text; no full account of literature sources, but a discussion of selected
references at the end of each chapter. Worked out examples and questions
are also given.
The questions not only serve to let the reader test whether he or she
can make use of what has been treated but also serve as further illustrations.
To that end, most questions are followed by worked out answers. By the
nature of food science and technology, the questions often involve a number
of different aspects, and the reader may not be familiar with all of them.
Hence do not worry when you cannot immediately find a full answer, so
long as you can understand the reasoning given.
The readers are assumed to be familiar with elementary mathematics
(up to simple calculus) and with the basics of chemistry, and to have
attended (introductory) courses in food chemistry and food engineering (or
food processing).
The book tries to treat all physicochemical aspects of importance
for foods and food processing. On the one hand, this means that it gives
more than most teachers will want to treat in a course, so that a selection
should be made. On the other hand, it makes the book also suitable as a
work of reference. Some additional factual information is given in the
appendix.
1.2.4 Equations
As mentioned, physical chemistry is aquantitativescience, which implies
that equations will frequently be given. It may be useful to point out that
equations can be of various types. Some equationsdefinea property, like
‘‘pressure equals force over area.’’ Such an equation is by definition exact.
Generally, the sign for ‘‘is defined as’’ (:) is used rather than ‘‘is equal to’’
(¼).
Most equations are meant to bepredictive. According to their validity
we can distinguish those that are assumed to be
Generally valid. For instance ‘‘force ¼ mass 6 acceleration’’
(although even this one breaks down in quantum mechanics).
Of restricted validity. The restriction is sometimes added to the
equation, by indications like ‘‘forx>1’’ or ‘‘ifz?0.’’ Another
variant is that a ‘‘constant’’ in the equation has restricted validity.
Approximate. Then the&sign is used.
A scaling relation, which means that only a proportionality can be
given. This is done by using the!sign (some use the*sign), or by
putting an ‘‘unknown constant’’ after the¼sign.