When you've grown up hearing warnings about the dangers of home canned foods, it takes a bit of courage to try old fashioned methods of preserving foods that use no heat. This week I opened one of the three jars of blueberries I put up using a recipe from Finland. Before eating them, my husband and I said to each other, Well, if we wake up dead, we'll know why.
The blueberries were still firm and tasted like fresh. Way better than frozen blueberries that have been thawed.
Here's the method for anyone who wants to try it this summer (taken from Keeping Food Fresh from the gardeners and farmers of Terre Vivante):
Soak the jars for 12 hours. This is supposed to allow any mold spores to hatch. Then sterilize the jars. Crush the berries slightly while filling the jars so that their juice covers them. Fill the jars to 1/2 inch from the top. At the top, add some of the berries preserved the previous year. Coat the inside of the lids with honey and close the jars. Store in a cool place.
Since I didn't have any berries from the previous year, I used about a tablespoon of whey from plain yogurt with live cultures. This is to give a boost to the natural preservation process. However, I think the blueberries alone would be fine. That fine white coating (which you also see on plums and grapes) helps prevent bad bacteria from growing.
Here's a link to "4 Ways to Preserve Blueberries" on the Traditional Cooking School. Be sure to read the comments referring to preserving raw with honey.