Onion Extract

Onion extract comes from the food flavoring trade, not from a waste stream. Onions are crushed so their own enzymes release sulfur flavor compounds, and the juice is then concentrated.^10,11

1. 01 // Source Whole onions Fresh bulbs are about 89% water. Most of the rest is sugar and, in drier bulbs, fructans.
2. 02 // Process Peeled and washed Outer skins come off and the bulbs are washed before crushing.
3. 03 // Process Crushed and squeezed Crushing lets the enzyme alliinase turn stored sulfur precursors into the volatile compounds that taste like onion.
4. 04 // Process Concentrated The pressed juice is concentrated under reduced pressure to drive off water, then the product is pasteurized.
5. 05 // Output Onion extract A pasteurized juice concentrate sold to food makers as a condiment and seasoning.

1. 01

   Savory flavor

   Crushing onion lets alliinase turn sulfur precursors into thiosulfinates, which quickly become sulfides and disulfides, the compounds that carry onion taste. Seasoning makers value the extract for that fraction.^10,11

2. 02

   Listed as a safe flavoring

   FDA's animal feed rules list onion among natural extractives generally recognized as safe for their intended use, so a maker needs no separate approval to add it.¹²

How much No source publishes a pet food inclusion rate. Dog studies fed toxic doses instead, such as 30 g of cooked onion per kg of body weight daily.³

1. Vets say

   Onions cause anemia in dogs

   Evidence

   1. Strong
   2. Some
   3. Thin
   4. None

   Controlled feeding studies agree. Six Pekingese fed cooked onion at 30 g per kg for 2 days lost red cells, and one dose of dehydrated onion cut packed cell volume by 19 points within 5 days. Those were large doses.^2,3

2. Owners say

   Any onion in dog food is dangerous

   Outruns the evidence

   Evidence

   1. Strong
   2. Some
   3. Thin
   4. None

   Clinical signs start at 15 to 30 g of raw onion per kg of body weight, or 150 to 300 g for a 10 kg dog. No study has fed flavoring-level extract daily, so harm at that dose is unmeasured, not shown.^1,6

3. Owners say

   Onion is good for a dog's heart

   Outruns the evidence

   Evidence

   1. Strong
   2. Some
   3. Thin
   4. None

   In 6 dogs with damaged coronary arteries, 2 g per kg of raw onion cut ex vivo platelet clumping by 44%. That was one large raw dose in a lab model, and nobody measured heart disease outcomes.⁵

4. Brands say

   Onion's quercetin gives dogs antioxidant protection

   Outruns the evidence

   Evidence

   1. Strong
   2. Some
   3. Thin
   4. None

   Onion does carry quercetin glucosides, about 2,300 mg per 100 g combined in one dried powder. Dogs absorbed only about 4% of an oral quercetin dose, and no trial shows a benefit from onion extract.^8,9

5. Owners say

   Cooked or processed onion is safe for dogs

   Outruns the evidence

   Evidence

   1. Strong
   2. Some
   3. Thin
   4. None

   The evidence points the other way. A hemolytic compound was isolated from boiled onions, the Pekingese trial used cooked onion, and a 2016 review states that cooking, drying and processing do not remove the toxic effect.^3,4,6