TABLE OF
CONTENTS.
CHAPTER ONE
Definition
Introduction
CHAPTER TWO
Different
Methods of Production of Protein Hydrolysate Using Enzymatic and Chemical
Methods
Uses of
Protein Hydrolysates in Food System
Advantages
of Protein Hydrolysates over Native Protein
Limitations
of Protein Hydrolysates in Food System
Methods of
Debittering the Hydrolysates
CHAPTER THREE
Conclusion
REFERENCES
CHAPTER ONE
INTRODUCTION
Definition: Protein hydrolysate could be defined as the
end product of protein hydrolysis using chemical and enzymic methods.
Protein
hydrolysate have many uses in specialty foods such as non allergenic infant
formular, diets foods and other special nutritional foods.
The
drawback of many hydrolysates such as Soya or Casein hydrolysates is the bitter
taste that develops when they are hydrolysated into small peptides with
protease enzymes.
Protein
maldigestion which is often associated with cystic fibrosis and allergy to milk
protein may be overcome by replacing intact in the diet with synthetic amino
acid mixture, or with enzymic protein hydrolysates. Hydrolysates may be the
treatment of choice for two reasons. The amino acids and small peptides
constituents of protein hydrolysates have been shown to be more readily
ascribed from the small intestine than their equivelent pure amino acid
mixture, more over, protein hydrolysates are considerably less expensive than
synthetic amino acid mixtures. Nonetheless, protein hydrolysates suffer from a
serious drawback, namely, the occurrence of a bitter taste which develops
during the course of the enzymic hydrolysis.
Murray r (1952) demonstrated that a
treatment of enzymic casein hydrolysates with activated carbon resulted in a
substantial improvement in the taste of preparations. However, authors regarded
this method of improving the taste as impractical due to the simultaneous loss
of a large proportion of the hyptophan during treatment. A different approach
was presented in move recent studies in which a casein hydrolysate relatively
free of bitter taste was obtained by the sequential employment of papa in and
of pig’s kidney homogenate – the latter serving as a source of exopeptidases.
However, extended time periods of hydrolysis were required, which necessitated
the use of dolor form to control bacterial growth.
There
is a variety of food and biomedical applications for protein which have been
solubilized by enzymatic hydrolysis. Their enhanced solubility, heat stability,
and resistance to precipitation in acidic environs, where many proteins are
insoluble, offer attractive features to biochemists and nutritionists involve
the research and development of high protein food formulations.
Applications
of these valuable protein supplements may have merit in the diet of persons
with digestive disorders, pre and post operative abdominal surgical patient,
geriatric and convalescent feeding , and for other who for various reasons do
not ingest a well balanced diet. Unfortunately, the use of enzyme – treated
hydrolysates in dietary food applications has in many instances, been limited
due to the presence of bitter flovour component. The unpalatability of these
hydrolysate arises mainly from the
formation of bitter peptide and amino acids liberated during the hydrolytic
process. The bitterness appease to be closely related to the content and
sequence of hydrophobic amino acids in the peptides.
Further
hydrolysis of pepsin digested soy protein using a bacterial proteins or an exopeptidase, reduced bitterness. Also,
chemotropic plastering protein hydrolysates. Similarly, clegg and Mc Millan
(1974) have reported that a combination enzyme treatment of case in using
papain for 18 hr followed by the addition of a homogenate of swine kidney cortex,
also produced a hydrolysate with reduced bitterness.
As
another approach to resolving the bitter flavor problem, it seemed reasonable
to attempt flavor improvement of protein hydrolysates by reducing the
hydrophobic peptide and amino acid content of the digests. It was recognize
many years earlier that activated carbon would absorb the aromatic amino acids tryptophan, tyrosine, and
phenycalaline. At a later date, Murrgy and Baker utilized carbon to treat a
commercial enzymic hydrolysate of casein and reported the taste was greatly
improved. A bitter tasting polypeptide fraction was elutated from the carbon.
Various
phenol-formaldehyde resins with structures similar to carbon are available
commercially and are used in a wide variety of ion-exchange and absorbent
applications. Therefore the ability of a phenol-fomaldeliyde resin polymer to
interact preferentially with the monoplane groups present in hydrophobic
peptide was determined from the findings a hydrophobic chromatography process
for debittering protein hydrolysates was developed.
It
has been well documented that the main problem in the preparation of soluble
hydrolysate from protein such as casein is the difficulty in preventing the
formation of bitter peptides or in removing them from the hydrolysate. Among
several studies on casein hydrolysates the process developed by clegg and Mc
Millan (1974) using skim milk as substrate, should be mentioned. By hydrolyzing
skim milk protein with papain, a bitter testing hydrolysate is formed which is
rendered bland by subsequent hydrolysis with exopeptidase from pig kidney
tissue. Unfortunately, the procedure is both lengthy and costly. Anther costly
debittering process involves hydrophobic chromatography of enzymatic protein
hydrolysate on hexyls sepharose. An extraction method using azeotropic
secondary butyl alcohol by which complete removal of bitter compounds is also
achieved.
In
the course of a study aimed a producing at a reasonable cost, bland, soluble
skim milk hydrolysate without a significant loss of nutritional value, a
comparison was made of adsorption methods of debittering pronase- and
ficinhydroly-zed skim milks. The result of the comparison and the partial
identification of the bitter peptides formed in the skim milk hydrolysates is
reported. Due to the minimum changes in taste and appearance afforded to soft
drinks or fruit juices by addition of this treated skim milk, the resultant
beverages are expected to appear and taste like the original beverages with
almost full nutritional value of skim milk.
It
is widely known that bitterness sometimes is produced in sake and other
fermented products, so decreasing their qualities. This bitterness is produced
by bitter peptides and their derivatives formed during the ageing process of
these fermented products. Enzymatic hydrolysis of protein also produces bitter
peptides very often to decrease the value of the products.
Since
those bitter peptides are known to be produced by enzymatic hydrolysis, several
attempts to reduce the production of bitter peptides during the enzymatic
hydrolysis process by changing the enzymes and or conditions of the reactions
have been made.
Skim
milk, soybean casein, whey protein concentrate (NPC) and casein hydrolysate of
course composed of amino acids. Because a debittering method for bitter
peptides was being looked for protein and peptides could block the bitterness.
Creaming powder, Vegetable oil and margarine are fatly substances, which could
block hydrophobic groups of bitter peptides by their character to reduce the bitterness.
Some acidic amino acids were added in order to confirm their ability for
masking bitterness, Asp, Glu and tau being used for the study. Although taurine
(Tau) is not an acidic amin acid, it has a very strongly acidic function.
Taurine was expected to reduce the bitterness as well as other acidic amino
acids or peptides.
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