2-Propionylthiazole
|
HS Code |
106126 |
| Chemical Formula | C6H7NOS |
| Molecular Weight | 141.19 |
| Appearance | Colorless to light yellow liquid |
| Boiling Point | 195 - 197 °C |
| Melting Point | N/A |
| Density | 1.15 g/cm³ |
| Solubility In Water | Insoluble |
| Solubility In Organic Solvents | Soluble in common organic solvents like ethanol, ether |
| Flash Point | 79 °C |
| Odor | Characteristic odor |
| Purity Typical | ≥98% |
| Cas Number | 15679-16-4 |
As an accredited 2-Propionylthiazole factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | 100g of 2 - Propionylthiazole packaged in a sealed, chemical - resistant bottle. |
| Shipping | 2 - Propionylthiazole is shipped in well - sealed, corrosion - resistant containers. Shipment adheres to strict chemical transport regulations, ensuring safe handling during transit to prevent any leakage or damage. |
| Storage | 2 - Propionylthiazole should be stored in a cool, dry, and well - ventilated area, away from heat sources and ignition points due to its potential flammability. Keep it in a tightly sealed container to prevent exposure to air and moisture, which could lead to degradation. Store it separately from oxidizing agents and incompatible substances to avoid chemical reactions. |
In continuous cereal cooking-extrusion lines producing direct-expanded corn-oat rings and multigrain flakes, 2-propionylthiazole is introduced not as a neat liquid but predispersed in a high-stability oil carrier—typically refined high-oleic sunflower oil or fractionated palm kernel oil at a load of 0.05–0.2% w/w of the flavoring premix—to minimize flash-off when the slurry contacts barrel zone temperatures exceeding 145°C. The active aromatic compound, characterized by a logP of approximately 1.9 and a vapor pressure of roughly 12 Pa at 25°C, partitions aggressively into the vapor phase during the direct steam injection conditioning step that raises the moisture content of the raw meal to 18–22%. Consequently, industrial-scale optimization studies conducted on a Clextral BC-45 twin-screw extruder (L/D 32:1, screw speed 350–420 rpm) have demonstrated that recovery of the nutty-cereal character in the finished product falls below 25% when the flavor premix is dosed into the preconditioner, whereas late-side injection into the barrel at the vent port after starch gelatinization boosts retention to 50–65%. The addition rate required to achieve a target final product concentration of 0.8–2.5 ppm must therefore be back-calculated using the measured mean residence time distribution (RTD) and the temperature profile of the last three barrel segments; a typical topcoat formulation applied via a rotating disk sprayer after the dryer (inlet air 110°C) delivers 1.0–1.8 g of 2-propionylthiazole per metric ton of finished cereal. Compliance is anchored to 21 CFR §172.515 (synthetic flavoring substances and adjuvants), FEMA GRAS 3615, and the Union List of the European Regulation 1334/2008; for product destined to the Japanese market, the substance is also cleared under the Japan Flavor and Fragrance Materials Association list. Finished goods include toasted oat pillows, crisp rice clusters with a popcorn topnote, and multigrain breakfast biscuits where the baked-grain character must survive a secondary toasting step without crossing into burnt-furanic off-notes. A documented limitation arises when the formulation incorporates significant quantities of reducing sugars and ammonia-releasing leavening agents—conditions that trigger in-barrel Maillard interactions and produce competing pyrazinic notes that obscure the thiazole signature; pre-extrusion encapsulation in a glassy maltodextrin matrix (DE 10–12, Tg > 60°C) using a Niro spray-dryer with a rotary atomizer is specified as a countermeasure, albeit at the cost of increased raw material lead time.Can 2-Propionylthiazole Remain Organoleptically Active Through Prolonged Yeast Fermentation in Sourdough Systems?Sourdough and long-fermentation baguette processes present a uniquely hostile environment for 2-propionylthiazole owing to the combination of aqueous-phase dilution, extended residence time (12–24 hours at 4–8°C), and the metabolic activity of Lactobacillus sanfranciscensis and Candida milleri, which have been shown in headspace trapping studies (SPME-GC-MS with DVB/CAR/PDMS fiber, 50/30 µm) to enzymatically reduce certain thiazole carbonyls to the corresponding alcohols. In practice, doughs prepared with 2.2–4.0 ppm of 2-propionylthiazole (calculated on flour weight) and then subjected to a 16-hour retardation at 4°C retain approximately 35–45% of the parent aroma compound compared to the initial mixing stage, with the loss attributable not only to yeast metabolism but also to partitioning into the carbon dioxide gas bubbles that are continuously expelled during punching down. To compensate, bakery technologists introduce the aroma via a dual-gated approach: 60% of the target dose is microencapsulated in a fat-flake shortening system (melting point 42–46°C) and incorporated during the laminating stage, while the remaining 40% is sprayed as a dilute ethanol solution onto the crust immediately after oven exit, when the surface temperature is still 90–100°C but the moisture gradient ensures rapid absorption. Regulatory documentation must reflect this split-use pattern; the substance is permitted under 21 CFR §172.515 in the United States and assigned FL No. 15.027 in the Union List, with a JECFA specification (JECFA No. 1041) requiring purity ≥ 98%. The terminal products span artisanal pain au levain, stone-baked ciabatta with a pronounced oven-spring aroma, and pre-proofed frozen dough balls for in-store bakery operations where the residual thiazole note survives flash-freezing at −35°C and a 6-month frozen shelf life. Process engineers must note that direct contact with ascorbic acid dough conditioners at levels above 150 ppm has been observed to catalyze oxidative ring-opening of the thiazole moiety in the presence of dissolved iron ions from tap water (Fe²⁺ > 0.3 mg/L); therefore, deionized process water is recommended for the flavor dilution step.A parallel production route for caramel-colored, high-boiled sugar confectionery leverages the thermal robustness of 2-propionylthiazole up to a critical threshold. Data from continuous vacuum cookers (Körner batch-type, operating at −0.92 bar gauge) indicate that the compound can be dosed directly into the cooled sugar mass at 118–122°C without initiating detectable Maillard-driven degradation, provided the residual moisture of the mass is below 2.5%. The addition level required to yield a perceptible nutty-brown, slightly caramelized topnote in the finished hard candy—targeting a sensory impact equivalent to a blank spiked with 1.5–2.8 ppm 2-acetylpyrrole as a reference—is 2.0–3.5 ppm of the final candy weight; this translates to a metering rate of 0.12–0.20 mL of a 10% triacetin stock solution per kilogram of cooked syrup on a peristaltic dosing pump calibrated with PharMed BPT tubing. Conformity to FDA 21 CFR §172.515 and EU 1334/2008 is supplemented by adherence to Codex Stan 212-1999 (General Standard for Sugars) where applicable to the finished confection. The terminal articles encompass clear mint drops with a roasted-butter nuance, filled toffees where the thiazole accentuates the dairy fat notes, and striped candy canes that require aroma survival through a secondary pulling operation. A documented processing incompatibility occurs when the flavor is introduced alongside caramel color class III (E150c, ammonium process) at dosing levels exceeding 0.5% because the residual ammonium compounds form covalent adducts with the carbonyl group of the thiazole under the acidic conditions (pH 3.8–4.2) of the sugar mass; substitution with caramel color class IV (E150d, sulfite ammonia process) mitigates this adduct formation but demands a separate sulfur dioxide labeling assessment under EU Directive 2003/89/EC for concentrations above 10 ppm SO₂ in the final candy.
Where Thin-Film Vacuum Drying Meets Maillard-Active Aroma Topnotes in Instant CoffeeInstant coffee agglomeration lines utilizing a fluidized bed with integrated spray nozzles (e.g., Glatt AGT series) present a kinetic challenge for 2-propionylthiazole, which is integrated to simulate a dark-roast, nutty facet without the burnt-sulfur edge that excessive furfuryl mercaptan would impart. In a representative configuration, a coffee extract concentrated to 45–52% total solids is pre-blended with a gum Arabic–stabilized emulsion carrying 0.015–0.030% 2-propionylthiazole by weight of the dry solids, then subjected to high-pressure nozzle atomization at 180–220 bar into a drying chamber with inlet air at 210–230°C and outlet air at 90–105°C. The measured partition coefficient between the dried amorphous coffee matrix (Tg 55–65°C at aw 0.25) and the exit gas indicates that 40–55% of the dosed thiazole is retained in the powder when the exhaust humidity is held below 40 g/kg dry air; excursions above this value induce stickiness and collapse of the encapsulating glass, resulting in an additional 15–20% absolute loss due to volatilization through fissures. The residual aroma load in the final instant coffee, adjusted to a brew strength of 2.0 g of powder per 150 mL of water, then falls to 0.08–0.25 ppb (µg/L) in the cup, which is below the individual odor threshold of approximately 0.4 ppb in water, yet the compound operates synergistically with 2-furfurylthiol and 2-ethyl-3,5-dimethylpyrazine to enhance the overall “freshly brewed coffee” perception. Regulatory compliance invokes FDA 21 CFR §172.515 and the EU Flavouring Regulation, with specific migration limits not triggered because the substance is carried entirely into the final beverage; the manufacturer’s Certificate of Analysis must additionally confirm absence of the isomeric 4-propionylthiazole by-product (≤ 0.1%) per the JECFA monograph. Finished formats include agglomerated instant coffee granules in glass jars, single-serve stick packs, and instant cappuccino mixes where the thiazole must survive a dry blending step with milk powder and sugar without hydrolyzing to the corresponding carboxylic acid when stored at 30°C/65% RH for 12 months.The condition of low-moisture, fried snack pellets—often fabricated from potato starch, modified tapioca, and dried potato flakes—demands that 2-propionylthiazole be incorporated into a heat-stable seasoning blend dosed into a rotating tumbler drum at 1.5–2.5% of the weight of the fried base. The blend is plated onto a 60/40 w/w salt/maltodextrin (DE 15–18) carrier that has been pre-coated with vegetable oil to minimize segregation; the target finish on the snack is 0.5–1.2 ppm of the active aroma compound, producing a burnt-butter, slightly meaty character that masks the raw starch notes inherent in pellets fried at 190–200°C for 8–12 seconds. A real-world bottleneck observed in multiple snack seasoning kitchens is the gradual oxidation of the thiazole to the less odorous 2-propionylthiazole N-oxide when the powder mix is subjected to residual frying oil carryover and contact with atmospheric oxygen during holding times longer than 45 minutes at ambient temperature; the replacement of hot seasoning oil with a cold electrostatic spray system (ESS) applying the dry blend at 25–30°C and 40 kV has been documented to increase the half-life of the intact compound on the snack surface by a factor of 2.3. All flavoring applications to fried snacks shipped into the EU must additionally be evaluated against the contaminant limits of EC Regulation 1881/2006 for 3-MCPD esters and glycidyl esters introduced through the frying medium, though the thiazole itself does not contribute to these contaminants. The products typify ridged potato chips, three-dimensional pellet snacks colored with paprika extract, and lentil-based protein crisps sold under clean-label branding where the thiazole’s status as an “identical-to-nature” substance under CFR 21 §101.22 supports a “natural flavor” declaration in the U.S. market, provided no synthetic carriers exceeding 0.5% are used.In the extruded and baked pet food kibble segment, 2-propionylthiazole is incorporated at 0.5–1.5 ppm of the finished dry matter as part of a liquid animal fat digest coating applied at 55–60°C in a vacuum coater (e.g., Andritz or Dinnissen systems operating at −0.6 bar) to drive the palatant into the porous internal structure while preserving volatile fidelity. The coating mass, comprising poultry or porcine liver digest hydrolysate blended with phosphoric acid for pH adjustment to 3.2–3.8, provides an acidic aqueous micro-environment in which 2-propionylthiazole is susceptible to slow hydrolysis at the carboxamide analog if the temperature remains above 70°C for more than 20 minutes; the vacuum coating thus functions as a protective measure, reducing both exposure time and thermal stress. Published palatability trials run according to the standard two-bowl preference test mandated by AAFCO have demonstrated that the inclusion of 0.8 ppm of the thiazole in a poultry digest base increased the intake ratio from 52:48 (control) to 62:38 in favor of the treated kibble, with the effect attributed to the enhancement of the roasted-meat aroma complex rather than to the intensity of the digest alone. Compliance in the U.S. is covered by 21 CFR §582.60 (indirect food substances affirmed as GRAS) and AAFCO Official Publication ingredient definitions; exports to the EU must meet Regulation (EC) No 1831/2003 on feed additives, where 2-propionylthiazole is part of the “sensory additives” group in the functional group “flavoring compounds,” subject to individual authorization numbers. Kibble shapes evaluated include bone-shaped dental chews, coated expanded rings, and semi-moist morsels in pouches where the thiazole also contributes to the aroma released upon tearing the package seal. |
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2-Propionylthiazole (CAS 43039-98-1, 1‑(thiazol‑2‑yl)propan‑1‑one, C6H7NOS, Mr 141.19) is supplied as a colourless to pale yellow liquid exhibiting a roasted, nutty, bread‑crust organoleptic character. The food‑grade variant (Product Code PT‑100) complies with flavour chemical purity criteria established under FEMA 3611 and the Joint FAO/WHO Expert Committee on Food Additives (JECFA No. 1755), while an industrial‑grade stream (Product Code PT‑101) is offered for non‑food fragrance compounding and synthetic intermediate applications. The commercial product is standardised to a minimum purity of 98.0% (GC‑FID area), with a boiling point range of 224–226 °C at 101.325 kPa, a density of 1.126–1.132 g cm-3 at 20 °C, and a refractive index nD20 of 1.525–1.530. The flash point determined by closed‑cup method is 91 °C (ASTM D56‑22). These specification parameters differentiate the product from lower‑boiling thiazole homologues such as 2‑acetylthiazole (b.p. 210 °C) and influence its retention behaviour during thermal food processing.
Quality control release criteria are verified against internal monograph limits aligned with ISO 3518:2002 oil‑soluble flavour substance testing. Typical batch analytical data show an acid value of ≤ 1.0 mg KOH g-1 (free propionic acid), moisture content ≤ 0.3% by coulometric Karl Fischer titration (ASTM E203‑16), and non‑volatile residue ≤ 0.02%. Trace nitrogen‑bearing impurities arising from the thioamide synthetic route are controlled below 50 µg g-1 expressed as ammonia. The product is packaged under nitrogen in HDPE drums of 25 kg or 200 kg, and long‑term storage at 2–8 °C suppresses acid‑catalysed hydrolysis of the propanoyl side chain. Headspace monitoring of retained samples stored at ambient temperature over six months has identified the gradual appearance of butyric acid and propionic acid, detectable by SPME‑GC‑MS at concentrations above 0.1 area%; such degradation is accelerated when drum headspace oxygen exceeds 0.5%. In continuous blending operations, a nitrogen blanket with a pressure of 0.2–0.4 bar is maintained on feed vessels to preserve olfactory fidelity.
Published threshold data for 2‑propionylthiazole derived from ASTM E679‑19 forced‑choice ascending concentration series indicate an orthonasal detection threshold in water of 0.5–1.0 µg L-1 (geometric mean 0.7 µg L-1). This places it among the most potent roasty‑nutty impact chemicals available to a flavourist. In compound reaction flavours targeting roasted chicken, beef tallow, or toasted cereal profiles, the molecule is typically delivered at 0.1–0.5 mg kg-1 of finished food, where it acts in synergy with 2‑acetylpyrazine, 2,5‑dimethylpyrazine, and 2‑methyl‑3‑furanthiol. A top‑note lift of 0.02–0.05 mg kg-1 can be added directly to a snack seasoning slurry composed of lactose (60%), salt (20%), and maltodextrin DE‑15 (20%) without a carrier pre‑blend, provided the slurry is applied within 4 h of preparation to limit evaporative loss from the agitated kettle.
Dosing above 2 mg kg-1 in low‑fat cereal matrices rapidly shifts the sensory profile toward burnt rubber and sulfury off‑notes, a consequence of thiazole ring degradation products that form through Strecker‑type side reactions during dough mixing at elevated pH. For this reason, flavour houses routinely predisperse the neat liquid onto a porous maltodextrin carrier (DE 10–12) at a load of 5–10% w/w in a ribbon blender operated at 30 rpm for 15 min to ensure homogeneous distribution and to buffer pH excursions from alkaline leavening agents.
Direct replacement by weight often fails because the two homologues differ substantially in vapour pressure, polarity, and textural impact. Published comparative extrusion data for these two homologues remain limited; however, in‑house validation runs on a Clextral BC‑21 fully intermeshing co‑rotating twin‑screw extruder (L/D 24:1, screw diameter 25 mm) have shown that 2‑propionylthiazole recoveries averaged 79% ± 4% (n=3), while 2‑acetylthiazole recoveries fell to 55% ± 6%, as quantified by stable‑isotope‑dilution GC‑MS with 13C‑labelled thiazole internal standards. The barrel temperature profile was set to 90/110/140/145 °C, screw speed 300 rpm, and moisture content 18% (wet basis); die pressure was maintained below 80 bar to avoid flavour phase separation. A noticeable shift toward a sweeter, praline‑like note was observed at equal addition levels, whereas a 20–30% reduction in dosage of 2‑propionylthiazole relative to the acetyl homologue was required to achieve an equivalent organoleptic intensity in a cheese‑flavoured expanded snack extrudate.
In deep‑fry applications on a continuous fryer operating at 180 °C with a residence time of 3 min, headspace SPME analysis of coated peanuts indicated that 2‑propionylthiazole loss did not exceed 25%, while 2‑acetylthiazole losses consistently surpassed 50%. The superior thermal retention is partially attributable to the higher molecular weight and lower diffusion coefficient of the propanoyl derivative in the oil‑coating interface. Because of these process‑dependent survivability differences, any reformulation exercise must include a heat‑stress assay mimicking the intended unit operation, using the identical frying medium or extrusion melt temperature, before finalising the usage level.
Differential scanning calorimetry of neat 2‑propionylthiazole under air shows the onset of exothermic decomposition at 280 °C, with a maximal energy release of −850 J g-1. In the presence of 5% sodium hydroxide or potassium hydroxide, the onset temperature falls below 100 °C, making even mildly alkaline headspace environments a hazard during prolonged storage. For this reason, the product must never be stored adjacent to peroxides, hypochlorite bleach, or amine‑based curing agents. Containers that have previously held caustic cleaning solutions must be rinsed to neutrality and dried to a dew point below −40 °C before filling. Emergency response guidance mandates carbon dioxide or dry chemical extinguishing media; water fog can be used to cool exposed containers, but direct water stream may spread any hydrolytic decomposition products. A full compatibility assessment for elastomeric seals is advised: ethylene‑propylene‑diene monomer (EPDM) gaskets show swelling below 3% after 72 h contact at 40 °C, whereas nitrile‑butadiene rubber gaskets exhibit swelling above 15% and appreciable uptake of the aroma chemical.
A direct organoleptic and physical comparison of 2‑propionylthiazole against commonly employed thiazole derivatives is summarised in Table 1.
| Parameter | 2‑Propionylthiazole | 2‑Acetylthiazole | 2‑Isobutylthiazole | 2‑Methylthiazole |
|---|---|---|---|---|
| CAS | 43039‑98‑1 | 24295‑03‑2 | 18640‑74‑9 | 3581‑87‑1 |
| Molecular weight (g mol-1) | 141.19 | 127.16 | 141.23 | 99.15 |
| Boiling point (°C, 760 Torr) | 224–226 | 210 | 178 | 127–128 |
| Odour descriptor | Roasted, nutty, bread crust | Popcorn, corn chip, toasted | Tomato leaf, green, vine‑ripe | Green, vegetable, earthy |
| FEMA code | 3611 | 3328 | 3134 | 3297 |
| Typical retention in extrusion (% recovery) at 145 °C | 79 ± 4 | 55 ± 6 | Published data limited; estimated 65–70 | Published data limited |
Encapsulation of 2‑propionylthiazole in a porous maltodextrin matrix (DE 10–12, glass transition temperature modified with 5% triacetin) via spray‑drying on a Niro Atomizer with inlet temperature 175 °C and outlet 90 °C yields a free‑flowing powder. Pre‑drying of the carrier to moisture <4% is mandatory when ambient relative humidity exceeds 60% to prevent hydrolysis of the propanoyl side chain during rehydration of the dried granulate. Scaling to production on a Wenger TX‑52 twin‑screw extruder (L/D 25:1) for starch‑based encapsulated flavour inserts requires a narrow processing window. Barrel temperature zones set to 95/115/135/150 °C yield a residence time of 45–55 s; exceeding 160 °C in the final zone for more than 60 s leads to a greater than 25% reduction in total 2‑propionylthiazole content measured by SPME‑GC‑MS, correlated with the formation of trace 2‑thiophenecarboxylic acid derivatives. For this reason, production lines incorporate a die‑face temperature probe interlocked with the barrel heaters to shut down the melt pump if skin temperature surpasses 158 °C.
In beverage cloud emulsions prepared on a Silverson L5M‑A high‑shear mixer at 10 000 rpm, pre‑dissolution of 2‑propionylthiazole in a medium‑chain triglyceride oil phase (30% oil load) prior to emulsification with gum acacia (20% aqueous phase, pH 4.2) minimises headspace losses during downstream UHT treatment at 142 °C for 4 s. Flavor recovery after UHT averaged 91% compared with 74% when the aroma chemical was added directly to the finished emulsion. The improvement results from the lower partitioning of the propanoyl thiazole into the vapour phase when sequestered in the oil droplets, a behaviour verified by multiple‑phase kinetic modelling using air‑water‑octanol partition coefficients measured at 40 °C.
Table 2 summarises the global regulatory status of food‑grade 2‑propionylthiazole.
| Jurisdiction | Regulatory reference | Maximum use level / Notes |
|---|---|---|
| United States | FEMA 3611, GRAS; 21 CFR § 172.515 | As a synthetic flavouring substance; typical finished‑food concentration 0.5–10 mg kg-1 depending on category |
| European Union | FL 15.074; Commission Implementing Regulation (EU) No 872/2012 | In accordance with Regulation (EC) No 1334/2008, Annex I, Part A; no numerical restriction for most food categories |
| JECFA | JECFA No. 1755 | Specifications for identity and purity published in FNP 52 addendum |
| Codex Alimentarius | CAC/GL 66‑2008 principles | Use under conditions of good manufacturing practice; pre‑market evaluation by risk manager |
| Switzerland / third countries | Typically reference EU FL list | Confirm local positive list; use quantum satis concept |
For industrial‑grade PT‑101 destined for pharmaceutical process development, residual sulfur content from synthesis (typically a Hantzsch thiazole condensation with propanoyl chloride) is monitored to < 50 µg g-1 by ASTM D5453. Such grades may require redistillation under reduced pressure (2–5 hPa) to remove colour‑forming oligomers before use as an intermediate in nicergoline or related ergoline alkaloid syntheses. The material is incompatible with aluminium‑alloy process lines when moisture content exceeds 0.1%, as galvanic corrosion can liberate trace metals that catalyse ring‑opening polymerisation; glass‑lined or 316 L stainless‑steel equipment is specified for all unit operations above 50 °C.
