S-methylmethionine sulfonium in fruits of citrus hybrids

Methanethiol, an Off-Flavor Produced from the Thermal Treatment of Mandarin Juices: A Study of Citrus Sulfur Volatiles

The off-flavor produced after thermal stabilization of mandarin (Citrus reticulata, Blanco) juices has limited the production of commercial juices. Methanethiol, a putrid-smelling sulfur volatile, has been identified for the first time in heated mandarin juices. Identification was achieved using a combination of capillary gas chromatography with two dissimilar columns and a dual sulfur-specific pulsed flame photometric detector and selected ion mass spectrometry detection. Static headspace solid-phase microextraction quantitation found that average odor activity values (OAVs) in heated juices were 25.5 for methanethiol compared to 10.8 for dimethyl sulfide. OAVs for methanethiol and dimethyl sulfide in fresh juices were ND (not detected) and 5.5, respectively. Hydrogen sulfide, carbonyl sulfide, carbon disulfide, and dimethyl disulfide were also identified and quantitated. Thermal decomposition studies of nonvolatile sulfur-containing potential precursors indicated that methionine was the major source of methanethiol. Additional heating studies with model juices demonstrated that ascorbic acid greatly accelerated the formation of methanethiol and methional, as well as dimethyl di and tri sulfides.

Determination of S-methyl-L-methionine (SMM) from Brassicaceae Family Vegetables and Characterization of the Intestinal Transport of SMM by Caco-2 Cells

The objectives of the current study were to determine S-methyl-L-methionine (SMM) from various Brassicaceae family vegetables by using validated analytical method and to characterize the intestinal transport mechanism of SMM by the Caco-2 cells. The SMM is well known to provide therapeutic activity in peptic ulcers. The amount of SMM from various Brassicaceae family vegetables ranged from 89.08 ± 1.68 μg/g to 535.98 ± 4.85 μg/g of dry weight by using validated ultra-performance liquid chromatography-electrospray ionization-mass spectrometry method. For elucidating intestinal transport mechanism, the cells were incubated with or without transport inhibitors, energy source, or a metabolic inhibitor. Phloridzin and verapamil as inhibitors of sodium glucose transport protein (SGLT1) and P-glycoprotein, respectively, were not responsible for cellular uptake of SMM. Glucose and sodium azide were not affected by the cellular accumulation of SMM. The efflux ratio of SMM was 0.26, implying that it is not effluxed through Caco-2 cells. The apparent coefficient permeability (P_app ) of SMM was 4.69 × 10^-5 cm/s, indicating that it will show good oral absorption in in vivo.

Identification of S-methylmethionine in Petit Manseng grapes as dimethyl sulphide precursor in wine

A procedure for the extraction of free amino acids was applied to isolate S-methylmethionine (SMM) from late harvest Petit Manseng grapes. Grapes were destemmed and crushed, and the obtained clarified must was percolated through cation-exchange resins (Dowex 50 WX4-100). The retained compounds were eluted with ammonia solution and the extract was finally concentrated. Taking into account the potential DMS (PDMS using heat-alkaline treatment assay) of the initial grape juice used (51.5nmolmL(-1)) and the concentration factor of the extract (17.9-fold), the PDMS of the final extract (678nmolmL(-1)) gave an overall recovery of 73.5% for juice SMM. This compound was identified and quantified (484.5nmolmL(-1) relatively to [(2)H(3)]-SMM used as internal standard) by its selective detection in this extract without derivatization by MALDI-TOF-MS using instrumentation and procedures previously reported to analyze SMM in complex natural extracts. SMM and 22 other amino acids in the initial must and in the final SMM extract were also determined using a Biochrom 30 amino acid analyser with post-column ninhydrin derivatization. SMM peak identification and quantification (401.2nmolmL(-1) relatively to norleucine used as internal standard) were carried out by comparison with commercial SMM.

Contribution of dimethyl sulfide to the aroma of Syrah and Grenache Noir wines and estimation of its potential in grapes of these varieties

The contribution of dimethyl sulfide (DMS) to the aroma of Syrah and Grenache Noir wines from the Rhone Valley of France was investigated by sensory analysis, and its levels in these wines were measured. The potential DMS in the corresponding grapes and wines, susceptible to release during wine aging, was evaluated. Free DMS and potential DMS assessed by a heat-alkaline treatment were measured in grape juices and wines by SPME-GC-MS using methods previously reported and slightly modified. A relationship between potential DMS from grapes and the total DMS levels in wine was demonstrated. Furthermore, a linear regression between the ratio of free DMS levels to these total DMS levels in wine and time of storage was found. Free and potential DMS levels in grapes and wines depended on grape variety, vintage, and vine location. DMS imparted a noticeable and complex contribution to the aroma of the wines investigated, depending on the mode of sensory perception used, either before or after glass swirling. It significantly enhanced the fruity notes of the wines, and additional truffle and black olive notes.