JPH0258908B2 - - Google Patents

Description

[Detailed description of the invention]

This invention relates to a method for treating soybean extraction residue. It is generally difficult to dehydrate the soybean extraction residue (wet okara) that is separated from the process of water extraction of soybeans or defatted soybeans to less than 80% by simple squeezing or centrifugation, and bacteria can grow. It has the property of being easily damaged and has storage problems. In an attempt to improve the dehydration efficiency of such extraction residue, it has been proposed to add acidic wastewater, specifically fermented soybean whey, to the soybean extraction residue. However, although this proposed method has the advantage of reducing drying costs due to improved mechanical dewatering efficiency, the water originally contained in the residue will be combined with whey and dehydrated, resulting in wastewater The drawback is that the amount of treatment increases and the cost of wastewater treatment increases. For this reason, the above method is difficult to employ in cases where the advantage of reducing drying costs cannot necessarily be taken advantage of, such as in the production of so-called raw okara. While conducting various studies on the development of an efficient dehydration method suitable for the production of raw okara, etc., which does not necessarily involve a drying process, the present inventor decided to use acidic fresh water instead of using acidic waste liquid, that is, soybean whey. We found that the dehydration efficiency was improved when using acidic water compared to using waste liquid, and that there was a negative correlation between the solid content concentration in acidic water and the dehydration efficiency. The inventors have discovered that the resulting liquid part can be used as the liquid part in the extraction process, and therefore, the amount of waste water can be completely avoided. This invention provides a treatment for soybean extraction residue that consists of a first step of extracting soybeans or defatted soybeans with water, a second step of adding water to the soybean extraction residue separated from the extraction step, and a third step of dehydrating the soybean extraction residue under acidic conditions. In the method, the solids content of the water added in the second step is 0.5% or less,
This method of treating soybean extraction residue is characterized in that the acidic water dehydrated and separated in the third step is recycled to the first step after adjusting the pH if necessary. The target of the treatment in this invention is the soybean extraction residue separated from the extraction process. It is obtained as a residue after rough separation of the soluble portion, and the residue usually contains around 80% water. Clear water is added to this residue and dehydrated under acidic conditions. As shown in the examples and figures below, the higher the degree of clarity of the water added to the residue, that is, the lower the solids content, that is, the higher the dewatering efficiency is, the higher the water is added to the residue. In this invention, at least the solid content of the water added is 0.5% by weight or less,
Preferably it is 0.2% by weight or less,
When using acidic soybean waste liquid (soybean whey), it is preferable to dilute it with purified water or use a membrane permeate liquid such as UF or RO. Unless the amount of water added is at least twice the weight of the wet residue, the dehydration rate will not be improved. In addition, in order to continuously process the slurry after adding water by pumping it or applying it to a dehydrator, it is recommended to add 2.5 times more water. In addition, when heating is performed after adding water as described below,
If the amount of water added is too large, a large amount of thermal energy will be consumed, so in such a case, it is desirable to suppress the amount of water added to 4.5 times or less. When raw okara is produced, that is, when no drying treatment is performed after dehydration, heat treatment is performed after adding water and before dehydration to further improve storage stability. In this case, the desired degree of heating is preferably 10 minutes or more at 80° C. or higher. The pH during dehydration is 3.5 to 5 to increase dehydration efficiency.
is good, preferably in the range of 4 to 4.5. If the PH is too low, measures must be taken to improve the acid resistance of the equipment used, and if the PH is too high, the dehydration efficiency will be low.
Regardless of whether the acid used is organic or inorganic,
Various types can be used. For mechanical dehydration, known devices such as a centrifuge, filter press, screw press, etc. can be used, and a dehydrated residue is thus obtained. This dehydrated residue may be dried to produce a dried product, but it is a product with sufficient shelf life as it is. In this invention, the dehydrated and separated acidic water is
Circulate to extraction process. Since the water added to the residue is usually not soybean whey itself but highly clear water, the dehydrated and separated acidic water can be used as part or all of the primary or secondary extracted water of soybeans or defatted soybeans. This makes it possible to reduce the amount of clarified water originally required for extraction, thereby suppressing an increase in the amount of wastewater. This invention will be explained below using experimental examples and examples. Example 1 Soybean whey (PH4.5) with a solid content of 2% was prepared from the production process of isolated soybean protein, and this and tap water were mixed at various ratios, and acidic water was prepared by adjusting the pH to 4.5 with hydrochloric acid. did. Similarly, the wet extraction residue with a moisture content of 84% obtained after centrifugation after two water extraction steps from the production process of isolated soybean protein was added with the above various acidic waters equivalent to 3 times its weight, and then centrifugal dehydration. (1000×g10
The water content in the dehydrated residue is as shown in the figure, and the solid content of soybean whey in acidic water is
The dehydration efficiency was particularly excellent at 0.2% or less. Example 2 To the wet extraction residue with a moisture content of 84% obtained in the same manner as in Example 1, 3 times the weight of water was added to adjust the pH to 4.5, and the mixture was introduced into a container and heated at 80°C for 10 minutes by blowing steam into it.
After heat treatment for a minute, water content was measured after dehydration using a filter press or screw press.
The results are shown in the following table with reference to the case where soybean whey with a solid content of 2% prepared in the same manner as in Example 1 was used as the acid water.

[Table] Reference example Wet extraction residue with a moisture content of 84% (PH7.0) and dehydrated residue with a moisture content of 76.5% (PH7.0) mentioned in the above example.
4.5) (Example 1) and the residue dehydrated to 75% moisture after heat treatment (PH4.5) (Example 2).
50g was placed in a 100ml chalet, the lid was kept in a flan container at 30℃, and the odor and taste were checked every day. The product had a putrid odor after 4 days, whereas the heat-dehydrated product had no putrid odor even after 10 days. Example 3 The acidic water dehydrated and separated in Example 2 was neutralized to pH 7.0 with sodium hydroxide, and this was circulated to the second extraction process of defatted soybeans in the production of isolated soybean protein, and an equal amount of It was mixed with tap water and used as a 5-fold amount of extract for extraction. With tap water, PH
A control experiment was also conducted in which the extraction water was adjusted to 7.0. After extraction, the solid contents of the residue and the separated liquid were both 2.1%, with no difference between this example and the control example, and no difference was observed in the odor or taste of the liquid.

[Brief explanation of drawings]

The figure shows the results of Example 1, where the vertical axis shows the water content (%) in the dehydrated residue, and the horizontal axis shows the solid content (%) in the acidic water.

Claims (1)

[Claims] 1. Soybean extraction consisting of a first step of extracting soybeans or defatted soybeans with water, a second step of adding water to the soybean extraction residue separated from the extraction step, and a third step of dehydrating under acidic conditions. The residue treatment method is characterized in that the solid content of the water added in the second step is 0.5% or less, and the acidic water dehydrated and separated in the third step is circulated to the first step after adjusting the pH if necessary. A method for processing soybean extraction residue. 2. The treatment method according to claim 1, which includes heat treatment before dehydration.