Isoflavone Changes in Immature and Mature Soybeans by Thermal Processing

Abstract

The isoflavone changes occurring in mature soybeans during food processing have been well studied, but less information is available on the changes in immature soybeans during thermal processing. This study aimed to determine the effect of thermal processing by dry- or wet-heating on the changes in the isoflavone profiles of immature and mature soybeans. In the malonylglycoside forms of isoflavone, their deglycosylation was more severe after wet-heating than after dry-heating regardless of the soybean maturity. The malonyl forms of isoflavones in the immature seeds were drastically degraded after a short wet-heating process. In the acetylglycoside forms of isoflavone, dry-heating produced relatively low amounts of the acetyl types in the immature soybeans compared with those in the mature soybeans. These results were explained by the content of acetyldaidzin being relatively less changed after dry-heating immature soybeans but increasing four to five times in the mature soybeans. More of the other types of acetylglycoside were produced by dry-heating soybeans regardless of their maturity. Acetylgenistin in wet-heating was a key molecule because its content was unchanged in the immature soybeans during processing but increased in the mature soybeans. This determined the total acetylglycoside content after wet-heating. In contrast, most of the acetyl forms of isoflavone were produced after 90 to 120 min of dry-heating regardless of the seed maturity. It can be suggested that the pattern of isoflavone conversion was significantly affected by the innate water content of the seeds, with a lower water content in the mature soybeans leading to the greater production of acetyl isoflavones regardless of the processing method even if only applied for a relatively short time. The results suggested that the isoflavone conversion in the immature soybeans mainly follows the wet-heating process and can be promoted in the application of stronger processing.

Accumulation of Antioxidative Phenolics and Carotenoids Using Thermal Processing in Different Stages of Momordica charantia Fruit

“…Furthermore, hot-air drying is one of the most commonly employed heat treatments that alters not only the physical properties (such as hardness) but also the chemical properties (such as polyphenol decomposition) of food materials. Heat treatment increases taste preferences by promoting nonenzymatic reactions in food or inducing a change in flavor components [ 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 ]. Heat treatment can cause an increase in phenolic compounds and antioxidant activity in various fruit crops such as citrus, persimmon peel, and eggplant fruit [ 10 , 14 , 15 ].…”

“…Phenolic compounds can be increased or decreased depending on the crops, maturity, and processing methods. It was reported that the phenolic content decreased as the olive fruit matured, while it increased as soybean seed matured [ 9 , 22 ]. Moreover, the total phenolic content decreased during thermal processing in the flesh of persimmon fruit with the decrease in antioxidant activity, while it increased in the peel [ 10 ].…”

Tissue-Specific Antioxidant Activities of Germinated Seeds in Lentil Cultivars during Thermal Processing

“…The kaempferol contents in LG and LR increased from 446.73 μg/g DW and 93.80 μg/g DW in the NGS after a 30 °C treatment to, respectively, 482.87 μg/g DW and 163.81 μg/g DW after treatments at higher temperatures. During heat processing, either the release of bound flavonoids or the acceleration of the extract ratio might account for this sort of increase [ 24 , 28 , 37 ]. The GS showed relatively low level of flavonoids in comparison with the NGS ( Table 2 ).…”

Thermal Control Using Far-Infrared Irradiation for Producing Deglycosylated Bioactive Compounds from Korean Ginseng Leaves

“…This can be explained by the different progressions of thermal processing (methods, time, temperature, etc.) affecting different substances [ 13 , 37 , 38 , 39 , 40 , 41 ], as Rk3 and Rh4 are the deglycosylated products of Rg6 and F4 at C-6, respectively. Ginsenoside mutations in ginseng leaves during heat treatment have not been widely studied in the literature, especially in terms of dry-heat treatment.…”