Alkaline Hydrolysis Essay

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2.1.2. Alkaline hydrolysis
Alkaline hydrolysis is a simple process in which the protein is solubilized by heating followed by the addition of calcium, sodium or potassium hydroxide as alkaline agents and maintaining the temperature at a range between 25-55 °C (Pasupuleti & Braun, 2010). During alkaline hydrolysis of proteins, some amino acids like serine and threonine are damaged during alkaline hydrolysis, however, tryptophan remains intact. Also, this process causes racemization of amino acids, by modifying its structure and converting L-amino acid in its isomeric forms D-amino acids (Wisuthiphaet & Kongruang, 2015). Disulphide bonds are also fragmented with loss of cysteine, serine, and threonine and formation of lysinoalanine, ornithinoalanine,
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Therefore, enzymatic hydrolysis is considered as the most effective way to obtain protein hydrolysates with bioactive properties (Clemente, 2000; Shahidi et al., 1995). Any hydrolysis process involves at least five independent variables: (i) protein substrate concentration (%N × 6.25), (ii) enzyme-substrate ratio (E/S) in % or in activity units per kg N × 6.25, (iii) pH, (iv) temperature, and (v) time (Adler-Nissen, 1984). Generally, there is an optimum combination of both pH and temerature, where the enzyme shows the highest activity. Physicochemical conditions of the hydrolysis reaction such as temperature, pH and enzyme/substrate ratio must be adjusted to optimize the activity of the proteolytic enzyme (Kim & Wijesekara, 2010; Santos, Martins, Salas-Mellado, & Prentice, 2011). At the beginning and at the end of hydrolysis process the mixture must be heated to about 85-95 °C for 5-20 min in order to terminate the endogenous and exogenous enzyme activity respectively. In industry, the production process of protein hydrolysates can be coupled to membrane technology, reducing the cost associated with enzyme inactivation at the end of the hydrolysis process (Guerard, 2007). Some Industrial food-grade proteinases derived from microorganisms have been used to produce bioactive peptides by enzymatic hydrolysis such as Alcalase®, …show more content…
Proteases are classified by their principal functional group in their active site (serine, thiol, carboxyl and metallo) and their hydrolysing mechanism (endo or exon-proteases). Endo-proteinases are more widely used in food protein hydrolysis than exo-proteases. Moreover, endo-proteinases produce relatively large peptides while exopeptidases hydrolyse the terminal peptide bonds removing amino acids from either the N terminus (aminopeptidases) or the C terminus, (carboxypeptidases) (Kristinsson & Rasco, 2000). The degree of hydrolysis (DH) is a fundamental parameter for the production and characterization of a protein hydrolysate. It is defined as the percentage of broken peptide bonds in relation to the original protein. The degree of hydrolysis achieved in the hydrolysis is determined by the conditions used in the process such as substrate concentration, enzyme / substrate ratio, incubation time as well as the physicochemical conditions such as pH and temperature. Moreover, another factor that will determine the degree of hydrolysis is the nature of the enzyme, characterized by its specific activity and type of activity. Thus, the nature of the enzyme used will not only influence the degree of hydrolysis, but also in the type of peptides produced (Wang et al.,

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