Flavor Characteristics of Glutathione in Raw and Cooked Foodstuffs

Abstract

The flavor of glutathione (y-L-glutamyl-L-cysteinylglycine, GSH) was examined by several sensory evaluations. The measurement of a point of subjective equality (PSE) showed that the peptide increases the flavor characteristics but did not affect the intensity of basic tastes, such as sweetness, saltiness, sourness, and umami. However ~ the threshold value of GSH decreased significantly in an umami solution containing 0.05% each of monosodium glutamate (MSG) and disodium inosinate (IMP). This suggests that GSH interacts with the umami substance and has a certain effect on the flavor.GSH had a characteristic kokumi flavor, such as continuity, mouthfulness, and thickness in the umami solution as well as in a model beef extract constructed from analyzed components at a concentration of 0.02(1., w Iv. Some foodstuffs, including' meat, were found to contain GSH above its threshold value, which implicates the contribution of GSH to the flavor.The thermal degradation study suggested that a part of GSH have changed into its disulfide, pyroglutamic acid (peA), and cyc10cysteinylglycine in cooked foodstuffs.Key words: glutathione; flavor characteristics; kokumi flavor; food; thermal degradation Glutathione (Y-L-glutamyl-L-cysteinylglycine, GSH) is a well known tripeptide in organisms. The HPLC method for measuring GSH in foodstuffs was developed by Takahashi et al. 1,2) Although many studies on the chemistry and biological significance of GSH have been done, little is known about the flavor characteristics of this peptide except that GSH elicits sourness in water because of its acidic nature. We have previously studied the characteristic flavors of sulfurcontaining compounds in garlic and onion, and showed that the content of GSH was much lower than other sulfurcontaining components such as S-alk(en)y1cysteine derivatives. .4 ) GSH is also known as one of the precursors of meat aroma. When GSH is heated in an aqueous solution some meaty aroma compounds, such as furanthiols, pyrazines, and thiols are formed.5 ) However, non-volatile compounds from GSH during cooking have not been studied in detail.In this study, we examined the flavor characteristics of GSH in connection with basic tastes, such as saltiness, sweetness, sourness, and umami, and the degradation mechanism of the peptide in an aqueous solution. Materials and MethodsDeodori:::atioJ1 of GSII. Commercial GSH (Merek & Co.) has unique odors, which affect sensory tests. It was dissolved in distilled water at a concentration of 10% vv·/v. mixed with activated charcoal (Takeda Chern. Co., 1% w/v). stirred moderately for 30 min, filtered and lyophilized. The deodorized material was used in all the experiments. Measurement of'threshold vallles of' GSH ill water and umal1li solutions.Absolute threshold values in water and umami solutions were measured by the triangle difference test according to the method of Yamaguchi and Kimizuka.6 ) All the test solutions were adjusted to pH 7.0 with 1M HCI or NaOH. Taste eff'ects of' GSH on basic taste solutions. GSH was added to fou...

Involvement of the Calcium-sensing Receptor in Human Taste Perception

“…Recently, new kokumi taste substances have been isolated from an extract of edible beans, and these have been characterized by human sensory analysis (10). The active substances were identified as the ␥-Glu dipeptides ␥-Glu-Val and ␥-Glu-Leu, which appear in the list of CaSR agonist peptides that we identified (Table 1).…”

“…GSH (␥-glutamylcysteinylglycine), a typical kokumi taste substance, is abundantly present in food-grade yeast extract, which is commercially available and has been used to make foods taste savory and hearty. The kokumi taste was first characterized by Ueda et al (9,10), who isolated a kokumi taste substance from water extracts of garlic and onion and identified GSH as the main active ingredient. GSH itself is tasteless; however, in the presence of small amounts of umami taste substances such as monosodium glutamate (MSG) and IMP, GSH synergistically reinforces those tastes.…”

Supercritical Fluid Extraction of “Koku” Enhancing Compounds from Fish and Fishery by-Products

“…The "koku" enhancing activities of individual extracted fractions were evaluated for effects on sensory perception using Japanese noodle soup, following the modified method of Ueda et al (1997). Japanese noodle soup was prepared according to the method described by Shah et al (2009), diluted with six volumes of distilled water and used as the control solution.…”

“…Furthermore, it was reported that pyrazines and some peptides, generated together in certain foods during the process of boiling or aging for extended periods, M. Shibata et al 1200 form "koku" (Ogasawara, 2003). It is also known that some γ-glutamyl peptides such as glutathione enhance "koku" (Ueda et al, 1997;Kawajiri, 1999;Dunkel et al, 2007;Toelstede et al, 2009). …”

Evaluation of wheat gluten hydrolysates as taste-active compounds with antioxidant activity

“…Therefore, the food seasoning manufacturers have made a lot of efforts to meet the consumer preference for natural products. For example, Japanese manufacturers were able to develop a naturally-made ingredient from fermented products, enzymatic hydrolysate, vegetable and fishery extracts, and yeast extracts (Ueda et al 1990(Ueda et al , 1997Tomohiko 2006). Hedwig and Amado (2002) also reported that peptides derived from vegetable proteins, such as soybeans, wheat, and corn, by enzymatic hydrolysis were associated with umami, a savory taste produced by glutamic acid or pyroglutamic acid.…”