WO1987006800A1

WO1987006800A1 - Treatment of soybeans

Info

Publication number: WO1987006800A1
Application number: PCT/AU1987/000135
Authority: WO
Inventors: Thomas John Rowland
Original assignee: Thomas John Rowland
Priority date: 1986-05-12
Filing date: 1987-05-12
Publication date: 1987-11-19
Also published as: JPH01502316A; KR880701077A; AU596423B2; AU7398587A

Abstract

A method of treating soybean meal (SBM), by application of steam, to remove trypsin inhibitor/urease without destroying nutritionally valuable protein. The process, conducted at the natural pH of the soybean, involves the steps of grinding the soybean, adding moisture, raising the temperature to between 100 and 110°C and the moisture content to between 20 and 30 % (W/W) by the addition of steam, maintaining the SBM at between 95 and 105°C for 10 to 30 minutes, reheating the SBM to between 100 and 110°C with steam, and pelletizing the treated SBM.

Description

TREATMENT OF SOYBEANS

The present invention relates to a process and plant for the treatment of soybean meal (SBM) to reduce the levels of trypsin inhibitor and urease present in raw SBM while substantially preserving the nutritionally available lysine content of the SBM, and to the product produced by this process.

Soybean meal is of particular use in animal feeds as a protein source, however, raw soybeans contain proteolytic-inhibiting substances and urease. The most important proteolytic inhibiting substance in animal nutrition is trypsin inhibitor. Trypsin is an enzyme produced in the pancreas and is required for protein digestion. It is known that raw soybeans, due to their trypsin inhibitor content, cause an enlargement of the pancreas and have a growth retarding effect on the growth of chicks.

It is therefore common practice to heat raw soybeans to destroy the trypsin inhibitor, however, too much heat can destroy the protein contained in the SBM while not enough will result in the SBM containing active trypsin inhibitor. Steam heat will destroy proteolytic-inhibiting substances, however overheating will destroy or render unavailable several essential amino acids particularly lysine and arginine. In order to overcome this problem of heating to destroy trypsin inhibitor resulting in an accompanying destruction of nutritionally valuable protein in the soybean it has been proposed to conduct the treatment at certain pHs. In this regard US Patents 3,220,851 and 3,845,229 are directed toward processes for the treatment of soybean involving adjusting the pH of the soybeans to 8-9 by adding an alkali and then cooking the soybeans with steam at a temperature of 100-110°C. The process exemplified in US 3,220,851 also involves the use of a proteolytic enzyme in the treatment process, whilst US 3,845,229 exemplifies the use of urea to raise the pH of treatment mixture and the use of solvent to extract oil from the soybean.

British Patent Specification 1,459,422 also relates to adjusting the pH of the soybeans prior to heating, however, in contrast to the US patents discussed above, this specification relates to a method of treatment in which the pH is adjusted to less than 5.5 prior to heating. The combined teaching of this prior art is that if soybeans are to be treated to destroy trypsin inhibitor whilst preserving other nutritionally important protein content of the soybean, it is essential that the pH be controlled. Contrary to the teaching of this prior art the present inventor has discovered that no pH control is required providing a strict treatment regimen is followed. The present inventor has discovered a soybean treatment process involving 6 steps with no alteration of the natural pH of the soybean. From various trials using this process the present inventor has found that each step is crucial - if one step is omitted a product is obtained in which trypsin inhibitor is still present.

The process of the present invention results in a product in which the trypsin inhibitor has been inactivated whilst the lysine present has not been rendered nutrionally unavailable.

The present invention consists in a process for the treatment of soybean meal (SBM) , the process comprising the following steps: 1. passing the SBM through a grinding means to grind the SBM;

2. adding moisture to the ground SBM;

3. adding steam to the moistened ground SBM to achieve a moisture content of between 20 and 30% w/w and a temperature of between 100 and 110°C; 4. maintaining the SBM from step 3 at a temperature of between 95° and 105°C for 10 to 30 minutes;

5. adding steam to the SBM from step 4 to raise the temperature of the SBM to between 100 and 110°C; and

5 6. pelletizing the SBM by means of a pelleting mill. In a preferred embodiment of the present invention step 4 is carried out at a temperature between 100 and 105°C. In a further embodiment the moisture content achieved in step 3 is 25% w/w and the duration of step 4 10 is 20 minutes.

In a further preferred embodiment of the present invention the grinding means is provided by a ripple mill. In a further embodiment the ground SBM is put over a sieve to remove larger particles which are returned to 15 the grinding means.

In another embodiment of the present invention the moisture content and temperature of the pelletized SBM is decreased in a cooler/dryer .to obtain SBM pellets of ambient temperature having a moisture content of 10-12% 20 w/w.

In a further embodiment of the present invention the SBM during steps 2 to 5 is agitated to ensure uniform treatment.

In yet another preferred embodiment of the present 25 invention the pelletized treated SBM is ground in a ripple mill, passed over a sieve to remove large particles, which are returned to the ripple mill, and the finely ground treated SBM stored as a powder.

The invention will now be described by means of an 30 example. , It has been shown that destruction of urease in SBM by heat treatment, approximately parallels the destruction ^ of trypsin inhibitor. As urease activity is readily measured this criteria is used as an index of the adequacy 35 of soybean treatment. Table 1 shows the results of different treatment regimes. Sample 1, untreated ground soybean; Sample 2, 10 minute heat soak then pelleted; Sample 3, 15 minute heat soak then pelleted; Sample 4, 20 minute heat soak then pelleted; Sample 5, 5% moisture precondition, 10 minute heat soak then pelleted; Sample 6, 5% moisture precondition, 15 minute heat soak then pelleted; Sample 7, 5% moisture precondition, 20 minute heat soak then pelleted. The soybean in each case was ground as fine as possible and the heat soak was carried out in sealed plastic drums.

TABLE 1

SAMPLE UREASE ACTIVITY AVAILABLE LYSINE

( pH) (%)

1 2.17 1.60/1.72 2 0.20 3 0.13 4 0.18 1.82/1.86 5 0.08 6 0.01 7 0.00 1.73/1.72

Hereinafter, given by way of example only, are preferred embodiments of the present invention described with reference to the accompanying drawing in which:

Figure 1 is a flow chart illustrating the process of the present invention.

With reference to Fig. 1 the process for the treatment of SBM according to a preferred embodiment of the present invention can be seen to comprise a number of steps the first being the grinding of raw soybeans in a first ripple mill. The ground SBM is then screened to remove large particles which are returned to the first ripple mill. Moisture is then added to the ground SBM. The moistened SBM is then passed through a first feeder following which the moistened SBM is conditioned by the addition of steam in a first conditioner. The SBM from the first conditioner is then retained in a ripener to allow ripening to occur. The ripened SBM is then passed through a second feeder following which a further addition of steam to the ripened SBM takes place in a second conditioner. The SBM is then pelleted in a pellet mill and the SBM pellets cooled and dried in a cooler/dryer. These SBM pellets are then ground in a second ripple mill and the ground SBM passed through a screener to remove large particles which are returned to the second ripple mill. The finely ground treated SBM is then stored until required. As mentioned previously the contents of the feeders, conditioners and ripener are agitated to ensure thorough mixing.

Claims

CLAIMS :

1. A process for the treatment of soybean meal (SBM), the process comprising the following steps:

1. passing the SBM through a grinding means to grind the SBM;

2. adding moisture to the ground SBM;

3. adding steam to the moistened ground SBM to achieve a moisture content of between 20 and 30% w/w and a temperature of between 100 and 110°C;

4. maintaining the SBM from step 3 at a temperature of between 95° and 105°C for 10 to 30 minutes;

6. pelletizing the SBM by means of a pelleting mill.

2. A process as claimed in claim 1 in which at step 4 the SBM is maintained at temperature of between 100 and 105°C.

3. A process as claimed in either claim 1 or 2 in which the moisture content achieved in step 3 is 25% w/w and the duration of step 4 is 20 minutes.

4. A process as claimed in any one of claims 1 to 3 further comprising the step of decreasing the moisture content and temperature of the pelletized SBM in a cooler/dryer to obtain treated SBM pellets of ambient temperature having a moisture content of 10 to 12% w/w.

5. A process as claimed in any one of claims 1 to 4 in which the grinding means is a ripple mill.

6. A process as claimed in any one of claims 1 to 5 further comprising the steps of assaying the SBM following grinding to remove large particles and returning the large particles to the ripple mill.

7. A process as claimed in any one of claims 1 to 6 in which the SBM during steps 2 to 5 is agitated to ensure uniform treatment.

8. Pelletized soybean meal obtained according to process as claimed in any one of claims 1 to 7.

9. A process for the treatment of soybean meal substantially as hereinbefore described with reference to the accompanying drawing.

f.