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Glass

GLASS IS A MATERIAL KNOWN SINCE ANCIENT TIMES AND, UNTIL A CENTURY AGO, WAS UNUSABLE FOR COOKING BECAUSE OF ITS LACK OF RESISTANCE TO THERMAL GRADIENTS. THE EXPANSION DIFFERENCE BETWEEN HOT AND COLD PARTS OF THE GLASS CAN EASILY CAUSE IT TO FRACTURE.

UTENSILS USING THIS MATERIAL ARE PRODUCED BY QUICKLY COOLING A MOLTEN MASS FORMED OF MAINLY SILICEOUS MATERIALS.

Did you know that?

In 1915, Jesse Littleton discovered that the addition of boron oxide to crystalline silica drastically reduces the effects of thermal expansion and increases resistance to temperature variations. Thus, borosilicate glass was born, better known under the trade name Pyrex.

Borosilicate glass is used in the kitchen for cooking in receptacles that do not come into direct contact with the flame. Nor can they be subjected to sudden warming or cooling, otherwise they would break.

The thermal conductivity is a great deal less than that of steel, but higher than that of ceramic. These characteristics, together with its transparency that allows food being cooked to be checked, make borosilicate glass a particularly suitable material for slow cooking in the oven.

MATERIAL: TRANSPARENT, WHICH ALLOWS THE FOOD TO BE CHECKED AS IT COOKS. THIS MAKES BOROSILICATE GLASS PARTICULARLY SUITABLE FOR SLOW BAKING IN THE OVEN. DELICATE AND LIGHT, IT IS NOT RESISTANT TO THERMAL SHOCK. HOWEVER, BECAUSE IT IS NON-POROUS, IT IS RESISTANT TO CORROSION AND CHEMICALS.

THERMAL CONDUCTIVITY: VERY LOW, ONLY A LITTLE HIGHER THAN CLAY.

USE: IDEAL FOR OVEN COOKING. IT CAN ASLO BE USED IN MICROWAVE OVENS. DIRECT HEAT MUST NOT BE APPLIED TO THE RECEPTACLE.

MAINTENANCE AND HYGIENE: EASY CLEANING, PREFERABLY WITH HOT WATER AND NEUTRAL SOAP. SUITABLE FOR DISHWASHERS.

Structures And Forms In Cooking

COOKWARE, IN THE MOST GENERAL SENSE OF THE TERM, COMPRISES RECEPTACLES SUITABLE FOR COOKING FOOD. THEREFORE, THEY MUST HAVE TWO FUNDAMENTAL CHARACTERISTICS:

• MATERIALS SUITABLE FOR REMAINING IN CONTACT WITH THE FOOD WITHOUT IT BECOMING CONTAMINATED

• A STRUCTURE AND FORM SUITABLE FOR TRANSMITTING HEAT TO THE FOODSTUFF

Firstly, we must bear in mind that materials that come into contact with food should not react chemically with food.

This is an essential condition which generally excludes most plastics and also many types of metal. But it also should be noted that whether or not a material will contaminate the food depends on the temperature: some plastics are not suitable for cooking, but they are perfect for the microwave or the water bath.

The second condition is much more complex and varied. Materials must withstand cooking temperatures without significant structural changes. This means that they should not melt and must be resistant to thermal shocks.

As for heat transfer, we need to be more specific. There are different ways to transmit heat (as we explained above) and there are suitable cooking vessels for each of these methods.

The fundamental distinction depends on whether or not there is direct contact between the vessel and the heat source. In the first case, we talk about transmission by conduction (in the case of fluids, if they are in motion, we talk about convection), in the second case, transmission by radiation

Heat transfer through empty space is known as radiation. With radiation, heat is transferred in the form of radiant energy, or wave movement, from one body to another body. That is, it does not require matter to heat. Modern technology has introduced two new kitchen tools which work through radiation but which have peculiar characteristics and therefore have to be treated as examples of their properties: the microwave oven and the magnetic induction hob.

Convection Conduction Radiation

Structures And Forms In The Kitchen

We will look further at these aspects. At the moment, what we are interested in highlighting is the difference in structure between those cooking vessels designed for direct contact with the heat source and the others. In fact, the part of the container that comes into contact with the heat source inevitably takes on a different function from the other parts and often requires a specific structure, because it is also the part that comes into contact with food. There are two important exceptions, which are cooking by total immersion in liquid (water or oil) and some types of steaming.

BUT APART FROM THESE, WE CAN SAY THAT THE TYPICAL STRUCTURE OF RECEPTACLES FOR COOKING IN DIRECT CONTACT IS COMPRISED OF THREE OR FOUR FUNCTIONALLY AND STRUCTURALLY DIFFERENT PARTS: