Review

Al222 (25419 pt) • 2025-Nov-07 14:44

Green onion extract
(from leaves and tender pseudostems of Allium fistulosum L., and/or young Allium cepa ; family Amaryllidaceae )

Description

• Concentrated flavour ingredient obtained by extracting chopped green onion with food-grade solvents (water, hydroalcoholic systems, glycerol) and optionally concentrating or spray-drying to a powder; may also be produced as a clarified liquid.
• Delivers clean scallion/green-onion notes without particulates; available as single-strength liquids, concentrates, or powder on carriers (e.g., maltodextrin).
• Typical targets (liquids): °Brix 0.2–4.0 depending on style; pH ~5.3–6.2 (low-acid → validated heat treatment required); clarity from clear to lightly hazy per filtration grade.

Indicative nutrition values (composition varies by solvent/strength; examples below)

• Liquid, unsalted, single-strength (per 100 ml): energy 0–5 kcal; carbohydrate 0–1.0 g (sugars ≤0.5 g); protein 0–0.3 g; fat ~0 g — SFA (saturated fatty acids; advisable to keep low overall) minimal; MUFA/PUFA negligible; sodium <20 mg; potassium 10–60 mg.
• Spray-dried powder on carrier (per 100 g): energy 200–380 kcal (carrier-driven); carbohydrate 45–95 g (sugars 2–10 g); fibre 1–5 g; protein 2–10 g; fat 0–2 g (SFA minimal); sodium formulation-dependent (often low unless salted).

Key constituents

• S-alk(en)yl-L-cysteine sulfoxides (ACSOs): methiin, isoalliin (onion precursors).
• Thiosulfinates/disulfides (formed after cutting by alliinase): e.g., dipropyl disulfide family driving onion aroma; decline with heat and oxygen.
• Fructans (FOS): short-chain inulin-type oligosaccharides (reduced in clarified liquids; higher in whole-juice or powder styles).
• Phenolics/flavonoids: quercetin/kaempferol derivatives (low in clarified liquids), traces of chlorogenic acids.
• Minerals/organic acids: potassium prominent; traces of malate/citrate.
• To control: excessive reactive sulfur (harshness), pesticide residues ≤ MRL, heavy metals, elevated 5-HMF (over-heating).

Production process

• Raw material: fresh, sound green onions; trim roots/damaged tissue; optional blanch to soften pungency.
• Extraction: maceration or short infusion in potable water (or hydroalcoholic/glycerol), with tight time/temperature/oxygen control.
• Clarification: coarse filtration → fining/centrifugation (optional) → polishing filtration; deaeration to limit oxidation and aroma loss.
• Standardisation: adjust °Brix/pH; optional aroma capture/return.
• Concentration (where applicable): mild vacuum evaporation.
• Drying (powder styles): spray-drying on carriers (e.g., maltodextrin), set water activity and particle size; anti-caking as permitted.
• Thermal processing & packing: HTST + aseptic fill for liquids or retort for jars; barrier packs (light/O₂) with reduced headspace (nitrogen).

Sensory and technological properties

• Aroma/flavour: fresh green-onion leaf; heat develops sweet, lightly caramelised onion notes.
• Functionality: contributes savoury top-notes and mild sulfur cues; participates in Maillard under heat; slight reducing capacity.
• Solubility: liquids disperse readily; powders reconstitute in water; emulsions may need stabilisers in high-fat systems.
• Stability: sulfur volatiles are oxygen/heat-labile → gradual flavour fade; clarified styles remain clear if well filtered.

Food applications

• Soups, broths, sauces, gravies, dressings (clean onion note without particulates).
• Marinades/glazes, pickling brines; rice/noodle/vegetable seasonings.
• Plant-based meats and meat systems (binder brines, emulsions) for top-note onion flavour.
• Snack seasonings, culinary concentrates/cubes, ready meals.
• Dry blends (powder extract) where consistent dispersion and shelf stability are needed.

Nutrition & health

Green onion extract contributes flavour with minimal energy and negligible fat in liquid styles; powder nutrition is largely defined by the carrier. Fibre and many micronutrients present in whole scallions are reduced by clarification, so whole vegetables or purées provide more dietary fibre and phytochemicals.
The extract carries onion sulfur precursors and some thiosulfinates, which underpin flavour and show antimicrobial activity in model systems. In real foods their levels are modest and decline with heating and storage.
People sensitive to FODMAPs should note that fructans can persist—usually low in clarified liquids but tolerance is individual. Sodium is not inherent; keeping added salt modest enables low-sodium formulations.

Portion note: Typical usage 0.05–0.5% (w/w or v/v) in finished foods for liquids; 0.1–1.0% for powder extracts, titrated by sensory trials and extract strength.

Quality and specifications (typical topics)

• Identity/composition: solids (°Brix or dry matter), pH, titratable acidity; pyruvate test (pungency index); volatile sulfur profile (if instrumented).
• Appearance: clarity/turbidity (NTU), colour (APHA/CIELAB), absence of sediments.
• Chemistry: low 5-HMF; peroxide value (if any lipid phase) minimal; ethanol/residual solvent within legal limits for hydroalcoholic extracts.
• Residues/contaminants: pesticides ≤ MRL; heavy metals within limits; sulphites declared if used/≥10 mg/kg.
• Microbiology: pathogens absent/25 g; APC/yeasts/moulds per spec; water activity controlled for powders.
• Functional: heat-step flavour retention, light/O₂ stress, salt/acid compatibility; bulk density and particle size (powders); carrier % and anti-caking level.

Storage and shelf-life

• Store cool, dark, and dry; avoid temperature cycling.
• Liquids (aseptic ambient): typically 9–12 months; after opening refrigerate 0–4 °C, use within 3–7 days.
• Powders: barrier packaging (moisture/oxygen/light); 12–24 months typical; keep tightly sealed.
• Main risks: flavour fade (loss of sulfur volatiles), slight yellowing, haze/sediment if filtration was mild; caking in powders if humidity rises.

Safety and regulatory

• Designations: “green onion extract”, “spring onion extract”, or botanical “Allium fistulosum extract,” with solvent/carrier disclosure as required.
• Category: culinary flavouring/vegetable extract; liquids at pH >4.6 are low-acid and require validated thermal schedules under GMP/HACCP.
• Allergen/intolerance: Allium sensitivity is uncommon but reported; note FODMAP considerations.
• Claims: flavouring use; nutrition/health claims generally not applicable unless fortified or compositionally qualified; residual solvent limits apply where ethanol is used.

Labeling

• Name of ingredient, botanical source, solvent/carrier (e.g., water; ethanol; glycerol; maltodextrin), and any antioxidants/acids.
• Declare added salt if present; origin/lot/date marking; storage instructions.
• Optional “no added salt/no added sugar” where applicable.

Troubleshooting

• Harsh/metallic sulfur notes: over-extraction or metal contact → shorten extraction time/temperature, avoid Cu/Fe, consider chelators where permitted.
• Weak flavour: excessive heat/oxygen → shorten thermal holds, deaerate, use aroma capture/return.
• Browning/yellowing: non-enzymatic reactions → lower heat load, protect from light/O₂.
• Haze/sediment: insufficient clarification → tighten filtration/centrifugation; cold stabilise before filling.
• Caking (powders): high humidity → improve barrier pack, add permitted anti-caking, include desiccant.

Sustainability and supply chain

• Raw material: valorise field trim/off-grade sizes; seasonal contracts to cut waste.
• By-products: spent solids to compost, feed, or bioenergy.
• Operations: heat/air recovery, CIP water reuse, wastewater treatment toward BOD/COD targets; recyclable/lightweight packaging.
• Systems: supplier audits, traceability, pesticide-residue programs under GMP/HACCP.

Conclusion

Green onion extract is a clean-label flavour tool that provides bright scallion notes with excellent processability in liquid and dry systems. Success depends on fresh raw material, oxygen/heat management, clarification/drying quality, and protective packaging, matched to the target intensity and application.

INCI functions (cosmetics)

• Allium Fistulosum (Green Onion) Extract: skin-conditioning; antioxidant claim potential linked to phenolics; characteristic odour to be managed in formulation; usage and claims subject to local cosmetic regulations.

Mini-glossary

• SFA: Saturated fatty acids — high intakes can raise LDL-cholesterol; desirable to keep low overall.
• MUFA: Monounsaturated fatty acids — favourable when replacing saturates.
• PUFA: Polyunsaturated fatty acids — include n-6/n-3 families; beneficial when balanced and protected from oxidation.
• ACSOs: S-alk(en)yl-L-cysteine sulfoxides, the non-volatile onion precursors that generate flavour volatiles via alliinase.
• FODMAP: Fermentable carbohydrates that can trigger GI symptoms in sensitive people (onion fructans are FODMAPs).
• 5-HMF: 5-hydroxymethylfurfural, a marker of excessive heat/sugar degradation.
• MRL: Maximum residue limits for pesticides on foods.
• GMP/HACCP: Good manufacturing practice / hazard analysis and critical control points — preventive hygiene/process-control systems.
• BOD/COD: Biochemical/chemical oxygen demand — wastewater impact metrics guiding treatment and discharge limits.

References__________________________________________________________________________

Kim SH, Yoon JB, Han J, Seo YA, Kang BH, Lee J, Ochar K. Green Onion (Allium fistulosum): An Aromatic Vegetable Crop Esteemed for Food, Nutritional and Therapeutic Significance. Foods. 2023 Dec 16;12(24):4503. doi: 10.3390/foods12244503.

Abstract. In recent years, there has been a shift towards a greater demand for more nutritious and healthier foods, emphasizing the role of diets in human well-being. Edible Alliums, including common onions, garlic, chives and green onions, are staples in diverse cuisines worldwide and are valued specifically for their culinary versatility, distinct flavors and nutritional and medicinal properties. Green onions are widely cultivated and traded as a spicy vegetable. The mild, onion-like flavor makes the crop a pleasant addition to various dishes, serving as a staple ingredient in many world cuisines, particularly in Eastern Asian countries such as China, Japan and the Republic of Korea. The green pseudostems, leaves and non-developed bulbs of green onions are utilized in salads, stir-fries, garnishes and a myriad of culinary preparations. Additionally, green onions have a rich historical background in traditional medicine and diets, capturing the attention of chefs and the general public. The status of the crop as an important food, its culinary diversity and its nutraceutical and therapeutic value make it a subject of great interest in research. Therefore, the present review has examined the distribution, culinary, nutritional and therapeutic significance of green onions, highlighting the health benefits derived from the consumption of diets with this aromatic vegetable crop as a constituent.

Puišo J, Paškevičius A, Žvirgždas J, Dimitrova TL, Litvakas A, Adliene D. Application of Red Onion Peel Extract for Green Synthesis of Silver Nanoparticles in Hydrogels Exhibiting Antimicrobial Properties. Gels. 2023 Jun 19;9(6):498. doi: 10.3390/gels9060498.

Abstract. UV-initiated green synthesis of metal nanoparticles by using plant extracts as photoreducing agents is of particular interest since it is an environmentally friendly, easy-to-maintain, and cost-effective method. Plant molecules that act as reducing agents are assembled in a highly controlled way which makes them suitable for metal nanoparticle synthesis. Depending on the plant species, their application for green synthesis of metal nanoparticles for diverse applications may contribute to the mediation/reduction in organic waste amounts, thus enabling the implementation of the circular economy concept. In this work, UV-initiated green synthesis of Ag nanoparticles in hydrogels and hydrogel's thin films containing gelatin (matrix), red onion peel extract of different concentrations, water, and a small amount of 1 M AgNO3 have been investigated and characterized using UV-Vis spectroscopy, SEM and EDS analysis, XRD technique, performing swelling experiments and antimicrobial tests using bacteria (Staphylococcus aureus, Acinetobacter baumannii, Pseudomonas aeruginosa), yeasts (Candida parapsilosis, Candida albicans) and microscopic fungi (Aspergillus flavus, Aspergillus fumigatus). It was found that the antimicrobial effectiveness of the silver-enriched red onion peel extract-gelatin films was higher at lower AgNO3 concentrations as compared to those usually used in the commercially available antimicrobial products. The enhancement of the antimicrobial effectiveness was analyzed and discussed, assuming the synergy between photoreducing agent (red onion peel extract) and silver nitrate (AgNO3) in the initial gel solutions leading to the intensification of Ag nanoparticles production.

Kumar, K. S., Bhowmik, D., Chiranjib, B., & Tiwari, P. (2010). Allium cepa: A traditional medicinal herb and its health benefits. Journal of Chemical and Pharmaceutical Research, 2(1), 283-291.

Abstract . Allium cepa is highly valued for its therapeutic properties. It has been used as a food remedy from time immemorial.Research shows that onions may help guard against many chronic diseases. That's probably because onions contain generous amounts of the flavonoid quercetin. Studies have shown that quercetin protects against cataracts, cardiovascular disease, and cancer. In addition, onions contain a variety of other naturally occurring chemicals known as organosulfur com-pounds that have been linked to lowering blood pressure and cholesterol levels.Although rarely used specifically as a medicinal herb, the onion has a wide range of beneficial actions on the body and when eaten (especially raw) on a regular basis will promote the general health of the body. The bulb is anthelmintic, anti-inflammatory, antiseptic, antispasmodic, carminative, diuretic, expectorant, febrifuge, hypoglycaemic, hypotensive, lithontripic, stomachic and tonic. When used regularly in the diet it offsets tendencies towards angina, arteriosclerosis and heart attack. This is used particularly in the treatment of people whose symptoms include running eyes and nose. The onions ability to relieve congestions especially in the lungs and bronchial tract, is hard to believe until you have actually witnessed the results. The drawing of infection, congestion and colds out of the ear is also remarkable. The onion will relieve stomach upset and other gastrointestinal disorders and it will also strengthen the appetite. Pharmacologically know as Allium cepa, onion is found in every household. The purple skinned onion tastes great. Additionally, it has several health benefits and is part of many home remedies and beauty solutions.

Lee, H. J., Lee, I. Y., Park, J. H., & Joo, N. (2025). Comparison of phytochemicals and antioxidant activities of onion (Allium cepa L.) bulbs, onion leaves, and green onion (Allium fistulosum L.) leaves. International Journal of Food Properties, 28(1), 2507121.

Abstract. Onion (Allium cepa L.) is a vegetable widely used in the culinary world. It is also remarkable as a source of nutrition and bioactive compounds. Onion leaves, which are inevitable byproducts of onion production, are morphologically similar to green onion leaves with similar taste profiles. Although they have potential as new sources of food, they are largely considered waste products. This study was conducted to investigate phytochemical compositions, quantities of phytochemicals, and antioxidant activities of onion (Allium cepa L.) leaves. Onion bulbs and green onion (Allium fistulosum L.) leaves were included for comparisons. A total of 27 phenolic compounds, predominantly flavonols, were identified from extracts of three samples, with quercetin-4’-O-glucoside and quercetin 3,7-O-diglucoside being the most significant. Hierarchical clustering analysis showed that onion leaves and green onion leaves shared distribution of bioactive compound compositions, indicating their potential as alternative food sources. Quantification results showed that: 1) onion leaves were exceptionally abundant in quercetin 4’-O-glucoside; 2) green onion leaves were more abundant in hydroxycinnamic acids, and 3) onion bulbs had relatively lower contents of analytes. Antioxidant activities of samples measured by DPPH and FRAP assays reflected quantification data, with onion leaves showing the most potent antioxidant activities. Hence, onion leaves are not only great substitutes for green onions but also have potential to provide more powerful health benefits.

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