Michele Dannatt, age 11, of Rochester, New York for her question:

Who thought of putting food in cans?

Peaches and peas, tomatoes and spinach are seasonal crops and our ancestors enjoyed their fruits and vegetables mostly at harvest times. True, they stored root crops such as potatoes in cool underground cellars, preserved fruit in sugary jams and transformed cucumbers into spicy pickles. But the pioneers had no stores of canned foods to enhance their year round menus.

The idea that led to canning food was born about 170 years ago. Like most of history's great ideas, it grew in stages as first one, then another thoughtful person added an improvement. Possibly our remote ancestors dreamed of a way to preserve their meat, fruits and vegetables through the year. But in the 1790s, certain Frenchmen de¬cided to do something practical about the problem. Napoleon's armies were stomping through Holland and people back home were learning an ancient lesson of history. In¬stead of hoped for rewards, their military conquests brought only hardship to both the army and the home front. Times were bad. There were bread riots in Paris and enemies were at the borders of France.

The main problem was food    food to supply rations for the soldiers and food to feed the hungry folk at home. And in those days, there were no methods for preserving large quantities of seasonal foods. So the practical minded French government de¬vised a clever plan to solve this basic problem. They offered a sizeable prize of 12,000 francs to anyone who had a workable method for preserving meats. Such a prize appealed to many hopeful inventors    especially to Francois Appert, who ran a bakery and candy store in the hungry city of Paris.

Francois turned his baking talents to preserving meat, toiling by trial and error. History does not record the results of his errors. But as he worked he discovered that meat does not spoil when it is well cooked and sealed in air tight glass bottles. Packaged in this manner, meat was shipped to the hungry troops and, in 1809, Francois Appert received the government's cash prize. Later, still experimenting, he added other foods to his list and found time to write a book of recipes. Naturally other countries borrowed his basic idea    and improved on it. So far as we know, Peter Durand of London was the first to preserve foods in tin cans. The lids had holes to be sealed after cooking. In the 1850s, America's Gail Borden added condensed milk to the growing list of canned goods. Two improvements in the cooking process were made in Baltimore. Isaac Soloman added calcium chloride to the boiling water and reduced the cooking time.

Then 13 years later, in 1829, the cooking was done faster and better in vats of steam. By the 1890s, tin cans were being sealed with whole lids in one operation.

Some 50 years after Appert's success, another Frenchman, the great Louis Pasteur, discovered the secret of canning. He proved that food spoilage is caused by micro¬scopic decay bacteria. Most of them are killed in the cooking heat. The sealed con¬tainer shuts out new arrivals. Nowadays, there is no guesswork, no trial and error in our superb canneries. Located near fresh food supplies, they can the pick of the crops at the peak of perfection    with every safeguard known to modern science.