Residual Sulfur Metabolites in Isolated Soy Proteins: Sulfite to Cysteine

Boatright, W.L.; Stine, J.

doi:10.1111/j.1365-2621.2004.tb13358.x

Cited by 7 publications

(27 citation statements)

References 44 publications

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“…To our knowledge there is no published work addressing the synthesis of hexanal in ISP; however, in previous research in our laboratory into the effect of various reducing agents on the sulfur-containing odorants in ISP [18], we observed that when 6.5 mM dithiothreitol (DTT) was added to aqueous slurries of commercial ISP there were large increases in headspace hexanal levels compared with the levels in the controls. Monma et al [19] and Kemal et al [20] indicated that soybean LOX-1, LOX-2 and/or LOX-3 activities were inhibited by DTT.…”

Section: Introductionmentioning

confidence: 90%

Hexanal Synthesis in Isolated Soy Proteins

Boatright

2007

J Americ Oil Chem Soc

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Sodium erythrobate (2.3 mM) and dithiothreitol (6.5 mM) caused headspace hexanal from aqueous slurries of commercial isolated soy proteins (ISP) to increase by as much as 13-fold compared with headspace hexanal in the controls. When linoleic acid was also added, headspace hexanal levels from commercial and laboratory-prepared ISP were further increased by as much as 18-and 136-fold, respectively, compared with the levels in the controls. When 13 Clabeled linoleic acid was added to aqueous mixtures of laboratory-prepared ISP along with reducing agents, 96% of the resulting hexanal contained the 13 C isotope. Commercial ISP samples had about 40% of the isotopically labeled carbon incorporated into hexanal. These large increases in hexanal were almost completely prevented by heating the aqueous ISP to 100°C or above prior to adding the reducing agent and linoleic acid. Adding cysteine or sodium sulfite reduced headspace hexanal levels from aqueous ISP slurries by more than 88%. Thiol blockers, iodoacetic acid and N-ethylmaleimide, did not affect hexanal levels.

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Section: Introductionmentioning

confidence: 90%

Hexanal Synthesis in Isolated Soy Proteins

Boatright

2007

J Americ Oil Chem Soc

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“…50 The ability of this class of enzymes to break C-S linkages appears to be dependent on the bacterial species, as a recent study showed that Lactobacillus casei was able to cleave cysteine but this did not occur in Lactobacillus helveticus. 58,59 Methionine γ-lyase purified from Brevibacterium spp. was shown to cleave L-methionine into ammonia and 2-oxobutyrate but also L-cysteine to ammonia, hydrogen sulphide and pyruvate.…”

Section: Bioconversion Of Cysteinementioning

confidence: 99%

The role of cysteine and cysteine–S conjugates as odour precursors in the flavour and fragrance industry

Starkenmann

Troccaz

2008

Flavour & Fragrance J

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Volatile sulphur compounds are important odorants in the flavour and fragrance industries. Recent developments in the field have reinvigorated sulphur compound research, particularly with regard to the precursor compounds of volatile thiols. The present review concentrates on the role of cysteine and cysteine-S conjugates as precursor compounds for a variety of aromas and examines the chemical and enzymatic pathways of degradation and biotransformation. Cysteine is an important source of sulphur in flavour chemistry and may be degraded into hydrogen sulphide, which can further participate in other reactions. Direct reactions of cysteine and the pathways particular to various flavours and fragrances are discussed, with an emphasis on the precursor compounds cysteine-S conjugates. The importance of cysteine precursors in plants, including onion, wine, passion fruit, bitter orange, asparagus and bell pepper and the formation of natural scents in cats and humans are discussed. Reactivity of Cysteine with Aldehydes and Ketones Reaction of cysteine with saturated carbonylsCysteine 1 is a bidentate nucleophile. The nitrogen is considered a hard nucleophile and the sulphur atom a soft nucleophile. 5 This leads to the formation of the Schiff base when cysteine 1 reacts with saturated aldehydes 2

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“…The actual sulfite content in ISP slurry might be significantly higher due to release of bound sulfite from cysteine‐S‐sulfonates. The modified Monnier‐Williams method used by Boatright and Stine (2004) is only capable of detecting the free sulfite that exists in dry ISP. Boatright and others (2006) found as much as 43 mg/kg cysteine‐S‐sulfonates in ISP samples but the method employed used extensive enzymatic hydrolysis of the protein prior to HPLC analysis.…”

Section: Resultsmentioning

confidence: 99%

“…In a 250‐mL flask, 100 mL of 20‐mM Tris buffer, pH 7.2 containing 3.6 μM MnCl 2 , and 3.2 mM L‐methionine (or L‐methionine‐methyl‐ 13 C 1 ) were combined with varying levels of sodium sulfite (0 to 250 μM). After mixing for 60 min at 22 °C, 10 mL of the static headspace was withdrawn and analyzed by gas chromatography/mass spectroscopy (GC/MS) as described by Boatright and Stine (2004). For methanethiol, m/z 47 was used and m/z 48 was used for methanethiol‐ 13 C.…”

Section: Methodsmentioning

confidence: 99%

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Sulfite‐Radical Anions in Isolated Soy Proteins

Lei¹,

Boatright²

2007

Journal of Food Science

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Aqueous mixtures of manganese and sulfite, at levels found in isolated soy proteins (ISP) and defatted soy flakes, spontaneously react in the presence of oxygen to produce methanethiol from the 1-electron oxidation of methionine. The carbon and sulfur of methanethiol originate from the methyl-carbon and sulfur of methionine. Similar aqueous mixtures of sulfite, manganese, and oxygen also produce sufficient levels of free radicals to degrade fluorescein. The degradation of methionine by free radicals generated in the sulfite, manganese, and oxygen reaction mixture is inhibited by the free radical spin trapping agent 5,5-dimethyl-1-pyrroline N-oxide. Processing ISP with either L-cystine or potassium iodate reduces the free sulfite content of ISP and reduces the headspace methanethiol from aqueous ISP slurries to nondetectable levels. ISP processed without additives contained sufficient levels of free radicals to generate methanethiol from the oxidation of added methionine. There were no detectable levels of methanethiol produced when methionine was added to ISP processed with iodate.

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Residual Sulfur Metabolites in Isolated Soy Proteins: Sulfite to Cysteine

Cited by 7 publications

References 44 publications

Hexanal Synthesis in Isolated Soy Proteins

Hexanal Synthesis in Isolated Soy Proteins

The role of cysteine and cysteine–S conjugates as odour precursors in the flavour and fragrance industry

Sulfite‐Radical Anions in Isolated Soy Proteins

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