食品科學(xué)與工程專業(yè)外文翻譯--酶法提取大豆油的改進(jìn)（英文）

1、Hindawi Publishing Corporation International Journal of Agronomy Volume 2012, Article ID 543230, 7 pages doi:10.1155/2012/543230Research ArticleImprovement of Soybean Oil Solvent Extraction through Enzymatic Pretreatment

2、F. V. Grasso,1 P. A. Montoya,1 C. C. Camusso,1, 2 and B. G. Maroto1, 21Facultad de Ciencias Exactas, F´ ?sicas y Naturales, Universidad Nacional de C´ ordoba, Avenue Velez Sarsfield 1200, 5000 C´ ordoba, A

3、rgentina 2Facultad de Ciencias Agropecuarias, Universidad Nacional de C´ ordoba, Avenue Valpara´ ?so s/no, 5000 C´ ordoba, ArgentinaCorrespondence should be addressed to F. V. Grasso, fgrasso@agro.unc.edu.

4、arReceived 5 November 2011; Revised 14 February 2012; Accepted 6 March 2012Academic Editor: Bertrand Matth¨ ausCopyright © 2012 F. V. Grasso et al. This is an open access article distributed under the Creative

5、Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.The purpose of this study is to evaluate multienzyme hydrolysis as a

6、 pretreatment option to improve soybean oil solvent extraction and its eventual adaptation to conventional processes. Enzymatic action causes the degradation of the cell structures that contain oil. Improvements in terms

7、 of extraction, yield, and extraction rate are expected to be achieved. Soybean flakes and collets were used as materials and hexane was used as a solvent. Temperature, pH, and incubation time were optimized and diffusio

8、n coefficients were estimated for each solid. Extractions were carried out in a column, oil content was determined according to time, and a mathematical model was developed to describe the system. The optimum conditions

9、obtained were pH 5.4, 38?C, and 9.7 h, and pH 5.8, 44?C, and 5.8 h of treatment for flakes and collets, respectively. Hydrolyzed solids exhibited a higher yield. Diffusion coefficients were estimated between 10?11 and 10

10、?10. The highest diffusion coefficient was obtained for hydrolyzed collets. 0.73 g oil/mL and 0.7 g oil/mL were obtained at 240 s in a column for collets and flakes, respectively. Hydrolyzed solids exhibited a higher yie

11、ld. The enzymatic incubation accelerates the extraction rate and allows for higher yield. The proposed model proved to be appropriate.1. IntroductionSeed oils represent 70% of global oil production, of which 30% is soybe

12、an oil. Oilseeds are the most important export items in Argentina [1]. In oilseeds, the vacuoles within cells contain oil, and both cell walls and vacuoles have to be broken in order to improve solvent extraction. Theref

13、ore, the preparation of the seed before solvent extraction is critical to maximize oil recovery. An alternative pretreatment to facilitate the release of oil from the seed could be enzymatic degradation. In this way, the

14、 partial hydrolysis of soybean seed cell structures with appropriate enzymes would increase permeability, which would in turn increase mass transfer [2]. An enzymatic treat- ment stage could be incorporated for industria

15、l purposes without significant changes to conventional processes. The oil release obtained using this method could result in a higher extraction yield and/or smaller quantities of the organic solvents used [3].In solvent

16、 extraction, pretreated oilseeds (porous solid matrix) come into contact with a pure solvent or a solvent mixture (miscella) to transfer the oil from the solid matrix to the liquid medium. While the principle of extracti

17、on is relatively simple, it is a complex mechanism [4]. In order to describe this process, the mass transfer phenomena involved and the eventual resistance to mass transfer in the solid phase (solid soybean) and in the l

18、iquid phase (hexane) should be analyzed. This process involves several phenomena: oil is diffused through the internal pores to the surface of the solid (internal mass transport) and is then passed to the bulk liquid by

19、means of a convective mechanism produced by the concentration difference between the solution occluded in the pores and the bulk solution (external transport). Because the oil to be extracted is contained within an insol

20、uble solid network with occluded miscella, the diffusion occurs mainly between the occluded solution and the solid, greatly affecting the extraction rate since the solid matrix resists diffusive transport [5].Internation

21、al Journal of Agronomy 3proposed by many authors [12–14], and Carr´ ?n and Crapiste [4]:?c ?t = Def ?2c?x2 (1)with the following initial and boundary conditions for an unlimited and perfectly agitated volume of bulk

22、 liquid:for t = 0, c = co,for t > 0, c = 0, in x = ?l, x = l. (2)The solution to (1) was obtained for plate and sphere, according to the solid that was considered. The following was obtained by integrating each soluti

23、on and taking into account that the series obtained converge rapidly. For plate with thickness 2l,qq0 = 8π2 e?π2(Dt/(2l)2). (3)For sphere with radius r,qq0 = 6π2 e?π2(Def· t/r2). (4)Because the triglycerides present

24、 in vegetable oil have differ- ent molecular weights and structures, it is easier to measure the amount of oil in relation to solid mass. Therefore, the c/co concentration ratio was turned into a q/q0 quantity ratio in b

25、oth equations [12]. Equations (3) and (4) were linearized and represented according to time t. The slope of both lines was used to evaluate the effective diffusion coefficients.Mathematical Model for Column Extraction. T

26、he fixed bed was regarded as a section of an extraction column to which a steady stream of hexane, QLo, is supplied and from which the same flow of miscella, QL, is extracted. The mass balances for each phase were the fo

27、llowing. Solid:?dcSdt = kS ·AVS? ? cS ? Keq ·cL ? . (5)Liquid:dcL dt = ?QL ·cLVL + kL ·AVL? ? cS Keq ? cL?. (6)In the mass balance estimation, it was assumed that the bed was made up of porous particl

28、es-isotropic and spherical particles for collets with and without enzymatic pretreatment and for flakes with enzymatic treatment. The oil content in each of the solids is uniform in all particles, and the oil behaves as

29、a single component, since its triglycerides are highly soluble in hexane [12]. The solids contain macropores in which the oil globules reside; the solvent penetrates these pores and dissolves the oil instantly, forming t

30、he miscella (stagnant phase) [4, 15]. An equilibrium relationship is established between the oil content in the stagnant phase in the pores and the residual oil content in the solid. Theoil transfer occurs from the pores

31、 to the miscella due to the oil concentration gradient. The column length-particle diameter ratio is high enough to neglect the radial concen- tration gradient. The porosities of the bed and particle are uniform and cons

32、tant throughout the extraction process. No heat of mixing is produced, and the temperature is constant and uniform throughout the extraction. The equilibrium relationship determined experimentally includes the effect of

33、solid moisture; the volumetric flow is constant because the flow of pure hexane supplied into the system is equal to the flow of miscella extracted from the system. The mass transfer constants in the liquid were estimate

34、d using the empirical correlation for fixed beds proposed by Geankoplis [6] and the mass transfer constants in the solid phase were estimated by equaling (5) (mass balance) with the equations that describe the diffusive

35、phenomenon, taking into account the corrections due to material porosity [16]. The solution to (5) and (6) was numerically found using MatLab 2008a.3. Results and DiscussionOptimization of Enzymatic Treatment. The amount

36、 of oil that can be extracted from soybean flakes using the Soxhlet method is 16% on the dry basis (DB), and 18.54% (DB) for soybean collets. An increase in yield is observed for all experimental runs with enzymatic pret

37、reatment (see Table 2). The RSM analysis enabled us to obtain the experimental conditions for the enzymatic aqueous pretreatment, through which the maximum theoretical yield in oil (% DB) is obtained for each type of sta

38、rting material. The ANOVA analysis (see Table 3) was used to define the polynomial coefficients of the response.(a) Flakes. Both linear and quadratic effects of temperature were significant, exceeding 95% of confidence l

39、evel in both cases, and so did the quadratic effect of incubation time. For the pH variable, the variation was not statistically significant (P > 0. 05). It can also be inferred that there were no significant effects

40、for interaction terms between variables. Therefore, the response function was defined as Y(%) = 27.055 – 0.06 T – 3.68 T2 – 0.04 t2 + error.(b) Collets. The quadratic effects of temperature and incuba- tion pH were signi

41、ficant, exceeding 98% of confidence level in both cases, and so did the crossover effect of pH and incubation time. For the other linear terms, the variation was not statistically significant (P > 0. 05). It can also

42、be inferred that there were no significant effects for interaction terms between the temperature and incubation time variables. Therefore, the response function was defined as Y(%) = 26.566 + 0.186 pH· t – 3.10 T2 –

43、 0.7274 pH2+ error. As it can be observed, the P value indicates that the model is significant for all cases with more than 98% of confidence. On the other hand, the adequacy of the quadratic model with 98% confidence, a