MANUFACTURE OF EDIBLE MATERIAL FROM PULSES

Abstract: Pulses such as peas and beans, are autoclaved and separated by air-classification into protein-rich and starch-rich fractions. The moist thermal treatment leads to an enhanced crude protein content in the protein-rich fraction, compared to that obtained using other forms of heat treatment prior to fractionation.

Description: MANUFACTURE OF MATERIAL The present invention relates to the manufacture of material from pulses such as peas and beans. The invention is particularly concerned with the processing leguminous seeds (pulses) which contain substantial amounts of starch granules. It is known that such pulses can be milled and fractionated into relatively starch-rich and protein-rich flours. Examples of common pulses to which such treatment can be applied are peas, field beans, kidney beans, navy beans and lentils. Such pulses can be distinguished from other members of the Leguminosae family in which the main energy store is lipid rather than starch, for example soya beans and lupin seeds. The invention provides a process for the preparation of an edible material from starchy pulses, in which process whole pulses are subjected to a moist thermal treatment under superatmospheric pressure, the treated pulses are ground, and the ground pulses are physically classified to separate therefrom at least one protein-rich fraction. The process of the invention can yield a protein-rich fraction of which the crude protein content is enhanced relative to that of protein-rich fractions derived by conventional methods from the same pulse starting material. It will be appreciated that different varieties and species of pulses vary widely both in their protein contents and in the relative ease with which they can be fractionated into protein-rich and starch-rich fractions Taking any given variety of starchy pulse, however, there will generally be a significant improvement in crude protein content in a protein-rich fraction when produced according to the invention An additional advantage of the invention is that the starch-rich fraction will generally have an enhanced digestibility when compared to corresponding starch-rich fractions made by conventional methods from the same pulse starting material. We have demonstrated this by means of an in vitro test in which an enhanced rate of enzymatic starch hydrolysis was observed. The protein-rich fraction obtained by the process of the invention typically contains at least 30%, and often at least 50%, by weight crude protein and generally has a trypsin inhibitor activity of less than 5 mg/g, and often less than 2 m/. preferably the duration and intensity of the thermal treatment should not be such that the pulses become overcooked, ie disintegrate into a pulp or mush. Preferably the thermal treatment is conducted at a temperature in excess of 1000c but not exceeding 150 C, and preferably is achieved by contacting the pulses with the live stream. Preferably the pressure under which the thermal treatment is conducted exceeds atmospheric pressure by from l to SO psig. Preferably the thermal treatment is conducted for from 1 to 60 minutes. An ideal method for physically classifying the ground pulses is air-classification. Indeed, we believe that it is a particular advantage of the invention that moist thermal treatment of pulses leads to improved efficiency in a subsequent air classification. In order for the physical classification of the ground pulses into protein-rich and starch-rich fractions to be conducted efficiently, the treated material must be ground to an appropriately small particle size. We have found that for optimum air-classification of this material, it should be milled such that at least 50%, and preferably at least 70%, by weight of the material can pass through a 45 micron sieve. This milling can be effected using conventional equipment, such as pin mills. Preferably the pulses should be de-hulled after the thermal treatment but prior to milling, as this increases the efficiency of the milling operation. Moreover, de-hulled pulses tend to stick together during the thermal treatment, which is inconvenient for subsequent processing. De-hulling can be conducted using conventional equipment. In a particularly preferred process according to the invention, whole peas/beans are autoclaved at a temperature of 110 to 125"C and a pressure exceeding atmospheric by from 5 to 20 psig, for a period of 5 to 30 minutes, the autoclaved peas/beans are dried (preferably to a moisture content in the range of 8 to 132 by weight), de-hulled and milled (preferably such that at least 70% by weight of the milled material passes a 45 micron sieve), and the milled material is air-classified. A protein-ricr. pulse fraction obtained by the process of the invention can be used as an ingredient in foods or humans or animals. In particular it can be used to enhance the protein content of compound animal fees when blended with conventional feed ingredients such as cereals (for example oats, barley, rice, rye, wheat and maize), oil seed meal (for example groundnut, rape, mustard, sunflower and soya), fibrous matter (for example hay, straw, potato pulp, beet pulp and citrus pulp), other proteinaceous materials (forexample fish meal), lipids (for example vegetable oils, tallows and fish oils), and various mineral and vitamin sources. The invent ion is illustrated by the following examples. Example 1 A batch of whole peas (variety MARY) was divided into seven identical samples identified as A to G. Samples A and B were processed according to the invention. Samples C to G were subjected to alternative processes for the purposes of comparison. Sample A was placed in an autoclave and exposed to live steam at a temperature of 1164C and a pressure above atmospheric of 10 psig for a period of 10 minutes. After autoclaving, the peas had a moisture content of about 20% by weight and this was reduced to about 8 % by weight by drying in an oven at SO"C. Following drying, the hulls of the peas were removed using a conventional de-huller and the de-hulled peas were coarsely ground in a Christie-Norris hammer mill using lmm screen, and then finely milled in a K pin mill (7" horizontal disc fitted with sauare studs) run at 9600 rpm. 76% by weight of the milled peas passed through a 45 micron sieve. The milled material was separated into a fine fraction and a coarse fraction using an Alpine Laboratory air classifier (Multiplex 100 MZR) operated at a rotor speed of 7000 rpm with maximum air flow. The fine (protein-rich) fraction was subjected to analysis for its crude protein content and its trypsin inhibitor activity (TIA) using standard analytical procedures. Sample B was treated in a manner identical to that applied to sample A except that the autoclaving was conducted for 15 minutes instead of 10 minutes. The remaining samples were subjected to the following procedures. Sample C: the peas were not subjected to any heat treatment whatsoever, and the raw peas were de-hulled, milled and air-classified using the same conditions as applied to samples A and B. Samples D and E were both subjected to a microwave heating treatment instead of the autoclaving. In the case of sample D the microwave treatment was conducted for 22 minutes, and in the case of sample E the period was 25 minutes. In both cases the treatment was conducted in a Mercury 955 laboratory microwave oven, and heating was carried out in periods of 1 minute for the first 10 minutes and then for 2-minute periods thereafter. Stirring was performed between each heating to prevent the formation of "hot spots". Following the microwave treatment both samples were de-hulled, milled and air-classified using the same procedure as described above. Samples F and G were subjected to dry oven heating instead of autoclaving. Both samPles were heated in a thin TABLE I Sample Thermal treatement Crude protein content Trypsin inhibitor of fine fraction activity (% by weight) (mg/g) A Autoclave 116 C, 59.1 1.5 10 psig, 10 minutes B Autoclave 116 C, 58.6 1.5 10 psig, 15 minutes C None 56.8 18.2 D Microware, 22 Minutes 56.8 6.6 E Microware, 25 Minutes 54.8 5.0 F Dry oven, 150 C 56.9 11.5 45 minutes G Dry oven, 150 C 55.2 11.7 60 minutes layer in a shallow aluminium tray at 150"C. In the case of sample F the period was 45 minutes, and in the case of sample G the period was 60 minutes. Following the dry oven heating the samples were de-hulled, milled and air-classified using the identical procedure as applied to the other samples. The analytical results for each sample are given in Table I, which shows that in the process according to the invention (samples A and B) enhanced the crude protein content of the fine fraction. As can also be seen from Table I, the process according to the invention (samples A and B) led to a very low level of trypsin inhibitor activity in the protein concentrate at 1.5 mg/g. By way of comparison, the raw peas produced a protein concentrate having a trypsin inhibitor activity of 18.2 mg/g. The dry oven treatment reduced this to approximately 11.5 mg/g, and the microwave treatment reduced this to 5 mg/g at best. Example 2 This example demonstrates the enhancement of protein content associated with applying moist thermal treatment to peas prior to milling and air classifying. A sample of peas (variety MARO) was exposed to live steam at 116"C and 10 psi for 30 minutes. The final moisture content of the peas was 20% by weight, and this was reduced to about 8% by air-drying at about 50"C. The dried peas were de-hulled, milled in an Alpine 250 CE pin mill, and then air-classified in an Alpine 400 MPS classifier. A second sample of the same peas was treated in an identical manner, except that no steaming was applied and the classification was conducted in an Alpine 100 MZR laboratory classifier. Experience has shown, however, that the process is relatively insensitive to the type of classifier employed, and so any major differences in the final product will be due primarily to the presence or absence of steaming, which is the only other variable. On analysis, the protein-rich fractions had the following properties: Air-classified Protein-rich fraction Yield (*) Protein (%) With thermal treatment 19.4 67 No thermal treatment 19.5 59 These results indicate that the process involving moist thermal treatment of the whole peas led to a substantially higher concentration of protein in the protein-rich fraction, -with no loss of yield.

Claims: CLAIMS 1. A process for the preparation of an edible material from starchy pulses1 such as peas and beans, characterised by the steps of subjecting whole pulses to a moist thermal treatment under superatmospheric pressure, grinding the treated pulses, and physically classifying the ground pulses to separate therefrom at least one protein-rich fraction. 2. A process according to claim 1, characterised in that the physical classification is conducted by means of air-classification. 3. A process according to claim 1 or claim 2, characterised in that the thermal treatment is conducted at a temperature in excess of 100 C but not exceeding 1504C. 4. A process according to any one of claims 1 to 3, characterised in that the thermal treatment is conducted at a pressure exceeding atmospheric pressure by from 1 to 50 psig. 5. A process according to any one of claims 1 to 4, characterised in that the thermal treatment is conducted for from 1 to 60 minutes. 6. A process according to any one of claims 1 to 5, characterised in that the thermal treatment is conducted in an autoclave. 7. A process according to any one of the preceding claims, characterised in that the treated pulses are ground such that at least 50%, and preferably at least 70%, by weight of the ground material can pass through a 45 micron sieve. 8. A process according to any one of the preceding claims, characterised in that the pulses are de-hulled after the thermal treatment but prior to grinding. 9. A process for the preparation of an edible material from starchy pulses such as peas and beans, characterised by the steps of autoclaving whole pulses at a temperature of 110 to 125"C and a pressure exceeding atmospheric pressure by from 5 to 20 psig for a period of 5 to 30 minutes, drying the autoclaved pulses to a moisture content in the range 8 to 13% by weight, de-hulling and milling the dried pulses such that at least 70% by weight of the milled material can pass through a 45 micron sieve, and air-classifying the milled material to separate therefrom at least one protein-rich fraction. 10. A protein-rich fraction of pea or bean flour, made by a process according to any one of preceding claims.

Inventors: DUNCKLEY, MARTIN NOEL, EVANS, PHILLIP JOHN, MACINTOSH, IAIN KELLAR
Applicants: UNILEVER NV, UNILEVER PLC
Application year: 1982
Main classification: A23L1
IPC codes: A23L1, A23J1