The Lemon Garlic Blues

January 27, 2026

Why so blue?

After Eleanor insisted the garlic she used was brand new, I tasted it and was delighted to find it was not only fresh but blissfully citrusy. A quick google search confirmed my suspicion: there is a chemical reaction between garlic enzymes and acid (often seen when pickling) that produces blue pigments. Blue is a rare color in nature, so I decided to unpack this a bit further.

The flavor of garlic comes from sulfur-containing compounds such as alliin. When tissue is broken down during cutting or crushing, alliinase converts alliin into thiosulfinates such as allicin. Allicin (and isolalliin, etc.) give garlic its characteristic odor - thank you allicin! 

Thiosulfinates act as preliminary reactants along with amino acids naturally found in garlic which in the presence of acid like lemon juice can form pyrroles. Eventually, allicin and related thiosulfinates help crosslink pyrrole units into multi-pyrrole pigmunts giving the garlic a blue-green hue. These compounds have a max absorbance around 440nm to 590nm. Aromatics have delocalized electrons which allow the compounds to absorb in the visible range, similar to how β-carotene gives carrots an orange color.

Once I learned this, I was able to relatively easily recreate it by crushing garlic, adding lemon juice, and sticking it in the microwave for 30 seconds. It would be interesting to try to isolate the pigments in the future