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350
Korean J. Food Sci. An.
Vol. 35, No. 3, pp. 350~359(2015)
DOI http://dx.doi.org/10.5851/kosfa.2015.35.3.350
Improved Functional Characteristics of Whey Protein Hydrolysates
in Food Industry
Renda Kankanamge Chaturika Jeewanthi
1,†
, Na-Kyoung Lee
1,†
, and Hyun-Dong Paik
1,2,
*
1Department of Food Science and Biotechnology of Animal Resources, Konkuk University, Seoul 143-701, Korea
2Bio/Molecular Informatics Center, Konkuk University, Seoul 143-701, Korea
Abstract
This review focuses on the enhanced functional characteristics of enzymatic hydrolysates of whey proteins (WPHs) in food applica-
tions compared to intact whey proteins (WPs). WPs are applied in foods as whey protein concentrates (WPCs), whey protein isolates
(WPIs), and WPHs. WPs are byproducts of cheese production, used in a wide range of food applications due to their nutritional validity,
functional activities, and cost effectiveness. Enzymatic hydrolysis yields improved functional and nutritional benefits in contrast to heat
denaturation or native applications. WPHs improve solubility over a wide range of pH, create viscosity through water binding, and pro-
mote cohesion, adhesion, and elasticity. WPHs form stronger but more flexible edible films than WPC or WPI. WPHs enhance emulsi-
fication, bind fat, and facilitate whipping, compared to intact WPs. Extensive hydrolyzed WPHs with proper heat applications are the
best emulsifiers and addition of polysaccharides improves the emulsification ability of WPHs. Also, WPHs improve the sensorial prop-
erties like color, flavor, and texture but impart a bitter taste in case where extensive hydrolysis (degree of hydrolysis greater than 8%).
It is important to consider the type of enzyme, hydrolysis conditions, and WPHs production method based on the nature of food appli-
cation.
Keywords: whey protein, whey protein hydrolysate, enzymatic hydrolysis, functionality, food application
Received February 3, 2015; Revised April 6, 2015; Accepted April 27, 2015
Introduction
Whey protein (WP) is now recognized as a value-added
ingredient because of its highly functional and nutritional
properties. WPs are used widely by dairies, bakeries, con-
fectionaries, meat processing plants, canned goods, and
beverage establishments for their various functions in
food quality and stability (de Wit, 1998; Foegeding et al.,
2002). Because of their nutritional and functional proper-
ties, researchers have intensified efforts to expand the uti-
lization of WPs as food ingredients. Technological advan-
ces have enabled researchers to enhance the functionality
and utilization of WP by producing more concentrated
and specialized forms. Pressure-driven membrane pro-
cesses have been used to concentrate and separate whey
protein concentrates (WPCs) or whey protein isolates
(WPIs) in order to maintain their functional properties
and make them suitable for other purposes in the food
industry (Suarez et al., 1992). Today, WP ingredients are
used to replace other proteins or to improve the functional
properties of many food products (Spellman et al., 2005).
WPs are comprised mainly of β-lactoglobulin (β-Lg),
α-lactalbumin (α-La), bovine serum albumin (BSA), and
immunoglobulin, and the effects of WP functionality have
been studied extensively (Foegeding et al., 2002; Smith-
ers et al., 2008). β-Lg, a globular and amphiphilic protein
with two disulfides and one free cysteine, is the main
constituent of WP (around 55% of proteins) and is known
to contribute the most to the WP functionality (Bouaouina
et al., 2006). Conformation and functionality of WPs are
interrelated and dictated by changes in their globular fol-
ded structure. Their functional properties are affected by
several factors within a food application, including con-
centration, state of the WPs, pH, ionic environment, (pre-)
heat treatment, pressure treatments, and the presence of
lipids (Burrington, 1999). The functionality of WPs can
be improved by chemical, enzymatic, and physical proce-
sses. High pressure treatments are used to enhance the
functionality of WPC, but still remain below the expected
levels of the industrial food applications (Kresic et al.,
†These authors contributed equally to this work.
*Corresponding author: Hyun-Dong Paik, Department of Food
Science and Biotechnology of Animal Resources, Konkuk Uni-
versity, Seoul 143-701, Korea. Tel: +82-2-2049-6011, Fax: +82-
2-455-3082, E-mail: hdpaik@konkuk.ac.kr
ARTICLE
Functionality of Whey Protein Hydrolysates
351
2006). Enzymatic modifications are highly acceptable and
applied in the industry not only for functionality improve-
ment but also for bioactive enhancement (Athira et al.,
2014; Sharma et al., 2011). These hydrolysates are also
being used as protein supplements for infants, senescent,
athletes, and bodybuilders (Sousa et al., 2004). The resul-
ting peptides are more easily absorbed but the level of
hydrolysis has to be carefully controlled to avoid the for-
mation of bitter peptides (Mann, 2000).
Enzymatic hydrolysis is preferred by food manufactur-
ers due to the availability of a wide range of enzymes that
are considered safe and natural. Several enzymes are cur-
rently used in the industry as food-grade enzymes and
others are being researched for the production of WPHs
with tailored functionality and biological activity. The
most researched and used enzymes for the production of
WPHs are the digestive enzymes trypsin, pepsin, and chy-
motrypsin (Konrad et al., 2005; Pouliot et al., 2009), plant
enzymes mainly papain and bromelain (Nakamura et al.,
1993), bacterial proteases mainly those originating from
Bacillus licheniformis (Creusot et al., 2006; Creusot and
Gruppen, 2007a, 2007b; Doucet and Foegeding, 2005)
and Bacillus subtilis (Madsen et al., 1997), or a mixture
of some of these enzymes (Kim et al., 2007). The objec-
tive of this review is to emphasize the improvement in
functional characteristics of WPHs over those of intact
WPs in food applications.
Manufacture of Whey Protein Products
Whey protein concentrates (WPCs) and whey pro-
tein isolates (WPIs)
The most valuable component of whey is its protein,
which delivers both enhanced functionality and nutritio-
nal quality to many formulations. WPs are able to concen-
trate, fracture, and dehydrate efficiently and cost-effec-
tively without damaging the protein structure (Fig. 1). By
these methods WPs are produced and introduced to the
market as whey protein concentrates (WPCs, 35-80% pro-
tein) and whey protein isolates (WPIs, 90-96% protein).
Whey protein hydrolysates (WPHs)
Two main methods of improving WP functionality are
modification of proteins through physical treatments, and
enzymatic means. Chemical modifications of proteins are
possible but due to the necessity to prove the safety of such
modifications to humans, they are not generally practiced.
Chemical hydrolysis causes loss of some essential amino
acids, such as tryptophan, and can result in products with
high amounts of free amino acids, which can encumber
the body’s osmotic balance (Mahmoud, 1994).
For WPs hydrolyzing, enzymatic hydrolysis is the most
applicable method in food industry. The functional and
biological properties of the WPHs depend to a great extent
on the type of enzyme used (specificity and selectivity),
hydrolysis conditions (enzyme-to-substrate ratio, incuba-
tion temperature, pH, and time) employed, and the source
of the protein, native or denatured, WPI vs. WPC, memb-
rane or ion-exchange product, etc. Researchers have shown
that limited enzymatic hydrolysis of WPs can result in
markedly improved functionality and biological activities
(Creusot and Gruppen, 2008; Pouliot et al., 2009; Spell-
man et al., 2009).
Functional benefits
WPs have typically a globular structure, with high lev-
els of secondary and tertiary structures, in which acidic/
basic and hydrophobic/hydrophilic amino acids are dis-
tributed in polypeptide chains. The functional benefits
depend on (a) hydration, (b) aggregation and gelation, (c)
Fig. 1. Production steps of whey products.
352
Korean J. Food Sci. An., Vol. 35, No. 3 (2015)
interfacial, and (d) sensorial properties of the food protein
(Fig. 2) (Kresic et al., 2006). Hydration properties have
an important effect on swelling, adhesion, dispersibility,
solubility, viscosity, water absorption, and water holding.
Aggregation and gelation properties, on the other hand
are related to protein-protein interactions while Interfacial
properties include emulsification and foaming character-
istics. Sensorial properties include flavor, color, and tex-
ture properties of the protein.
Hydration properties
Solubility
The solubility of WPCs at a low pH is a unique prop-
erty that allows it to function in acidic foods and bever-
ages (Kumar et al., 2010; Pelegrine and Gasparetto, 2005).
It has a great potential as a food ingredient for the protein
enrichment of soft drinks and beverages. Heating WPs
can result in a loss of solubility due to the denaturation of
the proteins, especially in the pH range of 4.0-6.5 (Burr-
ington, 1999). Most foods are heat processed in some way,
and WPs are susceptible to changes during heating.
Denaturation at low pH leads to aggregation and insolu-
bility. One challenge for WP is maintaining solubility
during heat processing. Solubility of WPCs decreases as
temperature increases (Pelegrine and Gomes, 2012). How-
ever, the maximum intermolecular aggregation of β-Lg
without heat does occur near the iso-electric point due to
neutralization of charges and interaction via hydrophobic
forces (Majhi et al., 2006; Mehalebi et al., 2008; Schmitt
et al., 2009). Increasing the ionic strength results in salt-
ing in of β-Lg (Majhi et al., 2006).
In many cases, limited hydrolysis leads to increased
solubility due to the reduced molecular weight and the
increased hydrophilicity resulting from the increase in
free carboxyl and amine groups. Researchers proposed
that hydrolyzing WPs with various proteolytic enzymes
under different conditions can be used to improve the sol-
ubility over a wide range of pH (Mutilangi et al., 1996;
Perea et al., 1993). WPHs had shown less solubility in pH
4 while showing the highest solubility around pH 6-10
(Jeewanthi et al., 2014). More extensive hydrolysis has
been shown to increase solubility (Flanagan and Fitzger-
ald, 2002; Jeewanthi et al., 2014). Also, heat stability was
improved upon partial hydrolysis due to loss of the sec-
ondary structure, thus contributing to reduced structural
changes upon heating (Foegeding et al., 2002).
Adhesion, cohesion, elasticity, and water-binding
The adhesion properties of WPCs help to improve the
homogeneous texture of food products. WPCs may be
used to bind breadcrumbs or batter to meat, poultry or
fish. Effective adhesion between meat pieces is an impor-
tant quality characteristic in the manufacture of products
such as chicken nuggets or restructured ham. The actual
meat particle binding occurs during cooking as heat set-
ting of the proteins takes place. WPs aid in this binding
by forming strong, irreversible gels that restructure into
Fig. 2. Classification of functional properties of WPHs in food applications.
Functionality of Whey Protein Hydrolysates
353
an extended three-dimensional network, thereby helping
to adhesion (Prabhu, 2006). WPCs decreased the average
hardness and chewiness values and increased cohesive-
ness of the sausages. The adhesion of the WPs is affected
by temperature due to denaturation of protein structure
(Goode et al., 2013).
Moisture binding is especially important during the
cooking stage when the denaturing salt soluble meat pro-
teins experience a progressive decline in water holding
capacity (Tsai et al., 1998). Barbut (2007) reported that
poultry treated with WPHs had the lowest cooking loss
and highest yield with higher water retention capacity
compared to those treated with WPI, casinate, β-Lg, and
whole milk proteins. The water-binding abilities of WPs
can help reduce formula costs as the proteins holds addi-
tional water. Viscosity development is closely related to
gelation and other protein-protein interactions (Burr-
ington, 1999).
Aggregation and gelation properties
Gel formation
Gelation is an important functionality that is useful in
baked goods, processed meats, surimi, desserts, and sour
cream. A gel is an intermediate structure between solid
and liquid, which carbohydrates or protein strands cross-
link to form a network. Gelation is favored by large mol-
ecules of proteins since they form extensive networks by
cross-linking in three dimensions and by the ability of the
denaturing. Rinn et al. (1990) reported that WPCs pre-
pared by microfiltration through 0.6 µm pores exhibited
superior gels at 4-5% protein. In restructuring new meat
products, WPCs have been utilized for their abilities to
exhibit heat-coagulating and heat gelling properties (Morr
and Ha, 1993). Cold-set gelation of WPs has also been
noted by Bryant and McClements (1998). Hydrolyzed â-
Lg also has the ability to form networks associated with
gels (Foegeding et al., 2002).
In their un-denatured form, WPs form rigid gels that
hold water and fat, and provide structural support. The
formation of disulfide bonds and ionic bonding controlled
by calcium ions determine gel structure (Burrington,
1999). Hydrophobic interactions can play a major role in
partially hydrolyzed proteins and consequently unfolding
the protein structure (Pinterits and Arnteld, 2007). This
exposes buried hydrophobic groups and other interactive
groups which are then free to interact with neighboring
polypeptides (Kang et al., 1994). This promotes protein
aggregations and subsequent gel setting. The effect of
hydrolysis on the gelation ability of WP is dependent on
environmental conditions and on the degree of hydrolysis
(DH). On the other hand, extensive hydrolysis of WPI can
weaken its gelation properties (Huang et al., 1999). Non
heat-set gelation forms strong elastic gels during exten-
sive hydrolysis of WPI at high solid content (20% w/v)
with Alcalase 2.4L, a protease from Bacillus lichenifor-
mis (BLP) than the heat induced gels (Doucet et al., 2001).
Among the enzymes investigated for the production of
WPH with enhanced gelation properties, BLP is well stu-
died (Creusot et al., 2006; Creusot and Gruppen, 2007a,
2007b; Creusot and Gruppen, 2008; Doucet and Foeged-
ing, 2005; Spellman et al., 2005). Further, Spellman et al.
(2005) showed, after isolating subtilisin and glutamyl en-
dopeptidase (GE) activities from Alcalase 2.4L, that the
GE is the enzyme responsible for the peptide aggregation
in WPHs. With enzymatic hydrolysis performing under
different conditions, researchers were able to produce gels
with different rheological properties (Table 1). The increa-
sed net charge on proteins results in increased repulsion
between peptides. Interestingly, limited proteolysis with
enzymes can also be used to control the gelling ability as
well as the gel strength.
Trypsin also showed gelation properties after hydroly-
sis of WPs. Tryptic hydrolysis of WPs at 6.7 and 2.3%
DH prevented gelation at pH 3 and 7, whereas hydrolysis
to 2.3% DH with BLP dramatically increased the gelling
ability and gel strength at neutral pH (Ju et al., 1995). The
aggregates formed upon hydrolysis of β-Lg by BLP con-
sisted of 6-7 major peptides (2-6 kDa) (Otte et al., 1996b).
Peptides from β-Lg formed aggregates with other pep-
tides and with intact β-Lg and α-La via hydrophobic inter-
actions leading to gelation. Some researchers have found
the key fragments that act as the initiators of aggregation
of WPHs (Table 2).
Film formation
In food systems, edible, and permeable film coatings
are used to control the transfer of aroma, flavor com-
pounds, moisture, oxygen, and lipid. WP has been shown
to make transparent films with good oxygen and aroma
barrier properties (Mate and Krochta, 1996; Miller et al.,
1997). McHugh et al. (1994) produced WPCs films by
heating 8-12% (w/w) solutions of WPC at 75-100°C. The
suggested optimal condition for producing these films is to
heat 10% WPC solutions at 90°C. Exposure of internal S-
H and hydrophobic groups after denaturation by heating
of WPs support improved film formation. The intramolec-
ular S-S bonds of heat denatured WP films form insoluble
354
Korean J. Food Sci. An., Vol. 35, No. 3 (2015)
films while native proteins form soluble films (Perez-
Gago and Krochta, 2002). Various measures have been
studied to improve barrier capacity and mechanical
strength of WPC films. Due to protein chain-to-chain
interactions, films with high brittleness are created.
To overcome this and improve the flexibility of the
films, hydrolysis of WP provided a much better approach
than the addition of plasticizers. Hydrolysates improve
the film tensile properties and yield better oxygen barrier
(Sothornvit and Krochta, 2000b). WPHs made good films
with oxygen permeability and water vapor transmission
rate values similar, but with more flexibility, than WPI
films at the same glycerol content (Schmid, 2013; Soth-
ornvit and Krochta, 2000a). Increasing the WPH content
leads to a decrease in the molecular weight, in WPI-based
films, and also significantly increases film flexibility,
compared to films entirely produced from WPHs (Schmid
et al., 2013).
Table 1. Different gel characteristics resulting from whey protein hydrolysates made with BLP under several conditions
Gelation characteristics Enzyme Whey product Hydrolytic condition Reference
Very high gelation
Subtilisin Carlsberg +
Glutamil endopeptidase
(Alcalase 2.4L)
Hydrolysates of WPC 80%
50°C,
> 0.4 DH,
pH 7
Spellman et al., 2005
Gelation BLP(aq) 2% (w/w) Hydrolysates of WPI Limited or Extensive Creusot and Gruppen,
2007a
Gelation BLP(aq) 2% (w/w) Hydrolysates of WPI 4°C,
Extensive Creusot et al., 2006
Strong gelation BLP Hydrolysates of WPC Salt/polysaccharide
added Rocha et al., 2009
Strong and faster gelation BLP Hydrolysates of WPI Below pH 6.2 Ipsen et al., 1997
Translucent strong gelation BLP Hydrolysates of WPI Limited Otte et al., 1999
Cold gelation BLP Hydrolysates of WPI Salt added/
acidification
Rabiey and Britten,
2009a
Rabiey and Britten,
2009b
Soft gelation BLP Hydrolysates of WPI Limited
DH 2.2% Otte et al., 1996a
White, soft, and
thixotropic gelation BLP Hydrolysates of WPI 45°C,
1 h hydrolysis Ju and Kilara, 1998
Stable gelation
over wide pH range Subtilisin Carlsberg Hydrolysates of WPI Extensive Doucet et al., 2003a
Doucet et al., 2003b
Thin strong gelation BLP Hydrolysates of WPI
(heat induced) pH 7 Ju et al., 1995
Strong elastic gelation Alcalase 2.4L Hydrolysates of WPI Extensive Doucet et al., 2001
BLP, protease from Bacillus licheniformis; DH, degree of hydrolysis.
Table 2. Key peptides of gelation properties in different types of whey protein hydrolysates
Whey product Enzyme Hydrolysis
condition Peptides Reference
Hydrolysates of WPI Alcalase Limited β-Lg [f135-158] Doucet and Foegeding,
2005
Hydrolysates of WPI BLP (aq) DH 6.8%
pH 7
β-Lg [f1-45]
β-Lg AB[f90-108]-S-S-α-La [f50-113],
α-La[f12-49]-S-S-α-La [f50-113],
β-Lg AB[f90-108]-S-S-α-Lg AB[f90-108],
β-Lg A[f90-157],
β-Lg AB[f135-157/158]
Creusot and Gruppen,
2007b
Hydrolysates of WPI BLP (glutamyl
endopeptidase) pH 8 Peptides of β-Lg and α-La Ipsen et al., 2000
Hydrolysates of β-Lg Trypsin 5-50°C,
pH 4 β-Lg [f1-8], β-Lg [f15-20], β-Lg [f41-60] Groleau et al., 2003a
Groleau et al., 2003b
Hydrolysates of WPI Trypsin > pH 2 β-Lg [f1-8] Pouliot et al., 2009
BLP, protease from Bacillus licheniformis; β-Lg, β-lactoglobulin; α-La, α-lactalbumin; DH, degree of hydrolysis.
Functionality of Whey Protein Hydrolysates
355
Interfacial properties
Emulsification
WPCs are used to improve emulsification in infant for-
mula, meal replacement beverages, soups, gravies, and
coffee whiteners (Gauthier et al., 1993). Food emulsions
of the oil-in-water type are often stabilized by proteins.
Temperature, pH, ionic strength, protein concentration,
protein to oil ratio, and oil volume fraction are among the
major parameters that affect the physical properties of the
emulsion (Guzey and McClements, 2006).
Limited enzymatic hydrolysis was found to be success-
ful in improving interfacial properties (both foaming and
emulsification properties) of WPCs (Foegeding et al., 2002;
Kilara and Panyam, 2003). Emulsification can be impro-
ved through controlled heat denaturation. As the WP un-
folds, hydrophobic amino acid residues are exposed, which
enhance the ability of the protein to orient at the oil/water
interface. Extensive hydrolyzed WPHs can be used as
emulsifiers with proper homogenization conditions and
careful selection of concentrations (Agboola et al., 1998).
The emulsion stability can also be improved by addition
of polysaccharides in to the WPHs media (Ye et al., 2004).
The interactions between charged polysaccharides and
proteins can be used to improve the thickness of the sur-
face layer or to create multi layers of surface (Decher,
1997). The tryptic hydrolysates are reported to be more
active on surface and have more emulsification properties
than the chymotryptic hydrolysates (Turgeon et al., 1991).
Fat binding and whipping formation
WP also has emulsifying properties allowing fat glob-
ules to be structural elements in heat induced WP gels.
These emulsifications properties have led to the develop-
ment of new cheese, meat, and confectionary products
(de Wit, 1998). Approximately 5-10% of WP is BSA, the
smallest protein component of whey and BSA has valu-
able fat binding properties (Francis and Wiley, 2000). In-
creased fat binding capacity was associated with an in-
crease in hydrophobicity of the protein (Voutsinas and
Nakai, 1983).
Foaming and aeration
Proteins stabilize foams by strongly adsorbing to the
air-water interfaces, forming viscoelastic adsorbed layers
and leading to a protein network with high viscosity (Rul-
lier et al., 2010). Foaming properties are best when the
WPs are undenatured, not competing with other surfac-
tants at the air/water interface, and stabilized by an inc-
rease in viscosity when foam formation occurs. Defatted
WPCs can be used as egg substitutes to induce and stabi-
lize foams in aerated food products such as meringues
and Madeira-type cakes (de Wit, 1998). Innocente et al.
(1998) reported that proteose peptone 3, a component that
results from the milk fat globule membrane protein, has
good foaming properties. At proteose peptone 3 concen-
trations of 0.05, 0.10, and 0.20 g/100 mL, equilibrium
surface tensions at the air-water interface were reported to
be 44.75, 36.14, and 32.11 mN/m, respectively. Zhu and
Damodaran (1994) suggested that the addition of prote-
ose peptone sharply decreased the foam stability of WPI
but did not affect the foam capacity.
Compared to intact WPs, limited enzymatic hydrolysis
promotes foaming and aeration through more rapid ab-
sorption at the interface by reducing the peptide size (van
der Ven et al., 2002). In WPH-35, Alcalase 2.4L resulted
in the highest foaming expansion capacity of 287.5%
after 5 h hydrolysis with 9.5% DH compared to trypsin,
pepsin, protease A, and protease M hydrolysates (Jee-
wanthi et al., 2014). Davis et al. (2005) also reported on
the superior forming ability of Alcalase 2.4L and pepsin
hydrolysates of β-Lg compared to trypsin. They declared
native β-Lg is resistant to hydrolysis by pepsin, which has
a broad specificity with a preference for cleaving after
hydrophobic residues. In WPH-30, the highest foaming
ability has reported by flavourzyme enzyme (Yoon et al.,
2010). Excessive hydrolyzed WPHs were showed poor
foaming stability due to very short peptides production
(Kilara and Panyam, 2003; Ye and Sing, 2006). van der
Ven et al. (2002) declared that large molecular fractions
than 7 kDa has the highest foam stability compared to 44
hydrolysates of WPs. Interfacial films used to stabilize
emulsions and foams also have designed from WPHs
(Foegeding et al., 2002).
Sensorial properties
Color, flavor, and texture
The flavor profile for whey products ranges from a
sweet/dairy (sweet whey) flavor, to virtually no (WPCs,
WPIs) perceivable flavor (Keaton, 1999). Acid whey is
used in dairy products such as in cheese powders, sauces,
and sherbets where a tangy flavor is desired (Kosikowski,
1979). In the bakery industry, acid whey is used in bread,
biscuits, and crackers for the gold surface color it pro-
vides (Kosikowski, 1979). Color found in whey may re-
sult from naturally occurring xanthophylls, Maillard reac-
tion products, and annatto addition (Smith, 2004). Another
356
Korean J. Food Sci. An., Vol. 35, No. 3 (2015)
added benefit of WPC is that it can improve mouth feel of
foods by creating a richer, fuller flavor. This can be espe-
cially important when formulating reduced-fat or low-fat
meat products where some of the flavor contributed by fat
is lost. The incorporation of WPC can be an economic
alternative to other high priced flavor enhancing additives
(Prabhu, 2006). Baking time and temperatures may re-
quire adjustment because crust color might develop more
rapidly with whey-based ingredients. WPC 34-80% have
been found to improve the color, thickness, and chewi-
ness of full fat and low fat cookie formulations. WPIs has
identified as an anti-browning agent that able to suppress
enzymatic browning effect which reduce the brown color
in apple juice and fresh cut apples (Perez-Gago et al.,
2006; Yi and Ding, 2014). Also, some of the benefits rec-
ognized by consumers include good crust color devel-
oped through the Maillard browning reaction while using
high temperature in food. WPCs are also bland tasting
and contribute no foreign or off-flavors when used as
ingredients (Burrington, 1999). Aldehydes including hex-
anal, have been suggested as the compounds responsible
for off-flavors in liquid and dried whey products (Tomaino
et al., 2004; Wright et al., 2009). Concentrations increa-
sed with storage time concurrent with increased off-fla-
vors (Wright et al., 2009). Off-flavors in whey products
can carry into ingredient applications and negatively affect
consumer acceptance (Drake et al., 2009; Wright et al.,
2009).
A major disadvantage of protein hydrolysis is the release
of bitter-tasting peptides that limits the use of WPHs to
low concentrations at which bitterness is not detected
(Sinha et al., 2007). Rios et al. (2004) have mentioned
that limiting the hydrolysis to less than 8% is a better
option to minimize the bitter peptides. Small hydrophobic
peptides and non-protein nitrogen released during the
enzymatic hydrolysis are the major contributors to the
bitter taste (Adler-Nissen, 1986; Matoba and Hata, 1972).
Hydrophobic amino acids were bitterer when both the α-
amino and carboxyl groups were involved in peptide bond
formation than when the bond formation occurred at the
N- or C-terminus of peptides (Matoba and Hata, 1972).
WPHs produced with Alcalase 2.4L were bitterer than
hydrolysates generated with Prolyve or Corolase, under
similar reaction parameters (Spellman et al., 2009). On
the other hand, free amino acids are also converted to fla-
vorful compounds by heat and chemical interaction with
other compounds. When WPs are enzymatically hydro-
lyzed, they develop flavor enhancing properties. WPHs
can refine, brighten, accentuate, and naturally enhance key
flavor notes in soups, sauces, dips, and meat products
(Prabhu, 2006). WPHs have the tendency to bind a vari-
ety of flavor chemicals. As a flavor enhancer, WPH addi-
tion to liquid whey and further production to spray dried
WPC successfully led to a decrease in cardboard flavor
and short chain aldehyde concentration compared to the
control liquid whey and WPCs. WPH has its own distinct
flavor and aroma as well (Drake et al., 2009).
Conclusion
WP products are used in food applications considering
their functional benefits over the other proteins in the
industry. The major functional activities of the protein
depend on their hydration, gelation, interfacial, aggrega-
tion, and sensorial properties. These properties are better
enhanced via enzymatic hydrolysis than via chemical or
technical means. WPHs enhance functionality due to their
ability to expose the globular protein structure, reduce the
average molecular weight and, increase the ionic strength,
molecular charges, and protein-to-protein interactions,
properties which are lacking in non-hydrolyzed WPCs
and WPIs. Moreover, the enzymatic hydrolysis avoids the
heat denaturation of proteins and maintains the function-
ality through the food production process. The optimum
functional ability of WPHs would be achieved by using
proper homogenization conditions, hydrolysis conditions
(enzyme-to-substrate ratio, temperature, pH, and time),
the type of enzyme, and environmental conditions in food
industry.
Acknowledgements
This work was supported by Priority Research Centers
Program through the National Research Foundation of
Korea (NRF) funded by the Ministry of Education, Sci-
ence and Technology (2009-0093824).
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