Method for preparing improved soybean products

Abstract

A method is provided for producing an improved soybean product for use in food applications. The process enables the efficient denaturation of undesirable soy enzymes and removal of oligosaccharides from soybeans, preferably whole soybeans, without the development of off-flavors. The general method comprises: (1) heating an aqueous solution of a water soluble calcium salt to at least about 65° C. to provide a heated salt solution; (2) mixing soybeans with the heated salt solution to form a mixture; (3) heating the mixture for a time and at a temperature effective for deactivating protease inhibitors and lipoxygenase and removing oligosaccharides from the soybeans; (4) removing the aqueous solution from the mixture after the heating step; and (5) collecting the improved soybean product. The improved soybean product may be further processed for use in various food applications.

Description

FIELD OF THE INVENTION [0001] The present invention relates generally to a method of preparing soybeans for use in food applications. The process enables the rapid and efficient deactivation of soy enzymes without the development of off-flavors and the rapid and efficient removal of undesirable oligosaccharides from whole soybeans to provide a soybean material having an improved nutritional profile. After initial processing, soybeans may be further processed for use in various food applications. BACKGROUND OF THE INVENTION [0002] The health benefits of soybeans have been known for some time. For centuries, soybeans have been the primary source of protein in Asian countries, and in recent years the popularity of soy-based products has increased in the United States. Along with a tendency to lower cholesterol levels, soybeans have recently been linked with, or suggested as having, a possible role in inhibiting cancerous or tumor cells. Additionally, soy protein contains an amino acid ...

AI Technical Summary

Benefits of technology

[0006] The present invention provides a simplified, low-cost method to prepare soybeans for use in a wide variety of food applications. The method provides in situ deactivation of enzymes, including trypsin inhibitor, in the treated soybeans and removal of oligosaccharides from the treated soybeans without the development of off-flavors or other undesirable characteristics. Generally, the process of the present invention also improves the overall nutritional profile of the treated soybeans relative to the original soybeans. The treated beans may then be further processed or used directly in food applications. Preferably, soybeans used directly in food applications are in the form of whole soybeans.

[0007] The method of the current invention provides several benefits over prior methods of processing soybeans for food applications. Significantly, the method of the current invention provides a means for efficiently extracting / deactivating undesirable compounds found in soybeans by means of a simple one-step process wherein the integrity of the soybeans can be maintained. Additionally, the process of the current invention results in virtually no loss in the yield of soybeans. Traditional processes which require crushing soybeans to deactivate enzymes and remove oligosaccharides have a significantly lower yield, as substantial levels of desirable soy solids are lost during processing. Moreover, the rapid processing of the method of the current invention minimizes the chances for developing off-flavors, since enzymes are deactivated in situ and, thus, do not have significant contact with soy materials or components. In traditional soy processing where the soybeans are soaked in water prior to heating, water activates the enzymes and causes undesirable off-flavors such as “beany,”“cooked cereal,” and oxidized notes. Such off-flavors are avoided or minimized in the present process. Additionally, the traditional process generally provides soybeans having an undesirable greyish color. The rapid processing and preservation of the whole bean in the present process allows soybeans to retain their natural golden-yellow color and, therefore provide a more desirable product.

[0008] The present method includes heating an aqueous solution of a water soluble calcium salt to about 65 to about 100° C., mixing soybeans with the heated calcium salt solution, and heating the mixture for a time and temperature which is effective for enzyme deactivation in the soybeans and rendering the proteins in the soybeans insoluble in water. During the heating step, the time and temperature should be at least sufficient to take the beans to a point where they cease swelling. Generally, this is done by heating the bean aqueous salt solution mixture at about 65 to about 100° C. for about 0.5 to about 2 hours (and preferably at about 90 to about 100° C. for about 0.5 to 1 hour). Preferably, dry soybeans are plunged into the hot calcium salt solution and then the solution heated to maintain the temperature at the desired level. The calcium salt solution then is removed and the treated soybeans collected. If desired, the treated soybeans may be washed with water to reduce the levels of calcium salts and / or other components. During heat treatment in the calcium salt solution, the oligosaccharides are leached from the soybeans and remain dissolved in solution when the calcium salt solution is removed from the mixture. Generally, the present process is effective for treatment of whole soybeans, broken or fractured soybeans, or soybean grits. Preferably, however, it is preferred that dehulled, whole soybeans are used in the present process.

[0009] Although not wishing to be limited by theory, enzyme deactivation in the soybeans appears to occur via the exposure to heat and calcium. Again, although not wishing to be limited by theory, it appears the calcium also immobilizes soy proteins rendering them insoluble, thereby preventing the loss of desirable soy solids during processing. Thus, the combination of heating and calcium appears to effectively denature and immobilize soy proteins and deactivate the soy enzymes, including trypsin inhibitor and lipoxygenase, in their native, undisturbed cellular structure. By preventing the release of enzymes and their respective substrates trapped in sub-cellular structure, the enzymatic reactions can be minimized (and perhaps even eliminated). Rapid deactivation of lipoxygenase effectively prevents the formation of off-flavor precursors. Thus, the flavor reversion problem commonly associated with dry soy ingredients such as soybean oil, soy flour, and soy protein concentrate is significantly reduced and, in some cases, eliminated. Cooking the beans in hot calcium solution and subsequent soaking allows the water soluble oligosaccharides to be removed with cooking media and soaking water.

Problems solved by technology

Traditional processes which require crushing soybeans to deactivate enzymes and remove oligosaccharides have a significantly lower yield, as substantial levels of desirable soy solids are lost during processing.

In traditional soy processing where the soybeans are soaked in water prior to heating, water activates the enzymes and causes undesirable off-flavors such as “beany,”“cooked cereal,” and oxidized notes.

Additionally, the traditional process generally provides soybeans having an undesirable greyish color.

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