Mechanisms Determining Crispness and Its Retention in Foods with a Dry Crust - Food Colloids: Self-Assembly and Material Science - page 485

Chapter 34
Mechanisms Determining Crispness and Its
Retention in Foods with a Dry Crust
Ton van Vliet, 1,2 Jendo Visser, 1,2 Wim Lichtendonk 1,4 and
Hannemieke Luyten 1,3
1 WAGENINGEN CENTRE FOR FOOD SCIENCES, P.O. BOX 557, 6700
AN WAGENINGEN, THE NETHERLANDS
2 WAGENINGEN UNIVERSITY AND RESEARCH CENTRE, P.O. BOX
8129, 6700 EV WAGENINGEN, THE NETHERLANDS
3 AGROTECHNOLOGY AND FOOD INNOVATIONS, P.O. BOX 17,
6700 AA WAGENINGEN, THE NETHERLANDS
4 TNO NUTRITION AND FOOD RESEARCH, P.O. BOX 360, 3700 AJ
ZEIST, THE NETHERLANDS
34.1 Introduction
Various popular food products consist of a crispy crust and a non-crispy moist
inner part. Well-known examples are many bread types and deep-fried battered
snacks like fried fish. For the first type the crust has originally the same
chemical composition as the rest of the food product, while for the second type
the crust stems from a coating with another (composite) material. 1 For both
types there are changes in the local composition during the manufacturing
process - especially the concentration of water and its distribution. The crust
can be characterized as a cellular solid material. After production, the crust
loses its crispy behaviour at various rates. This process takes several hours for
most types of bread; but for many deep-fried battered snacks it happens much
faster, often within half a hour. 2,3
It is generally accepted that the crispy behaviour of a food is related to its
fracture behaviour. The characteristic requires brittle fracture accompanied by
acoustic emission 1,4-6 Not all brittle food products are crispy. For instance,
hard candies and chocolate bars may fracture in a brittle way; but, though it
may differ between countries, they are mostly not called 'crispy'. In other cases
products may be considered to be more hard than crispy. To be crispy
(or crunchy) the consumer must perceive multiple fracture events and the work
of fracture during mastication must be relatively low. These requirements set
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