foam-mat freeze drying of egg white and ... - McGill University

which is completely reversible. This property is unique, which make it popular for many
different food preparations. The surface active nature of methyl cellulose imparts the
stability, when added to a foam (Karim & Wai 1999). Methyl cellulose is also used to
make edible coatings (Arvanitoyannis & Biliaderis 1999; Maftoonazad & Ramaswamy
2005).
3.5 Drying
Drying or dehydration is one of the oldest and popular preservation methods.
Records indicate that drying of vegetables was practiced as early as 18 th century. Still it is
one of the major fields in food processing operations. Development in drying has been
gradual and it addresses issues on industrial requirements. During World War periods
(both first and second) the research and development got greater impetus because of the
greater requirements. During drying simultaneous heat and mass transfer takes place, this
imparts changes in the dried product. Drying and dehydration are often used alternatively
without much of difference. But they are not same, according to US Department of
Agriculture; dehydrated food cannot have moisture content above 2.5% on dry basis. But
dried food can have moisture content above 2.5% (dry basis). Different kind of dryers
have been developed to address specific requirements such as solar drying, drum drying,
spray drying, spouted bed drying, fluidized bed drying, microwave drying and freeze
drying (Mujumdar 1995; Vega-Mercado et al. 2001)
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