The present invention relates to a process for the production of a vegetable-oil product from oilseed, in which process the seed is comminuted and slurried in water and the slurry is treated so that the oil is detached from the seed tissue, whereafter the oil is separated from the aqueous phase and is refined to produce the final product. In addition, the inven¬ tion relates to a vegetable-oil product produced by the pro¬ cess.

Conventional methods for preparing vegetable oil are based on the separation, by extraction, of the oil from the other con¬ stituents of the seed. Before the extraction step, crushed seed is heated and pressed, and in certain cases these steps may substitute for the extraction. Organic solvents, such as hexane, have been used for the extraction.

The disadvantages of oil separation by extraction include the high capital costs of the necessary equipment, as well as high operating costs. In addition, solvent residues which may con¬ stitute a safety and health hazard and to which maximum values have therefore been set in legislation are left in the oil ob¬ tained and also in the seed material which is left over from the separation and is used for fodder.

In addition to the above-mentioned disadvantages, the pressing and extraction process involves a problem in that the phospho- lipids, i.e. phosphatides, present in the seed end up in the extract, together with the oil. In this case the phosphatides must be removed from the oil in the first step of the refining so that they will not disturb the subsequent steps of the re-

fining, in which the oil is purified of aldehydes and of free fatty acids, as well as of pigments.

The removal of phosphatides as part of oil refining has most commonly been carried out by using water or an acid. In each case, owing to their amphoteric character, the phosphatides hy- drolyze and become insoluble in oil. Thereupon they can be sep¬ arated from the oil by centrifugation, for example. Other meth¬ ods for removing phosphatides include the use of membranes ac¬ cording to GB Patent 7 421 813 and the adsorption methods using bleaching clay or silica according to US Patents 635762 and 823217.

The object of the present invention is to provide a method sim¬ pler than previous ones for the preparation of a vegetable-oil product, eliminating the separate phosphatide removal step be¬ longing to the refining. The process according to the inven¬ tion is characterized in that an enzyme is added to an aqueous slurry of the seed so that the oil is separated under its ac¬ tion to form a separate phase, whj-le the phosphatide present in the seed remains mainly in the aqueous phase, that the oil phase is separated and that the separated oil is transferred directly to physical refining, which consists of a treatment with an adsorbing agent and/or of deodorization.

What is accomplished with the enzyme addition according to the invention is that, as early as the primary oil separation step, the phosphatides remain in the aqueous phase left over from the separation, whereupon the obtained oil phase can, sub¬ stantially without intermediate steps, be transferred to the subsequent physical refining. For the physical refining there suffices, according to need, an adsorption treatment mainly for the removal of pigments and/or a deodorization for the removal of the aldehydes or free fatty acids present. Since

the separation of the oil phase from the aqueous phase can be by mechanical means, for example, by centrifugation, the use of an organic solvent for the extraction of the oil is avoided in the invention, as is also the separation of the oil from the solvent, and an oil is obtained which is completely devoid of hazardous solvent residues.

The mechanism of the enzyme action, which in itself in no way restricts the invention, in the separation of oil and the other constituents of seed according to the invention is obviously as follows. In seed, such as rapeseed, oil. is pres¬ ent in the cytoplasm of the seed tissue, in the form of small bodies separated from each other by monomolecular phosphatide layers. Under the action of the enzymes, the said walls be¬ tween the bodies are hydrolyzed, breaking down so that the oil can separate from the cytoplasm. The hydrolyzing phosphatides at the same time become insoluble in the oil phase. The phos¬ phatides thus remain, dissolved, in the aqueous phase and are separated from the oil definitively in the centrifugation or other such mechanical separation. According to the observa¬ tions made, an oil phase which has been separated according to the invention by an enzyme treatment and centrifugation has an even lower phosphatide content than has an oil which has been separated from seed by conventional prior-art methods and has been treated separately for the removal of phosphatides.

With respect to the state of the art it should be noted that the use of enzymes in the treatment of oilseed is not in it¬ self novel but a procedure known per se. For example, GB Appli cation 2 127 425 discloses a method in which an enzyme is used to promote the extraction of oil by means of hexane. Further¬ more, enzymes have been used in the separation of coconut oil (Mc Glone et al. J. Food Sci. 51, 1986, pp. 695-697) and avoca do oil (Buenrostro et al., Biotechnol. Lett. 8., 1986, pp. 505-

506). However, the literature contains no mention of the ac¬ tion of enzymes on phosphatides, and there is no information given on the phosphatide contents in oils separated from seed by using enzymes. The separation of oil would thus be followed by a conventional refining treatment with the conventional steps for the removal of phosphatides, the adsorption of pig¬ ments, and the deodorization of the oil. By contrast, in the present invention, which is substantially based on the action of enzymes on the phosphatides present in the seed, it is es¬ sential that the obtained oil phase is transferred, without any separate steps for the removal of phosphatides, directly to the physical step of the refining, in which the oil is given an adsorption treatment and/or is deodorized. ^•

The first step of the process for the preparation of a vegeta¬ ble-oil product according to the invention is the comminution of the seed, for example by flaking or by coarse milling. Thereafter the seed is preferably heated so that its inherent enzymes are destroyed. Thus it is ensured that the action of the subsequently added enzyme acting on phosphatides will not be disturbed and that the enzymatic reactions will occur in the desired manner, with control. After the heating, the comminution of the preliminarily comminuted seed is continued using a disc attrition mill, a pin mill or some other fine- milling equipment. The finely milled seed is slurried in water, and the slurry is cooked for 10-60 min, preferably 30- 40 min. If the cooking is continuous, the solids content of the slurry may be within the range 20-70 %, preferably 40-50%. On the other hand, if batch cookers are used for the cooking, the solids content of the slurry may be within the range 10- 60%, preferably 15-40 %. After the cooking,the slurry can be wet milled by using, for example a colloid mill. After possible dilution and cooling, the slurry is ready for the ad¬ dition of the enzyme having action on phosphatides.

The enzyme used has typically some optimal pH value to which the slurry is adjusted by adding an acid or a base. Thereafter the enzyme is added in a dose which may be 0.1-5.0 % by weight, most commonly 0.5-3.0 % by weight of the solids of the slurry, depending on the type of the seed and the enzyme used. After the adding of the enzyme, the slurry is incubated at the operational optimum temperature of the enzyme for 0.5-6 hours, preferably 3-4 hours. In this context it should be pointed out that the optimum conditions for the enzyme action in the pro¬ cess according to the invention are not necessarily those re¬ ported by the enzyme manufacturer on the basis of his charac- terizational studies; they have to be determined separately by experimentation. The enzymes used may vary according to the complexity of the cell walls of the seed; multi-activity enzymes have proven to be suitable, although carbohydralases have also yielded good results.

By the end of the incubation step, the desired division of the material into an oil phase, an aqueous phase and the remaining solids of the seed has taken place. By the use of the enzyme it has, according to the invention, been accomplished that the phosphatide present in the seed has in the main hydrolyzed and passed into the aqueous phase. The incubated slurry is heated to the temperature range 50-95 °C, preferably 70-95 °C, and is centrifuged in a decanting vessel in order to remove the solid seed material and any oil drops possibly adhering to it. The remaining liquid phase is maintained at a temperature of 70-95 °C and is clarified in a clarifier centrifuge, in which solid material will still separate out from the liquid. The so lids obtained from the decanter are reslurried in water at a temperature of 60-80 ^C C, and the seed hulls are separated using a vibratory screen. The separated hulls are drained, pressed to dewater, and dried. The solids separated in the clarifier centrifuge are slurried in the washing water which

has passed through the vibratory screen. The obtained slurry- is heated to the temperature range 60-80 °C and is divided in the-clarifier centrifuge into a solid phase and a liquid phase. The liquid phases obtained form the clarifier in the said two steps are pooled together, maintained at a tempera¬ ture of 50-95 °C, preferably 70-90 °C, and divided in a puri- . fier centrifuge into an oil phase and a liquid phase. The so¬ lids obtained from the clarifier are homogenized and dried using, for example, a spray drier. To the obtained oil phase there is added, at a temperature of 30-70 °C, preferably 40-60 °C, approx. 0.1-3 % filter aid mixed with 0.1-0.5% so¬ dium sulfate, whereafter mixing is carried out in a mixing tank. The oil is filtered using a conventional filter, such as a plate filter, and, when so desired, it can be further dried in a vacuum dryer. The phosphatide content in the oil obtained is so low that, after this, a mere physical refining treatment will suffice, without the chemical step normally carried out for the removal of phosphatides.

The physical refining of the oil may comprise, as the first step, an adsorption treatment in which, by using siliceous earth or other similar adsorption agent, mainly pigments and possibly remaining phosphatides are removed from the oil. The duration of the treatment may be, for example, 50 min. There¬ after the oil can be subjected to deodorization, which may be carried out, for example, by blowing steam through the oil for approx. an hour at a temperature of approx. 250 °C. The deodor¬ ization removes from the oil free fatty acids, aldehydes and other oxidation products, and the oil obtained is ready for use, for example, as a foodstuff.

Example 1

Low-glucosinolate rapeseed (Westar) were flaked and steam cooked at 95 °C for 30 min in order to inactivate the yro- sinase enzyme inherently present in the seed. The cooked, flaked seed was thereafter comminuted in a disc attrition mill fitted with serrated discs. A slurry with a solids content of 40 % was prepared from the comminuted seed, and this slurry was cooked for 30 min. The slurry was then diluted with cold water to a 20 % solids content, whereby the temperature of the slurry was also lowered. The pH of the slurry was adjusted to 4.0 by using acetic acid. Thereafter, an enzyme mixture con¬ sisting of the enzymes Novo SP-249 and Pectinex 3XL was added to the slurry at 2 % of the dry weight of the slurry, and the slurry was incubated at 45 °C for 24 hours. After the incuba¬ tion the slurry was heated to 80 °C and was centrifuged in a laboratory centrifuge so that three separate phases were ob¬ tained, i.e. the solid sediment, the aqueous phase, and the oil phase. The aqueous phase was centrifuged in a bucket cen¬ trifuge, whereby a solid sediment not containing hull material and an aqueous phase containing practically no oil were ob¬ tained. The solid sediments obtained in the centrifugation operations were resuspended in water at 70 °C and were cen¬ trifuged once more into three separate phases. The two oil phases obtained in the centrifugation operations were pooled together, and a mixture containing filter clay 1 % by weight of the oil amount and sodium sulfate 0.2 % by weight of the oil amount were added to them. The oil was mixed at 50 ^C C, whereafter it was filtered. The obtained crude oil was finally dried under vacuum. The measurement results characterizing the quality of the oil are given in the following table.

Table

Process Peroxide Iodine Free fatty- Chlorophyll Phosphate value value acids

(meg/kg) (cg/lOOg) (%) (ppm) (ppm)

Solvent extraction 3.1 117.5 0.80 21.5 121.5

Process of Example 1 7.8 116.1 0.77 18.4 2.9

The reference process in the table is a solvent extraction in which the oil was produced in a laboratory, by using ≤oxhlet apparatus, from the same heat treated and flaked seed as in the enzyme process, by using hexane as the solvent.

Example 2

Rapeseed (Westar) was treated for the adding of the enzyme as in Example 1. After the cooking and dilution, the pH was ad¬ justed as in Example 1 and the temperature was maintained at 50 °C. Enzyme Pectinex 3XL (Novo) was added to the slurry, and the slurry was incubated for 4 hours. After the incubation the oil was separated as described in Example 1. The measurement results characterizing the quality of the oil are presented in the following table.

Table

Process Peroxide Iodine Free fatty Chlorophyll Phosphate value value acids

(meg/kg) (cg/lOOg) (%) (ppm) (ppm)

Process of Example 2 (Pectinex 3XL) 10.2 116.0 0.55 19.5 1.8

Example 3

Low-glucosinolate rapeseed (Tobin), which differed from the seed used in Example 1, was treated for the adding of enzyme as described in Example 1. After the cooking, the slurry was wet milled in a Siego mill. The milled slurry was diluted to a solids content of 20 %, the pH was adjusted to 4.5 and the tem¬ perature to 50 °C. Enzymes .Olease (Biocon) and Pectinex 3XL (Novo) at 2 % by weight of the solids of the slurry were added to the slurry. The slurry was incubated for 4 hours, and the oil was separated as described in Example 1. The measurement results characterizing the quality of the oil obtained are pre¬ sented in the following table:

Table

Process Peroxide Iodine Free fatty Chlorophyll Phosphate value value acids

(meg/kg) (cg/lOOg) (%) (ppm) (ppm)

Process of

Example 3

(Olease +

Pectinex

3XL) 4.6 115.2 1.0 19.1 1.2

Example 4

Rapeseed (Tobin), which was the same as that used in Example 3, was treated for the adding of enzyme as described in Ex¬ ample 1. After the cooking and dilution, the pH was adjusted to 5 and the temperature to 50 °C. Olease (Biocon) at 2 % by weight of the solids of the slurry was added to the slurry, and the slurry was incubated for 4 hours. After the incubatio the oil was separated as described in Example 1. The measure-

ment results characterizing the quality of the oil obtained are presented in the following table:

Table

Process Peroxide Iodine Free fatty Chlorophyll Phosphate value value acids

(meg/kg) (cg/lOOg) (%) (ppm) (ppm)

Process of

Example 4

(Olease) 3.9 115.9 0.82 14.0 1.4

Example 5

Rapeseed (Westar) was treated for the adding of enzyme as de¬ scribed in Example 1. After the cooking and dilution, the pH of the slurry was adjusted to 4.5 and the temperature to 50 °C. The enzyme mixture according to Example 1 at 2 % by weight of the solids of the slurry was added to the slurry, and the slurry was incubated for 4 hours. The oil was separ¬ ated as described in Example 1, and its quality charac¬ teristics were determined. The measurement results obtained are presented in the following table.

Thereafter the oil was subjected to a physical refining, at the beginning of which the oil was treated with 100-400 ppm ci¬ tric acid at 60 °C for 20 min. Adsorption clay was added to the oil, and the oil was maintained at 100 °C under a pressure of 310 Pa generated by using an inert gas. After the adsorp¬ tion step the oil phase was deodorized under a pressure of 0.4 kPa at 245 °C by blowing steam through it for one hour. Fi¬ nally the oil was cooled, clarified by filtering it with clay, and analyzed by measuring the parameters characterizing the

quality of the oil. The measurement results are presented in the following table.

Table

Process Peroxide Iodine Free fatty Chlorophyll Phosphate value value acids

(meg/kg) (cg/lOOg) (%) (ppm) (ppm)

Process of Example 5 Crude oil 0.44 119 0.74 17.1 3.0

Physically refined oil 0.00 117 0.04 0.0 <0.2

The examples show that the phosphorus content of the crude, un refined oil was in all cases at maximum 3 ppm. In conventional rapeseed oil production processes, the upper limits of phos¬ phorus for degum ed and superdegummed oils are 200 ppm and 50 ppm (Canadian General Standard Board). The phosphorus content of the crude rapeseed oil obtained according to the invention is thus only a fraction of the said values, and also consider¬ ably lower than the upper limit, 15 ppm, set for refined rape¬ seed oil (Canadian General Standard Board) . It can be seen from the results of Example 5 that in the physical refining .step of the process according to the invention the phosphorus content of the oil further considerably decreases.

It is evident for an expert in the art that the different em¬ bodiments of the invention are not restricted to the examples presented above but can vary within the accompanying claims. Thus it is.possible to use, instead of the rapeseed cultivars used in the examples, other types of oilseed, such as sun¬ flower seed or soybean or cotton seed, or even corn.