð35 þ 012125X 1 þ 014125X 2 02875X 3 16 0 90 100 110 120 130 140 02425X 1X 2 þ 035X 1X 3 0025X 2X 3 Evaporating temperature of 2 2 2 294125X 1 056625X 2 125875X 3Þ=100 (a) wiped-film molecular still, °C ð3Þ 40 0.20 Y 2 ¼ð87833 þ 62X 1 1875X 2 05X 3 005X 1X 2 þ 045X 1X 3 þ 105X 2X 3 1 −

l 38 0.16 2 2 3 4266X 1 2266X 2 601667X 3Þ=100 ð4Þ 0.12

g 100 m 36 2

in the distillate, % The value for R and small probability P (Po005 Tocopherol content Recovery of FAME, 0.08 34 when significant) were 09176 and 00294 for Eqn (3), 40 50 60 70 80 90 and 09378 and 001533 for Eqn (4), respectively. Also, Feed temperature of the predicted results, according to models for concen- (b) wiped-film molecular distillation, °C tration and recovery of tocopherol, were close to the observed experimental responses. These indicated that 42 1.8 the generated models adequately explained the data variation and significantly represented the actual re-

1 41 . − 1 5 lationships between the reaction parameters. l 40 1.2 3.3.2. Effects of parameters

g 100 m 39 Many parameters can influence the separation per- in the distillate, % 0.9 Tocopherol content formance of tocopherol. The most important para- Recovery of FAME, 38 meters were evaporator temperature, feed flow rate, 40 80 120 160 200 240 vacuum and wiper rolling speed. For practical opera- Rolling speed of wiped-film − tion, the lowest vacuum (266 Pa) should be used to (c) molecular still, min 1 maximise the separation efficiency. Fig. 2. The effects on the recovery of biodiesel (m) and Equations (3) and (4) showed that concentration and tocopherol (J) of: (a) evaporating temperature; (b) feed recovery of tocopherol have a complex relationship with temperature and (c) wiper rolling speed independent variables that encompass both first- and second-order polynomials and may have more than one lower, because the raw material was the low erucic acid maximum point. Analysing the contour plots for rapeseed seed. From Table 4, it was shown the obtained concentration and recovery of tocopherol was the best FAME in the present study was acceptable as an way to evaluate the relationships between responses, alternative diesel fuel. variables and interactions that existed herein. The three- dimensional response surfaces were plotted in Figs 4–7, as a function of the interactions of any two of the 3.3. The recovery of tocopherol from rapeseed oil variables by holding the other one at high value. All four deodoriser distillate plots in Figs 4–7 showed similar relationships with respect to the effects of each variable. The response Since FAME were the most volatile components and obtained were convex nature suggesting that there were were recovered first at lower temperature, they were well-defined optimum operating conditions. However, omitted in order to facilitate the recovery of tocopherol. the convexity was not high enough, as the surfaces were By increasing the evaporating temperature, it was rather symmetrical and a little flat near the optimum possible to recover in the vapour phase with MAG which meant that the response optimised value based on and DAG. Phytosterols were recovered in the liquid combined effects evaporating temperature, feed flow phase also called residue. rate and feed temperature may not vary widely from the ARTICLE IN PRESS 中国科技论文在线 http://www.paper.edu.cn 388 S.T. JIANG ET AL. single variable optimised conditions. Figures 4 and 6 whereas, in Figs 4, 5 and 7, evaporating temperature revealed that wiper rolling speed did not show sig- showed significant variation both above and below the nificant variation on the concentration of tocopherol, optimum values. With the increase of temperature, an

8.65 100 1295

11.28 336

10.97 799 14.32 298

12.83 Relative intensity, % 126 7.18 137

. 3.64 5 54 11 12

0 5.00 10.00 15.00 20.00 25.00 Time, min Fig. 3. Total ion gas chromatogram of fatty acid methyl ester

Table 3 The components of biodiesel from deodoriser distillate and relative content t, min Component Molecular formula Molecular weight Relative content, %

718 Hydrocarbon C20H38 2782990 401 865 Palmitic methyl ester C17H34O2 2702559 3361 1097 Linoleic methyl ester C19H34O2 2942559 1825 1108 Oleic methyl ester C19H36O2 2962694 1614 1128 Stearic methyl ester C19H38O2 2982872 881 1283 Gondoic methyl ester C21H40O2 3243005 378 1432 Erucic methyl ester C23H44O2 3523341 739

Note: The content of erucic acid methyl ester in rapeseed oil deodoriser distillate is 302%.

Table 4 The properties of biodisel, No.0 diesel and their mixture

Physical–chemical properties Biodiesel No.0 diesel(GB25294) Mixture of biodiesel and diesel

Density at 25 1C, kg m3 87825 85832 86075 Viscosity at 25 1C, mPa s2 800 736 754 Cold filter plugging point, 1C 400 400 200 Colour number 1500 1600 1600 Acid value, mg [KOH] g1 066 049 054

Note: Colour number means the colour of diesel determined by GB25294, China. The mixture of biodiesel and diesel is composed of biodiesel and No.0 diesel with ratio of 1:1 (v/v). ARTICLE IN PRESS 中国科技论文在线 http://www.paper.edu.cn RECOVERING TOCOPHEROL AND FATTY ACID ESTERS 389

Table 5 Central composite design and experiment data

Run Independent variables Responses

Evaporating temperature Wiper rolling speed Feed flow rate (X3), Y1 %Y2 % 1 1 (X1), 1C (X2), min ml min 10 1 13350 850 20 113463 820 30 1 13320 750 40 1 13280 762 5 1013090 720 6 1012940 700 71 0 13150 842 81 0 13140 840 9 1 103120 752 10 1103260 757 11 1 103087 870 12 1 1 0 3130 873 13 0 0 0 3540 874 14 0 0 0 3470 881 15 0 0 0 3490 880

31 250 32 32 5 5 . . 33 32 33 . . 5 5 5 31 . 33 30 31 32

31 32 31 30 140

32 1 31 33 − 200 1 − 120 33 34 h l 33 34

31 32 31 32 32 33 32

. . . 30 5 . 5 5

5 31 31 100 32

150 .

5

34 33 80 32 33

3 100 3 Rolling speed, min 31 32 32 5 5 34 . . 60 29 . 33 30 . 32 32 5 5 Feed flow rate, m 31 32 31 . . 5 30 5 31 34 31 50 40 170 180 190 200 210 220 230 33 32 170 180 190 200 210 220 230 Evaporating temperature, °C Evaporating temperature, °C

. 33 34 5 34 . 34 32 5 35 33 33.5 32 34 33 32 . 33 31 5 32.5 31 32 31 31 32

tocopherol, % 30

Concentration of . 30 . 30 5 tocopherol, % 31 5

29 Concentration of 250 29 31 30 150 Rolling sp 240 200 Feed flow 240 30.5 150 220 29.5 100 220 200 200 eed, min100 180 rate, m50 180 30 50 160 °C 0 160 °C − l − 1 Evaporating h 1 Evaporating temperature, temperature,

Fig. 4. Contour plot and response surface curve showing Fig. 5. Contour plot and response surface curve showing predicted response surface of yield of tocopherol as a function predicted response surface of yield of tocopherol as a function of evaporating temperature and rolling speed (feed flow rate of of evaporating temperature and feed flow rate (wiper rolling rate 150 ml h1, feed temperature of 80 1C) of 250 min1, feed temperature of 80 1C) ARTICLE IN PRESS 中国科技论文在线 http://www.paper.edu.cn 390 S.T. JIANG ET AL.

. 31 30. 3 250 30 8 . 31 8 0.6 80 31 2 68 31.2 70 140 31 31.4 74 76 78 .2 31.4 31 31.6 31 82

. 1 4 31. 72

. −

1 31 . 6 31 8 6

− 120 31 31. 31 82 8 . 200

h 32 4 l

. 8 80 31 32 31 100 31

.

. 78 6 76 8 32 74 . 8 32 150 80 31

72 32 . 4 82 31 31.8 . 31 60 31 . .6 31 8 .6 80 4 31 100 Feed flow rate, m 31. . 2 31 6 . 31 3 . 4 78 1 31 31 76 4 74 . 70 40 31.2 31 2 rolling speed, min Wiper 30. 31 .8 .6 30.6 8 31 30 30 72 82 50 100 150 200 250 50 Wiper rolling speed, min−1 170 180 190 200 210 220 230 Evaporating temperature, °C

32 32.5 31.8 82 . 85 32 31 6 80 31.4 80 31.5 78 31.2 31 75 76 31 . tocopherol, % 30 5 70 74 Concentration of 30.8 30 150 30.6 65 72

250 Recoveryof tocopherol, % Feed flow100 rate, m 250 200 30.4 200 240 70 50 150 220 100 Wiper rolling150 −1 200 0 50 speed, min 100 180 68 l − Wiper rolling ° h 1 50 160 C − Evaporating speed, min 1 temperature, Fig. 6. Contour plot and response surface curve showing predicted response surface of yield of tocopherol as a function Fig. 7. Contour plot and response surface curve showing of wiper rolling speed and feed flow rate (evaporating predicted response surface of recovery of tocopherols as a temperature of 230 1C, feed temperature of 80 1C) function of evaporating temperature and wiper rolling speed (feed flow rate of 150 ml h1, feed temperature of 80 1C)

increase in the amount of condensate in the cold trap distillate). When the operating temperature was in- was observed; therefore, this may influence the risk of creased to 230 1C, part of phytosterol and MAG began evaporator temperature of volatiles into the pumps. A to be recovered in the vapour phase too; however, this temperature about 200 1C was therefore suggested. was not of interest because at this temperature, the The effect of wiper rolling speed was tested. The phytosterols started to distillate and this reduces the function of the roller was to distillate the material evenly purity of tocopherol. on the surface of the internal heating wall and to control the thick of the material film on the wall. There a certain 3.3.3. Verification of the model speed should be used to efficiently supply the materials By partial differential coefficient operation to this and maintain surface because noise was brought out model, and equal to zero, then the point of curved when fast wiper rolling speed is applied. From Figs 4 surface was determined (X 1 ¼ 0; X 2 ¼ 0; X 3 ¼ 0; Y 1 ¼ and 6, when the wiper rolling speed was about 35%; Y 2 ¼ 87833%). According to the response sur- 150 min1, tocopherol content was above 31%. face methodology (RSM) result, an experiment with an Recovery of tocopherols as a function of evaporating evaporating temperature of 200 1C, feed flow rate of temperature and wiper rolling speed (feed flow rate of 90 ml h1 and wiper rolling speed of 150 min1 was 90 ml h1) is shown in Fig. 7. It can be observed in Fig. 4 conducted in order to investigate the effect of RSM. The that for a feed flow rate of 90 ml h1 and evaporator experiment was carried out at the optimised conditions. temperature of 200 1C, the tocopherol content was The content and recovery of tocopherol was above almost 35% recovered in the vapour phase (also called 347%, 895% after molecular distillation and was in ARTICLE IN PRESS 中国科技论文在线 http://www.paper.edu.cn RECOVERING TOCOPHEROL AND FATTY ACID ESTERS 391 good agreement with the predicted one. The model Hass M J; Michalski P J; Runyon S; Nunez A; Scott K M equation developed can be used for predicting purifica- (2003). Production of FAME from acid oil, a by-product of tion of tocopherol. vegetable oil refining. Journal of the American Oil Chemist’s Society, 80, 97–102 Ibanez E; Benavides A M H; Senorans F J; Reglero G (2002). Concentration of sterols and tocopherols from olive oil with 4. Conclusions supercritical carbon dioxide. Journal of the American Oil Chemist’s Society, 79, 1255–1260 From the data obtained in this study, a process was Iglesias M T; Lozano J E (2004). Extraction and characteriza- proposed for recovering fatty acid methyl esters tion of sunflower pectin. Journal of Food Engineering, 62, (FAME) (purity: 490%) and tocopherol (pur- 215–223 ity:435%) from rapeseed oil deodoriser distillate. The Kusdiana D; Saka S (2004). Two-step preparation for catalyst- overall recovery of tocopherols and FAME were around free biodiesel fuel production. Applied Biochemistry and 50% and 90%, respectively, of the original content in Biotechnology, 113, 781–790 Lutisan J; Cvengros J; Micov M (2002). Heat and mass transfer raw material. Model of separation of tocopherol was in the evaporating film of a molecular evaporator. Chemical developed on the basis of the analysis of response Engineering Journal, 85, 225–234 surface methodology. The evaporating temperature was Mendes M F; Pessoa F L P; Uller A M C (2002). An economic the most important parameter about recovery of FAME evaluation based on an experimental study of the vitamin E and tocopherol. This process was feasible from an concentration present in deodorizer distillate of soybean oil economic point of view and was a promising measure using supercritical CO2. Journal of Supercritical Fluids, 23, for further utilisation of agricultural products. 257–265 Moreira E A; Baltanas M A (2004). Recovery of phytosterols from sunflower oil deodorizer distillates. Journal of the American Oil Chemist’s Society, 81, 161–167 Acknowledgements Ramamurthi S; McCurdy A R (1993). Enzymatic pretreatment of deodorizer distillate for concentration of sterols and This work was supported by Natural Science Foun- tocopherols. Journal of the American Oil Chemist’s Society, dation of Anhui Province (no. 03041302). And the 70, 287–295 authors gratefully acknowledge the contribution of the Ru Y J (2003). Analysis of Oil and Fat. 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