my ginger-garlic paste has turned green in color within 3 days i prepared..why does it happen?!
Answers:
Remember in high school chemistry class those little strips that were used to test pH level, they turned different colors? Those strips are made using anthocyanins, water-based pigments that naturally occur in the plant world. Anthocyanins change colour according to the pH level of a solution (base = green/yellow, neutral = blue/purple, acidic = red). Anthocyanins in garlic appear on the base end of the scale because the vegetable is low acid.
Probably what happened here is that the sulfur compounds released by the onions mixed with water released by the ginger (or did you add some water?) to create a weak sulfuric acid (the same reaction that makes us cry when cutting onions). The sulfuric acid changed the pH level in the mixture causing a reaction that turned the anthocyanin in the garlic blue/green. The change occurs on a molecular level, altering light absorption and reflection, similar to the way leaves change color in the fall.
It is harmless to eat......................
I bet the last poster is right. Garlic apparently can sometimes turn blue or green when it's pickled (as in soaked in vinegar, which is acidic, like onions). It just depends on the specific chemistry of the onions and ginger involved this time. If it doesn't smell funky, it's probably fine.