5-Acetyl-2,4-Dimethylthiazole
|
HS Code |
585745 |
| Chemical Formula | C7H11NOS |
| Molecular Weight | 157.23 |
| Appearance | Colorless to pale yellow liquid |
| Odor | Characteristic, pungent |
| Boiling Point | 195 - 197 °C |
| Melting Point | N/A |
| Density | 1.065 g/cm³ (approximate) |
| Solubility In Water | Insoluble |
| Solubility In Organic Solvents | Soluble in common organic solvents like ethanol, ether |
| Flash Point | 76 °C (closed cup, approximate) |
As an accredited 5-Acetyl-2,4-Dimethylthiazole factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | 100 - gram vial of 5 - Acetyl - 2,4 - Dimethylthiazole, securely sealed. |
| Shipping | 5 - Acetyl - 2,4 - Dimethylthiazole is shipped in well - sealed, corrosion - resistant containers. Transport follows strict chemical safety regulations to ensure secure delivery, minimizing risk during transit. |
| Storage | 5 - Acetyl - 2,4 - Dimethylthiazole should be stored in a cool, dry, well - ventilated area away from heat sources and open flames. Keep it in a tightly sealed container to prevent evaporation and exposure to air and moisture, which could potentially cause degradation. Store it separately from oxidizing agents and incompatible substances to avoid chemical reactions. |
The interaction of 5-Acetyl-2,4-Dimethylthiazole with cysteine-rich protein hydrolysates in a closed-jacketed reactor at 100–115 °C for 45–90 min yields a distinct roasted meat mid-note that bridges the gap between initial sulfurous impact and lingering fatty mouthfeel. A typical Maillard reaction charge combines hydrolysed vegetable protein (40–55 % w/w), xylose (8–12 %), L-cysteine hydrochloride monohydrate (3–6 %), and sodium chloride, with the thiazole introduced at 0.02–0.15 % of the paste weight after the temperature drops below 60 °C during the cooling phase. Pre-dispersion in propylene glycol (1:10 w/w) is mandatory when batch size exceeds 200 kg, as neat metering through magnetic-drive gear pumps with a stroke volume below 0.5 mL fails to deliver the 0.5–5 g quantities typical for this raw material at production scale. The final reaction flavour paste, adjusted to pH 5.2–6.0 with food-grade phosphoric acid, is spray-dried on a maltodextrin (DE 12–18) and gum arabic carrier at an inlet temperature of 180–195 °C and outlet 85–95 °C, achieving a retention of 68–82 % as measured by stable isotope dilution assay (SIDA-GC-MS). The resulting powder is applied at 0.3–1.2 % in bouillon cubes and dry soup mixes compliant with EU Regulation 1334/2008 (FL 15.004) and FEMA 3267. An unavoidable process conflict arises when the holding time exceeds 120 min under reflux: 5-Acetyl-2,4-Dimethylthiazole undergoes retro-aldol cleavage, depressing the roasted character and elevating mercaptan-like off-odours that surpass the odour detection threshold of 0.008 ppb in water, forcing batch rejection unless the deviation is caught within 15 min and quenched with 0.1 % citric acid.What Limits the Bake-Through Stability of Nut-Cocoa Topnotes in High-Ratio Cakes?When 5-Acetyl-2,4-Dimethylthiazole is pre-blended into the shortening phase of a high-ratio cake batter—flour/sugar 1:1.1–1.3, batter specific gravity 0.85–0.95—the compound partitions preferentially into the lipid fraction, which provides a transient protective effect during the first 12–18 min of baking at 175–190 °C. At a use level of 0.8–2.5 ppm relative to batter weight, the surviving concentration in the cooled crumb, quantified by headspace solid-phase microextraction (HS-SPME) under the conditions of ISO 15303:2001, falls to 22–35 % of the added dose. To compensate, formulators adopt an over-addition factor of 2.8–4.5×, calculated against the target delivery of 0.5–1.2 ppb in the consumed slice, a window constrained by the bitter aftertaste that emerges above 3.5 ppb in a standard sugar/fat matrix. An alternative strategy involves encapsulating the thiazole in a melt-emulsified sucrose-fatty acid ester shell (HLB 3–5) using a rotating disk atomiser operated at 8,000–12,000 rpm, which shifts the release peak to the final 3–5 min of baking and raises crumb retention to 50–65 %. The encapsulated form is incorporated into industrial cake dry blends premixed in ribbon blenders of 3,000–5,000 L working capacity at 18–23 rpm, with an allowable blend time of 8–12 min to prevent segregation without rupturing the capsule shell. Finished goods labelled as “cocoa-enhanced” or “nut-flavoured” must comply with the labelling thresholds of Regulation (EC) 1333/2008 and carry a specification that the free thiazole content does not exceed 0.1 % of the flavouring preparation before dough hydration, verified by a UV-Vis method at 278 nm as per the JECFA 1740 identity monograph. A documented incompatibility exists when the batter pH is buffered above 7.8 with sodium bicarbonate without sufficient acidic leavening: the thiazole ring undergoes alkaline hydrolysis within 8–10 min of bench time, producing a sulfhydryl off-note that masks the desired cocoa nuance.Cold-extracted coffee concentrate: stabilising 5-Acetyl-2,4-Dimethylthiazole against headspace loss in retort-sterilised RTD beveragesIn ready-to-drink coffee beverages sterilised in a hydrostatic retort at 121 °C for 15 min with an F₀ value of 10–12 min, 5-Acetyl-2,4-Dimethylthiazole added at 1.0–3.0 ppb in the chilled extract before UHT preheating is almost completely lost to the headspace of the headspace-steam mix zone unless the compound is bound to a high-molecular-weight coffee melanoidin fraction isolated by tangential-flow filtration (10 kDa membrane). The binding protocol requires agitation of the thiazole-melanoidin suspension under nitrogen blanket at 4–8 °C for 4–6 h, achieving a loading of 0.12–0.25 % (w/w) confirmed by LC-MS/MS against an isotopically labelled internal standard. Post-retort analysis of the product headspace via selected-ion flow tube mass spectrometry (SIFT-MS) demonstrates residual headspace concentrations of 0.05–0.15 μg/L, which correlates to a perceived roasty aroma intensity of 3.5–4.5 on a 10-point QDA spectrum, compared to 0.5–1.2 for an unprotected spike. The preparation falls under the definition of a “food flavouring” in 21 CFR 172.515 and, when sold as a compounded coffee flavour, must list the thiazole as an artificial flavouring substance unless the natural origin can be demonstrated through ¹⁴C radiocarbon analysis meeting the 0.1 dpm/gC threshold for natural source materials. A critical operating constraint is the oxygen permeability of the PET monolayer bottle wall: at oxygen transmission rates exceeding 0.03 cc/pkg/day/atm at 23 °C and 50 % RH, the thiazole oxidises to the corresponding sulfoxide within 14 days of ambient storage, detected as a metallic astringency that is irreversible and renders the batch non-compliant with internal sensory release specifications.In the continuous seasoning of expanded corn-based snacks with a bulk density of 50–80 g/L, 5-Acetyl-2,4-Dimethylthiazole is dosed as part of a spray-dried flavour powder deposited onto the hot pellet surface immediately after frying while the surface temperature remains between 75 °C and 95 °C. The seasoning powder, formulated in a 500 kg ploughshare mixer with a chopper speed of 2,800–3,600 rpm, incorporates the thiazole at 0.015–0.040 g/kg finished powder, pre-blended in a 1:99 solid-state dilution with fine anhydrous dextrose (D₅₀ ≤ 25 μm) to ensure the standard deviation of the blend uniformity remains below 6 % RSD across ten consecutive thief samples taken according to ASTM D6062-19. The adhesion of the flavour powder is governed by the residual surface oil content on the snack, which is controlled at 22–28 % for conventional fried curls by adjusting the de-oiling vibratory conveyor speed and airflow; below 20 % the fraction of thiazole retained on the product after packaging drops to 40–55 % of the applied quantity, while above 30 % the free-oil carryover into the seasoning tumbler accelerates flavour agglomeration and creates zones of 5–10 mm diameter with bitter taste intensity exceeding the rejection threshold. The finished product must meet the volatile marker standard of ISO 13301:2018 and is typically monitored by a rapid headspace GC-FID method calibrated with the pure substance. In jurisdictions where the snack is exported, compliance with the flavouring provisions of CODEX STAN 192-1995, as revised, and a declaration of the FEMA 3267 status on the technical data sheet is a prerequisite to Customs clearance. An operational incompatibility is noted when the tumbler drum is cleaned with hot water above 65 °C between production runs: the residual thiazole hydrolyses in the steam-laden atmosphere, generating a persistent polythiane residue that transfers to the next batch within the first 15 min of runtime unless a citric acid rinse at pH 4.0–4.5 is instituted.When plant-based patties are processed through a high-moisture extruder, how does 5-Acetyl-2,4-Dimethylthiazole interact with the shear-induced thermomechanical environment?In the production of texturised vegetable protein chunks using a twin-screw extruder with a barrel length-to-diameter ratio of 44:1 and a die pressure maintained at 35–55 bar, the incorporation of 5-Acetyl-2,4-Dimethylthiazole at 0.02–0.08 % of the dry blend introduces a specific operational hazard: the compound’s saturated vapour pressure of approximately 0.12 mmHg at 25 °C causes a rapid shift from the melt phase into the steam exhaust dome at the vent port positioned at L/D 28–32, resulting in a measured loss of 40–65 % unless the injection point is repositioned to the thermal soaking zone just upstream of the die plate, where the melt temperature is deliberately lowered to 115–125 °C. The thiazole is injected as a cold-pressed emulsion in deodorised coconut oil (5 % w/w) via a positive displacement piston pump calibrated to deliver 2.5–5.0 g/min into a throughput of 80–120 kg/h hydrated protein mass. The resultant extrudate demonstrates a roasted-beef character that survives a subsequent retorting step at 128 °C for 25 min in the final assembled meal kit, with sensory panel difference-from-control scores that remain below the critical d’ of 1.0 after 6 months of ambient storage, as evaluated under the guidelines of ISO 4120:2021. Producers operating under USDA FSIS inspection must include the substance on the label either by its specific name or as “artificial flavour” in accordance with 9 CFR 317.2, and maintain a lot-specific GC chromatogram demonstrating purity exceeding 98.5 % as determined by the procedure of JECFA 1740. A measured interaction threshold exists: when the soy protein concentrate used has a residual hexanal level above 15 µg/kg, the perceived nutty-cocoa facet of the thiazole is almost entirely masked by the green/beany oxidation note, requiring the raw material specification to include a hexanal ceiling of 5 µg/kg verified by dynamic headspace analysis.Dry pet food kibble coated with a palatability-enhancing fat slurry post-extrusion has a markedly short window for the retention of volatile heterocyclic thiazoles. 5-Acetyl-2,4-Dimethylthiazole is dissolved in refined chicken fat heated to 48–52 °C at a concentration of 5–15 ppm (mg/kg of fat), and the mixture is metered onto the surface of the kibble at a ratio of 8–12 % by weight in a continuous enrobing drum rotating at 12–18 rpm. The fat solidifies within 3–5 min as the kibble passes over a vibratory cooling conveyor supplied with filtered air at 10–15 °C, entrapping the thiazole in a crystalline lipid matrix that limits headspace loss to less than 10 % over a 24-hour holding period before bagging. The palatability driving force is measured in a two-bowl preference test conforming to ISO 8589:2007 sensory booth protocols adapted for animal panels, where a consumption ratio exceeding 0.65 on a standard deviation basis is accepted as significant. Typical inclusion strategies generate a preference ratio of 0.72–0.81 for the thiazole-enhanced variant over the negative control, provided the thiazole is accompanied by a 0.1–0.2 % addition of tetrasodium pyrophosphate to buffer the salivary pH during mastication. All materials entering the pet food application must conform to the requirements of AAFCO Official Publication ingredient definitions and, for exports to the European Union, the specific migration limit for the thiazole from the packaging must be verified against Regulation (EC) 1935/2004 using the simulant D2 (vegetable oil) at 40 °C for 10 days. An empirical handling limit observed in production environments is that relative humidity in the coating room must not exceed 55 % because the hygroscopic nature of the dried kibble surface draws moisture that hydrolyses the acetyl group of the thiazole, shifting the odour character from roasted to a sharp, acetic-sulfury note within 48 h of exposure. |
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5-Acetyl-2,4-dimethylthiazole (CAS 38205-73-3; FEMA 3267; JECFA 1055; FL No. 15.024) is a heterocyclic methyl ketone with molecular formula C₇H₉NOS and molecular weight 155.22 g/mol. The commercially supplied product is typically a clear, pale-yellow liquid with a characteristic roasted-meat, nutty, and coffee-like aroma. Standard industrial lots are released with a purity specification of ≥98% by capillary GC-FID, refractive index nD20 in the range 1.535–1.540, and density at 20°C between 1.100 and 1.120 g/mL (ASTM D4052-22). Its boiling point at atmospheric pressure is reported near 228–230°C, with a closed-cup flash point of 91°C, placing it in combustible liquid classification for transport. The compound is sparingly soluble in water (~0.1% w/w at 25°C) but freely miscible with ethanol, propylene glycol, triacetin, and medium-chain triglyceride oils, which define its primary solvent vehicles in compounded flavors.
The simultaneous substitution of the thiazole ring with an acetyl group at the 5-position and methyl groups at the 2- and 4-positions creates a steric and electronic profile that profoundly shifts odor character and threshold compared to mono- or differently substituted analogues. Organoleptic evaluation by trained panels against reference compounds reveals that 2-acetylthiazole (FEMA 3328) yields a pronounced popcorn, corn-chip nuance with a threshold around 0.5–1.0 µg/L in water, while 2,4-dimethylthiazole (FEMA 3264) delivers a greener, dusty-cocoa note with a threshold near 3.0 µg/L. In contrast, 5-acetyl-2,4-dimethylthiazole presents a roasted meat, roasted coffee, and toasted onion character, with published sensory threshold data clustering in the range 0.1–0.4 µg/L in water, making it roughly 2–10 times more potent than the non-acetylated 2,4-dimethylthiazole. The ketone function also increases polarity and hydrogen-bond acceptor strength, altering its partitioning behavior in complex food matrices—a feature that becomes critical in fat-rich emulsions discussed below. Table 1 compiles comparative data drawn from industry-formulated quality-control panels and published GRAS monographs.
| Compound | Odor Character | Typical Threshold in Water (µg/L) | FEMA No. | Synonym Key |
|---|---|---|---|---|
| 5-Acetyl-2,4-dimethylthiazole | Roasted meat, coffee, toasted onion | 0.1–0.4 | 3267 | 2,4-Dimethyl-5-acetylthiazole |
| 2-Acetylthiazole | Popcorn, corn chip, nutty | 0.5–1.0 | 3328 | Methyl thiazolyl ketone |
| 2,4-Dimethylthiazole | Green, dusty cocoa, vegetative | 2.0–4.0 | 3264 | — |
| 4-Methyl-5-vinylthiazole | Musty, cocoa, meaty at trace levels | 2.5–5.0 | 3313 | — |
These differences become operationally significant when a flavor house attempts to replace one thiazole with another in a seasoning blend designed for snack coating. Direct weight-for-weight substitution of 2-acetylthiazole with 5-acetyl-2,4-dimethylthiazole without adjusting the dosage often results in a burnt, sulfury top-note that unbalances the finished product. Therefore, reformulation trials typically start at a usage level of 20–50% of the original thiazole contribution and are validated by triangle tests following ISO 4120:2021 sensory protocols.
The C-acetyl substituent on the thiazole ring is relatively robust compared to o-acyl derivatives, but prolonged exposure to temperatures exceeding 180°C in aqueous systems at pH values above 8.5 can initiate hydrolytic deacetylation, reverting the compound to 2,4-dimethylthiazole and releasing acetic acid. This mechanism has been monitored in model retort systems by quantitative GC-MS using deuterated 5-acetyl-2,4-dimethylthiazole-d3 as internal standard. In a buffered phosphate system at pH 9.0 and 121°C for 30 minutes, measured degradation approached 8–12%, whereas at pH 5.5 under identical thermal load, loss was <1%. For canned meat sterilisation (F0 ≈ 6–8 min), the compound is therefore considered sufficiently stable when the product pH remains below 6.5. High-acid products (pH 3.0–4.5) present no degradation issue, though headspace losses via steam distillation during retorting can still reach 15–20% without appropriate encapsulation.
In a production environment where the thiazole is pre-blended into a liquid spice extract and injected directly into a meat emulsion before cooking, foaming in the mixing vessel and vacuum losses in the cutter are commonly underappreciated sources of yield variation. At a large-scale cooked sausage line operating with a bowl cutter under -0.8 bar vacuum, plant personnel have reported aromatic intensity shifts equivalent to a 0.3–0.5 ppm sensory differential when vacuum hold times varied by 2–3 minutes. Plating the thiazole onto fine-grain salt (NaCl, 60–80 mesh) prior to addition reduces the effective vapor pressure of the flavor and has been shown to stabilise the headspace concentration over a 2-hour stuffing and cooking window.
When the thiazole is deployed in extruded pet food kibble, a different loss vector dominates: flash-off at the die plate. Twin-screw extrusion trials with an L/D ratio of 40:1, barrel temperature profile 90/110/130/140/150°C from feed to die, and screw speed 300 rpm have shown that introducing 5-acetyl-2,4-dimethylthiazole at the preconditioner together with the dry mix results in retention of only 35–45%, as measured by extraction and GC-FID against an encapsulated internal standard. Injection of the same neat compound into the barrel melt zone via a high-pressure metering pump (at 50–80 bar) improves retention to 55–65%. The most consistent results—retention above 85%—are achieved when the thiazole is first encapsulated in a vegetable fat jacket (melting point 58–62°C) and applied as a topical coating post-extrusion, using a rotary drum coater with atomising nozzles operating at 1.5–2.5 bar air pressure. The fat encapsulate also protects the thiazole from atmospheric moisture and oxidative interactions during the 8–12 week shelf life of the kibble under modified atmosphere packaging. It should be noted that direct contact with strong oxidising agents, such as peroxyacetic acid-based sanitisers used in clean-in-place cycles, will rapidly oxidise the thiazole sulfur, and equipment sanitised with these agents must be thoroughly rinsed and dried before production restarts.Routine quality assurance of incoming lots relies on a combination of methods prescribed in the current Joint FAO/WHO Expert Committee on Food Additives (JECFA) monograph for 1055. Gas chromatographic analysis on a polyethylene glycol stationary phase (e.g., column dimensions 30 m × 0.25 mm × 0.25 µm) programmed from 80°C to 240°C at 10°C/min resolves the main peak and quantifies impurities that may include 2,4-dimethylthiazole (retention index ~1090) and trace 5-acetylthiazole. Acceptance criteria mandate a single impurity maximum of ≤1.0% and total impurities ≤2.0%. Residual solvent analysis by headspace GC-FID, guided by USP <467> methodology, ensures that ethanol or ethyl acetate used in the final purification step remains below 0.1%.
| Parameter | Acceptance Range | Test Method |
|---|---|---|
| Assay | ≥98.0% (as 5-acetyl-2,4-dimethylthiazole) | GC-FID, internal normalisation |
| Moisture (Karl Fischer) | ≤0.1% w/w | ISO 760:1978 |
| Refractive index (nD20) | 1.535–1.540 | ISO 280:1998 |
| Density (20°C) | 1.100–1.120 g/mL | ASTM D4052-22 |
| Flash point (closed cup) | ≥91°C | ASTM D93-20 (Pensky-Martens) |
Batch-to-batch odor reproducibility occasionally emerges as a concern when shipments originate from different synthesis routes. The commercial route via Friedel-Crafts acylation of 2,4-dimethylthiazole using acetyl chloride and a Lewis acid catalyst (commonly zinc chloride or aluminum chloride) can leave trace chlorinated by-products detectable by a trained sniff port evaluator even when the GC-FID purity appears acceptable. Plant sensory QC panels therefore compare each new lot against an in-house reference standard at a 1 ppm dilution in sucrose syrup (5% w/w) using a paired-comparison forced-choice protocol. Lots exhibiting a chlorinous off-note at this level are automatically rejected, even if instrumental purity exceeds 99%. This practice has proven essential for maintaining consistency in dry-segment soup mixes, where the thiazole may constitute less than 0.02% of the total seasoning weight but dominates the aroma character.
Regulatory clearance for the compound is harmonised across major markets: it is affirmed as GRAS by FEMA (3267) and listed by the EU Flavouring Regulation (EC 1334/2008) with FL No. 15.024. In its current JECFA evaluation, no ADI is specified, and the “no safety concern at estimated levels of intake” assessment remains valid for use in food categories including bakery, meat products, soups, gravies, and snack foods. Documentation for a full TSCA compliance statement in the United States is normally supplied with the Certificate of Analysis.
