Onion Oleoresin Extraction Plant
Spices Oleoresin Extraction Plants

Onion Oleoresin Extraction Plant

Onion Oleoresin Extraction Plant

Onion Oleoresin Extraction Plant

Mechotech designs and manufactures industrial solvent extraction plants for Onion Oleoresin, derived from Allium cepa. The oleoresin is rich in quercetin and quercetin glycosides (200–600 mg/100g dry onion), propanethial S-oxide (the lachrymatory factor from alliinase action), organosulfur flavour volatiles, and flavonoids, making it valuable for food flavouring, functional food, cardiovascular nutraceuticals, and cosmetics. Our plants are engineered for onion's unique lachrymatory chemistry and quercetin preservation.

Mechotech's Onion Oleoresin extraction plants use food-grade ethanol extraction at 40–55°C to extract quercetin and flavonoid glycosides, sulfur-containing volatiles, and fixed compounds from dehydrated onion flakes or powder. Ethanol is preferred over hexane for its ability to extract the polar quercetin fraction, while low-temperature evaporation preserves the thermolabile sulfur volatiles. Fully enclosed processing with activated carbon air scrubbing manages the strong lachrymatory emissions. All systems comply with ATEX Zone 1, WHO-GMP, and FSSAI standards.

Manufacturing Process

1

Raw Material Preparation

Dehydrated onion flakes or powder (Allium cepa, moisture ≤6%, from red, yellow, or white onion varieties) are inspected and ground to 40–60 mesh in a SS hammer mill. The choice of onion variety significantly affects the quercetin and sulfur profile: red onions are highest in quercetin and anthocyanins; yellow onions have the most intense sulfur flavour; white onions are milder with lower flavonoid content.

2

Solvent Extraction

Ground onion powder is immediately loaded into sealed SS 316L percolators and extracted with food-grade ethanol (70–95%) at 40–55°C. Ethanol efficiently extracts quercetin glycosides (polar), propanethial S-oxide, diallyl and dipropyl sulfides, and resinous compounds. Counter-current circulation over 3–5 stages extracts maximum flavonoid and sulfur volatile content in a 4–6 hour cycle.

3

Miscella Filtration

The dark amber miscella is filtered through sealed sparkler and cartridge filters. All filtration equipment is enclosed within a negative-pressure extraction room fitted with activated carbon air scrubbers, as propanethial S-oxide and sulfur volatiles in the miscella represent a significant lachrymatory and odour nuisance. Filtration speed is maximised to reduce contact time with sulfur compounds.

4

Evaporation & Concentration

Filtered onion miscella is concentrated in a falling-film evaporator at 45–55°C under vacuum (−0.08 MPa) to preserve heat-sensitive sulfur volatiles. A wiped-film evaporator strips residual ethanol to below 25 ppm. Recovered ethanol vapour passes through an activated carbon guard bed before the condenser to capture sulfur compound co-evaporates and maintain recovered ethanol purity for reuse.

5

Standardization

The concentrated oleoresin is tested by HPLC for quercetin and quercetin glycoside content, and by GC-FID for total sulfur volatile profile (propyl propanethiosulfinate, DPDS). Flavonoid content is reported as quercetin equivalents per gram. Batches are blended to meet customer-specified quercetin content or flavour intensity level and adjusted with food-grade carrier oil for viscosity.

6

Packing & Storage

Finished onion oleoresin is filled into food-grade amber HDPE drums or aluminium tins under nitrogen blanketing to prevent quercetin oxidation and sulfur compound volatilisation. Containers are stored at 5–15°C in a dedicated, odour-isolated, ventilated cold store. Every container is sealed with a PE inner bag liner to prevent odour migration through container walls.

Applications

  • Food flavouring in soups, sauces, dressings, processed meats, and snack seasonings for standardised onion intensity without variability from fresh onion
  • Functional food ingredient — quercetin is marketed for antioxidant, anti-inflammatory, and cardiovascular-protective health claims in functional foods and beverages
  • Cardiovascular nutraceutical supplements — quercetin and onion sulfur compounds are clinically studied for blood pressure reduction, platelet aggregation inhibition, and LDL oxidation prevention
  • Cosmetics and personal care — quercetin and flavonoids incorporated in anti-ageing serums, anti-hyperpigmentation creams, and scalp treatment products
  • Pharmaceutical anti-inflammatory preparations incorporating quercetin as an active or adjunct ingredient in joint health, allergy, and immune support formulations
  • Dehydrated food industry — concentrated onion oleoresin added back to onion powder products for flavour enhancement and standardisation
  • Animal feed palatability and gut health products leveraging onion-derived quercetin's antioxidant and prebiotic-like properties in poultry and swine feed

Key Features

  • Quercetin Preservation

    Ethanol-based extraction at 70–95% concentration is optimised for quercetin glycoside solubility. Evaporation temperatures are maintained below 55°C to prevent quercetin aglycone decomposition and Maillard browning reactions that reduce flavonoid potency in the finished oleoresin.

  • Lachrymatory Control Engineering

    Onion's propanethial S-oxide (lachrymatory factor) and sulfur volatiles require dedicated engineering controls. Mechotech's plant features fully enclosed negative-pressure extraction rooms, activated carbon air scrubbers on all vent lines, and sealed CIP cleaning circuits to protect operators and prevent neighbourhood odour complaints.

  • Explosion-Proof Design

    All electrical equipment in ethanol-handling zones is ATEX Zone 1 / IECEx certified. The combination of ethanol vapour and sulfur volatile emissions requires additional LEL monitoring sensitivity, and Mechotech's LEL detector network is calibrated to respond to both ethanol and organosulfide concentrations.

  • GMP Compliant Construction

    SS 316L product-contact surfaces, hygienic construction, and WHO-GMP compliant layout support FSSAI licensing and pharmaceutical-grade quercetin extract production. The onion oleoresin plant is physically isolated from non-allium products to prevent cross-product odour contamination.

  • Multi-Spice Platform

    The low-temperature ethanol extraction platform also processes garlic, leek, spring onion, and chive oleoresins on the same equipment, enabling allium-specialist producers to maximise asset utilisation. CIP circuits with activated carbon-scrubbed venting manage the intense odour profile of all allium materials.

Frequently Asked Questions

What is the quercetin content in the finished onion oleoresin?
Quercetin content in onion oleoresin varies with raw material variety. Red onion dehydrate (highest quercetin content, 600–1200 mg/100g dry weight) produces oleoresin with the highest flavonoid content. Using ethanol extraction of standard yellow dehydrated onion, Mechotech's plants routinely produce oleoresin standardised to 200–600 mg quercetin equivalents per 100g by HPLC, suitable for nutraceutical label claims.
Which onion variety is best for quercetin-rich nutraceutical oleoresin production?
Red onion varieties (Allium cepa var. cepa, red cultivars) have 2–3 times the quercetin content of yellow onions and also contain anthocyanins that add antioxidant value. For nutraceutical applications targeting quercetin potency, Mechotech recommends sourcing red dehydrated onion flakes as the preferred raw material. For food flavouring applications where sulfur intensity is prioritised over quercetin content, yellow onion varieties perform better.
How is the lachrymatory odour from onion processing managed in the facility?
The lachrymatory factor (propanethial S-oxide) and associated sulfur volatiles require multi-layered engineering controls. Mechotech's plant design uses negative-pressure sealed extraction vessels, activated carbon scrubbers on all process vent lines, odour-isolated plant rooms with independent HVAC systems, and dedicated PPE (chemical goggles, nitrile gloves, half-face respirators) for personnel. Waste streams containing onion compounds are collected in sealed containers before disposal.
Can onion oleoresin be produced to meet the quercetin specifications required for dietary supplement labelling?
Yes. Mechotech's standardisation step includes HPLC quercetin quantification traceable to certified reference standards, enabling batch-to-batch consistency for dietary supplement label claims. The plant can produce onion oleoresin standardised to any specific quercetin level (e.g. 20%, 40% quercetin as dried basis) through blending multiple batches, and can issue COAs with the analytical data required for DSHEA (USA) or EU Novel Food/supplement registration submissions.

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