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

Abstract

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.

Flavour stability of sterilised chickpeas stored in pouches

“…This was in line with the sensory test where the aroma of boiled potato was increasing in intensity during storage time in chickpeas stored in plastic pouches. Methional can be formed by the degradation of methionine ( Cheng et al, 2020 ). For other compounds, changes could not be linked to the sensory results in section 3.1 .…”

Identification of Key Off-Flavor Compounds in Thermally Treated Watermelon Juice via Gas Chromatography–Olfactometry–Mass Spectrometry, Aroma Recombination, and Omission Experiments

“…In thermally processed muskmelon juice, volatile sulfur compounds, and small molecular aliphatic aldehydes also contributed to the off-odors [31]. Methanethiol and dimethyl sulfide were the key off-flavor compounds identified in thermal mandarin juices [32]. Thermal degradation of sulfur-containing amino acids and unsaturated fatty acid, as well as Maillard reactions in juice, contributed to the generation of the thermal-induced off-notes [33,34].…”

Targeted Metabolomics With a Chemometric Study of Oxygenated Heterocyclic Aglycones as a Tool for Preliminary Authenticity Assessment of Orange and Grapefruit Juices

“…To be noted, Satsuma mandarin ( Citrus unshiu Marc. ), which is well-known to produce strong sulfuric off-flavors after heating and storage ( 30 ), is not often used for addition into orange juice. Therefore, the data of Satsuma juices were not included.…”