Changes in the Profile of Genistein, Daidzein, and Their Conjugates during Thermal Processing of Tofu

Abstract

Profiles of genistein, daidzein, genistin, daidzin, and their acetyl- and malonyl-beta-glycosides were determined in tofu as affected by temperature and time. Tofu was heated in water at 80, 90, and 100 degrees C for 0 (control), 10, 20, 30, and 40 min, and the contents of the isoflavones of interest were quantified using reversed-phase HPLC. Total isoflavone content decreased most likely due to leaching of isoflavones into the water. Because the content of the isoflavones of the genistein series was little affected by the treatments, the decrease in the total isoflavone content was almost exclusively due to a decrease of the daidzein series. Changes in the profile of the daidzein series suggest little decarboxylation of the malonylglycoside to the acetylglycoside, but considerable de-esterification of the malonyl- and acetylglycoside to the beta-glucoside. Strongly temperature dependent decreases of the aglycon suggest possible thermal degradation of daidzein in addition to losses due to leaching.

Thermal stability of kudzu root (Pueraria Radix) isoflavones as additives to beef patties

“…The heat of cooking did not affect the stability of the isoflavones in beef patties treated with kudzu root extract. These results are in agreement with other researchers (Grun et al 2001;Hendrich and Murphy 2001;Jackson et al 2002;Uzzan and Labuza 2004) who reported that isoflavones are not destroyed by heat during cooking, rather the isoflavones are lost when they leach into the discarded cooking liquid. There are other researchers (Uzzan and Labuza 2004), however, who have observed qualitative and quantitative degradations of isoflavones when isoflavones are heated to higher temperatures or longer times than normal food processing conditions.…”

Teores de isoflavonas e capacidade antioxidante da soja e produtos derivados

“…As isoflavonas apresentam-se em 4 formas químicas, somando assim 12 isômeros: as agliconas daidzeína, genisteína e gliciteína; os β-glicosídeos daidzina, genistina e glicitina; e os derivados glicosilados acetilados 6''-O-acetildaidzina, 6''-O-acetilgenistina, 6''-O-acetilglicitina; e glicosilados malonilados 6''-O-malonildaidzina, 6''-O-malonilgenistina e 6''-O-malonilglicitina [14,11]. Os derivados protéicos da soja, como farinhas desengorduradas, isolados, concentrados e texturizados protéi-cos são amplamente utilizados na indústria alimentícia em decorrência de suas propriedades funcionais.…”

Isoflavone and protein content in soybeans grains submitted to flooding at different stages of development

“…However, in this research, it was noted that the types of isoflavones found in greater quantities in the grains of plants that were flooded at the R4 stage, were the glycosyl isoflavones and those that can be converted to aglycones, which are benefic to human health, during the industrial processing of grains. According to GRUN et al (2001), in products derived from soybeans, like tofu and many others, when subjected to certain heat treatments, the malonyl forms suffer biotransformations and become aglycones, thus increasing the levels of the components responsible for its functional effects. Similarly, several authors report that the levels of aglycone isoflavones increased due to the processing and that the malonyl levels are reduced by cleavage of ester groups and by the heat that the extract is subjected to (PARK et al, 2001;CARRÃO-PANIZZI et al, 2003;GÓES-FAVONI et al, 2004; Ciência Rural, v.41, n.12, dez, 2011.…”