194 Chapter 8
ing the PER (protein effi ciency ratio). The
whey proteins meet the minimum require-
ments for essential amino acids.
Whey proteins contain high levels of the
branched chain amino acids leucine, isoleu-
cine, and valine. These amino acids can be
metabolized as an energy source and thus are
considered to be useful in sports drinks,
where they assist both as an energy source
and as a protein source, and for muscle build-
ing or sparing (Ha and Zamel 2003 ).
It is also relevant to consider the lactose
content of ingredients, especially where
there is a risk of a fi nal product being fed to
lactose - intolerant people. Recent develop-
ments in whey processing, with the use of
ion exchange and microfi ltration for whey
protein isolation, have led to the generation
of ingredients with less than 1% to 2% lactose
that are suitable for reduced - lactose and
lactose - free end products, depending on their
formulation.Biological Properties
There is mounting evidence relating to the
potential health benefi ts of whey and its
components. At present most of the data
come from in vitro and in vivo animal studies,
with limited human clinical trials. Table 8.8
summarizes the current trends (Harper 2000,
2001 ). However, to date there has been
minimal commercial exploitation of this
knowledge.high - protein concentrations, thus reducing
the need to consume large volumes of liquid
to get the required protein intake. Heating
whey proteins causes an increase in viscosity
and an increase in water - binding capacity,
but a potential decrease in solubility (de Wit
1989 ). In addition, the formation of protein
aggregates increases the volume occupied by
the protein, which is a key contributor to the
increased viscosity.
Nutrition
Milk proteins provide an excellent source of
high - quality protein (Ha and Zamel 2003 ).
There are many different means of assessing
protein quality. World health authorities
(Food and Agriculture Organization/World
Health Organization; FAO/WHO) have
established an amino acid profi le that refl ects
the daily requirements of essential amino
acids to ensure maintenance of good health.
By comparing the amino acid content of a
protein with this ideal composition, it is pos-
sible to estimate the extent to which the
product fulfi lls the body ’ s requirements for
essential amino acids (Table 8.7 ).
The amino acid score based on the FAO/
WHO requirements is combined with the
protein digestibility measurement to give
the PDCAAS (protein digestibility corrected
amino acid score). Protein digestibility is
now the most commonly used biological
method for measuring protein quality, replac-
Table 8.7. Preschool age amino acid requirements set by FAO / WHO
(1989).
Essential amino acid Recommended
requirement
(mg/g protein)WPC 80
(mg/g protein)Isoleucine 28 54
Leucine 66 119
Lysine 58 94
Methionine + Cysteine 25 52
Phenylalanine + Tyrosine 63 68
Threonine 34 66
Tryptophan 11 20
Valine 35 51
Histidine 19 21