Effect of Acid Hydrolysis on Tableting Properties of Chitin Obtained from Shrimp Heads

J Rojas,J Madrigal,J Ortiz

doi:10.4314/tjpr.v14i7.3

Abstract

Purpose: To assess the effect of acid hydrolysis on the degree of acetylation, crystallinity, and molecular weight of chitin obtained from shrimp heads as well as to evaluate their tableting properties.Methods: The effect of acid hydrolysis conditions such as reaction temperature (46, 60, 80, 100, 114°C), hydrochloric acid concentration (4.6, 6, 8, 10 and 11.4 M) and reaction time (0.6, 2, 4, 6 and 7.4 h) were examined. The degree of acetylation and molecular weight were found by Fourier transform spectroscopy (FT-IR) and viscometry methods, respectively. The degree of crystallinity degree and its compact tensile strength were determined by x-ray and Fell & Newton methods, respectively.Results: The combined effect of high temperature (> 80 oC), HCl concentration (> 2 M) and reaction time (> 4 h) led to high depolymerization, reduction in degree of acetylation, crystallinity, chitin yield and thus, decreased tensile strength and accelerated compact disintegration time. Optimal reaction conditions were achieved at an acid concentration of 2.2 M, temperature of 60 oC and reaction time of 4 h. These conditions rendered compacts with tensile strength of 25.7 MPa and disintegration time of 25.3 min.Conclusion: The optimal HCl hydrolysis conditions for shrimp heads rendered chitin suitable for the preparation of compacts with good tensile strength and moderate disintegration time.Keywords: Chitin, Compressibility, Deacetylation, Acid Hydrolysis, Tableting Performance, Central Composite Design

Highlights

Chitin is the poly-β-(1-4)-N-acetyl-D-glucosamine polymer found in the exoskeleton of a wide variety of invertebrates such as crustaceans, insects and in the cell wall of fungi and yeast [1]
Concentration and reaction time were significant (p < 0.02) for molecular weight and compact disintegration. This means that a large molecular weight is a condition for a compact to have a large disintegration time and tensile strength
A large molecular weight make the polymer chains able to get closer upon compaction forming a tight hydrogen bonding network, which is boosted by the polymer length

Summary

Introduction

Chitin is the poly-β-(1-4)-N-acetyl-D-glucosamine polymer found in the exoskeleton of a wide variety of invertebrates such as crustaceans, insects and in the cell wall of fungi and yeast [1]. Chitin has a structural function comparable to that of collagen in higher animals and cellulose in terrestrial plants. It occurs in nature as ordered crystalline microfibrils associated to proteins. It possesses excellent biocompatibility; it is ecologically safe and has a very low toxicity [2]. The degree of acetylation (DA) is > 50 % indicating the presence of some amino groups in its structure (C-2) since some deacetylation might take place during extraction. When the degree of acetylation is < 50 % it is regarded as chitosan [4]

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