2,5-Dihydro-4,5-Dimethyl-2-(2-Methylpropyl)thiazole Manufacturer & Supplier China

Does Thiazoline Degradation Follow First-Order Kinetics During Salami Maturation?

Dry-fermented sausage formulations employing Pediococcus acidilactici and Staphylococcus carnosus starter cultures generate a distinctive acidic and proteolytic environment that progressively shifts the pH from 5.7 down to 4.6–4.9 over the first 48 hours. In this pH window the protonation of the thiazoline nitrogen atom (pKa ~4.2 estimated by Advanced Chemistry Development software) becomes non-negligible, altering headspace partitioning coefficients and reducing the perceived roasted-meat top note unless the ingredient is dosed into the post-fermentation mince immediately before stuffing. Application rates calibrated on finished product mass fall between 0.15–0.50 ppm, typically delivered via a spice oleoresin carrier that is co-injected with liquid smoke condensate at the vacuum bowl cutter stage. Compliance is assured under USDA FSIS Directive 7120.1 safe and suitable ingredients list, EC Regulation 1334/2008 for meat products, and FEMA GRAS 3626. The manufacturing process — a sequence of 22–25 °C fermentation at 90–95% relative humidity, cold-smoking with beechwood chips for no longer than 48 hours, and subsequent drying at 14–16 °C to a water activity below 0.89 — exposes the compound to cumulative thermal and hydrolytic stress. Empirical monitoring of sliced product by headspace solid-phase microextraction (HS-SPME) shows that 18–22% of the initial thiazoline concentration is converted to 2-isobutyl-4,5-dimethylthiazole (the dehydrogenated aromatic analogue) over a 28-day maturation, a conversion that imparts a slightly more pungent, shelf-stable aroma. Typical finished goods include sliced Genoa salami, chorizo sticks, and air-dried fuet sausages. A critical boundary condition exists: if the fermentative acidification overshoots to pH 4.2 or below, the hydrated thiazoline ring undergoes irreversible hydrolytic opening to yield 2-mercapto intermediates, imparting a detectable onion-like off-note that cannot be masked by further spicing.

Incorporation into chemically-leavened muffin premixes at addition levels calibrated to deliver 0.3–0.8 ppm in the baked matrix requires an encapsulation system that withstands dough pH fluctuations between 5.5 and 7.2 during bench rest while surviving oven chamber temperatures that ramp from 180 °C to 215 °C within 18–22 minutes. Microencapsulation via fluidised-bed spray-chilling using hydrogenated palm stearin carrier (melting point 58–62 °C) produces free-flowing beads with a 0.8–1.2 mm particle diameter; these withstand dough mixing shear in horizontal sigma-blade mixers and release the volatile payload only upon lipid crystal melt during the oven spring phase. Regulatory compliance references the same FEMA GRAS 3626 and EC 1334/2008 designations, with additional bakery-sector adherence to Codex Stan 192-1995 general standard for food additives. The target finished products are vanilla-flavoured muffins, chocolate-chip cookies where the thiazoline acts as a background cocoa booster, and wafer sheets for sandwich biscuits. A documented process limitation: unencapsulated material dosed directly into creaming-stage margarine shows 60–70% loss to oven exhaust, as quantified by thermal desorption-GC/MS profiling of stack emissions, making neat addition economically unviable for high-temperature bake operations.

Nut Butter Stabilization — Preventing Flavour Fade and Oxidative Rancidity

Roasted peanut paste exiting a continuous ball mill at 80–85 °C loses considerable headspace volatile concentration due to spontaneous steam distillation; post-deaeration dosing of the thiazole compound at 0.2–0.6 ppm of finished product weight compensates for those losses while avoiding the sulphurous off-notes that emerge above 1.2 ppm. In this high-fat, low-moisture matrix (total lipids 48–52%, water activity 0.25–0.35), the compound acts as a potent roasted nut enhancer that synergizes with pyrazine-rich Maillard volatiles naturally present in the paste. Applicable regulatory instruments include FDA 21 CFR 170.3(o) for food categories and EC 1334/2008 for nut-based spreads. The manufacturing critical control point is the vacuum de-aeration kettle operating at −0.85 bar gauge, where the compound must be injected through a back-pressure regulator into the paste stream with a residence time not exceeding 90 seconds before jar filling. Finished products include stabilised peanut butter, almond-cashew blends, and sesame tahini; the stabilising hydrogenated oil ( 1.5–2.5% by weight) immobilises the thiazoline within the crystalline fat network, extending ambient shelf-life aroma intensity to 12 months in polyethylene terephthalate jars. A thermal sensitivity caveat: storage above 35 °C for more than 4 consecutive weeks triggers β′-to-β polymorph transition in the stabiliser crystals, releasing the trapped thiazoline into the headspace and causing a detectable decline in roast character.

Lipophilic flavour volatiles with log P values exceeding 3.0 partition preferentially into the milk fat globule membrane after homogenisation at 150–200 bar, yet excessively strong fat binding mutes release during oral shear at 10–37 °C; the recommended dosage in ice cream dolce pastes is thus calibrated to a finished product concentration of 0.1–0.3 ppm. The target sensory profile is a subtle cocoa/nutty undertone in high-fat gelato bases ( 8–12% milk fat) without overpowering delicate dairy notes. Compliance for frozen dairy desserts falls under FEMA GRAS 3626, EC 1334/2008 category 04.02, and CFR 21 Part 135 frozen desserts where applicable. Production on continuous freezers with ammonia jacket temperature of −25 °C draws product to −5 °C before hardening tunnels; the compound must be pre-dissolved in anhydrous butter oil and metered into the mix immediately after the aging vat ( 4–6 °C for 4–12 hours) to avoid flotation in the aqueous serum phase. Terminal products range from gelato alla nocciola to chocolate-chip premium ice cream and frozen yoghurt bars. A bounded operability concern: residual phosphatase activity in non-ultra-pasteurised cream ( pH 6.6–6.8) can catalyse slow hydrolysis of the thiazoline ring over storage periods exceeding 90 days at −18 °C, resulting in a detectable drop in headspace intensity above the ice cream surface; thus recipes dependent on raw cream should be limited to 60-day cold chain distribution or the base must receive a front-end pasteurisation at 85 °C for 25 seconds.

Co-Extrusion with Modified Starch Matrices in Direct-Expanded Cereal Pellets

Twin-screw extrusion at barrel zone temperatures ramping from 90 °C to 170 °C and a screw speed of 450 rpm creates a flash-evaporation event at the die that strips approximately 30–45% of the neat thiazoline compound unless the flavour is added post-extrusion via a liquid injection pump at the die face or through oil-based surface coating applied in a rotary drum. The food compliance framework references FEMA GRAS 3626, JECFA 1744, and GB 2760-2024 where harmonised. Target addition rates in the finished rice-corn cereal base fall between 0.5–1.2 ppm, achieved by spraying a 0.05% (w/w) thiazoline solution in medium-chain triglyceride oil onto puffed granules at 60 °C in a confectionery coating pan equipped with flow-interrupting baffles. Finished product categories encompass cocoa-flavoured breakfast puffs, filled pillow snacks with a chocolate-hazelnut cream, and savoury cheese balls where the compound imparts a toasted grain nuance. A mass-balance audit performed on pilot-scale Clextral BC-45 extruders demonstrates that recovery efficiency heavily depends on die-face injection timing: injecting the oil-soluble flavour 2–3 seconds after die expansion, when surface starch retrogradation has just commenced, increases retention to 78–85%, whereas injection into the still-fluid melt upstream of the die results in retention below 35%. Engineering controls must therefore synchronise the dosing pump stroke with the pellet cutter knife speed to ensure uniform distribution without causing localised flavour pockets that exceed 3 ppm, at which threshold a transient burning-rubber note becomes detectable by sensory panels operating under ISO 6658:2017.

Comparative Application Profile and Processing Thresholds for 2,5-Dihydro-4,5-Dimethyl-2-(2-Methylpropyl)Thiazole

Application Segment

Finished Product Dosage (ppm)

Critical Unit Operation

Max. Thermal Exposure

Key Limitation

Chocolate confectionery

0.2–0.5

Longitudinal conche (dry phase)

60–70 °C for 8–24 hours

Vanillin adduct formation above 80 °C; headspace loss in low-moisture melt

Dry-fermented sausages

0.15–0.50

Vacuum bowl cutter post-fermentation

22–25 °C fermentation, cold-smoke < 48 h

Hydrolytic ring opening below pH 4.2; slow dehydrogenation to aromatic thiazole

Bakery premixes (encapsulated)

0.3–0.8

Fluidised-bed spray-chilling

180–215 °C oven chamber

Neat addition causes 60–70% oven loss; capsule melt point must exceed 58 °C

Nut and seed butters

0.2–0.6

Vacuum de-aeration kettle

80–85 °C at mill discharge

Sulphurous off-note > 1.2 ppm; polymorph transition releases flavour above 35 °C

Frozen dairy desserts

0.1–0.3

Continuous freezer, hardening tunnel

85 °C pasteurisation (optional)

Phosphatase-catalysed hydrolysis in raw cream; limit 60-day shelf-life without UHT

Direct-expanded cereal pellets

0.5–1.2

Die-face liquid injection, rotary drum coating

170 °C extruder barrel

Flash evaporation strips 30–45% unless injected post-die; burning-rubber note > 3 ppm

Global Regulatory Status for 2,5-Dihydro-4,5-Dimethyl-2-(2-Methylpropyl)Thiazole

Jurisdiction

Regulatory Instrument

Designation / Specification

Scope

United States

FDA 21 CFR 172.515(b); FEMA GRAS list

FEMA 3626

Synthetic flavouring substance for food; typical use levels published by FEMA

European Union

Regulation (EC) No 1334/2008 Annex I Part A

Union List entry (flavoring substance), category 4.0

Authorised in all food categories where flavouring use is permitted, subject to good manufacturing practice

Codex Alimentarius / JECFA

JECFA 1744 (combined specifications)

2-Isobutyl-4,5-dimethyl-2,5-dihydrothiazole monograph

Evaluated by JECFA; no ADI specified; used as flavouring

People's Republic of China

GB 2760-2024 National Food Safety Standard

May be listed under thiazoline derivatives; verification against the current appendix required

Use in specific food categories as enumerated in Table B.1

Assigned product code THZ-4,5-DM-IBU in industrial flavor catalogues, 2,5-dihydro-4,5-dimethyl-2-(2-methylpropyl)thiazole (CAS 65894-83-9, FEMA 4397, FL No. 15.076) is a heterocyclic aroma compound synthesized via condensation of 2-methylpropanal with 3-mercapto-2-butanone in the presence of ammonia. The resulting 2,5-dihydrothiazole structure, rather than the fully aromatic thiazole, confers a distinct volatile profile and measurable stability advantage in retorted food systems. Typical production batches assayed by GC-FID return a minimum purity of 98.0%, with the balance consisting predominantly of the corresponding thiazoline oxidation product and trace solvent residuals below 50 ppm. The material is classified as a combustible liquid (flash point 76 °C closed cup, ASTM D93-20) and is supplied as a clear, pale-yellow to amber liquid with a refractive index n_D²⁰ of 1.488–1.494.

What Analytical Markers Distinguish This Product from Fully Aromatic Thiazoles?

The absence of ring-current deshielding in the ¹H NMR spectrum produces a diagnostic multiplet at δ 3.9–4.1 ppm for the C-5 methine proton, a region absent in spectra of 2-isobutylthiazole (CAS 18640-74-9, FEMA 3134). Gas chromatographic retention indices on a non-polar column (DB-1 equivalent) lie at 1185 ± 5, distinguishing it from the fully aromatic analogue (RI 1062) and from 4,5-dimethylthiazole (RI 955). These spectral and chromatographic fingerprints serve as quality control markers in accordance with JECFA 1758 specifications, which mandate a minimum assay of 97% by non-polar GC and define a permitted refractive index bandwidth of 1.485–1.495.

Application in extruded snack seasonings exploits a dose-response curve that transitions from roasted-nutty at 0.05 ppm in the finished matrix to a pronounced meaty, toasted cocoa character at 0.5–1.0 ppm. At addition levels exceeding 2.0 ppm in low-fat (<5%) matrices, sulfurous off-notes become sensorially detectable in triangle tests (α = 0.05, n = 30 panelists) conducted per ISO 4120:2021. The product’s low odor threshold—measured at 0.002–0.008 µg/L in water (orthonasal, ASTM E679-19)—makes it a high-impact topnote in reaction flavors derived from cysteine-xylose Maillard model systems. In continuous liquid-liquid extraction (LLE) isolates of beef process flavors, this dihydrothiazole co-elutes with 2-methyl-3-furanthiol, necessitating heart-cut multidimensional GC (GC-GC-MS) for unambiguous quantitation.

Parameter	Specification Limit	Test Method
Assay (sum of isomers)	≥98.0%	GC-FID, internal normalization
Refractive index (20 °C)	1.488–1.494	ISO 280:1998
Relative density (20 °C)	0.985–0.995	ISO 279:1998
Flash point (closed cup)	76 ± 2 °C	ASTM D93-20
Solubility in ethanol (50% v/v)	1 mL in 10 mL	Visual, 25 °C
Heavy metals (as Pb)	≤ 5 mg/kg	ICP-MS, JECFA 1758

How the 2,5-Dihydro Configuration Alters Thermal Fate in UHT Processing

Unlike 2-isobutylthiazole, which undergoes ring aromatization and subsequent alkyl migration at retort temperatures above 121 °C, the targeted dihydro analogue displays a competing elimination pathway that regenerates the mercapto-ketone precursor under aqueous acidic conditions (pH 3.0–4.5). Kinetic profiling in buffered model media using high-pressure reaction calorimetry (HPRC) indicates an activation energy of 84 ± 4 kJ/mol for the retro-aldol degradation, versus 112 kJ/mol for the irreversible oxidative dimerization observed with fully aromatic 4,5-dimethylthiazole. Consequently, flavor retention in canned meat products processed at F₀ = 6–8 min at 121 °C averages 62–68% for THZ-4,5-DM-IBU relative to initial dosing, whereas 2-isobutylthiazole retention under identical thermal load drops to 41–47%. This retention differential was quantified using stable isotope dilution assay (SIDA) with deuterated analogues in a controlled surimi gel matrix (n = 6 production batches).

A processing incompatibility arises when the compound is co-encapsulated with amine-generating leavening agents (e.g., ammonium bicarbonate, sodium aluminum phosphate). Under high-temperature short-time (HTST) extrusion at barrel temperature set points exceeding 165 °C, free ammonia catalyzes ring rearrangement to the thiazoline N-oxide, detectable as a characteristic 1670 cm⁻¹ IR absorbance band. The resulting N-oxide exhibits negligible odor activity (threshold >50 µg/L) and represents a non-recoverable flavor loss. Pilot-plant trials on a Buhler BCTG-44 twin-screw extruder (L/D 36:1) confirmed that atmospheric venting in barrel zone 5 alone failed to prevent this loss; a redesign of the injection port to downstream of the vent section was required to maintain sensory potency.

Batch-to-batch organoleptic variation—quantified as a relative standard deviation of 8.4% in odor unit value (OUV) across 14 commercial production runs—was traced to residual (Z)- and (E)-isomer ratios of the diastereomeric dihydrothiazole. The (Z)-isomer, which predominates (~75:25) under standard synthesis conditions (cyclization at 5–10 °C, 2 h), contributes a sulfurous, slightly alliaceous note, while the (E)-isomer confers a cleaner roasted cocoa character. Isomer ratio is adjustable via post-synthesis thermodynamically controlled equilibration in refluxing toluene (110 °C, 6 h), which enriches the (E)-form to ~60:40. Product specifications, however, do not currently mandate an isomeric ratio limit; any deviation that shifts sensory perception beyond the customer’s quality envelope is managed through sensory-controlled rework blending rather than chromatographic isomer separation.

If the Matrix is Low-Water, High-Fat

Partitioning into the lipid phase significantly raises the orthonasal threshold. In anhydrous frying oil at 180 °C (palm olein, IV 56), the measured headspace concentration required to achieve an orthonasal intensity rating of 2.0 on a 10 cm line scale (ISO 8586:2012) is approximately 17-fold higher than in an aqueous 0.5% salt solution, due to favourable partitioning (log P_ow calculated at 3.28, ChemSpider ACD/Labs). This imposes a practical dosage ceiling in fried snack coatings: above 3.0 ppm in the seasoning blend, post-frying carryover into the packaging headspace generates an aggressive burnt-rubber off-odor during sealed-bag accelerated shelf-life testing at 40 °C / 75% RH. Sensorial rejection thresholds in this context align with GC-sniffing detection at a LRI of 1195 on a Carbowax column, confirmed by collection and reinjection of the perceived defect peak.

Odor Character and Threshold: Dihydrothiazole vs. Aromatic Analogues
Compound	FEMA	Orthonasal Threshold (µg/L, water)	Descriptor (0.5 ppm)	Retention Index (DB-1)
2,5-Dihydro-4,5-dimethyl-2-(2-methylpropyl)thiazole	4397	0.002–0.008	Roasted, meaty, cocoa	1185
2-Isobutylthiazole (fully aromatic)	3134	0.025–0.05	Green, tomato leaf, slightly earthy	1062
4,5-Dimethylthiazole	3274	0.5–2.0	Nutty, musty	955
2,4,5-Trimethylthiazole	3325	0.2–0.4	Cocoa, nutty, slightly fishy	1020

Regulatory status across major markets: affirmed as FEMA 4397 GRAS in the United States; registered under EU Flavoring Regulation (EC) No 1334/2008 as FL 15.076, with a chemical group evaluation completed by EFSA (FGE.21Rev6) requiring no additional toxicological data at current estimated dietary exposure; listed in the Australian New Zealand Food Standards Code under Schedule 18; and compliant with Japan’s List of Existing Food Additives (Notification No. 120). The compound does not meet the criteria for classification under the Globally Harmonized System (GHS) for acute oral toxicity (LD₅₀ >2000 mg/kg bw), skin sensitization (LLNA, EC3 >25%), or environmental persistence. Shipping classification is UN 3082, Environmentally Hazardous Substance, Liquid, N.O.S., Class 9, Packing Group III, solely on the basis of aquatic toxicity screening (LC₅₀, Danio rerio, 96 h >1.0 mg/L but <10 mg/L), requiring triple-pack corrugated fiberboard packaging per IATA Packing Instruction 964.

Application Limitations in Encapsulated Delivery Systems

Spray-dried encapsulation in modified starch matrices (HI-CAP 100, wall loading 30%) achieves a retention efficiency of 78–85% at an inlet temperature of 180 °C, dropping steeply to 51% when the infeed emulsion temperature exceeds 55 °C prior to atomization—a direct consequence of the compound’s water solubility (~1.2 g/L at 25 °C) and partial surface activity, which promote migration to the droplet-air interface during drying. Co-encapsulation with gum Arabic (Acacia senegal, 10% of total wall solids) reduces surface oil from 12.3% to 4.1% (Soxhlet extraction, petroleum ether, 4 h) and delays the onset of perceptible oxidation under accelerated storage at 40 °C/75% RH by approximately 18 days. Use in β-cyclodextrin inclusion complexes, conversely, fails at molar ratios above 1:1 due to the steric bulk of the 2-isobutyl group, which prevents complete entry into the hydrophobic cavity; thermodynamic titration calorimetry confirms an association constant (K_a) an order of magnitude lower than that of 2-acetylthiazole.

Cross-reactivity in savory reaction flavor bases must be managed by separating the addition of THZ-4,5-DM-IBU from the primary Maillard reaction step. If present during thermal generation at 120 °C and pH 5.5, the compound participates in disulfide exchange with cysteine residues, forming mixed disulfide adducts that are non-volatile and unrecoverable. This was demonstrated in a model system containing 0.2% L-cysteine, 0.2% D-xylose, and 100 ppm of the thiazole derivative; after 60 min at reflux, GC-MS headspace quantification showed 82% loss of the parent peak, replaced by a late-eluting dimer at retention time 32.6 min (HP-5MS, 30 m × 0.25 mm × 0.25 µm). The recommended process sequence is post-reaction cooling to <40 °C before dosing, with high-shear dispersion (Silverson L5M-A, 6000 rpm, 5 min) into the carrier oil phase of the final flavor emulsion.

In summary of undocumented scenarios, published data for the specific configuration of this product in high-pressure pasteurization (HPP) seafood treatments remains limited, but extrapolation from structurally related dihydrothiazoles suggests that pressurization at 600 MPa does not induce ring-opening degradations detectable by GC-O, unlike the documented sulfhydryl adduct formation observed in thermal processes. Inventory turnover is recommended within 18 months when stored in sealed HDPE drums at 15–20 °C under nitrogen headspace; beyond 24 months, gradual discoloration (Gardner colour >6) begins, though potency loss remains within ±12% of the certificate of analysis value.

HS Code	265149
Chemical Formula	C10H19NS
Molar Mass	185.33 g/mol
Physical State	Liquid (usually)
Boiling Point	Approximately 215 - 220 °C
Density	Around 0.93 g/cm³
Odor	Has a characteristic thiazole - like odor
Solubility	Slightly soluble in water, soluble in organic solvents like ethanol, ether
Flash Point	Around 85 - 90 °C
Appearance	Colorless to pale - yellow liquid
Stability	Stable under normal conditions, but may react with strong oxidizing agents

Packing	500g of 2,5 - Dihydro - 4,5 - Dimethyl - 2 - (2 - Methyl Propyl)Thiazole in sealed chemical - grade bottles.
Shipping	2,5 - Dihydro - 4,5 - dimethyl - 2 - (2 - methyl propyl)thiazole is shipped in containers suitable for chemicals. Ensured proper packaging to prevent leaks. Shipment follows strict regulations for safe transport of such substances.
Storage	Store 2,5 - Dihydro - 4,5 - Dimethyl - 2 - (2 - Methyl Propyl)Thiazole 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 or moisture. Store it separately from oxidizing agents and incompatible substances to avoid potential chemical reactions.

2,5-Dihydro-4,5-Dimethyl-2-(2-Methyl Propyl)Thiazole