Dairy Chemistry And Biochemistry

10 Chemistry and biochemistry of cheese and

fermented milks

10.1 Introduction

Cheese is a very varied group of dairy products, produced mainly in Europe,
North and South America, Australia and New Zealand and to a lesser
extent in North Africa and the Middle East, where it originated during the
Agricultural Revolution, 6000-8000 years ago. Cheese production and con-
sumption, which vary widely between countries and regions (Appendices
10A and lOB), is increasing in traditional producing countries (2-4% p.a.
for several years) and is spreading to new areas. On a global scale, 30% of
all milk is used for cheese; the proportion is about 40% in North America
and about 50% in the European Union.
Although traditional cheeses have a rather high fat content, they are rich
sources of protein and in most cases of calcium and phosphorus and have
anticarigenic properties; some typical compositional data are presented in
Table 10.1. Cheese is the classical example of a convenience food: it can be
used as the main course in a meal, as a dessert or snack, as a sandwich filler,
food ingredient or condiment.
There are at least 1000 named cheese varieties, most of which have very
limited production. The principal families are Cheddar, Dutch, Swiss and
Pasta filata (e.g. Mozzarella), which together account for about 80% of total
cheese production. All varieties can be classified into three superfamilies
based on the method used to coagulate the milk, i.e. rennet coagulation
(representing about 75% of total production), isoelectric (acid) coagulation
and a combination of heat and acid (which represents a very minor

group).
Production of cheese curd is essentially a concentration process in which
the milkfat and casein are concentrated about tenfold while the whey
proteins, lactose and soluble salts are removed in the whey. The acid-
coagulated and acid/heat-coagulated cheeses are normally consumed fresh
but the vast majority of rennet-coagulated cheeses are ripened (matured) for
a period ranging from 3 weeks to more than 2 years, during which numerous
microbiological, biochemical, chemical and physical changes occur, resulting
in characteristic flavour, aroma and texture. The biochemistry of cheese
ripening is very complex and is not yet completely understood.