Thoughts on blanching (frozen, healthier, tomatoes, thawing)

[harry chickpea]

Some semi-random musings after reading the cauliflower thread.

I have frozen both blanched and raw veggies. Almost all the older freezing guides insist that blanching is required. So why do I sometimes skip the step and what are the dangers?

First, I am almost certain that the primary reason for blanching prior to freezing was an abundance of caution with food safety. Food that is properly stored at 0 degrees F or lower, does not change. It is effectively in stasis. Seeds and smaller items frozen quickly to reduce ice crystal formation can remain viable indefinitely, witness the entire IVF and egg and sperm storing industry. There is no danger from food pathogen growth while at sub-zero temperatures. So why the caution?

When food is thawed, there can be dangers. If you leave your veggies out on a counter for an afternoon to thaw, and the enzymes and pathogens can have a chance to act, and possibly act even more effectively on cell material where the cell walls have been damaged by ice crystals formed in freezing. In cases where the freezer is frost free, periods of above zero temps exist on the surface of the foods.

Freezing foods at home was a new idea when many of the rules were laid down. The prevalence of "summer fever" and other food borne illnesses was much higher then than now. Science was just beginning to make inroads into safe food preparation as a commonplace event in home kitchens. If there was a freezer, HOPEFULLY the icebox was replaced with a refrigerator as well, but there were no guarantees.

So, the first reason to blanch is sanitation. SOME of the surface bacteria are killed, and some of the dirt and schmutz removed by the boiling action. The cause of dysentery (once common) is destroyed. That means the thawing food is safer.

Now comes reason number two: the big misunderstanding. >>Blanching kills enzymes that destroy flavor<< In many cases this is pure BS. SOME veggies that have a tendency to turn bitter DO appear to benefit taste-wise from blanching; kale and the stronger crucifers release mustard oil (bitter) when cell walls are damaged, so frozen veggies that are thawed may seem more bitter than fresh, and blanching reduces that bitterness. Unless you are using the veggies out of the freezer with no further prep, I posit that it isn't particularly important. The cooking done after freezing will do much the same.

As further proof of point, anyone who has cooked poke or even collards knows to toss out the first boil water. With poke, it is a matter of life and death. With collards, it removes some of the bitter flavor. Blanching is simply another variation of a double boil.

Reason three is for brighter, more appealing color. I have to admit that watching broc turn from grey to a nice green in a pot or steamer is very satisfying. Nutritionally or food safety wise, it means little to nothing.

Reason four is reduced cooking time of the thawed veggies. Really? THAT makes a difference after waiting for the thaw cycle? Somebody was searching for a reason.


Now comes the big downside: For some veggies, killing the enzymes reduces their nutritional value. A, B, and C vitamins are lost in the blanching process. Steam blanching is a little better, but not much. Broccoli that is raw has more cancer-fighting compounds. Freezing it without the blanch and then a quick stir fry of it seems to be healthier than blanching. Carrots, OTOH, have more beta-carotine available when cooked.


Blanching is not only time critical,with a ice water shock to stop it, the size of the veggie being blanched is important. Generally, any piece has to be smaller than an inch cube. Florets may be a little bigger, but unless the internal temp reaches that blanching temp, any food safety is compromised.

So what do I do as an alternative for food safety? With foods that might be eaten raw anyway, a soak in a weak solution with GSE, hydrogen peroxide, or bleach can handle surface problems. Many veggies come to market pre-washed.

One of the side advantages of blanching is that veggies get cut to a size that allows a fast freezing that doesn't form large ice crystals. Freeze small florets of broc or cauliflower and they will generally be fine. Try to freeze the whole head and it will likely be mushy and watery when thawed.

[Kayekaye]

I haven’t frozen cauliflower but I do freeze fresh vegetables. I always blanch them. When I haven’t blanched them they turn to mush when thawed.

[Gerania]

I'm too tired to read and process that this evening. I remember that when my father bought a house with a decent yard, he grew killer tomatoes and too many green beans. Mom wrapped the excess beans in foil and put them in the freezer. They were tough and terrible after cooking.