Mark Lukasik, age 9, of St. Catharines, Ontario, Canada, for his question:

Are pasteurized and homogenized milk different?

Here we have two great big words    pasteurized and homogenized. Sometimes we find them both on the same container of milk. This gives our first clue to the question. If they mean the same thing, dairies would use only one of them. Since they use both words, then pasteurized and homogenized must be different.

When great grandpa was a young fella they drank the milk as it came from the cow. It was delicious. But nothing in this world is quite perfect. Our brown eyed cows do their best but their fresh milk needs a few improvements. The most important improvement is pasteurizing. This is a must. Another improvement is homogenizing. This gives everybody a fair share of the cream. When you know what milk is made of, it's easier to understand why they always pasteurize it and why they almost always homogenize it.

As you know, a glass of milk is a whitish drink    thicker than water. The liquid part is pale pale blue. The whitish color comes from zillions of tiny tiny fragments floating and suspended in the liquid. Some of them are miniature scraps of body¬building protein food. Some are minuscule blobs of creamy fat. Vitamins and minerals also are dissolved in the marvelous mixture. As a matter of fact, milk has samples of all the different foods that your body needs. This is why sensible people drink it every day of their lives.

The milk from the cow barn goes straight to the dairy and this spanking clean factory makes the necessary improvements without ruining the delicious flavor. Milk contains a lot of bacteria, tiny living things too small for our eyes to see. Most of them do us no harm and same are very good for us. But a few bacteria are dangerous germs that can make us sick. The fresh milk is inspected and if it has too many germs, the fussy dairy people refuse to buy it. But this does not happen often. The strained milk is put into the pasteurizer and slowly, slowly heated. There are thermometers, thermostats and other gadgets to control the heating process. Boiling would form a skim and ruin the flavor. So the milk gets so hot and no hotter. It stays at this temperature for a while and then gradually cools. The heat kills the stray germs without ruining the rest of the milk. Pasteurizing is a must because it makes our milk safe and germ free.

When a bottle of fresh milk stands for a while, its creamy particles float to the top. Some people use this top milk as cream in their coffee. But this takes away a lot of the richness. The milk in the bottom of the container is rather thin. The dairy solves this problem with a homogenizer. This machine hums while it works, pressing and forcing the milk through teeny tiny holes. The fine holes break the cream blobs into smaller bloblets. Now they are too small to squeeze through the other particles in the milk. So they cannot float to the top. Homogenized milk stays evenly mixed right down to the last drop in the bottle: Be sure you milk is pasteurized for good health. It may also be homogenized so that everybody gets a fair share of the cream.

The sparkling clean dairy does other interesting things. Some milk goes into a whirling separator that separates out the cream. The creamless mixture is skim milk. It can be made into cottage cheese and some people like to drink skim milk. Most of the separated cream is churned to make golden butter. Some is sold to make frothy whipped cream and some is thinned with a little milk and stirred into coffee cups. The dairy also has driers for separating the floating particles to make powdered milk.