Water in various products.

Water plays an important role in the human body and is involved in the basic biochemical reactions, e.g.

breathing.

• The water content in most plants and animals is about 60-90%. The human body of an adult contains about 65% of water, but various tissues have different water content. Teeth, bones, hair contain the lowest level of water whereas water content in other tissues exceeds 90%.

Water in food products :

• Bread: Bread contains approx. 30% of water, dry cookies such as crackers 3-4%, and cakes such as cheesecake and fruit pies - about 35%

• Dairy products: cheese - c. 38%, soft ripening cheeses (eg. Camembert) - 58%, butter and margarine- approx. 16%, milk - approx. 90%, dairy cream- approx. 48-79%.

• Fish and seafood: fish- an average of approx. 75% of water, shellfish- about 85%, smoked fish like mackerel- approx. 47%.

• Fruit: generally fruit contain approximately 75% of water, but fruits like watermelons, melons contain up to 90% of water.

• Meat: Roast beef- approx. 50%, poultry - 65-70%, sausages - 45-54%, salami-type sausages contain less water as it level reaches up to maximum of approx. 28%.

• Vegetables: they contain the most water from all food products. Vegetables like carrot or lettuce contain 89% of water, tomatoes-93%, and cucumbers can consist of 96% of water.

• The daily recommended intake of water depends on the climate, place of residence, physical activity and other factors. Please note that some liquids such as coffee or alcohol dehydrate, not without reason, so coffee espresso given a small glass of water.

• Both raw materials and finished food products contain large amounts of water. Because of the quantity and properties which are different from the other components water is an important factor influencing the physical, chemical and biological changes of food, thus it plays important role as far as food usability is concerned. Such specific physical properties of water as a crystallization in temperature of 0 ° C, boiling at 100 ° C at atmospheric pressure, an increase of density with simultaneous change of temperature between 0° C and +4 ° C significant physical parameters values such as the dielectric constant, surface tension, heat capacity, heat of fusion and evaporation, dissolution capacity of many substances and hydrating of natural polymers have a decisive effect on the consistency, structure, rheological properties, and many other physical characteristics and physics-chemical of raw materials, semi-finished products and finished food products.

• The water content determines the rate of progress of many chemical reactions in foods, and for certain types of reaction, f. e. hydrolysis water is absolutely essential. The activity of enzymes and bacterial growth is impossible without water. The specific properties of water are due to its molecular structure. The molecular weight and the dipole nature of water is particularly noteworthy. The molecular weight of the water is low; small size of water molecules (high molar volume) compared with the size of the molecules of other chemical compounds of other food products cause easy ingress of water between the molecules of other compounds.

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Group 2