4-Methyl-5-Acetyl Thiazole
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HS Code |
593080 |
| Chemical Formula | C6H7NOS |
| Molecular Weight | 141.19 |
| Appearance | Colorless to pale yellow liquid |
| Odor | Roasted, nutty, and meaty odor |
| Boiling Point | 191 - 193 °C |
| Density | 1.175 g/cm³ at 25 °C |
| Solubility | Slightly soluble in water, soluble in organic solvents like ethanol, ether |
| Flash Point | 78 °C |
| Stability | Stable under normal conditions, but may react with strong oxidizing agents |
| Usage | Used in the food industry as a flavoring agent |
As an accredited 4-Methyl-5-Acetyl Thiazole factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | 500g of 4 - Methyl - 5 - Acetyl Thiazole packaged in a sealed, chemical - resistant bottle. |
| Shipping | 4 - Methyl - 5 - Acetyl Thiazole is shipped in well - sealed, corrosion - resistant containers. Packaging ensures protection from physical damage and environmental factors during transit, following strict chemical shipping regulations. |
| Storage | 4 - Methyl - 5 - Acetyl Thiazole should be stored in a cool, dry, and well - ventilated area. Keep it away from heat sources, open flames, and oxidizing agents. Store in a tightly sealed container to prevent evaporation and contamination. Preferably, store in a dedicated chemical storage cabinet with proper labeling for easy identification and safety. |
What Limits the Shelf Stability of Wet Reaction Flavours Containing 4-Methyl-5-Acetyl Thiazole?Production of process meat flavours via the Maillard pathway commonly incorporates 4-Methyl-5-Acetyl Thiazole (FEMA 3206, JECFA 1030, FL-no 15.010) at weight-in levels ranging from 0.05% to 0.2% of the reaction substrate, yielding final product concentrations in the ready-to-eat food matrix of 0.1–2.0 mg/kg under 21 CFR 172.515 good manufacturing practice and EU Regulation 1334/2008 Annex I. In a 1,000 L jacketed stainless steel reactor equipped with a reflux condenser and a bottom-entrainment agitator operating at 60–90 rpm, the reaction mass — typically hydrolysed vegetable protein, xylose, L-cysteine hydrochloride, thiamine hydrochloride, and sodium phosphate buffer to maintain pH 5.0–5.8 — is heated to 102–110 °C for 90–150 minutes. The compound is pre-emulsified into the oil phase (e.g., refined chicken fat or palm olein) using a high-shear rotor-stator mixer at 3,000 rpm for 10 minutes before dosing into the aqueous-amino acid solution, a sequence critical to preventing localized thiazole oxidation at the liquid-air interface. A recurrent failure mode observed at pilot scale involves excessive headspace oxygen (> 2% v/v) during the heating ramp, triggering irreversible transformation of the acetylthiazole to sulfoxide and sulfone derivatives that introduce a distinctly medicinal off-note; this necessitates nitrogen blanketing and in-line monitoring of dissolved oxygen with optical probes. Final products include liquid pastes (moisture 38–42%) and spray-dried powders on maltodextrin carrier, which are subsequently deployed in bouillon cubes, instant gravies, retorted meat stews, and plant-based meat analogues. When transitioning from batch to semi-continuous operation, the residence time distribution in a scraped-surface heat exchanger must be held within ±3 minutes of the target 105 °C plateau to constrain the C5-thiazole ring-opening side reaction that accelerates once the temperature exceeds 112 °C. In high-pressure homogenised coffee concentrates intended for ready-to-drink (RTD) cold brew beverages and single-serve capsule extraction, 4-Methyl-5-Acetyl Thiazole is introduced at the liquid blending stage after vacuum evaporation at 45 °C and 120 mbar but upstream of the UHT sterilisation plate heat exchanger. Addition levels in the final reconstituted beverage typically fall between 0.2 mg/kg and 0.8 mg/kg as consumed; this range is endorsed within the same FEMA GRAS and EU Union List frameworks, with compliance also verified against JECFA 1030 specifications for purity — minimum assay 98% by GC, refractive index n20/D 1.540–1.550. The downstream manufacturing process relies on a pre-mix of the thiazole with propylene glycol (1:10 w/w) metered via a positive displacement diaphragm pump into the coffee concentrate at 8 °C, immediately followed by two-stage high-pressure homogenisation (first stage 200 bar, second stage 50 bar) to ensure colloidal dispersion and prevent creaming of the flavour-bearing micro-droplets during 6-month ambient shelf storage. Terminal products span aseptically filled PET bottles, aluminium capsule lidding films, and bag-in-box syrups for fountain dispensers. A notable operational constraint involves pH: if the coffee concentrate drops below pH 4.8 due to acidification for microbial stability, the thiazole undergoes proton-catalysed hydrolysis of the acetyl group, diminishing the roasted cereal character over the first 60 days of storage at 35 °C. Published data for this specific configuration is limited, but in-house accelerated aging protocols specify not exceeding pH 5.1 for formulations reliant on this compound as the primary roasted top note. Roasted Nut and Seed Seasoning: Mitigating Lipid Oxidation During Accelerated StorageAccelerated shelf-life testing at 40 °C and 60% RH on peanut, cashew, and sunflower kernel snacks seasoned with a dry-adhesive powder blend containing 4-Methyl-5-Acetyl Thiazole at 1.0–3.0 mg/kg (final snack weight) demonstrates that the compound's partition coefficient between the carbohydrate coating matrix and the nut lipid phase governs both aroma release and oxidative stability. Under FEMA 3206 and 21 CFR 172.515 GRAS provisions, the flavour is pre-plated onto a DE 10–12 maltodextrin carrier with 5% silicon dioxide anti-caking agent using a ribbon blender for 15 minutes, then topically applied in a rotating seasoning drum at 0.25–0.35% total powder-on-product. The downstream process continues with a hot-air impingement toaster set at 165 °C for 90 seconds to set the coating. Final consumer units include foil-laminated stand-up pouches nitrogen-flushed to residual oxygen below 1.5%. The primary incompatibility arises when the nut substrate carries residual frying oil peroxide values above 5 meq/kg: the acetylthiazole participates in radical-mediated addition across the thiazole C-2 position, detectable as a rapid decline in sensory impact within 3 weeks and quantifiable by SPME-GC-MS as a 40–60% reduction in the m/z 141 molecular ion peak. Consequently, production specifications enforce incoming oil quality at PV ≤ 2 meq/kg and chelation of transition metals with rosemary extract containing 4% carnosic acid. When 4-Methyl-5-Acetyl Thiazole Is Dry-Blended Before Conching in Dark ChocolateUpon addition of the dry-blended premix consisting of 4-Methyl-5-Acetyl Thiazole encapsulated in 1:50 w/w hydrogenated palm stearin flakes directly into the conche at the terminal dry conching phase (50–55 °C, roller rotational speed 400 rpm), the compound imparts a toasted-cereal and faint popcorn nuance to 70–85% cocoa mass formulations without exceeding the 0.5–1.5 mg/kg final product concentration permitted under EU Regulation 1334/2008 Category 05.1 (confectionery) and JECFA 1030. The conching duration after addition is limited to 120 minutes maximum — exceeding this results in a 15–20% loss of the volatile headspace concentration of the thiazole, as verified by real-time PTR-ToF-MS monitoring at the exhaust duct, due to stripping by the dry air purge (flow rate 0.8 m³/h per 100 kg mass). Finished goods include single-origin dark chocolate bars, enrobed wafers, and couverture for confectionery moulding. A process conflict emerges when the same conche is used sequentially for milk chocolate containing lecithin and PGPR: residual phospholipids from inadequate cleaning catalyse hydrolytic degradation of the acetylthiazole to 4-methylthiazole, detectable as a sulfurous off-flavour; validated cleaning protocol mandates three hot cocoa butter rinses at 70 °C each for 20 minutes, with verification by non-target headspace GC-qMS until the signal at retention index 1140 (DB-WAX) falls below the 0.1 ppb detection limit. Thermal Losses During Tunnel Baking Determine Residual Character in Savoury CrackersDough piece core temperature during a 4-minute tunnel bake at 220–240 °C zone setpoint reaches 98–102 °C internally, conditions under which 4-Methyl-5-Acetyl Thiazole added to the dough at 2–5 mg/kg on flour weight (FEMA 3206, 21 CFR 172.515 GMP, ISO 22000-certified production line) undergoes substantial steam-distillation loss that can exceed 70–85% of the initial charge. To compensate, the industrial process adopts a split-addition approach: 30% of the formulation quantity is solubilised in the dough water phase along with sodium bicarbonate leavening, while the remaining 70% is sprayed as an oil-based suspension (5% w/w in high-oleic sunflower oil) onto the cracker surface immediately after exit from the baking band, at a product surface temperature of 95–105 °C, utilising an air-atomising nozzle array operating at 0.3 bar. Terminal SKUs range from fermented soda crackers to cheese-flavoured sandwich biscuits. The critical limiting factor is the cooling tunnel relative humidity setpoint: if the post-spray cooling stage operates above 55% RH, condensation on the product surface accelerates redistribution of the surface-deposited thiazole into the inner crumb structure, shifting the aroma burst from the initial fracture moment during mastication to a delayed background note perceived as less impactful in sensory time-intensity profiling; the operational specification therefore locks conveyor cooling air dew point at ≤ 8 °C. In the casing application stage of American-style blended cigarette tobacco, where an aqueous solution containing humectants (glycerol and propylene glycol at a 1:1 ratio totalling 25–30% of casing weight) and flavourings is sprayed onto cut lamina at 30–40% moisture addition, 4-Methyl-5-Acetyl Thiazole is dosed at 10–50 mg/kg tobacco dry weight, contributing to nutty and roasted sidestream character without triggering characterising flavour prohibitions under EU TPD 2014/40/EU for non-menthol cigarettes, provided the final smoke yield does not distinguish the brand on a perceptible flavour basis in a blinded panel. Regulatory registration is filed under national tobacco ingredient lists where the compound is explicitly authorised (e.g., German TabakerzV Anlage 2, and the European Commission's EMTOX database). The downstream process introduces the casing liquor via a rotating drum at 70–80 °C with a residence time of 2–3 minutes, before the cased tobacco is passed to a redryer cylinder operating at 120–140 °C air inlet temperature, reducing lamina moisture to 12–14%. Final manufactured forms encompass hard pack king-size cigarettes and fine-cut rolling tobacco. Concern centres on thermal degradation during re-drying: in-plant extractive FTIR measurements above the redryer exhaust indicate that a proportion of the thiazole volatilises and undergoes ring fragmentation when localised lamina surface temperatures momentarily exceed 150 °C; the mass balance deficit relative to the casing formulation input averages 18–25%, determined gravimetrically by Soxhlet extraction with dichloromethane followed by GC-FID on a DB-624 column. To minimise this loss, the casing nozzle configuration is adjusted to deliver larger droplets (volume median diameter 80–100 µm) that preferentially penetrate the lamina cut edges rather than resting on the surface.
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4-Methyl-5-acetyl thiazole (CAS 38205-66-2) is a heterocyclic flavor compound belonging to the thiazole family, characterized by a five-membered ring containing both sulfur and nitrogen with acetyl and methyl substituents at positions 5 and 4, respectively. Its molecular formula is C6H7NOS and its molecular weight is 141.19 g/mol. The compound appears as a pale yellow to amber liquid at 25 °C, with a boiling point measured at 228–230 °C under atmospheric pressure and a flash point of 92 °C (closed cup). In undiluted form, its odor profile is described as roasted, meaty, nutty, and slightly sulfuraceous, with a taste threshold in water reported at approximately 0.5–1.0 ppm.
In isomer comparisons, the 4-methyl substitution yields a distinctive sensory vector that departs from the simpler 2-acetylthiazole (CAS 24295-03-2), which delivers a predominantly popcorn-like, cereal character. The presence of the methyl group at the 4-position sterically and electronically modulates the ring’s electron density, increasing the roasted and meaty notes while reducing the harsh sulfury impact often associated with unsubstituted acetylthiazoles. When benchmarked against 2,4-dimethyl-5-acetylthiazole (CAS 38205-60-6), the 4-methyl-5-acetyl variant lacks the second methyl at position 2, resulting in a less sweet, less coffee-like profile and greater compatibility with savory reaction flavor bases where excessive sweetness would constitute a defect.
| Parameter | 4-Methyl-5-acetyl thiazole | 2-Acetylthiazole | 2,4-Dimethyl-5-acetyl thiazole |
|---|---|---|---|
| CAS | 38205-66-2 | 24295-03-2 | 38205-60-6 |
| Molecular weight (g/mol) | 141.19 | 127.16 | 155.22 |
| Boiling point (°C) | 228–230 | 212–214 | 240–242 |
| Predominant odor character | Roasted, meaty, nutty | Popcorn, cereal, nutty | Coffee, roasted, sweet |
| Taste threshold in water (ppm) | 0.5–1.0 | 0.1–0.5 | 1.0–2.0 |
These differences have practical consequences in flavor compounding. Formulators seeking a robust roasted backbone without the confectionary sweetness of the dimethyl analog or the pronounced popcorn top note of 2-acetylthiazole often select the 4-methyl-5-acetyl isomer. The compound can be synthesized via Hantzsch thiazole condensation between thioacetamide and 3-chloro-2,4-pentanedione or equivalent α-haloketone intermediates, yielding a product that can be purified to ≥ 98% (GC area percent) by fractional distillation under reduced pressure.
When 4-methyl-5-acetyl thiazole is incorporated into extruded snack matrices via a flavor premix, its retention during high-temperature, high-shear processing is governed by the residence time distribution (RTD) in the twin-screw extruder barrel and the local water activity. Trials conducted on a co-rotating twin-screw extruder with an L/D ratio of 40:1 and screw diameter of 32 mm have indicated that at barrel temperatures exceeding 160 °C in the final zone, volatile losses of the thiazole compound can reach 22–28% when the moisture content of the melt drops below 12%. Encapsulation in a high-melting hydrogenated vegetable fat (dropping point 67–70 °C) prior to extrusion reduces losses to 8–12% under identical processing conditions, as measured by solvent-assisted flavor extraction (SAFE) coupled with GC-MS and quantified against an internal standard of 2-isobutyl-3-methoxypyrazine.
The compound’s thermal degradation pathway at temperatures above 200 °C primarily involves ring-opening and subsequent Maillard-type interactions with amine-bearing matrix components. Differential scanning calorimetry (DSC) scans of the neat compound show an exothermic onset at 240 °C, but this threshold shifts lower in the presence of reducing sugars. Because many snack seasonings are applied post-extrusion, the thermally stressed thiazole is more relevant in baked crackers and indirect-expansion pellets. In such applications, post-baking application via electrostatic powder coating at 30–45 kV and 0.5–1.5% addition rate on base weight yields a more predictable final aroma profile than extrusion-incorporated flavor. Published data on degradation kinetics specific to 4-methyl-5-acetyl thiazole in twin-screw extrusion is limited; the above retention figures derive from industry technical reports cross-referencing multiple acetylthiazole analogs and should be validated on a product-specific basis.
When 4-Methyl-5-Acetyl Thiazole Is Diluted in Triacetin for Beverage Cloud EmulsionsSolubility in common flavor solvents determines the handling and dosing accuracy of this thiazole compound in manufacturing. At 20 °C, the solubility in triacetin exceeds 50% w/w, while in propylene glycol it approaches 40% w/w. In 95% ethanol, a 10% v/v stock solution remains stable without turbidity for 30 days when stored in HDPE containers at 5 °C. In aqueous systems, solubility is less than 0.1% w/w, requiring emulsification with gum acacia or modified starch esterified with octenylsuccinic anhydride (E 1450) to achieve a stable oil-in-water emulsion. The recommended emulsifier-to-flavor ratio for a 5% loaded cloud emulsion is 1.5:1 to 2:1, homogenized at 150–250 bar in a two-stage high-pressure homogenizer. Emulsion droplet size distribution measured by laser diffraction (ISO 13320:2020) should yield a D[4,3] of 0.8–1.2 µm to prevent creaming over a 6-month shelf life at ambient temperature. Incorrect solvent selection—notably, prolonged contact with benzyl alcohol at elevated temperatures—can result in Schiff base formation due to trace amine impurities originating from synthesis, manifesting as a color shift from pale yellow to deep amber within 72 hours at 40 °C.
| Jurisdiction | Reference/Standard | Status | Comments |
|---|---|---|---|
| United States | FDA 21 CFR 172.515 | Approved as synthetic flavoring substance | FEMA GRAS No. 3266 |
| European Union | Regulation (EC) No 1334/2008 | Listed in Union List as FL No. 15.103 | Evaluated by EFSA (CoE 11633) |
| JECFA | JECFA Monograph 1050 | No safety concern at current estimated dietary intake | Specification for assay ≥ 97% |
| Japan | Japan’s Food Sanitation Law, List of Designated Additives | Permitted | Must meet purity criteria per Japan Flavor & Fragrance Materials Association |
Meeting the Food Chemicals Codex (FCC) monograph for 4-methyl-5-acetyl thiazole requires a purity of ≥ 97% by GC, a refractive index at 20 °C of 1.548–1.554, and a specific gravity at 25 °C of 1.165–1.175. Residual solvents are controlled to ≤ 50 mg/kg for methanol and ≤ 10 mg/kg for 1,2-dichloroethane, tested per USP <467> Method IV. Heavy metals as lead are limited to ≤ 1 mg/kg. Storage under inert gas (nitrogen blanket with O2 < 1% headspace) is advised for industrial bulk packaging to prevent oxidative dimerization, which forms disulfide-linked degradation products detectable as an increase in non-volatile residue (NVR) beyond 0.05%.
Shelf-Life Stability Under Accelerated Storage ConditionsBulk material held in epoxy-phenolic lined steel drums at 25 °C and 60% RH retains ≥ 99% of initial GC purity over 24 months. At 40 °C and 75% RH, purity decline to 96–97% is observed after 12 months, primarily due to the formation of trace amounts of 4-methyl-5-(1-hydroxyethyl)thiazole, the reduced alcohol analog, alongside minor quantities of ring-oxidized sulfoxide. Peroxide value of the storage container atmosphere has been shown to correlate with degradation rate; maintaining headspace O2 levels below 0.5% by nitrogen purging extends the 40 °C stability beyond 18 months. In solution, ethanolic stocks at 10% exhibit a 6-month useful life at 4 °C, after which a slight (0.2–0.5% area) unknown late-eluting peak becomes detectable on a polyethylene glycol GC column (film thickness 0.25 µm, ID 0.32 mm, length 30 m) under splitless injection at 250 °C. Inclusion of 0.02% butylated hydroxytoluene (BHT) as antioxidant is permissible in certain end-use formulations but must be declared to the flavor house buyer due to potential allergen labeling obligations under Regulation (EU) No 1169/2011.
In thermal process flavorings (reaction flavors) prepared under controlled Maillard conditions, 4-methyl-5-acetyl thiazole is frequently used at 0.05–0.5% of the finished reaction mass to impart roasted and meaty depth. Substitution of 2-acetylthiazole or 2-acetyl-4-methylthiazole with the 4-methyl-5-acetyl isomer can shift the perceived balance from popcorn/coffee toward grilled meat and roasted nut shell, an effect measurable by descriptive sensory analysis with a trained panel (ISO 8586:2012) using a 15 cm line scale. A direct 1:1 weight replacement is not always appropriate: the 4-methyl-5-acetyl isomer typically exhibits a potency in meaty matrices that is 30–50% lower than 2-acetylthiazole’s popcorn note at equal dosage, requiring a sensory-directed adjustment. In a model beef reaction flavor containing hydrolyzed vegetable protein, cysteine, thiamine, and xylose, the substitution of 0.2% 2-acetylthiazole with 0.3% 4-methyl-5-acetyl thiazole shifted the “roast beef” attribute intensity from 5.2 to 6.8 (p < 0.05) while suppressing a cereal off-note scored at 2.1 versus a control value of 3.9. This rebalancing is limited by dose ceilings: above 0.5%, a rubbery, slightly metallic aftertaste emerges, consistent with thiazole-mediated taint reported in the literature for the broader class.
Avoiding Incompatibilities with Amine-Rich Intermediate BasesFlavor intermediate bases containing free amino groups—particularly those derived from hydrolyzed vegetable protein with high free amino nitrogen (FAN) levels above 300 mg/100 g—can react with 4-methyl-5-acetyl thiazole’s acetyl carbonyl under prolonged holding at 60–80 °C. This aldol-type condensation is catalyzed by residual alkaline pH (> 8.0) and yields Schiff base adducts that both reduce active thiazole concentration and generate high-molecular-weight brown pigments. Processors handling reaction flavors with extended heat-holding phases should pre-dissolve the thiazole in the lipid fraction of the formulation rather than blending it directly into the aqueous amino acid phase, or should introduce it in the final cooling stage below 50 °C. When emulsions are prepared with gum acacia and subjected to UHT treatment (135–140 °C for 3–5 seconds), losses measured via stable isotope dilution assay (SIDA) using deuterated 4-methyl-5-acetyl thiazole-d3 can exceed 18% if the system pH is 6.8 or higher; at pH 4.0–4.5, recovery improves to 92–96%, consistent with reduced nucleophilicity of amine groups.
In solid fragrance applications outside the food sector—such as scented candles and air freshener gels—the compound is limited to use levels of 0.1–0.3% in the fragrance concentrate due to its tendency to discolor in the presence of certain aldehydes under UV exposure. While no ASTM standard specifically addresses thiazole photostability in consumer products, accelerated QUV testing (ASTM G154-23) using 340 nm UVA lamps for 200 hours can be employed to screen formulations for color stability, with a ΔEab threshold of 3.0 considered the maximum acceptable shift for a white candle base. In these non-food grades, technical material with a purity of 95–97% is often acceptable, with the primary difference from FCC-grade product being a slightly wider boiling range and the presence of 1–2% of the isomeric 4-methyl-5-(1-hydroxyethyl)thiazole, which contributes a milder, more fatty odor profile without significant impact on the overall hedonics at typical inclusion rates.
