Some further digging turned up this research paper from the African Journal of Biotechnology, which details the activity of alliinase relative to pH. Here’s a graph of the data:
Turns out alliinase is highly active at a neutral pH, with peak activity at a very slightly acidic pH of 6.5. As you get more and more acidic, its activity drops off precipitously. Lemon juice has a pH of just around 2. The study’s data goes down only to a pH of 3, but extrapolating that graph, we can guess that at pH 2, allicin’s activity is reduced to a quarter or less of its peak activity.
That’s what keeps garlic from becoming too harsh. Once enzymatic activity has stabilized, you can then incorporate that garlicky-but-not-harsh lemon juice mixture into your tahini sauce and hummus without fear.
I’ve since used the garlic-in-lemon trick in a number of applications, ranging from baba ganoush to a vinaigrette for some simple roasted cauliflower. Any time you have lemon and garlic in a recipe, it’s good to consider whether or not you might gain some advantage by upping the garlic flavor without upping its harshness.
This is my favorite kind of recipe: one that tastes great, but also teaches you an entirely new technique that has applications well beyond the scope of the original recipe.
Sorry, I’ll be right back. I’m heading off to purée some garlic. (After having a bite or two of hummus, that is.)
