Acid Hydrolysis of Casein

Marina- Kurbanova,Svetlana- Maslennikova

doi:10.12737/4124

Abstract

Protein hydrolysates have a high biological and nutritional value and are widely used in various sectors of the food, medical, and pharmaceutical industries. This article deals with the chemical hydrolysis of the milk protein casein in the presence of hydrochloric or sulfuric acid and reports the hydrolysis parameters minimizing the loss of amino acids. In casein hydrolysis, peptide bonds of protein molecules break to form di- and tripeptides and free amino acids, enhancing protein absorption by the body. Inadequate intake of digestible forms of protein leads to disruption of growth processes and impairs the immune resilience of the human body. To avoid the decomposition of labile amino acids, hydrolysis was performed with triply distilled 6 M hydrochloric or sulfuric acid in a vacuum in sealed ampoules for 4, 8, or 24 (±0.05) h at a temperature of 110 ± 5 deg. C and a substrate-to-acid ratio of 1:15, 1:20, or 1:25. The compositions of the casein hydrolysates obtained at various hydrolysis times are presented. For a more detailed evaluation of the properties of the casein hydrolysates, the hydrolysis time effect on the molecular weight distribution of proteins and peptides has been investigated. The problem of obtaining protein hydrolysates with the desired composition and properties remains topical.

Highlights

Protein hydrolysates are the products of the hydrolytic decomposition of proteins
As distinct from some globular proteins, caseins are readily decomposable by chemicals because, even in their native state, they are in a low-ordered conformation that is like a disordered structure of denaturated globular proteins [3]
This is explained by the very low proportion of -helices and by the low structural organization of the main casein components. This fact is due to the high proline content of these proteins (8.5 to 16%), which apparently deforms the helix into a disordered ball [1, 6]

Summary

INTRODUCTION

Protein hydrolysates are the products of the hydrolytic decomposition of proteins They consist mainly of separate amino acids, their sodium salts, and polypeptide residues. The peptide bonds in protein molecules break to yield di- and tripeptides and free amino acids, increasing protein assimilation in the living organism. Casein hydrolysates contain peptides that are capable to form stable coordination compounds (chelates) with calcium ions and to considerably raise the absorbability of the latter [2,3,4]. The peptide bonds (H–N–C=O) forming the polymer chain of a protein molecule undergo hydrolysis in the presence of an acid or alkali. This causes polymer chain scission and can lead to the constituent amino acids. We report a promising method of the acid hydrolysis of casein and characterize the resulting hydrolysates

OF STUDY

Amino nitrogen was determined spectrophotometrically using

RESULTS AND DISCUSSION

Initial casein sample

CONCLUSIONS