Cook's sauerkraut was sealed in barrels. No way light could affect it. It would not be affected by storage as badly as citrus juice; the salt content preserves it.

Leave a glass of lemon juice and a jar of sauerkraut out of the fridge and see which is still edible after a month.

You can buy sauerkraut preserved Cook's way at any Polish or Chinese food shop.

This storage method is better than Cook's but the loss of vitamin C is so slight it leaves a massive margin of effectiveness:

table covering a few months in storage