10.3 Aroma of Milk and Dairy Products 53910.2.10.4 Hydrolyzed Whey Syrups
The production of sweet whey syrups is be-
coming increasingly important due to the
use of carrier-bound lactase (β-galactosidase,
EC. 3.2.1.23). In these syrups, lactose is hy-
drolyzed to glucose and galactose. Concentration
to 60–75% solids is achieved by evaporation.
10.2.11 Lactose
For lactose production the whey is evaporated to
55–65% solid content, and the concentrate is then
seeded and cooled slowly to induce sugar crys-
tallization. The raw lactose (food quality) is re-
crystallized to yield a raffinade (pharmaceutical-
grade lactose). Lactose is used in manufactur-
ing of drugs (tablet filler), dietetic food products,
baked products, dehydrated foods, cocoa prod-
ucts, beverages and ice creams.
10.2.12 Cholesterol-Reduced Milk
and Milk Products
In the production of milk products with a reduced
cholesterol content, more than 90% of the choles-
terol is removed from water-free milk fat by ex-
traction with supercritical carbon dioxide or by
steam distillation. The fat is then recombined with
skim milk to give low-cholesterol milk, which is
used to make the usual milk products. The extent
Table 10.37.Effects of a 90% reduction of cholesterol
in butter oil on the cholesterol content of recombined
milk and its products
Food Fat (%) Cholesterol (mg/kg)
Ia IIa
Whole milk 3. 3 135 26
Butter 81 2400 300
Yoghurt 3. 5 124 26
Ice cream 10. 8 450 41
Cottage cheese 4. 6 150 12
Mozzarella 21. 6 786 68
Brie 20 .8 1000 75
Camembert 24. 6 714 57
Roquefort 30. 6 929 107
Cheddar 33 .1 1071 114
aProduct before (I) and after (II) cholesterol reduction.
of cholesterol reduction in a series of products is
listed in Table 10.37.
Recombined milk does not have the same proper-
ties as the original milk because, e. g., the mem-
brane composition of the fat globule changes in
the process. Cheese made from milk of this type
can exhibit texture defects. Since skim milk with
a fat content of 0.2% still contains about 18 mg/l
of cholesterol, skim milk must also be freed of
cholesterol for the production of cholesterol-free
products.10.3 Aroma of Milk
and Dairy Products10.3.1 Milk, CreamRaw or gently pasteurized milk has a mild but
characteristic taste.
In the AEDA of UHT milk (Table 10.38),
δ-decalactone, which contributes to the aroma
of butter (Table 10.40) as well as unripened and
ripened cheese (cf. 10.3.5), is the predominant
aroma substance. Apart from other lactones,
2-acetyl-1-pyrroline, methional, 2-acetyl-2-thio-
azoline and 4,5-epoxy-2-decenal are among the
identified aroma substances.
A higher thermal exposure of milk, e. g., by steri-
lization, allows the accumulation of Maillard
products, such as methylpropanal, 2- and 3-
methyl butanal and 4-hydroxy-2,5-dimethyl-
3(2H)-furanone.10.3.2 Condensed Milk, Dried Milk ProductsDuring the concentration and drying of milk,
reactions that are similar to those described
for heat-treated milk (cf. 10.1.3.5 and 10.3.1)
occur, but to a greater extent. Therefore, like the
aroma of UHT milk (cf. 10.3.1 and Table 10.38),
the aroma of condensed milk is also caused
byMaillardreaction products. The stale flavor
that appears when condensed milk is stored for
longer periods is due especially to the pres-
ence of the degradation product of tryptophan,
o-aminoacetophenone, which is aroma active
in concentrations≥1μg/kg. A rubbery aroma
defect results from higher concentrations of
benzothiazole.