The combined application of extrusion and enzymatic technology for extraction of soybean oil zy Suely Pereira Freitas, Leopold Hartman Sonia Couri, Fany H. Jablonka, and Carlos W. P. de Carvalho* zyx This paper desctibes a new technological process for soybean oil ex- traction. The process deals with the combined effect of thermoplastic extrusion of beans and the subsequent action of hydrolytic and pro- teolytic enzymes in aqueous medium to recover the oil, thus, avoid- ing solvent application. The thermoplastic extrusion is hndamental for the process, because it facilitates the zyxwvuts action of enzymes in oil con- taining cells, reduces the non-hydratable phosphatides and promotes protein denaturation by reducing the emulsion stability and thus en- hancing the oil extraction. The main parameters affecting the oil yield are: the temperature and diameter zyxwvutsrq of the die in the extrusion process, the dilution, the concentration of enzymes and the incuba- tion time of the enzymatic treatment.’Ihe highest yield was obtained under the following conditions: extrusion of beans at 9OoC and exit die of 6 mm, enzymatic incubation time of 6 h, extruded soylwater dilution ratio 1:lO and concentration of enzyme zyxwvutsrq 6%. With these con- ditions 88% of the oil were obtained after centrifugation. Moreover, the aqueous enzymatic extraction is easier than solvent extraction, and leads to high value products: a solvent-free meal more suitable for human consumption, a protein hydrolysate that can be used as in- gredient for liquid foods and an oil of better quality. The non-hydro- lyzed meal contains ca zyxwvutsrq 25% of original soybean protein and the resid- ual oil. The protein hydrolysate in the liquid phase contains ca 75% of the total protein in the original grain with a molecular weight be- low 20 kDa. 1 Introduction The conventional process for soybean oil extraction in- volves various stages of pre-treatment before solvent applica- tion. After being cleaned, dehulled and flaked the beans are fed into the expander and are heated. Initially developed for cooking of animal feed, expanders also inactivated trouble- some enzymes, such as urease in soybean and lipase rice bran. Extruders have been used in oilseed preparation since the early 1970s. The first application of extrusion for edible oil processing was with rice bran in 1964 [l]. High pressure, high temperature extrusion through small openings converts soy- bean into cooked and porous particles, deactivating lipoxyge- nases and increasing lecithin recovery. The extrudate was lar- ger, heavier and stronger than flakes and thus easier to process through a solvent extractor [2, 31. Previous studies on the application of enzymes for oil ex- traction from fruits and oilseeds have shown a higher quality of the oil and food and lower biochemical oxygen demand (BOD) and chemical oxygen demand (COD) values of the waste waters than for conventional processing [4,5]. Fullbrook [6] has developed a new process for soybean oil extraction by aqueous enzymatic treatment together with small quantities of organic solvent to extract released oil. * National Center for Food Technology Research, EMBRAPA- CTAA, Rio de Janeiro, Brasil. Kombinicrte Anwendung von Extrusion und Enzymtechnoiogie zur Extraktion von Sojaal. Dieser Beitrag beschreibt einen neuen tech- nologischen ProzeB zur Olextraktion aus Sojabohne. Der ProzeB beruht auf dem kombinierten Effekt der thermoplastischen Extrusion der Boh- nen und anschlieflenden Wirkung von hydrolytischen und proteolyti- schen Enzymen in wangem Medium, zur Gewinnung des 01s ohne Lo- sungsmitteleinsatz. Die thermoplastische Extrusion ist grundlegend fiir den ProzeB, da sie die Wirkung von Enzymen in Obenthaltenden Zellen erleichtert, den Anteil an nichthydrisierbaren Phosphatiden vemindert und die Proteindenaturierungunterstiitzt, indem sie die Emulsionsstabi- liEt erhoht und so die Olextraktion verbessert. Die Hauptpararneter,wel- che die Olausbeute beeinflussen, sind: die Temperatur und der Durch- messer des Extruders, die Verdiinnung,die Enzymkonzentrationund die Inkubationszeitbei der enzymatischen Behandlung. Die hochste Ausbeu- te wurde mit folgenden Bedingungen erreicht: Extrusion der Bohnen bei 9OoC und Ausgangsdurchmesserdes Extruders von 6 mm, Enzymmkuba- tionszeit 6 h, SojalWasser-VerduMungsverhiiltnis 1: 10 und Enzymkon- zentration 6%. Unter diesen Bedingungen wurden 88% des 01s nach dem Zentrifugieren erhalten. AuBerdem ist die wiil3rige enzymatische Extrak- tion einfacher als eine Losungsmittelextraktion und fiihrt zu hochwerti- gen Produkten: ein Losungsmittel-freies fZr den menschlichen Verzehr geeignetes Schrot, ein Proteinhydrolysat, das a)s Zusatz fiir fliissige Le- bensmittel venvendet werden kann und ein 01 besserer Qualitiit. D,? nichthydrolysierte Schrot enthiilt etwa 25% Originalsojaprotein und 01. Das Proteinhydrolysat enthiilt etwa zyxw 75Oh des Gesamtproteins des Aus- gangskoms mit einem Molekulargewicht unter 20 kDa. The present work shows the effects of processing soybean by thermoplastic extrusion followed by the action of hydro- lytic and proteolytic enzymes in aqueous medium to recover the oil. The study was conducted on a pilot plant scale (extru- sion) and laboratory scale (aqueous extraction). 2 Materials and Methods 2.1 Material Soybeans, cultivar BR 16 from the 1995/1996 crop were supplied by EMBRAPA-Serviqo de Produpio de Sementes Basi- cas-, (Ponta Grossa-PR, Brazil). Enzyme formulations were selected after preliminary runs with enzymes of different activities. Tab. 1 summarizes the se- lected enzymes for the treatment of soybean. 2.2 Methods The composition (water, protein, oil, carbohydrate and ash) of crude and extruded soybeans and meal was determined by standard methods of AOAC [7]. The amino acid composition of the hydrolyzed soluble fraction was analyzed using Amino Quant S2-1090. The oil for comparative studies was extracted by petro- leum-ether in a Butt apparatus. The filtered oil was analyzed by standard methods. For gas chromatography methyl esters were prepared according to Hartman and Lugo [8]; free fatty acids, peroxide values and phoshorus was analyzed according to AOCS-CaSa40 [9], IUPAC 2501 [lo] and Hurtman et al. [ll], FeWLipid 99 (1997). Nr. 9. S. 333-337 0 WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1997 0931-5985/97/0909-0333$17.50+.50~0 333