nutritional and functional properties of whey and lactose

NUTRITIONAL AND FUNCTIONAL PROPERTIES OF
WHEY AND LACTOSE PRODUCTS
Soluble Protein %
100
80
60
40
20
Whey
Casein
Soy
0
2
4
6
pH
8
10
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33

NUTRITIONAL PROPERTIES OF WHEY PRODUCTS
The composition of
whey products varies
considerably, depending
on milk source and the
manufacturing process
involved. In general, whey
is rich in proteins, lactose,
minerals and vitamins.
The proteins in milk and
whey are complete and
of exceptional quality.
They contain, in varying
amounts and in the
right proportion, all the
amino acids required by
humans. They are also
readily digestible and
completely bio-available.
Clearly, whey proteins
are among the most
valuable component of
whey. In many cases,
whey products are used
for their nutritional
benefits as they are
a very cost-efficient
source of protein,
carbohydrate
and minerals
such as
calcium.
PROTEINS
The proteins in whey are easily digested
and contain all the essential amino acids
in the proper proportions, and they rate
as an excellent nutritional source.
Using the Protein Digestibility-Corrected
Amino Acid Scoring (PDCAAS) method,
whey protein rates a value of 1.0 because
it is highly digestible and it meets or
exceeds the recommended amount
of each essential amino acid.
Using another method to measure
protein quality—the Protein Efficiency
Ratio (PER) value—whey also ranks high
on the scale. The higher the PER value,
the better the protein. Casein, the reference
protein, has a PER value of 2.5.
Proteins with a PER greater than 2.5
are considered to be quality proteins.
Whey protein, with a PER greater than
3.0, is considered to be a nutritionally
excellent protein.
Figure 3
Essential amino acid profile of sweet whey proteins
and nutritional requirements of selected groups (FAO/WHO)
Essential Amino Acids
Valine
Tryptophan
Threonine
Phenylalanine.+Tyrosine
Methionine.+Cystine
Lysine
Leucine
5
9
11
13
17
16
19
19
22
24
35
34
41
Virtually every amino acid present in
sweet-type whey exceeds Food and
Agriculture Organization/World Health
Organization (FAO/WHO) nutritional
intake recommendations, both for
children aged 2 to 5 and for adults
(see Figure 3). In many cases, for adults,
whey proteins offer more than double
the minimum FAO/WHO standards.
59
58
62
63
66
68
88
Whey Powder
Child, 2-5 years
Adult
103
Isoleucine
13
28
59
Histidine
20
19
16
0
20
40
60
mg/g Crude Protein
80
100
120
Source: Glass, L. and T.I. Hedrick. FAO/WHO. 1976
34
e34

Whey proteins compare favorably to
many common proteins that have a PER
of less than 2.5, including soya, peanuts,
corn and wheat gluten (see Figure 4).
These proteins have limited concentrations
of certain essential amino acids.
Because of whey protein’s balanced
amino acid profile, whey products
are excellent ingredients for protein
fortification. By fortifying certain vegetable
proteins with whey proteins,
scientists have achieved PER values
significantly greater than 2.5 and greater
than the average of the PER values for
the two proteins. In each blend, whey
protein contributed no more than
50% of the total protein.
VITAMINS
The water soluble vitamins in milk remain
in the serum and are collected with the whey.
The concentration of vitamin C is reduced
during processing, and whey is not considered
a significant source of vitamin C. The concentration
of other water soluble vitamins in sweet
whey powder is presented in Table 4.
Vitamins are large molecules and
they are concentrated by ultrafiltration.
Whey products will naturally fortify the
thiamin, riboflavin, pantothenic acid,
vitamin B 6 and vitamin B 12 content of
foods. Suppliers can provide specific
information on the vitamin contents
of their whey products.
Vitamin A is the most abundant fat
soluble vitamin in milk. Vitamins A, D, E,
and K are separated with the milk fat that
is entrapped in the curd and separated
with the whey cream.
Figure 4
Protein Efficiency Ratios (PER) of
Various Animal and Vegetable Proteins
Table 4
Water Soluble Vitamin Content of
Sweet Whey Powder
Casein
Whey Protein
Sodium Caseinate
Hen Egg
Peanut
Soya
Corn
1.8
2.2
2.2
2.5
2.6
3.2
3.9
WHO Recommended
Daily Intake*
Sweet Whey
Child Adult Powder
Vitamin 1–3 years male Content/100g**
Thiamin (B 1 ) 0.5mg 1.2mg 0.5mg
Riboflavin (B 2 ) 0.8mg 1.8mg 2.2mg
Niacin (PP) 9.0mg 19.8mg 1.3mg
Pantothenic Acid
5.6mg
Vitamin B 6
2.4µg
Folic Acid 100.0µg 200.0µg 12.0µg
Vitamin B 12 0.9µg 2.0µg 2.4µg
Wheat Gluten
0.8
*World Health Organization. 1974.
**Potosi and Orr. 1976.
0
1
2
PER
3
4
Source: Anon. 1972.
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35

‘‘In the future, one of
the most dynamic uses
of whey products will continue
to be as nutritional
ingredients. Whey proteins
are among the highest
quality proteins available
for human nutrition
and they are available in
ingredients and packaging
that can be shipped and
used virtually anywhere.’’
David L. Stiefer,
Vice President Business Development,
Milk Marketing Inc.,
Strongsville, Ohio
MINERALS
Data in Table 5 indicates that
whey powder is a good source of
certain essential minerals.
As the pH of milk decreases during
acid cheese production, more of the
salts dissociate. This results in higher
concentrations of soluble calcium,
magnesium, zinc and phosphorous
in acid whey.
The concentration of calcium and
other minerals may be altered during
whey processing. Mineral concentrations
are reduced by electrodialysis and ultrafiltration,
and adjusted to achieve unique
functional properties. Information for
mineral content of specific products
should be obtained from the supplier
of the product.
LACTOSE
Lactose is a disaccharide that is
hydrolyzed by the enzyme beta-galactosidase
into glucose and galactose molecules.
The slow hydrolysis of lactose by the
body during digestion generates a
prolonged energy supply. Lactose
stimulates the growth of acid forming
lactobacilli in the intestinal tract.
Recent nutritional studies suggest that
lactobacilli help fight intestinal disorders
and that lactose could be used in dietary
therapy for ailing infants.
Numerous studies have demonstrated
that lactose increases calcium absorption
and retention. It may also improve the
absorption of magnesium and zinc.
In animal studies, lactose extended
life expectancy and reduced the
accumulation of body fat.
Table 5
Essential Minerals Content of
Acid and Sweet Whey Powders
WHO Recommended Acid Whey Sweet Whey
Daily Intake* Powder Powder
Mineral Adult male Content/100g** Content/100g**
Calcium 500mg 2,054mg 796mg
Zinc 22mg 6.31mg 1.97mg
Magnesium 300mg 199mg 176mg
Phosphorus 1,348mg 932mg
*World Health Organization. 1974.
**Potosi and Orr. 1976.
36
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WHEY PROTEINS
They possess solubility; create
viscosity through water binding;
form gels; emulsify; bind fat; facilitate
whipping, foaming and aeration; enhance
color, flavor and texture; and bring with
them numerous nutritional benefits as
noted in the previous section.
Milk proteins are often divided into
two broad classes: caseins and whey
proteins. Approximately 80% of the
proteins in milk are caseins, and these
are coagulated and separated as the
cheese curd (see Table 6).
The whey proteins (also called
milk serum proteins) are the proteins
that remain soluble when caseins
are coagulated by either enzyme
or acid. The whey proteins include
beta-lactoglobulin, alpha-lactalbumin,
blood serum albumins, immunoglobulins
and protease-peptones fractions. Part
of the protease-peptones have been
identified as proteolytic degradation
products of beta-casein.
The heat-sensitive whey proteins (betalactoglobulin,
alpha-lactalbumin, blood
serum albumins and immunoglobulins)
differ in molecular weights and properties
such as isoelectric points (see Table 7).
The functional properties of whey
proteins are influenced by a number
of compositional and processing
variables including:
■ pH 12
■ Calcium ion concentration
■ Salt concentration
■ Previous heat treatments
■ Residual lipid content
■ Protein concentration
The term pH stands for the potential
hydrogen ion concentration in a solution.
At pH 7.0, the number of hydrogen and
hydroxyl ions in solution are equal to
each other, and the solution is neutral.
At pH values below 7.0, the number of
hydrogen ions exceeds the hydroxyl ions,
and the solution is acidic. At pH values
above 7.0, the number of hydroxyl ions
exceeds the hydrogen ions, and the
solution is alkaline.
Proteins make
up approximately
0.78% of fluid whey
and 11%–13% of solids
in dried whey. Whey
proteins are important
components of whey
because they possess
a host of functional
properties that make
them invaluable
food ingredients.
12The pH values increase logarithmically.
A pH 4.0 solution is 10 times as acid
as a pH 5.0 solution, and 100 times
as acid as a pH 6.0 solution. As the
concentration of hydrogen ions in
solution increases, the negative charge
on the proteins is neutralized. At the
pH identified as the isoelectric point
for a protein, the charge on the protein
becomes neutral, and the proteins will
not migrate in an electric field. At this
pH, the physical properties of proteins
(solubility, conductivity, stability and
degree of hydration) are at a minimum.
Table 6
Concentration of Major Milk Proteins
Approximate
% of Total
Protein Concentration (g/l) Protein
Caseins 24–28 80
• alpha-casein 15–19 42
• beta-casein 9–11 25
• kappa-casein 3–4 9
• gamma-casein 1–2 4
Whey proteins 5–7 20
• beta-lactoglobulin 2–4 9
• alpha-lactalbumin 1–1.5 4
• protease-peptones 0.6–1.8 4
• blood proteins 1.4–1.6 2
serum albumin 0.1–0.4 1
immunoglobulins 0.6–1.0 2
100
Table 7
Characteristics of Heat-Sensitive Proteins
in Cheese Whey
Approximate
% of Whey Molecular Isoelectric
Protein Proteins Weight Point
• beta-lactoglobulin 48 18,400–36,800 5.2
• alpha-lactalbumin 19 14,200 5.1
• Protease-peptones* 20 4,000–80,000 5.1–6.0
• Blood proteins: 13 69,000 4.8
serum albumin 5 69,000 4.8
immunoglobulins 8 160,000 5.5–6.8
100
*Degradation products of various milk proteins including beta-caseins.
Source: de Wit, 1981; Harper, 1984.
Source: Fennema, 1965.
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37

FUNCTIONAL PROPERTIES OF WHEY PRODUCTS
While the on-going
research into whey
proteins, utilization and
functionality continues,
whey ingredients already
offer numerous functional
benefits to food formulators.
They possess solubility,
create viscosity through
water binding, form gels,
emulsify, bind fat, facilitate
whipping, foaming and
aeration, enhance color,
flavor and texture, and
bring with them numerous
nutritional advantages.
SOLUBILITY
Whey protein is highly soluble, especially
when compared to sodium caseinate and
soy protein (see Figure 5). Solubility is
an important functional property in fluid
and semi-fluid products.
In ready-to-drink beverages, solubility
prevents protein flocculation or sedimentation,
which improves both product
appearance and texture.
In processed soups and sauces,
curdling, sedimentation and separation
associated with insoluble proteins are
highly undesirable.
In chopped meats, salad dressings,
dairy and bakery products, proteins
provide emulsification, gelation and
water binding. In most processed foods,
processing is simplified and product consistency
is improved by using ingredients
that are soluble and easily dispersed.
The effect of heating on solubility is
a second concern of food formulators.
Many foods are heat processed for
preservation purposes. Cream soups
and sauces may be canned and commercially
sterilized for shelf stability,
and these will be further heated by the
consumer. Denaturation and loss of
solubility can occur when protein solutions
with a pH of 3.5–5.5 are heated
to 60°C and higher. Loss of solubility
is enhanced by calcium ions in
the solution.
In high-acid systems with pH less than
3.5, such as fruit-flavored beverages
and salad dressings, undenatured whey
proteins remain soluble when heated
to temperatures of 90°C or higher for
5 minutes. Likewise, proteins in dilute
solutions above pH 6.5 remain soluble
when heated at a temperature of
80°C for10 minutes or longer.
In milk, as well as chocolate-, vanillaor
coffee-flavored beverages, a neutral
pH provides the best flavor characteristic.
Caseins and whey proteins are soluble in
these food systems, and protein choice
is based on other properties, including
nutrition, flavor and cost. In fruit- or
cola-flavored beverages and fruit juice
blends, an acidic pH enhances flavor.
While whey proteins are soluble in acidic
solutions, soy protein and caseins are
likely to precipitate.
Figure 5
Solubility of proteins as affected by pH
Soluble Protein %
100
80
60
40
20
Whey
Casein
Soy
0
2
4
6
pH
8
10
38
e38

WATER BINDING
AND VISCOSITY
Water binding and viscosity are related
functional properties. Products that bind
large quantities of water, such as starches
and gums, create viscosity. When whey proteins
are heated, the bonds that are responsible
for their globular structure break down.
As the protein molecule unfolds, additional
water binding sites are created, which
increases the viscosity of the solution.
In nutritional beverage products, low
viscosity allows product developers to
increase protein levels in a drink without
damaging visual appeal, taste or texture.
In addition, whey can add turbidity
or opacity.
In products such as puddings and
yogurts, water binding properties help
produce a more viscous texture and
control separation. Yogurts fortified
with WPC synerese (lose water) significantly
less than yogurts fortified
with nonfat dried milk.
In chopped meats and bakery products,
water binding contributes to the texture
of the meat emulsion and bakery dough.
In these products, water binding reduces
cooking and baking losses, improves
yields and contributes to the moistness
of the final product. Increased moisture
content in dairy foods helps enhance
the sensory profile by increasing
flavor release.
Water binding properties contribute to
the formulation of reduced-fat products
by adding fat-like attributes such as
lubricity and mouthfeel. In addition,
certain whey products add opacity to
reduced-fat dairy formulations.
GELLING
Under specific conditions, whey proteins
form non-reversible gels. Gel characteristics
depend upon the protein concentration, the
pH of the solution, calcium ion concentration
and sodium ion concentration.
For example, gels formed in solutions
with 3%–5% protein concentrations
and at a temperature of 55°–70°C tend
to be more translucent and softer. More
opaque gels are formed when higher
protein concentrations (10%) are heated
to higher (90°–100°C) temperatures.
In acidic conditions, gels tend to be
opaque, wet and weak. In neutral and
higher pH solutions, gels tend to be
more translucent and elastic.
Microparticles of whey protein gels
maintain moistness in baked goods
and meats; add opacity to beverages
and dairy products; and improve texture
and mouthfeel in reduced-fat products,
bakery products, processed cheese,
yogurt, puddings and custards, and
chopped meats and seafood.
EMULSIFYING
Whey proteins have both hydrophilic
(water attracting) and hydrophobic
(water repelling) groups.
Whey protein functions as well as
traditional emulsifiers (such as egg yolk
powder) in mayonnaise type dressings,
and they are lower in cholesterol. The
stability of whey protein emulsions can
be further enhanced by adding gums or
heating the system to create a protein
gel. The emulsification properties of
whey proteins can be an advantage in
most processed food products, including
margarine, sauces, chopped meats and
seafood, ice cream mixes, bread dough
and cake batters.
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39

FAT BINDING
Fat binding properties of whey products go
hand-in-hand with its emulsifying properties,
a result of the presence of both hydrophilic and
hydrophobic groups.
The hydrophobic groups are also
lipophilic (lipid attracting) in nature.
WPC, for example, is added to chopped
meat products for its fat binding and
retention properties.
WHIPPING, FOAMING
AND AERATION
Table 8
Flavor Descriptions Applied to Products Generated
by the Thermal Degradation of Amino Acids
Probable amino acid precursors
Phenylalanine, Glycine
Leucine
Glycine, Cystine
Alanine
alpha-Aminobutyric acid
Phenylalanine
Proline
Ornithine
Glutamine, Lysine
Arginine
Methionine
Leucine, Arginine, Histidine
The formation of a foam is similar to the
formation of an emulsion, only in this case,
whey proteins function to stabilize the
interface around the air micelle.
The speed of air incorporation and the
stability of the foam is dependent on a
number of parameters, including total
solids, protein and carbohydrate concentration,
pH, the concentration of calcium
and other ions, and whipping method.
Typical flavor description
of thermal products
caramel like
bread like, toasted
smoky, burnt
nutty
walnut
roast nuts, almonds
bakery, cracker
cracker like
buttery
popcorn
broth, beany
bread like
Whey proteins can be used to
partially replace or extend eggs in
bakery products, offering economic
and microbiological advantages as
well as a more consumer-friendly
label. Good whipping and foaming
properties are crucial to the production
of whipped toppings, icings, ice cream
and frozen yogurt.
FLAVOR
In their pure form, whey proteins are very
bland in flavor. However, depending on the
application, whey can either serve to bring out
already-present flavors or add flavor of its own.
For example, when whey proteins are
heated, volatile sulfides are produced.
Free amino acids are also converted to
flavorful compounds by the heat and
chemical interaction with other compounds
(see Table 8). Whey proteins
provide a range of flavors as well as
aroma to bakery products.
In other food categories, such as
beverages and confections, whey’s bland,
slightly sweet flavor allows other fruit
and chocolate flavors to come through.
In soups and sauces, spices and herb
flavors are accentuated.
Whey minerals also enhance dairy
and meat flavors. In applications where
the mineral flavor is a disadvantage,
demineralized whey or WPC with
lower mineral content are available
from U.S. suppliers.
Source: Kinsella, J. E. 1970.
40
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FUNCTIONAL PROPERTIES OF LACTOSE PRODUCTS
FLAVOR AND COLOR
ABSORPTION AND RETENTION
Lactose is several times more effective
than most sugars in attracting and holding
volatile aromas and flavors. It shows equal
affinity for aldehydes, ketones and esters—
the volatile flavor compounds that are
important in many foods.
In addition to absorbing flavors, lactose
enhances and renders many flavors more
distinguishable to the taste. Likewise,
lactose has a strong tendency to absorb
synthetic and natural colors. In tomato
sauce, for example, lactose can reduce
the acid taste, enhance the tomato flavor
and preserve the red color.
BROWNING
Lactose is a reducing sugar, and it will
react with amines to form typical Maillard
(non-enzymatic browning) compounds.
It also caramelizes, although the temperature
at which it caramelizes is higher than
most sugars.
The crust color of breads and rolls is
enhanced by high-lactose whey products,
and is more golden-brown than the
crust color produced by dextrose.
HYGROSCOPICITY
The alpha-lactose monohydrate form of
lactose is very stable. It is non-hygroscopic
and will remain free flowing in high
temperatures and high relative humidity.
This is one reason for using lactose as a carrier
for other ingredients such as high-intensity
sweeteners, flavors, and seasonings.
By controlling the drying of high-lactose
whey products, the percentage of lactose
in the alpha-monohydrate form can be
maximized. These whey products are
also non-hygroscopic and are excellent
bulking and flow agents in dry mixes.
The crystals also facilitate dispersion
in water.
Supersaturated solutions of lactose
may form a solid mass termed ‘‘lactose
glass’’ or ‘‘amorphous lactose.’’ Lactose
in this form is very hygroscopic. This
affinity for moisture is an asset in preserving
the moistness and tenderness
in baked goods and confections. Lactose
in solutions causes a decrease in the
vapor pressure of the moisture, retards
moisture loss and prolongs freshness.
Lactose provides
numerous functional
benefits to food formulators.
It possesses solubility;
acts as a bulking or
flow agent in dry mixes;
contributes solids and a
low level of sweetness;
enhances color, flavor
and texture; facilitates
browning; and can be
directly compressed
into tablets.
In both caramel-type confections
and bakery products, the color and
flavor development from the lactose
and amine-lactose interactions is desired.
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41

SWEETNESS
A10% sucrose solution is equal to a
20% lactose solution in perceived sweetness.
At common concentrations in foods,
lactose is one-fifth to one-third as sweet
as sucrose. This is an advantage because
excess sweetness does not limit the
use of lactose.
SOLUBILITY
Lactose is soluble, but less so than the
other common sugars such as sucrose,
fructose and dextrose.
The solubility of lactose is limited when
adding either lactose or dairy ingredients
with high concentrations of lactose to
foods. To avoid crystal formation and
sandy texture, WPCs are added for
the maximum concentration of whey
in frozen desserts. Reduced-lactose
whey is used to maximize total whey in
processed cheese foods. In confections,
addition of corn syrup and fat can aid
in controlling crystallization. In other
products, such as sweetened condensed
milk, crystallization is controlled by
adding lactose seed crystals to the
saturated solution. The crystals that
form are very small and impalpable.
When the size of the lactose crystals
is controlled, crystallization can be an
advantage in creating a desired texture
in some confection products. It can also
aid in controlling the hygroscopicity
of a product.
FERMENTATION SUBSTRATE
Lactose is converted to lactic acid by
lactic cultures.
This fermentation process is important
to both flavor and texture. Some cultures
also can convert lactose to propionic
acid. Dependent upon the concentration,
the propionic acid produced can control
mold growth. Lactose is not fermented
by bakers yeast. In yeast-leavened
bakery products, the lactose remains
available for crust color development,
emulsification of shortening and
water retention.
TABLETTING EXCIPIENT
Lactose can be directly compressed by
pressure into tablets without wet granulation.
When used in candy tablets, the other
properties, such as color and flavor
absorption and retention, and rapid
solubility are an advantage. Lactose
products have been developed with
exceptional flow properties for high
speed tablet machines. Because of
this functionality, lactose is also used
in pharmaceutical applications.
42
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