Onion juice concentrate (Allium cepa L.)

Description
• Ingredient obtained by vacuum concentration of pressed onion juice (from sound, mature bulbs), sometimes clarified with pectolytic enzymes and fine filtration.
• Characteristic onion profile with sulfur notes; intensity depends on cultivar, enzymatic treatment, and concentration degree.
• Used as a natural flavoring and clean-label sweetener/solids source in sauces, ready meals, bakery items, processed meats, and dressings.

Caloric value (per 100 g of product)
• Depends on °Brix (soluble solids):
– 40–50 °Brix: ~160–210 kcal/100 g.
– 55–65 °Brix: ~220–280 kcal/100 g.
– 70 °Brix: ~300 kcal/100 g.
• Typical macros at 60 °Brix: carbohydrates 55–65 g (mostly sugars), protein ~1–3 g, fat <0.5 g.

Key constituents
• Sugars: fructose, glucose, sucrose; variable FOS (fructo-oligosaccharides).
• Sulfur compounds (from S-alk(en)yl-L-cysteine sulfoxides): dipropyl disulfide, dipropyl trisulfide, etc. (key aroma drivers).
• Organic acids: malic, citric; pyruvic acid (pungency marker).
• Phenolics in traces (quercetin mainly in skins; low in juice).
• Minerals: potassium predominant; traces of calcium, magnesium; sodium low unless added.
• Typical specs: pH ~4.5–5.8; °Brix/TSS to target; color (L*, a*, b*); viscosity; turbidity.

Production process
• Preparation: selection, trimming, washing; optional steam peeling.
• Extraction: crushing/pressing; deaeration to limit oxidation.
• Clarification: pectolytic enzymes, flotation/filtration; optional enzyme stabilization (inactivate alliinase to temper pungency).
• Concentration: low-temperature vacuum evaporation or cold concentration (freeze/cryo) to target °Brix.
• Finishing: pasteurization, aseptic or hot-fill; barrier packaging under GMP/HACCP.

Sensory and technological properties
• Aroma/taste: oniony, sweet-savory; at high concentration slight caramelized/Maillard notes may appear.
• Functionality: adds body and sweetness, promotes browning and umami upon cooking; modulates acidity.
• Rheology: viscosity rises with °Brix; aw lowers vs single-strength juice.
• Compatibility: in dairy or high-protein matrices, over-dosage can create off-flavors.

Food uses
• Sauces and condiments (BBQ, gravy, dressings), culinary bases, ready meals, soups.
• Processed meats (marinades, fillings) for natural sweetness and flavor roundness.
• Savory bakery (flatbreads, crackers), snacks; “no added sugar” formulas leveraging intrinsic sugars.
• Typical inclusion: 0.2–3.0%, to be set via pilot trials.

Nutrition and health
• Energy mainly from sugars; fat negligible.
• FODMAP relevance: may contain rapidly fermentable sugars/FOS → caution for sensitive individuals.
• Sulfur compounds and trace phenolics contribute in-vitro antioxidant potential (often reduced after thermal concentration).
• Sodium low unless added; fits low-fat formulations.

Quality and specifications (typical topics)
• °Brix/TSS, pH, density/viscosity within spec.
• Markers: pyruvic acid (pungency), volatile sulfur profile (GC–MS), SO₂ absent/within limit if not used.
• Microbiology: pathogen-free; total count/yeasts-molds within spec; pack stability verified.
• Sensory: no burnt notes; sulfur notes controlled, no “sulfidic” defects.

Storage and shelf-life
• Closed aseptic packs: store cool and protected from light/oxygen; once opened, refrigerate (0–4 °C) and use within a few days.
• Prevent localized crystallization and browning; apply FIFO.

Allergens and safety
• Onion is not a major allergen; individual hypersensitivities may occur.
• Check presence/absence of sulfites (SO₂) if used as processing aids; label accordingly.
• Foreign-matter control (plant fragments) and pack integrity; hygiene under HACCP.

INCI functions in cosmetics
• Typical entries: Allium Cepa Bulb Extract, Allium Cepa Juice.
• Roles: skin conditioning, mild antioxidant, masking; used in gels/lotions (e.g., appearance-improving cosmetics).

Troubleshooting
• Browning (Maillard/caramelization): excessive time/temperature → gentler concentration, reduce O₂ (deaeration), use barrier packs.
• Over-intense sulfur or H₂S-like notes: inactivate alliinase, optimize heat curve, blend with sweet/acid bases.
• Haze/precipitates: insufficient clarification → fine/polish filtration, pectolytic enzymes.
• Phase separation: uneven °Brix → proper mixing/homogenization.
• Sugar crystallization pockets: temperature oscillations → stable storage, gentle remixing.

Sustainability and supply chain
• Valorize by-products (skins/outer layers) rich in quercetin for natural flavors or antioxidant extracts.
• Manage high-COD effluents with BOD/COD targets; apply heat recovery from evaporators.
• Recyclable packaging and optimized logistics; full traceability and hygiene per GMP/HACCP.

Conclusion
Onion juice concentrate delivers characteristic aroma, natural sweetness, and useful technological functions (body, browning, umami). Application performance hinges on °Brix, thermal/oxidative control, and proper clarification/packaging; with tight specs, stable and repeatable flavor profiles are achievable.

Mini-glossary
• °Brix — Percentage of total soluble solids (TSS); guides concentration and sweetness.
• TSS — Total soluble solids (sugars, acids, salts); relates to density and yield.
• pH — Acidity/alkalinity index; impacts aroma stability, color, and microbiology.
• aw — Water activity: decreases as solids rise; governs microbial stability.
• FOS — Fructo-oligosaccharides: fermentable carbohydrates (FODMAP) that may affect sensitive individuals.
• GC–MS — Gas chromatography–mass spectrometry: analytical method for volatile profiling.
• SO₂ — Sulfur dioxide: antioxidant/antimicrobial; if used, must be controlled and declared per regulations.
• GMP — Good Manufacturing Practice: hygiene and process-consistency standards.
• HACCP — Hazard Analysis and Critical Control Points: preventive safety system with defined CCP.
• BOD/COD — Biochemical/Chemical Oxygen Demand: effluent load indicators relevant to wastewater impact.
• FIFO — First In, First Out: stock-rotation practice using older lots first.

Research and Future Potential

Onions are being extensively studied for their bioactive compounds and potential health benefits. Recent research explores their role in preventing chronic diseases such as diabetes, cardiovascular conditions, and certain cancers. The food industry is developing new onion-based products to harness their nutritional and functional properties. In agriculture, researchers are working on climate-resilient onion varieties and improving post-harvest storage techniques to reduce food waste.

Studies

Onions have antioxidant and antibacterial properties and can help reduce the risk of certain chronic diseases. Quercetin, found in onions, has been linked to preventing age-related diseases such as diabetes, cancer, and neurodegenerative diseases.

Animal studies have shown the effectiveness of onion as an anticoagulant.

Human studies have found the usefulness of onion combined with other vegetables to prevent cardiovascular problems.

As an anti-inflammatory, a component of the onion, Onionin A found in the bulb, has been shown to perform an action to counteract inflammatory blood activity (1).

There would also appear to be an action to improve the balance of blood sugar.

It is recommended, along with garlic, shallots and chives to prevent prostate cancer (2).

The best known red onions in Italy are the red head of Tropea and Certaldo.

Red onion studies

References________________________________________________________________________

(1) Fujiwara Y, Horlad H, Shiraishi D, Tsuboki J, Kudo R, Ikeda T, Nohara T, Takeya M, Komohara Y. O

(1) Fujiwara Y, Horlad H, Shiraishi D, Tsuboki J, Kudo R, Ikeda T, Nohara T, Takeya M, Komohara Y. Onionin A, a sulfur-containing compound isolated from onions, impairs tumor development and lung metastasis by inhibiting the protumoral and immunosuppressive functions of myeloid cells.  Mol Nutr Food Res. 2016 Nov;60(11):2467-2480. doi: 10.1002/mnfr.201500995.

(2) Colli JL, Amling CL. Chemoprevention of prostate cancer: what can be recommended to patients?  Curr Urol Rep. 2009 May;10(3):165-71. Review.

Abstract. Prostate cancer is third to lung and colon cancer as the cause of cancer-related deaths in American men. It is estimated that there will have been more than 28,000 deaths and 186,000 new cases in 2008 that will impose a significant burden on national health care costs. Chemoprevention aims to reduce both incidence and mortality through the use of agents to prevent, reverse, or delay the carcinogenic process. This study provides clinicians with information on some chemoprevention agents that have been considered to reduce prostate cancer risks, including 5-alpha-reductase inhibitors; statins (a class of compounds used to reduce cholesterol); NSAIDs; selenium; vitamins E and D; lycopene; allium vegetables (garlic, scallions, onions, chives, and leeks); soy/isoflavones; and green tea polyphenols. The evidence to support prostate cancer risk reduction benefits for each chemoprevention agent based on a review of the literature is provided.

Tsuboki J, Fujiwara Y, Horlad H, Shiraishi D, Nohara T, Tayama S, Motohara T, Saito Y, Ikeda T, Takaishi K, Tashiro H, Yonemoto Y, Katabuchi H, Takeya M, Komohara Y. Onionin A inhibits ovarian cancer progression by suppressing cancer cell proliferation and the protumour function of macrophages. Sci Rep. 2016 Jul 12;6:29588. doi: 10.1038/srep29588.

Abstract. It is well known that tumour-associated macrophages (TAMs) play an important role in tumour development by modulating the tumour microenvironment, and targeting of protumour activation or the M2 polarization of TAMs is expected to be an effective therapy for cancer patients. We previously demonstrated that onionin A (ONA), a natural low molecular weight compound isolated from onions, has an inhibitory effect on M2 macrophage polarization. In the present study, we investigated whether ONA had a therapeutic anti-ovarian cancer effect using in vitro and in vivo studies. We found that ONA reduced the extent of ovarian cancer cell proliferation induced by co-culture with human macrophages. In addition, we also found that ONA directly suppressed cancer cell proliferation. A combinatorial effect with ONA and anti-cancer drugs was also observed. The activation of signal transducer and activator of transcription 3 (STAT3), which is involved in cell proliferation and chemo-resistance, was significantly abrogated by ONA in ovarian cancer cells. Furthermore, the administration of ONA suppressed cancer progression and prolonged the survival time in a murine ovarian cancer model under single and combined treatment conditions. Thus, ONA is considered useful for the additional treatment of patients with ovarian cancer owing to its suppression of the protumour activation of TAMs and direct cytotoxicity against cancer cells.

Li Q, Wang Y, Mai Y, Li H, Wang Z, Xu J, He X. Health Benefits of the Flavonoids from Onion: Constituents and Their Pronounced Antioxidant and Anti-neuroinflammatory Capacities. J Agric Food Chem. 2020 Jan 22;68(3):799-807. doi: 10.1021/acs.jafc.9b07418. 

Abstract. Onion is the most widely cultivated vegetable around the world. In this study, the isolation, concentration, quantification, and bioactivity evaluation of the phenolics in onion peels were investigated. Thirty-four phenolics, including 17 flavonoids and 17 nonflavonoid phenolics, were purified and identified. Among them, there were 2 new unusual epoxyflavanones and a new phenolic constituent, as well as 13 unreported constituents from the genus Allium. The total flavonoids were concentrated, and finally obtained 90.25% of flavonoid content extract. Fifteen main flavonoids were quantified using an ultra-performance liquid chromatography-photodiode array (UPLC-PDA), and quercetin (36.94%) and quercetin 4'-O-β-d-glucopyranoside (15.81%) were the richest contents of flavonoids. The antioxidant and anti-neuroinflammatory capacities were evaluated, and the bioactive results indicated that the flavonoids in onion exhibited pronounced activities. The study suggested that the flavonoids in onion peels could be used in functional food.

Yoo Y, Kim S, Lee W, Kim J, Son B, Lee KJ, Shin H. The prebiotic potential of dietary onion extracts: shaping gut microbial structures and promoting beneficial metabolites. mSystems. 2025 Jan 21;10(1):e0118924. doi: 10.1128/msystems.01189-24. 

Abstract. Onions are well-known vegetables that offer various health benefits. This study explores the impact of onion extracts on gut microbiome using an in vitro fecal incubation model and metabolome analysis. Fecal samples were collected from 19 healthy donors and incubated in the presence or absence of onion extracts for 24 h. To reduce inter-individual variability in the gut microbiome, we employed enterotyping based on baseline fecal microbiota: 14 subjects with a Bacteroides-dominant type (enterotype B) and 5 subjects with Prevotella-dominant type (enterotype P). Alpha diversity was significantly reduced in the onion-treated group compared to the non-treated control group in both Bacteroides- and Prevotella-dominant types. However, significant structural differences in bacterial communities were observed based on weighted UniFrac distance. Notably, short-chain fatty acid (SCFA)-producing bacteria, such as Bifidobacterium_388775, Feacalibacterium, and Fusicatenibacter, were overrepresented in response to onion extracts in enterotype B. Furthermore, genes related to butyrate production were significantly overrepresented in the onion-treated group within enterotype B. Consistent with the enriched taxa and the predicted metabolic pathways, SCFAs and their related metabolites were significantly enriched in the onion-treated group. Additionally, tryptophan metabolism-derived metabolites, including indolelactate (ILA) and indolepropionate (IPA), were elevated by 4- and 32-fold, respectively, in the onion-treated group compared to the control group. In vitro growth assays showed an increase in lactobacilli strains in the presence of onion extracts. These results provide evidence that onion extracts could serve as promising prebiotics by altering gut microbial structure and promoting the production of beneficiary metabolites, including SCFAs and indole derivatives, and enhancing the growth of probiotics.IMPORTANCEThis study is significant as it provides compelling evidence that onion extracts have the potential to serve as effective prebiotics. Utilizing an in vitro fecal incubation model and enterotyping to reduce inter-individual variability, the research demonstrates how onion extracts can alter gut microbial structure and promote the production of beneficial metabolites, including SCFAs and indole derivatives like ILA and IPA. Additionally, onion extract treatment enhances the growth of beneficial probiotics. The findings underscore the potential of onion extracts to improve gut health by enriching specific beneficial bacteria and metabolic pathways, thereby supporting the development of functional foods aimed at improving gut microbiota composition and metabolic health.

Dorrigiv M, Zareiyan A, Hosseinzadeh H. Onion (Allium cepa) and its Main Constituents as Antidotes or Protective Agents against Natural or Chemical Toxicities: A Comprehensive Review. Iran J Pharm Res. 2021 Winter;20(1):3-26. doi: 10.22037/ijpr.2020.112773.13940. 

Abstract. Onion (Allium cepa) is a member of the family Amaryllidaceae and one of the most widely cultivated species of the genus Allium. Onion has plentiful chemical compounds such as allicin, quercetin, fisetin, other sulphurous compounds: diallyl disulphide and diallyl trisulphide. Onion and its main components in specific doses have shown a lot of benefits including free-radical scavenging and antioxidant properties, anticholesterolemic, anti-heavy metals toxicity, antihyperuricemia, antimicrobial, anti-gastric ulcer, and anticancer. This study summarizes numerous in-vitro and animal studies on the protective effects of onion against natural and chemical toxicities. Onion and its main components can ameliorate the toxicity of chemical agents in kidney, liver, brain, blood, heart, reproductive system, embryo, pancreas through reducing lipid peroxidation, antioxidant effect, radical-scavenging, anti-inflammatory, chelating agent, cytoprotective activities, increasing protein synthesis in damaged tissues, suppressing apoptosis, as well as modulation of PKC-