Compounds Contributing to the “Beany” Odor of Aqueous Solutions of Soy Protein Isolates

Abstract

Using gas chromatography/olfactometry (GCO), major odors from the headspace of aqueous solutions of soy protein isolates were evaluated. Many corresponding odorants were identified by correlating GCO with GC/mass spectrometry (MS) on two separate stationary phases followed by comparing retention times, mass spectra, odor descriptions and odor intensities with authentic standards. Based on aroma extract dilution analyses, the most powerful odorants (strongest and most volatile first) were (1) dimethyl trisulfide, (2) trans,trans-2,4decadienal, (3) an unidentified burnt soy sauce-like odor, (4) 2-pentyl pyridine, (5) trans,trans-2,4-nonadienal, (6) hexanal, (7) an unidentified charred sweaty feet-like odor, (8) acetophenone, and (9) 1-octen-3-one. This is the first reported occurrence of dimethyl trisulfide in soy protein isolates.

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 .…”

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

“…Substances A and E were identified as n-pentanal and n-hexanal. Both aldehydes originated from lipid oxidation of linoleic acid and were previously described as compounds contributing to the beany off-flavour of soy products (Boatright & Lei, 1999;Rackis et al, 1979). They were characterised by low odour thresholds of 12 ppb (n-pentanal) (Buttery, Turnbaugh, & Ling, 1988) and 4.5 ppb (n-hexanal) in water (Buttery et al, 1999), respectively.…”

“…For this reason, the volatiles were trapped on Tenax TA using dynamic headspace sampling. n-Hexanal served as a lead compound, as it is well known as one of the main principles causing flavour deterioration in legume products (Boatright & Lei, 1999;Kobayashi et al, 1995;Rackis et al, 1979).…”

“…A masking or a modification of the off-flavour, at least on the short term, was achieved by either fermentation with Lactobacillus or Streptococcus strains, or by using soybean cultivars lacking lipoxygenase isozymes. n-Hexanal, a lipoxygenase derived degradation product of linoleic acid, was identified as a key off-flavour compound in legume products (Blagden & Gilliland, 2005;Boatright & Lei, 1999;Kobayashi, Tsuda, Hirata, Kubota, & Kitamura, 1995;Rackis, Sessa, & Honig, 1979).…”

Changes in aroma characteristics of simulated beef flavour by soy protein isolate assessed by descriptive sensory analysis and gas chromatography

“…Flavour related problems including ''beany'' odour (Boatright & Lei, 1999;Lei & Boatright, 2001;Wolf, 1975) and off-flavour (Inouye, Shiihara, Uno, & Takita, 2002;Maheshwari, Ooi, & Nikolov, 1995;McDaniel & Chan, 1988) have created technical obstacles to be overcome for the increased usage of soy proteins in human foods (Maheshwari et al, 1995). Aside from these undesirable yet hard-to-remove soy aromas, the interactions of soy proteins with desirable aroma components of added flavour formulations have presented a different challenge for soy based products.…”