Perfectly Practiced Preservation Part II, aka Radical Raspberry Jam

So far this summer I have been hanging out with some very awesome Young-at-Heart Americans and they are starting to rub off on me. Not only am I making my own dress, wearing cat-eye glasses, and helping out in the church office, today I made my own jam.

Jams are a great way to naturally preserve fruit past its prime. Microorganisms (mold, bacteria, etc.), once again, are the reason that fruit spoil. They eat away at the fruit and cause rotting and mold, yuck. I talked earlier about freezing and refrigeration as one way to slow down the organisms. You can also just kill them off. When you make jam you boil the fruit and the high temperatures make all the microorganisms croak. Vacuum sealing the jars keep new ones from getting in and the jam stays fresh.

Because you want goo, natural breakdown because of fats and enzymes is not a problem. But, you do have to worry about oxidation. When you cut a piece of fruit the cells along the cut line break open, releasing an enzyme (tyrosinase) that reacts with oxygen in the atmosphere and the ferrous phenols in the fruit to create a new brown chemical that is a cousin to the very famous iron oxide (aka rust). Rust is created the same way, when iron reacts with oxygen. To prevent the browning of fruit you use vacuum sealing to remove the oxygen.

So, how do you vacuum seal? Pressure is a measure of how often molecules hit a surface. When everything is open the pressure will equalize throughout a gas. Most gases follow the ideal gas law which states that pressure*volume = the number of molecules*the gas constant*temperature (PV=nRT). When you heat a jar and the gas inside of it without a lid on the pressure is the same as the air around, but the temperature is higher. When you put an airtight lid on the volume and the number of molecules can't change. So, as the jar, the jam, and the air inside cool down the pressure decreases and the air outside starts pushing really hard to try and get in. Eventually the outside pressure is so much greater that the little pop dot on the jar gets pushed in and the jar is "vacuum sealed". If you've ever wondered why the pop dot is there, that one reason. The other really important reason is, if there are still organisms in the jar they will start eating the jam and will give of gases as waste (like yeast) which eventually will pop the dot back up, indicating that the jam is spoiled. So, never use a jam with a popped up dot.

While the science behind jam can be confusing and complicated, the act of making jam is surprisingly easy. There are rarely more than 3 or 4 ingredients and the steps are fairly straight forward. One major hint, use really good fresh ripe fruit. My mom and I went an bought fresh raspberries at the farmers market and it was perfect. This jam is a little sweet, a little tart, and very very good. Good luck and enjoy.*

Raspberry Jam

Ingredients

4 pints fresh raspberries

5 cups sugar

2 Tablespoons lemon juice

5 half pint Ball or Kerr jars with lids and rims

Wash and lightly dry the raspberries. Place in a large stock pot or dutch oven and crush (I used a potato masher). Mix in the sugar and lemon juice and quickly bring to a boil. Boil, stirring frequently for 25 minutes. Remove from heat and skim off foam. Ladle hot jam into hot jars leave about a 1/4 inch between the lid and the jam. Seal using the jar's instructions (they will go something like this, boil jar and rims, place jar rims and lids in hot water, pour in jam, wipe rim clean with a damp cloth, center lid, add rim and tighten). Let cool and enjoy.

*Good news, the uploader thingy is working again. Better news I have an awesome new digital manual camera to take my pictures with, yay!