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

Abstract

Volatile compounds from soymilk were analyzed by gas chromatography/olfactometry/mass spectrometry (GCO/MS) with direct injection of various volumes of static headspaces. The most powerful odorants, determined by the minimum headspace volume required to detect by olfactometry, were (i) hexanal, (ii) acetaldehyde, (iii) methanethiol, (iv) dimethyl trisulfide (DMTS), and (v) 2-pentyl furan. Analyses of soymilk prepared with the addition of 100 ppm gallic acid revealed that the only two detectable odorants were hexanal and acetaldehyde. Sensory analyses of the soymilk treated with 100 ppm gallic acid produced a significantly lower score (P = 0.0006) for overall odor intensity compared with the control soymilk. Aqueous slurries of soy protein isolates (SPI) prepared with the addition of 100 ppm gallic acid also had lower odor intensities than the control SPI (P < 0.0001). GCO/MS analyses of headspace volatiles revealed that the gallic acid treatment had removed all detectable levels of methanethiol and DMTS while having no significant effect on the level of hexanal (P = 0.81).Paper no. J9897 in JAOCS 79, 317-323 (April 2002).

Olfactory Perception of Major Odorants Found in the Headspace of Aqueous Soy Protein Isolate Slurries

“…This was repeated with various levels of odorants until each odorant in the headspace closely matched the levels found in the headspace of aqueous SPI slurries. The levels of methanethiol, hexanal, 2-pentyl furan, and DTMS in the headspace above aqueous slurries of the SPI used in this investigation are similar to those observed in other commercial SPI (Boatright and Lei 2000;Lei and Boatright 2001;Boatright 2002).…”

“…Aldehydes and ketones resulting from lipid oxidation are generally believed to be responsible for oxidized offflavors (Heath and Reineccius 1986). Boatright andLei (1999, 2000) and Lei and Boatright (2001) revealed the presence of sulfur-containing odorants, methanethiol, and dimethyl trisulfide (DMTS) in the headspace of aqueous SPI and soy protein concentrate (SPC) slurries. The presence of methanethiol and DMTS in soymilk, and their contribution to soymilk odor, was also recently documented (Boatright 2002).…”

“…Quantification of odorants was achieved by setting a mass selective detector to detect selected ions (SIM) for increased sensitivity according to the method of Boatright (2002). A total of 6 replications were performed.…”

Residual Sulfur Metabolites in Isolated Soy Proteins: Sulfite to Cysteine

“…M ethanethiol and dimethyl trisulfide (DMTS) have been shown to make an important contribution to the odor of soy protein isolates, concentrates, and soymilk (Boatright and Lei 2000;Lei and Boatright 2001;Boatright 2002;Ang and Boatright 2003). Other foods that contain enough methanethiol to make a significant flavor contribution include fermented dairy products (Weimer and others 1999;Bonnarme and others 2001), Brassica vegetables (Hansen and others 1992;Forney and Jordan 1999), beef broth (Guth and Grosch 1994), and a meat-like flavoring from hydrolyzed soy protein (Wu and Cadwallader 2002).…”

Sulfite‐Radical Anions in Isolated Soy Proteins

“…A primary impediment to the use of soy proteins in human foods has been their objectionable flavor (McLeod 1988; Wilson and others 1990; Rah and others 2004). Methanethiol has been found to make a major contribution to the odor of soy protein products, with odor values (in air) ranging from 14 to 115 (Boatright 2002). Hexanal odor values (in air) ranged from 15 to 103.…”