An investigation on the physical and chemical properties of white, red, and brown onions was carried out to assess the potential applications of the different species sampled in this study. The physical properties monitored include refractive index, viscosity, and density. For red onion, the refractive index, viscosity, and density were measured as 1.35322, 1.631 cSt, and 1.1140 g/cm³, respectively. Brown onion exhibited values of 1.3571, 3.045 cSt, and 1.1130 g/cm³, while white onion showed 1.34926, 2.45 cSt, and 1.1036 g/cm³. These measurements indicate variations in optical and flow properties among the species, which may influence their suitability for different industrial and medicinal formulations. Regarding chemical properties, the iodine value, saponification value, free fatty acid (FFA), peroxide value, and acid value were evaluated. The iodine values were 15.2802%, 18.092%, and 28.1082% for red, brown, and white onions, respectively, suggesting differences in the degree of unsaturation of oils extracted from each species. The saponification values were determined as 3.927%, 15.708%, and 10.94%, while FFA values recorded were 23.04%, 20.48%, and 11.264% for red, brown, and white onions, respectively, indicating differences in hydrolytic stability and potential nutritional quality. Furthermore, the peroxide values were found to be 60%, 55%, and 45%, reflecting the extent of oxidation, whereas the acid values were 2.384%, 2.244%, and 2.106%, providing additional insights into the oil quality and freshness. Overall, the results demonstrate significant variations in both physical and chemical characteristics among the three onion species, highlighting their distinct compositional profiles. These differences suggest that the oils and extracts obtained from these onions possess diverse bioactive properties, making them suitable for applications in pharmaceutical, nutraceutical, and medical industries, particularly in areas such as antioxidant formulations, anti-inflammatory treatments, and natural preservative production. The findings underscore the importance of species-specific evaluation to optimize the use of onion-derived products for targeted industrial and therapeutic applications.

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1. Aherne SA, O’Brien NM. Dietary flavonols: Chemistry, food content, and metabolism. Nutr. 2002;18(1):75–81. doi: 10.1016/s0899-9007(01)00695-5.
2. Ali M, Bordia T, Mustafa T. Effect of raw versus boiled aqueous extract of garlic and onion on platelet aggregation. Prostaglandins Leukot Essent Fatty Acids. 1999;60(1):43–47. doi: 10.1054/plef.1998.0006.
3. Ali M, Thomson M, Afzal M. Garlic and onions: Their effect on eicosanoid metabolism and its clinical relevance. Prostaglandins Leukot Essent Fatty Acids. 2000;62(2):55–73. doi: 10.1054/plef.1999.0124.
4. Azuma K, Minami Y, Ippoushi K, Terao J. Lowering effects of onion intake on oxidative stress biomarkers in streptozotocin-induced diabetic rats. J Clin Biochem Nutr. 2007;40(2):131–140. doi: 10.3164/jcbn.40.131.
5. Abu-Darwish MS, Abu Dieyeh ZH, Mufeed B, Al-Tawaha AR, Al-dalain SY. Trace element contents and essential oil yields from wild thyme plant (Thymus serpyllum L.) grown at different natural variable environments. J Food Agric Environ. 2009;7:920–924.
6. Babu GD, Kaul VK. Variation in essential oil composition of rose-scented geranium distilled by different distillation techniques. Flavour Fragr J. 2005;20(2):222–231. doi: 10.1002/ffj.1414.
7. Benkeblia N, Onodera S, Shiomi N. Variation in 1-fructo-exohydrolase (1-FEH) and 1-kestose-hydrolysing (1-KH) activities and fructo-oligosaccharide (FOS) status in onion bulbs. Influence of temperature and storage time. J Sci Food Agric. 2005;85(2):227–234. doi: 1002/jsfa.1959.
8. Benkeblia N, Varoquaux P. Effect of nitrous oxide (N₂O) on respiration rate, soluble sugars and quality attributes of onion bulbs Allium cepa cv. Rouge Amposta during storage. Postharvest Biol Technol. 2003;30(2):161–168. doi: 10.1016/S0925-5214(03)00101-7.
9. Benkeblia N. Free-radical scavenging capacity and antioxidant properties of some selected onions (Allium cepa L.) and garlic (Allium sativum L.) extracts. Braz Arch Biol Technol. 2005;48(5). doi: 10.1590/S1516-8913200500060001.
10. Bianchini F, Vainio H. Allium vegetables and organosulfur compounds: Do they help prevent cancer? Environ Health Perspect. 2001;109(9):893–902. doi: 10.1289/ehp.01109893
11. Block E, Gulati H, Putman D, Sha DY, You NN, Zhao SH. Allium chemistry: Synthesis of 1-[alk(en)ylsulfinyl]propyl alk(en)yl disulfides (cepaenes), antithrombotic flavorants from homogenates of onion (Allium cepa). J Agric Food Chem. 1997;45:4414–4422.
12. Block E, Naganathan S, Putman D, Zhao SH. Organosulfur chemistry of garlic and onion: Recent results. Pure Appl Chem. 1993;65(4):625–632. doi: 10.5555/19950307981.
13. Boeing H, Jedrychowski W, Wahrendorf J, Popiela T, Tobiaszadamczyk B, Kulig A. Dietary risk-factors in intestinal and diffuse types of stomach-cancer – A multicenter case-control study in Poland. Cancer Causes Control. 1991;2(4):227–233. doi: 10.1007/BF00052138.
14. Bonaccorsi P, Caristi C, Gargiulli C, Leuzzi U. Flavonolglucosides in Allium species: A comparative study by means of HPLC-DAD-ESI-MS-MS. Food Chem. 2008;107(4):1668–1674. doi: 10.1016/j.foodchem.2007.09.053.
15. Boots AW, Haenen GRMM, Bast A. Health effects of quercetin: From antioxidant to nutraceutical. Eur J Pharmacol. 2008;585(2–3):325–337. doi: 10.1016/j.ejphar.2008.03.008.
16. Bordia T, Mohammed N, Thomson M, Ali M. An evaluation of garlic and onion as antithrombotic agents. Prostaglandins Leukot Essent Fatty Acids. 1996;54(3):183–186. doi: 10.1016/s0952-3278(96)90014-9.
17. Boyle SP, Dobson VL, Duthie SJ, Kyle JAM, Collins AR. Absorption and DNA protective effects of flavonoid glycosides from an onion meal. Eur J Nutr. 2000;39(5):213–223. doi: 10.1007/s003940070014.
18. Briggs WH, Folts JD, Osman HE, Goldman IL. Administration of raw onion inhibits platelet-mediated thrombosis in dogs. J Nutr. 2001;131(10):2619–2622. doi: 10.1093/jn/131.10.2619.
19. Burt S. Essential oils: Their antibacterial properties and potential applications in food. Int J Food Microbiol. 2004;94(3):223–253. doi: 10.1016/j.ijfoodmicro.2004.03.022.
20. Caridi D, Trenerry VC, Rochfort S, Duong S, Laugher D, Jones R. Profiling and quantifying quercetin glucosides in onion (Allium cepa L.) varieties using capillary zone electrophoresis and high performance liquid chromatography. Food Chem. 2007;105(2):691–699. doi: 10.1016/j.foodchem.2006.12.063.
21. Choi SI, Hong EY, Lee JH, Lee YS, Kim GH. Antioxidant and antimicrobial activities of the ethanol extract of Allium victoriallis L. var. platyphyllum. Food Sci Biotechnol. 2008;17(2):313–318.
22. Davis JM, Murphy EA, Carmichael MD, Davis B. Quercetin increases brain and muscle mitochondrial biogenesis and exercise tolerance. Am J Physiol Regul Integr Comp Physiol. 2009;296(4):R1071–R1077. doi: 10.1152/ajpregu.90925.2008.
23. Day AJ, Mellon F, Barron D, Sarrazin G, Morgan MRA, Williamson G. Human metabolism of dietary flavonoids: Identification of plasma metabolites of quercetin. Free Radic Res. 2001;35(6):941–952. doi: 10.1080/10715760100301441.
24. Dorant E, Van Den Brandt P, Goldbohm RA. A prospective cohort study on the relationship between onion and leek consumption, garlic supplement use and the risk of colorectal carcinoma in The Netherlands. Carcinogenesis. 1996;17(3):477–484. doi: 10.1093/carcin/17.3.477.
25. Dorant E, Van Den Brandt PA, Goldbohm RA, Sturmans F. Consumption of onions and a reduced risk of stomach carcinoma. Gastroenterology. 1996;110(1):12–20. doi: 10.1053/gast.1996.v110.pm8536847.
26. El-Demerdash FM, Yousef MI, Abou El-Naga NI. Biochemical study on the hypoglycemic effects of onion and garlic in alloxan-induced diabetic rats. Food Chem Toxicol. 2005;43(1):57–63. doi: 10.1016/j.fct.2004.08.012.
27. Elsharkawy ER. Anticancer effect and seasonal variation in oil constituents of Santolina chamaecyparissus. Chem Mater Res. 2014;6(3):85–91.
28. Elsharkawy ER, Elshathely M, Jaleel GA, Al-Johar HI. Anti-inflammatory effects of medicinal plants mixture used by Bedouin people in Saudi Arabia. 2013;59(3):77–87. doi: 10.2478/hepo-2013-0018.
29. Ewald C, Fjelkner-Modig S, Johansson K, Sjoholm I, Akesson B. Effect of processing on major flavonoids in processed onions, green beans, and peas. Food Chem. 1999;64(2):231–235. doi: 10.1016/S0308-8146(98)00136-8.
30. Gabler NK, Osrowska E, Imsic M, Eagling DR, Jois M, Tatham BG, et al. Dietary onion intake as part of a typical high fat diet improves indices of cardiovascular health using the mixed sex pig model. Plant Foods Hum Nutr. 2006;61(4):179–185. doi: 10.1007/s11130-006-0030-8.

An investigation on the physical and chemical properties of white, red, and brown onions was carried out to assess the potential applications of the different species sampled in this study. The physical properties monitored include refractive index, viscosity, and density. For red onion, the refractive index, viscosity, and density were measured as 1.35322, 1.631 cSt, and 1.1140 g/cm³, respectively. Brown onion exhibited values of 1.3571, 3.045 cSt, and 1.1130 g/cm³, while white onion showed 1.34926, 2.45 cSt, and 1.1036 g/cm³. These measurements indicate variations in optical and flow properties among the species, which may influence their suitability for different industrial and medicinal formulations. Regarding chemical properties, the iodine value, saponification value, free fatty acid (FFA), peroxide value, and acid value were evaluated. The iodine values were 15.2802%, 18.092%, and 28.1082% for red, brown, and white onions, respectively, suggesting differences in the degree of unsaturation of oils extracted from each species. The saponification values were determined as 3.927%, 15.708%, and 10.94%, while FFA values recorded were 23.04%, 20.48%, and 11.264% for red, brown, and white onions, respectively, indicating differences in hydrolytic stability and potential nutritional quality. Furthermore, the peroxide values were found to be 60%, 55%, and 45%, reflecting the extent of oxidation, whereas the acid values were 2.384%, 2.244%, and 2.106%, providing additional insights into the oil quality and freshness. Overall, the results demonstrate significant variations in both physical and chemical characteristics among the three onion species, highlighting their distinct compositional profiles. These differences suggest that the oils and extracts obtained from these onions possess diverse bioactive properties, making them suitable for applications in pharmaceutical, nutraceutical, and medical industries, particularly in areas such as antioxidant formulations, anti-inflammatory treatments, and natural preservative production. The findings underscore the importance of species-specific evaluation to optimize the use of onion-derived products for targeted industrial and therapeutic applications.

🔒 This is a subscription article

Full text is available to subscribers and institutional members. Please choose an option below to access it.

1. Aherne SA, O’Brien NM. Dietary flavonols: Chemistry, food content, and metabolism. Nutr. 2002;18(1):75–81. doi: 10.1016/s0899-9007(01)00695-5.
2. Ali M, Bordia T, Mustafa T. Effect of raw versus boiled aqueous extract of garlic and onion on platelet aggregation. Prostaglandins Leukot Essent Fatty Acids. 1999;60(1):43–47. doi: 10.1054/plef.1998.0006.
3. Ali M, Thomson M, Afzal M. Garlic and onions: Their effect on eicosanoid metabolism and its clinical relevance. Prostaglandins Leukot Essent Fatty Acids. 2000;62(2):55–73. doi: 10.1054/plef.1999.0124.
4. Azuma K, Minami Y, Ippoushi K, Terao J. Lowering effects of onion intake on oxidative stress biomarkers in streptozotocin-induced diabetic rats. J Clin Biochem Nutr. 2007;40(2):131–140. doi: 10.3164/jcbn.40.131.
5. Abu-Darwish MS, Abu Dieyeh ZH, Mufeed B, Al-Tawaha AR, Al-dalain SY. Trace element contents and essential oil yields from wild thyme plant (Thymus serpyllum L.) grown at different natural variable environments. J Food Agric Environ. 2009;7:920–924.
6. Babu GD, Kaul VK. Variation in essential oil composition of rose-scented geranium distilled by different distillation techniques. Flavour Fragr J. 2005;20(2):222–231. doi: 10.1002/ffj.1414.
7. Benkeblia N, Onodera S, Shiomi N. Variation in 1-fructo-exohydrolase (1-FEH) and 1-kestose-hydrolysing (1-KH) activities and fructo-oligosaccharide (FOS) status in onion bulbs. Influence of temperature and storage time. J Sci Food Agric. 2005;85(2):227–234. doi: 1002/jsfa.1959.
8. Benkeblia N, Varoquaux P. Effect of nitrous oxide (N₂O) on respiration rate, soluble sugars and quality attributes of onion bulbs Allium cepa cv. Rouge Amposta during storage. Postharvest Biol Technol. 2003;30(2):161–168. doi: 10.1016/S0925-5214(03)00101-7.
9. Benkeblia N. Free-radical scavenging capacity and antioxidant properties of some selected onions (Allium cepa L.) and garlic (Allium sativum L.) extracts. Braz Arch Biol Technol. 2005;48(5). doi: 10.1590/S1516-8913200500060001.
10. Bianchini F, Vainio H. Allium vegetables and organosulfur compounds: Do they help prevent cancer? Environ Health Perspect. 2001;109(9):893–902. doi: 10.1289/ehp.01109893
11. Block E, Gulati H, Putman D, Sha DY, You NN, Zhao SH. Allium chemistry: Synthesis of 1-[alk(en)ylsulfinyl]propyl alk(en)yl disulfides (cepaenes), antithrombotic flavorants from homogenates of onion (Allium cepa). J Agric Food Chem. 1997;45:4414–4422.
12. Block E, Naganathan S, Putman D, Zhao SH. Organosulfur chemistry of garlic and onion: Recent results. Pure Appl Chem. 1993;65(4):625–632. doi: 10.5555/19950307981.
13. Boeing H, Jedrychowski W, Wahrendorf J, Popiela T, Tobiaszadamczyk B, Kulig A. Dietary risk-factors in intestinal and diffuse types of stomach-cancer – A multicenter case-control study in Poland. Cancer Causes Control. 1991;2(4):227–233. doi: 10.1007/BF00052138.
14. Bonaccorsi P, Caristi C, Gargiulli C, Leuzzi U. Flavonolglucosides in Allium species: A comparative study by means of HPLC-DAD-ESI-MS-MS. Food Chem. 2008;107(4):1668–1674. doi: 10.1016/j.foodchem.2007.09.053.
15. Boots AW, Haenen GRMM, Bast A. Health effects of quercetin: From antioxidant to nutraceutical. Eur J Pharmacol. 2008;585(2–3):325–337. doi: 10.1016/j.ejphar.2008.03.008.
16. Bordia T, Mohammed N, Thomson M, Ali M. An evaluation of garlic and onion as antithrombotic agents. Prostaglandins Leukot Essent Fatty Acids. 1996;54(3):183–186. doi: 10.1016/s0952-3278(96)90014-9.
17. Boyle SP, Dobson VL, Duthie SJ, Kyle JAM, Collins AR. Absorption and DNA protective effects of flavonoid glycosides from an onion meal. Eur J Nutr. 2000;39(5):213–223. doi: 10.1007/s003940070014.
18. Briggs WH, Folts JD, Osman HE, Goldman IL. Administration of raw onion inhibits platelet-mediated thrombosis in dogs. J Nutr. 2001;131(10):2619–2622. doi: 10.1093/jn/131.10.2619.
19. Burt S. Essential oils: Their antibacterial properties and potential applications in food. Int J Food Microbiol. 2004;94(3):223–253. doi: 10.1016/j.ijfoodmicro.2004.03.022.
20. Caridi D, Trenerry VC, Rochfort S, Duong S, Laugher D, Jones R. Profiling and quantifying quercetin glucosides in onion (Allium cepa L.) varieties using capillary zone electrophoresis and high performance liquid chromatography. Food Chem. 2007;105(2):691–699. doi: 10.1016/j.foodchem.2006.12.063.
21. Choi SI, Hong EY, Lee JH, Lee YS, Kim GH. Antioxidant and antimicrobial activities of the ethanol extract of Allium victoriallis L. var. platyphyllum. Food Sci Biotechnol. 2008;17(2):313–318.
22. Davis JM, Murphy EA, Carmichael MD, Davis B. Quercetin increases brain and muscle mitochondrial biogenesis and exercise tolerance. Am J Physiol Regul Integr Comp Physiol. 2009;296(4):R1071–R1077. doi: 10.1152/ajpregu.90925.2008.
23. Day AJ, Mellon F, Barron D, Sarrazin G, Morgan MRA, Williamson G. Human metabolism of dietary flavonoids: Identification of plasma metabolites of quercetin. Free Radic Res. 2001;35(6):941–952. doi: 10.1080/10715760100301441.
24. Dorant E, Van Den Brandt P, Goldbohm RA. A prospective cohort study on the relationship between onion and leek consumption, garlic supplement use and the risk of colorectal carcinoma in The Netherlands. Carcinogenesis. 1996;17(3):477–484. doi: 10.1093/carcin/17.3.477.
25. Dorant E, Van Den Brandt PA, Goldbohm RA, Sturmans F. Consumption of onions and a reduced risk of stomach carcinoma. Gastroenterology. 1996;110(1):12–20. doi: 10.1053/gast.1996.v110.pm8536847.
26. El-Demerdash FM, Yousef MI, Abou El-Naga NI. Biochemical study on the hypoglycemic effects of onion and garlic in alloxan-induced diabetic rats. Food Chem Toxicol. 2005;43(1):57–63. doi: 10.1016/j.fct.2004.08.012.
27. Elsharkawy ER. Anticancer effect and seasonal variation in oil constituents of Santolina chamaecyparissus. Chem Mater Res. 2014;6(3):85–91.
28. Elsharkawy ER, Elshathely M, Jaleel GA, Al-Johar HI. Anti-inflammatory effects of medicinal plants mixture used by Bedouin people in Saudi Arabia. 2013;59(3):77–87. doi: 10.2478/hepo-2013-0018.
29. Ewald C, Fjelkner-Modig S, Johansson K, Sjoholm I, Akesson B. Effect of processing on major flavonoids in processed onions, green beans, and peas. Food Chem. 1999;64(2):231–235. doi: 10.1016/S0308-8146(98)00136-8.
30. Gabler NK, Osrowska E, Imsic M, Eagling DR, Jois M, Tatham BG, et al. Dietary onion intake as part of a typical high fat diet improves indices of cardiovascular health using the mixed sex pig model. Plant Foods Hum Nutr. 2006;61(4):179–185. doi: 10.1007/s11130-006-0030-8.