Basil blanch time before freezing: SDSU says 15 seconds, NMSU says 60. What do you actually do?

A disclosure first, because it matters for what I'm asking: I don't have a garden. I research and write about herbs and preserving, and this forum has the hands-on knowledge I don't. So I'm bringing you a documented conflict I ran into, and asking the people who actually do this.

I spent this month going through the extension-service literature on freezing basil. The blanch times don't agree - by a factor of four:

- SDSU Extension: 15 seconds for larger leaves like basil, then ice water and pat dry.
- Penn State Extension: also 15 seconds, same ice-water step.
- NMSU Extension (Guide E-320): one minute. And notably, basil is the only herb they say to blanch at all.
- NCHFP: no blanch time for basil anywhere. Their herb-freezing page skips blanching entirely, and basil doesn't appear in their blanching-times table.

What makes the gap matter is NCHFP's own warning about erring short: "Underblanching stimulates the activity of enzymes and is worse than no blanching." So if NMSU's minute is the real requirement, a 15-second dip isn't a milder version of the same thing - it's worse than skipping it. Depending on which sheet you're holding.

I could not find a study measuring PPO inactivation in basil at either time, so I'm not treating this as settled. It's a genuine disagreement between land-grant universities.

Two other things I could pin down:

Basil is the one herb where freezing beats drying on published numbers. Baritaux et al. (1992) dried basil at 45 C and tracked the essential oil through storage: 62% of total oil gone at six months, with methylchavicol and eugenol dropping hardest - the two compounds that carry basil's actual character. Clemson reaches the same conclusion in a sentence: freezing preserves flavour in herbs like basil that lose it when dried.

And the fridge is worse than most people assume. Basil takes chilling injury below about 12 C, and a 2023 UC Davis study found browning was worse at 5 C than at 10 or 15 C. A household fridge runs around 4 C - cold enough to injure a living leaf, not cold enough to stop the injury.

I wrote the full comparison up with every source here: https://growforageheal.com/how-to-preserve-basil/

What I can't get from a paper is what you actually do. Do you blanch basil before freezing at all, or skip it and accept the darkening? And for anyone who has run both - does blanched basil genuinely taste better six months in, or does the blanching cost more than the enzymes would have?

I must say, I've never blanched basil before freezing.  Somewhat like green cilantro, in processing for storage it seems best to work relatively fast...within one day...to harvest, mince leaves into small pieces, mix with olive oil, then freeze. For basil pesto, the extra steps are to use quickly sauteed garlic in olive oil, slivered almonds, small amount of nutritional yeast and salt-->into blender with basil to get desired consistency adding a bit of lemon juice along the way.  The final 'paste' is put into small freezer bags and frozen immediately.  The olive oil prevents from a really solid freezing so pieces of a size desired for the meal being made can be broken off without thawing the entire bag.  With cilantro, it loses the aromatics even worse than basil.   Hope that helps in some way!

Who is:  - SDSU Extension, NMSU Extension, and NCHFP?

I have always used the USDA, National Center for Home Preservation, though they do not list basil.

I have always dried basil.

I can see the advantage of freezing basil though is that the best solution?

I have never blanched it, I just freeze it. I don't expect it to come out looking fresh, I expect it to come out tasting good. The oils that give it it's flavor don't do well when cooked, that's why I add basil right at the end of cooking.

I don't blanche it. I puree and freeze in oil.

I chop it up tiny (or use a food processor) then add enough oil (olive or sunflower usually) to make it pourable and a dash of an acid (usually lime juice.) Then I pour it into something that'll make reasonably sized pucks and freeze.

I store the pucks in a freezer without a defrost cycle. I've no answer for the six months question - they get devoured before that.

I don't blanch it. I either dry it or freeze it in pesto or plain olive oil.