Chemistry Reference
In-Depth Information
less well known and the most controversial are low temperature and low
dimensionality, two domains that are of much interest to food scientists. It
seems that water in reduced spaces ''may be an even more extraordinary
substance than it is under normal conditions'' (Angell, 2001). This should
be relevant to water in living cells, but may be important also for water in
dairy products in any situation, as water may be confined in reduced space in
structured macromolecular systems (gels, emulsions), as well as in frozen or
low-water-content products.
The manufacture and ageing of cheese provide plenty of examples of the
importance of water relationships in food and of the problems resulting from
the heterogeneity of food structures and composition. The structures estab-
lished by the coagulation/gelation step, which will control the process of
water syneresis/retention, depend on the complex interactions of water with
macromolecular constituents, as influenced by pH, minerals, temperature,
etc. In the salting step, the diffusion of salt and water implies complex
modelling operation taking into account the influence of temperature, che-
mical composition of solids and fat content (Geurts et al., 1980; Hardy, 1983).
Water relationships still play a very important role during the ripening period
and storage until consumption. a
w
changes as influenced by evaporation, salt
migration and microbial/biochemical actions. It also shows the persisting
distribution heterogeneity (Hardy, 1983; Ruegg, 1985; Desobry and Hardy,
1994; Saurel et al., 2004). The distribution of water, on various scales, was
recognized as a most important issue in many food technology situations
during the ISOPOW 2000 (Karel and Reid, 2000). This is particularly true for
cheese. The lack of stability of low-moisture products, however, might also
result from the existence of higher water content regions on the microscopic
or sub-microscopic scale. Thanks to the rapidly developing of micro- and
nano-scale techniques for the study of food structures (ISOPOW, 2006), the
distribution of water in dairy products in connection with stability and
texture will probably receive a great deal of attention in the near future.
References
Ablett, S., Darke, A.H., Izzard, M.J., Lillford, P.J. 1993. Studies of the glass transition in malto-
oligomers. In: The Glassy State in Foods (J.M.V. Blanshard, P.J. Lillford, eds.), pp. 189-206,
Nottingham Press, Nottingham.
Abrams, D.S., Prausnitz, J.M. 1975. Statistical thermodynamics of liquid mixtures: a new
expression for the excess Gibbs energy of partly or completely miscible systems. AIChE J.
21, 116-128.
Aguilera, M., del Valle, J.M. 1995. Structural changes in low moisture food powders. In: Food
Preservation by Moisture Control. ISOPOW Practicum II (V. Barbosa-Canovas, J. Welti-
Chanes, eds.), pp. 675-691, Technomic, Lancaster, PA, USA.
