It is time to “put up” that glut of tomatoes coming in from your garden! But you may be dreading getting underway because of the time involved for canning or freezing. Good news: your crock pot is your new best friend.
This technique yields a thickened sauce. It has a slightly roasted tomato note to it because the tomatoes will be cooked a long time without adding additional water, leaving some of the natural sugars to caramelize a bit.
The best tomatoes to use for sauce are Roma tomatoes and other related paste-types, such as Big Mama, San Marzano, and Amish Paste. These varieties contain less water than beefsteak tomatoes, for example, and therefore cook down to sauce consistency more quickly. However, since you will be using the crockpot technique described below, any tomatoes will produce good results.
Whether you can or freeze the sauce is up to you. The most vital piece of equipment to sauce making of any kind is a food mill or tomato press, which will help you separate the pulp from the seeds and skin. You may use the traditional perforated metal food mill that sits over a pot, or a mill made especially for processing tomatoes. (If you are unable to obtain such a device, you may hand-remove the skins and seeds after the tomatoes are cooled by slipping off the skins and gently squeezing out the seeds. Then puree the pulp in a blender.) The instructions assume the use of a tomato press.
To begin, first choose ripe tomatoes. They should have a deep color, and be ripened up to the stem. Wash them, and remove the green tops along with any blemished areas or unripe spots. Leave them whole or in large chunks. Once you have them ready, load the tomatoes into your crock pot, and put the lid on. Set the crock pot to high, and let it cook overnight if processing in the morning. If processing during the evening, load the pot in the morning. Eight hours of cooking is a good rule of thumb to evaporate off a lot of the water and to achieve a beautiful sauce.
Once the tomatoes have finished cooking, it is time to run them through the press or food mill. Using a slotted spoon, remove the tomatoes from the crock pot and put them in the hopper of the press. Leave the liquid that has collected in the crockpot behind. This is the key to the technique: the tomatoes are left intact while the clear liquid (mainly water) stays in the pot. Translation: less cooking down of your sauce to get it to actual sauce consistency. You may wish to run the skin/seeds back through the press a few times to squeeze out all of the pulp. If the remainder looks very wet and juicy, it definitely has more pulp that could be extracted.
The next step is canning or freezing. You may wish to add lemon juice to your tomato sauce, as some varieties of tomato are not acidic enough to deter bacteria growth in a canning situation. A pinch of salt is also a good addition. Your best bet is to follow a published recipe for canning. With freezing, just be sure to use freezer containers and leave enough space for the sauce to expand without popping off the lids and spilling out.
The beauty of this technique is that much of the water that normally gets cooked off while babysitting a pot on the stove is done while you sleep or do other things. There is no waiting around for the sauce to cook down, no scorching on the bottom of the pot, and no stirring every few minutes. Even washing out the crock pot is easier than washing out a pot that has been cooking on the stove because there will be less sticking. Putting up the harvest just got easier!
