Liquid Milk
Preserved liquid milk comes in a number of forms, none of which are very similar to each other. The most common forms of these packaged milk are as follows:
Canned Milks
These are commonly called UHT milks (Ultra High Temperature) for the packaging technique used to put them up. They come in the same varieties as fresh liquid milks: whole, 2%, 1% and skim. Just recently I've even found whipping cream in UHT packaging (Grand Chef - Parmalat), though this may be offered only in the commercial/restaurant market. In the U.S. they have vitamin D added. The lesser fat content milks do not keep as long as whole milk and their "use by" dates are correspondingly shorter term. This milk is packaged in aseptic containers, either cans or laminated paper cartons. It has the same composition as fresh milk of the same type, and can be stored at room temperature because of the special pasteurizing process used. The milk has a boiled flavor, but much less than evaporated milk. I buy the whole milk and the dates are usually for as much six months. The milk is still usable past their dates, but the flavor soon begins to go stale and the cream separates. I am told by a friend who lived in Germany not long after this kind of canned milk began to come on the market there that they were dated for a year.
With only a six month shelf life this type of canned milk naturally requires a much faster rotation cycle than other types. The only brand name for this milk I've seen is Parmalat. It's a lot of bother, but to me it's worth it to have whole, fluid milk. Recently, I have discovered that it makes excellent yogurt, with the boiled tasted disappearing. We have begun using this method for using up our Parmalat as its dates come up and it is rotated out of storage.
Evaporated
This is made from fresh, unpasteurized whole milk. The process removes 60% of the water; the concentrate is heated, homogenized, and in the States vitamin D is added. It is then canned and heated again to sterilize the contents. It may also have other nutrients and chemical stabilizers added. A mixture of one part water and one part evaporated milk will have about the same nutritional value of an equal amount of fresh milk. There is generally no date or "use by" code on evaporated milk.
Health and nutrition food stores often carry canned, evaporated goat's milk, in a similar concentration.
Sweetened Condensed
This milk goes through much less processing than evaporated milk. It starts with pasteurized milk combined with a sugar solution. The water is then extracted until the mixture is less than half its original weight. It is not heated because the high sugar content prevents spoilage. It's very high in calories, too: 8 oz has 980 calories.
Although it is often hard to find, the label has a stamped date code which indicates the date by which it should be consumed. Sweetened, condensed milk may thicken and darken as it ages, but it is still edible.
Shelf Life of Canned Milks
Unopened cans of evaporated milk can be stored on a cool, dry shelf for up to six months. Canned milk (UHT) should be stored till the stamped date code on the package (3 - 6 months). Check the date on sweetened, condensed milk for maximum storage.
Corrosion Prevention of Canned Goods
Some areas have difficulty storing metal canned goods for long periods of time. This is usually caused by very high humidity or exposure to salt in a marine environment. If this is a problem, it is possible to extend the life of metal cans by coating their outsides. I've seen this used on boats here in Florida, especially when loading for a long trip. There are at least four methods that can be used to do this:
Paraffin Method
PARAFFIN METHOD: Using a double boiler, paraffin is melted and brushed on the clean, unrusted cans. Be certain to get a good coat on all seams, particularly the joints. If the can is small enough, it can be dipped directly into the wax. Care must be taken to not cause the labels to separate from the cans. Do not leave in long enough for the can to get warm.
Paste Wax Method
Combine 2-3 ozs of paste or jelly wax with a quart of mineral spirits. Warm the mixture CAREFULLY in its container by immersing it in a larger container of hot water. DO NOT HEAT OVER AN OPEN FLAME! Stir the wax/spirits thoroughly until it is well mixed and dissolved. Paint the cans with a brush in the same manner as above. Place the cans on a wire rack until dry.
Spray Silicone
A light coating of ordinary spray silicone may be used to deter rust. Spray lightly, allow to dry, wipe gently with a clean cloth to remove excess silicone.
Clear Coating
A clear type of spray or brush on coating such as Rustoleum (tm) may be applied. This is best suited for larger reseable cans, but will keep them protected from corrosion for years.
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