…and here’s is why I’m not going to write an article about it.

I recently found a really promising research paper that tested THIRTEEN different frozen vegetables for nutrition after boiling, pressure cooking, steaming and microwaving. Whenever I find a research paper before bearing down and reading it I always look at the data tables. Initially, I was so excited to find this jackpot of nutritional data on comparing different cooking methods on so many vegetables.

As I went through one vegetable after another, pressure cooking was either worse than or slightly better than boiling and retained VERY LITTLE folates, carotenoids, and vitamin C compared to non-pressure steaming and microwaving.

What?!?!

I was confused because this data went against EVERYTHING else I’d found so far – if true it would completely turn one of the values of pressure cooking on its head. But, it didn’t take me long to find a BIG FLAW in the data.

At the beginning of a paper, the researchers detail what equipment they used and how they measured the data. And that’s where something jumped out at me right away. For Boiling, Steaming and Microwaving the researchers instantly froze the cooked vegetable in liquid nitrogen for storage until they could measure the nutrient levels. BUT, the pressure cooked vegetables were thrown in an ice-water bath for 5 minutes first and THEN dipped in liquid nitrogen.

Hmm…. so how could this small alteration affect the results?

Well, I kept searching and found out that folates, carotenoids, and vitamin C are all WATER SOLUBLE. That means, they dissolve in water.

So, it is feasible that the pressure cooked vegetables lost additional nutrients in the ice water bath compared to all of the other cooking methods. So basically, the data on the pressure cooked vegetables is totally useless and cannot be compared to vegetables with other cooking methods that WERE NOT thrown in an ice bath for 5 minutes.

I have contacted the lead researcher to ask if they also measured the nutrients in the ice water – I haven’t heard back from them but I think it is unlikely since they did not state doing it in the paper.

I’m just putting this out there, in case anyone else stumbles on this research either thinking they found a GOTCHA and in the interest of full disclosure! If Dr. Bureau answers my query, I’ll share her response in the Hip Pressure Cooking forums (where I originally posted this text). Ciao, L

Citation: Bureau, S., Mouhoubi, S., Touloumet, L., Garcia, C., Moreau, F., Bédouet, V., & Renard, C. M. (2015). Are folates, carotenoids and vitamin C affected by cooking? Four domestic procedures are compared on a large diversity of frozen vegetables. LWT-Food Science and Technology, 64(2), 735-741.

Full Research Paper: http://prodinra.inra.fr/ft?id=C66710EF-3A38-4EF9-B349-55DE126A6457

And if you're curious to see the pressure cooker nutrition articles that I DID write, you can find them here: https://www.hippressurecooking.com/category/news-and-articles/nutrition/