Beany flavor

Soybeans. Soybeans are not eaten raw because they are too hard and have an unpalatable grassy—beany flavor. Small amounts are roasted and salted for snacks. Nut substitutes for baked products and confections are also manufactured from soybeans. Larger amounts are used in Oriental foods, some of which are increasingly popular in the United States. 

Soybean Protein Isolates. Soybean protein isolates, having a protein content of >90 wt%, are the only vegetable proteins that are widely used in imitation dairy products (1). Most isolates are derived from isoelectric precipitation, so that the soybean protein isolates have properties that are similar to those of casein. They are insoluble at thek isoelectric point, have a relatively high proportion of hydrophobic amino acid residues, and are calcium-sensitive. They differ from casein in that they are heat-denaturable and thus heat-labile. The proteins have relatively good nutritional properties and have been increasingly used as a principal source of protein. A main deterrent to use has been the beany flavor associated with the product. Use is expected to increase in part because of lower cost as compared to caseinates. There has been much research to develop improved soybean protein isolates. 

A process for making a soy milk having a minimum beany flavor is presented in Figure 5. The recommended compositions for a fluid and for a dry product are given in Table 16. 

Srinivas H, Swamylingappa B, Chand N. 1992. Secondary extraction of soybeans using hexane-acetic acid Effect on beany flavor removal and physiochemical properties. J Agric Food Chem 40 276-279. 

Quick bread (43) 5-15% pea flour No volume change Beany flavor at 10%... 

Soybean oil has poor oxidative stability, which is a major problem for the soybean industry. Crude soybean oil has a characteristic green-beany flavor, which is... 

Propylpyridine has a sweet, musty, beany flavor (Polak s Frutal Works et described with woody, burnt, chemical, dirty flavor (Chemisis, 1991). 

Deodorization. Volatile flavor components of soybean have been investigated in detail (79, 80, 81, 82). Arai et al. (83) have studied the interaction of denatured soybean protein with 1-hexanol and 1-hexanal which are the typical beany flavor compounds of raw and processed soybeans. These protein-bound compounds are liberated by treating the denatured soybean protein with pepsin (83). Noguchi et al. (84) observed that not only 1-hexanol and 1-hexanal but also other flavor compounds are effectively liberated and removed from a soybean protein isolate during treatment with an acid protease (Molsin). A subsequent study has ascribed this effect to the activity of aspergillopeptidase A, an endopeptidase, which has been identified as a main constituent of Molsin (85). Fujimaki et al. (88, 87) examined several protease preparations for their usefulness in deodorization and reported that a pepsin treatment followed by ether extraction is most effective for deodorizing some protein preparations of soybean and fish. 

Soymilk. In the traditional process, soybeans are soaked in water, ground into a slurry, cooked, and filtered to remove the insoluble cell wall and hull fractions. A number of modifications have been made in the process since the 1960s, including heat treatment before or during grinding to inactivate the enzyme lipoxygenase and thus prevent formation of grassy and beany flavors. The soymilks are available in plain and flavored, eg, vanilla and chocolate, forms (90,91). 

Chiba, H. N. Takahashi R. Sasaki. Enzymatic improvement of food flavor II. Removal of beany flavor from soybean products by aldehyde dehydrogenase. Agric. Biol Chem. 1979, 43, 1883-1889. 

Many techniques have been used to reduce or eliminate beany flavors. Four strategies are used to reduce beany flavors selecting the right beans, preventing beany flavor formation, striping off the responsible volatiles once they are formed, and masking the residual off-flavor with flavorings. 

A steam-infusion cooking process, known as hydrothermal cooking (HTC), was developed to produce soymilk continuously from ground full-fat soy flour (Johnson et al., 1981). It was claimed that soymilk processed by the HTC process had less beany flavors because of the much shorter time for lipoxygenase to be active and because steam flashing stripped volatiles. The process also increased recovery of dry matter and protein in the soymilk. 

Recently, a high-pressure procedure was found to inactivate lipoxygenase in soymilk. The beany flavor of the final product was not evaluated in the study (Wang et al., 2008). 

Since lipoxygenase activity is a major cause of beany flavor formation during processing of soy products, an alternative strategy to control beany flavor in soymilk... 

In recent years, some tofu products, such as deep-fried tofu and savory tofu, have been observed in the Western market and are gaining popularity. In general, these products are ready-to-eat and have much less beany flavor. Thus, they have received higher acceptance levels than regular plain tofu, with which Westerners are still not familiar in terms of preparation and texture. 

In North America, frozen vegetable soybeans have long appeared in the marketplace. Some of the products may be marketed under a brand name of Sweet Beans. They are gaining popularity due to their tender texture, low beany flavor, and resemblance in preparation to frozen corns and peas. In making frozen vegetable soybeans, freshly harvested beans are de-shelled, blanched, and frozen. 

Lipoxygenase- and other enzyme-catalyzed reactions, however, are not the sole source of beany flavors in soy products. Soybean oil is highly polyunsaturated, and these lipids are also prone to nonenzymatic oxidation, which can affect flavor characteristics of soy products. 

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