Skins - Brown Onion
Skins - Brown Onion
Mechotech designs and manufactures turnkey natural colour extraction plants for brown onion skins. In the Mechotech catalogue, Skins - Brown Onion is listed in both the Yellow Colour group and the Orange Colour group. According to Mechotech’s articles on yellow and orange colour extraction from brown onion skins, the raw material is the dry, papery outer skin of Allium cepa, a food-processing by-product that is among the richest known plant sources of the yellow flavonol quercetin, present free and as glycosides such as quercetin-4-glucoside and quercetin-3,4-diglucoside, at concentrations the yellow article says can reach several percent of skin dry weight. Quercetin dissolves readily in hot water to a deep golden-yellow liquor; the shade on fibre runs from buttery yellow through gold and amber to burnt orange depending on concentration, pH and mordant. Separate Mechotech pages cover onion oleoresin and onion bulb extracts.
Mechotech’s Skins - Brown Onion plant is configured around the raw material and the target colour extract. It is built in SS 316L with integrated solvent recovery, automation and full documentation, and is delivered as a commissioned turnkey system. The articles describe a straightforward route: skins collected from onion processing and screened, simmered in water below boiling (or extracted with ethanol or aqueous ethanol for a more concentrated, shelf-stable pigment, or under alkaline conditions for fibre dyeing), clarified by centrifugation or fine filtration, concentrated under gentle vacuum and dried to a quercetin-rich powder, with colour strength standardised and tested. The route and conditions for a given project are established during process development and pilot validation.
Technical Specifications
| Product | Skins - Brown Onion Natural Colour Extraction Plant |
|---|---|
| Raw Material | Brown onion skins (catalogue name: Skins - Brown Onion) |
| Botanical Name | Allium cepa (per Mechotech’s articles) |
| Plant Part / Feed Form | Dry, papery outer skins, screened and cleaned; coarsely crushed where throughput requires (per the articles); the exact feed form is confirmed with the client |
| Colour Group | Yellow Colour (see the Yellow Colour page) and Orange Colour (see the Orange Colour page) |
| Colour-forming Components | Quercetin (free and as glycosides, including quercetin-4-glucoside and quercetin-3,4-diglucoside) with tannins and other phenolics; mildly pH-responsive and mordant-dependent (per the articles) |
| Process Category | Natural Colour Extraction Plants |
| Extract Type | Natural colour extract (liquid concentrate or dried powder, per specification) |
| Extraction Method | Hot-water simmering below boiling, or ethanol / aqueous ethanol extraction, or alkaline extraction for fibre dyeing, with repeated extraction of the same batch (per the articles); route confirmed during process development |
| Product-contact Material | SS 316L |
| Filtration System | Plate-and-frame filter press with cartridge polish filters |
| Concentration System | Falling-film / vacuum evaporator with solvent recovery where a solvent is used |
| Drying System | Spray or vacuum dryer, where a powder is required |
| Automation | PLC-based |
| Plant Capacity | Configured to requirement |
| Utility Requirements | Steam, chilled/cooling water, compressed air and power (project-specific) |
| Compliance | GMP hygienic design; full documentation for qualification |
| Final Product Form | Natural colour extract (yellow and orange colour groups) |
Plant Capacities
| Plant Scale | Raw Material Throughput | Typical Use |
|---|---|---|
| Pilot | Configured to your feedstock and trial plan | Product development, parameter validation |
| Semi-Commercial | Configured between pilot and commercial scale | Scale-up trials, contract manufacturing |
| Commercial | Configured to raw-material supply and confirmed buyer volume | Commercial production |
Capacity is configured to raw-material supply, confirmed buyer volume and investment timeline; a pilot plant is recommended to validate parameters before scaling.
Manufacturing Process
Raw Material Preparation
Dry outer skins are gathered from food processors or peeling operations and screened to remove soil, mouldy pieces and onion flesh; the articles say clean, fully dried brown skins give the brightest colour and can be stored dry for long periods without meaningful pigment loss. Skins are washed, dried again and, where throughput requires, coarsely crushed so the flavonoids diffuse faster.
Extraction
The skins are simmered in water below boiling, which dissolves quercetin and its glycosides into a deep amber-gold liquor; the articles also describe ethanol or aqueous ethanol for a stronger, more shelf-stable concentrate and alkaline extraction to maximise the pigment load for fibre dyeing, with the liquor then neutralised or buffered. Repeated extraction of the same batch draws out remaining pigment; the route is set during process development.
Filtration
The extract is strained from the spent skins and clarified through centrifugation or fine filtration, in a plate-and-frame filter press and cartridge polish filters.
Concentration & Solvent Recovery
The liquor is concentrated under gentle heat or vacuum in a falling-film / vacuum evaporator, with solvent recovered through the condenser return system where ethanol is used.
Standardisation
The concentrate is standardised to a declared colour strength, with pH adjusted toward the target shade (the articles say raising pH shifts the colour toward deeper orange and that alum gives bright golden-orange lakes). Purified fractions can be produced for cosmetic and supplement use.
Drying & Quality Control
The standardised extract is supplied as a liquid or dried to a quercetin-rich powder, then released after assay, purity, heavy-metal, microbial and moisture testing; food-colour grades also require clean sourcing, thorough washing and filtration.
Major Plant Equipment
- Skin collection, screening and cleaning system
- Washing and drying unit
- Size-reduction (crushing) system
- Closed jacketed SS 316L extraction vessels with temperature and time control
- Centrifuge or fine filtration for clarification
- Plate-and-frame filter press
- Cartridge polish filtration
- Falling-film / vacuum evaporator
- Solvent recovery unit and condensers (ethanol route)
- pH dosing and standardisation / blending vessel
- Spray or vacuum dryer
- CIP system
- Automation and instrumentation
Plant Output
Applications
- Textile dyeing of wool and silk in yellow, gold, amber and burnt-orange shades, with olive and khaki from iron (per the articles)
- Food and cosmetic colour after purification, subject to the relevant food-additive approval in each market (per the articles)
- Antioxidant quercetin-rich extract for nutraceutical and cosmetic use (per the articles)
- Circular-economy and clean-label sourcing from a food by-product (per the articles)
Key Features
SS 316L Construction
Electropolished SS 316L product-contact surfaces with CIP operation between batches.
High-Quercetin By-Product Feedstock
The articles describe brown onion skins as among the most concentrated natural sources of quercetin and a free food by-product, so sourcing and cleaning are part of the plant design.
Water, Alcohol or Alkaline Routes
The articles describe three extraction routes with different concentration and stability; the plant is configured to the grade the client wants.
Shade Steered by pH and Mordant
Alum gives golden-yellow to orange, iron olive and khaki, and copper or tin warmer gold and orange, so one extract spans a warm palette, as the articles describe.
Handles a Light, Bulky, Seasonal Feed
The articles note the skins are light, bulky and seasonal, so cleaning, screening and dry storage are built into the line.
Scalable Batch Capacity
Plants are configured to requirement from pilot scale upward, with modular expansion.
Frequently Asked Questions
Does Mechotech supply the complete machinery for Skins - Brown Onion?
What specification can the Skins - Brown Onion plant achieve?
What production capacities are available for the Skins - Brown Onion plant?
Which industries use the Skins - Brown Onion plant?
Which part of the onion is processed?
What pigment makes onion skins yellow-orange?
Why does this page sit in two colour groups?
How do I make the colour more orange and less yellow?
Can onion-skin colour be used in food?
How is onion skin sourced at commercial scale?
How does this page differ from the other onion pages?
Where does this page sit in the Yellow Colour range?
Where does this page sit in the Orange Colour range?
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