Physical properties of water and ice

Water is an essential constituent of many foods. It may occur as an intracellular or extracellular component in vegetable and animal products, as a dispersing medium or solvent in a variety of products, as the dispersed phase in some emulsified products such as butter and margarine, and as a minor constituent in other foods. Table 1-1 indicates the wide range of water content in foods. Because of the importance of water as a food constituent, an understanding of its properties and behavior is necessary. The presence of water influences the chemical and microbiological deterioration of foods. Also, removal (drying) or freezing of water is essential to some methods of food preservation. Fundamental changes in the product may take place in both instances.
Some of the physical properties of water and ice are exceptional, and a list of these is presented in Table 1-2. Much of this information was obtained from Perry (1963) and Landolt-Boernstein (1923). The exceptionally high values of the caloric properties of water are of importance for food processing operations such as freezing and drying. The considerable difference in density of water and ice may result in structural damage to foods when they are frozen. The density of ice changes with changes in temperature, resulting in stresses in frozen foods. Since solids are much less elastic than semisolids, structural damage may result from fluctuating temperatures, even if the fluctuations remain below the freezing point.
The reason for the unusual behavior of water lies in the structure of the water molecule (Figure 1-1) and in the molecule's ability to form hydrogen bonds. In the water molecule the atoms are arranged at an angle of 105 degrees, and the distance between the nuclei of hydrogen and oxygen is 0.0957 nm. The water molecule...

Daugiau informacijos...

★ Klientai rekomenduoja

Šį rašto darbą rekomenduoja mūsų klientai. Ką tai reiškia?

Mūsų svetainėje pateikiama dešimtys tūkstančių skirtingų rašto darbų, kuriuos įkėlė daugybė moksleivių ir studentų su skirtingais gabumais. Būtent šis rašto darbas yra patikrintas specialistų ir rekomenduojamas kitų klientų, kurie po atsisiuntimo įvertino šį mokslo darbą teigiamai. Todėl galite būti tikri, kad šis pasirinkimas geriausias!