Headspace Evaluation of Methanethiol and Dimethyl Trisulfide in Aqueous Solutions of Soy‐protein Isolates

Abstract

Volatile compounds from 2 samples of aqueous soy-protein isolates (SPI) (7%) were analyzed using both static and dynamic headspace methods. Based on dynamic headspace analyses, the most powerful odorants were (1) dimethyl trisulfide, (2) methanethiol, (3) hexanal, (4) an unidentified charred, sweaty feet-like odor, (5) 2-pentyl furan, (6) 2,3-butadione, and (7) an unknown burnt-like odor. The most powerful odorants by static headspace analyses were (1) dimethyl trisulfide, (2) hexanal, (3) methanethiol, and (4) 2-pentyl furan. Using deuterium labeled DMTS as an internal standard, DMTS was quantified at 60.1 and 45.5 ppb in the SPIs. This corresponds to odor values of 6014 and 4554, respectively. Using a cool, on-column technique, direct injection of concentrated-headspace volatiles and solvent-recovered volatiles with an internal standard of d 6 -DMTS detected both methanethiol and DMTS at similar levels as with the traditional injection methods.

Changes in Volatile Sulfur Compounds in Strawberry Puree during Heating

“…There was no significant difference in the chromatograms obtained at the 3 temperatures, suggesting that there is little if any thermal conversion of the sulfur volatiles in the GC injector. This conclusion agrees with the study of Boatright and Lei (2000). They evaluated methanethiol and dimethyl trisulfide in soy protein isolates using GCO/MS with GC injector temperatures of 130 °C and 210 °C.…”

Effect of gallic acid on the aroma constituents of soymilk and soy protein isolates

“…We also compared the minimum level of methanethiol detectable by GCO and found that we could clearly detect 0.08 ng at the sniff port and 0.04 ng was not clearly detectable. Determinations of the minimum quantity necessary to detect these compounds by olfactometry was accomplished by the same two investigators that performed the olfactometry analyses in our previous investigations (18,29). By using 0.058 mg/m 3 as the odor threshold for hexanal, the calculated odor threshold for methanethiol using this method is 0.0014 mg/m 3 .…”

“…In a previous investigation (18), GCO was used to identify major odorants from the headspace of aqueous solutions of soy protein isolates (SPI) using both static and dynamic headspace methods. Based on dynamic headspace analyses, the most powerful odorants were (i) dimethyl trisulfide (DMTS), (ii) methanethiol, (iii) hexanal, (iv) an unidentified charred sweaty feet-like odor, (v) 2-pentyl furan, (vi) 2,3-butadione, and (vii) an unknown burnt-like odor.…”

Lactic fermentation to improve the aroma of protein extracts of sweet lupin (Lupinus angustifolius)

“…With its low odour threshold of 0.008 ppb in water (Milo & Grosch, 1996), dimethyl trisulfide is suggested to play an important part as key aroma compound in lupin protein extracts. Boatright and Lei (2000) found methanethiol as possible precursor of dimethyl trisulfide in the headspace of soy protein extracts.…”