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Comment by lifeformed | Hacker News Reader

How does the potassium get reduced by being grown in a clean room?

By being able to control the nutrients and how fast the lettuce grows. Potassium intake varies with how fast the plant grows, so adjusting the light and temperature (along with other nutrients, like nitrogen, salt, etc) allows the lettuce to grow quickly (possibly under lights 24hrs a day) without taking up excess potassium.

With a clean environment, potassium levels can be reduced as well, as high potassium soil (fertilized that way) will allow the plant to uptake more potassium and increase its resilience to disease and bug damage.

Its in the article, but somewhat hidden:

"No pesticide is used and because the lettuce is produced in a clean room, it stays fresh for about two weeks when stored at 10 degrees Celsius or lower."

They don't need to use pesticides because of the clean room, which in turn makes for lower potassium content in the lettuce.

This is deducing that pesticides increase potassium uptake and storage in the lettuce which is not true. You can, however, use lower potassium levels for plants that will not be subject to disease or bug stress. But there is not a direct relationship here.

That's whats implied in the article, and it may be true, or a part of the truth, aside from that, from growing up with my gentleman farmer uncle, I know low K results in weak stems/leaves. This was often a problem with his popcorn field (yes there are specific breeds of corn for popcorn its not just generic corn, although he also grew sweetcorn for picnics and stuff... he was a popular guy) Those lettuce plants would probably blow flat if you breathed on them hard, much less put them out in the wind. I would predict low-K lettuce is significantly less crunchy that normal lettuce.

> it stays fresh for about two weeks

That's hardly special. I've stored lettuce that I bought commercially for 4 weeks and it was fine. So that's 4 weeks plus however long it took to get to me. (I bought too much by mistake.)

Was that at 10°C or higher?

No, it was lower. In a fridge.

Then it sounds like better preservation would be expected. The article says it lasts two weeks at 10°C. I have no idea how exceptional that is as I've never knowingly stored lettuce at 10°C, but it probably doesn't last as long as lettuce as refrigerator temperatures.

Http://cooking.stackexchange.com/questions/33540/does-a-head-of-lettuce-really-need-to-be-refrigerated gives a table showing that leaf lettuce at 10 degrees C evaporates only about 30% faster than leaf lettuce at 5 degrees C. That difference isn't that large.

It also gives head lettuce at best two weeks at five degrees centigrade. So, two weeks at 10 degrees seems a good result.

On the other hand, the article says _about_ two weeks; they might mean 'ten days plus', and 'freshness' may be highly subjective (I bet there is a standard for measuring lettuce freshness)

Humidity is a huge component of lettuce lifespan. You can't just plop lettuce into your fridge near 0c as it is quite dry (hence why fridges have crispers that maintain higher humidity for veggies, and are selectable to low humidity for fruits).

Frankly, if you're not using a head of lettuce in 2 weeks something is wrong with your eating and/or buying decision making :-)

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