Surface activity and molecular characteristics of cuttlefish skin gelatin modified by oxidized linoleic acid

doi:10.1016/j.ijbiomac.2011.02.006

International Journal of Biological Macromolecules

Volume 48, Issue 4, 1 May 2011, Pages 650-660

https://doi.org/10.1016/j.ijbiomac.2011.02.006 Get rights and content

Abstract

Surface activity and molecular changes of cuttlefish skin gelatin modified with oxidized linoleic acid (OLA) prepared at 60, 70 and 80 °C at different times were investigated. Modification of gelatin with OLA could improve surface activity of resulting gelatin as evidenced by the decreased surface tension and the increased foaming and emulsifying properties. Interaction between OLA and gelatin led to the generation of carbonyl groups, loss of free amino content and the increase in particle size of resulting gelatin. Emulsion stabilized by modified gelatin had the smaller mean particle diameter with higher stability, compared with that stabilized by gelatin without modification.

Introduction

Gelatin, the denatured form of collagen, is used as foaming, emulsifying and wetting agents in food, pharmaceutical, medical and technical applications due to its surface active properties [1]. In emulsion, gelatin can adsorb at interfaces between oil and water and form a continuous viscoelastic membrane-like film around oil droplets, resulting in the improved stability of oil-in-water emulsion [2]. Gelatin is commercially made from skins and skeletons of bovine and porcine by alkaline or acidic extraction [3]. However, gelatin from aquatic sources (fish skins, bones, and fins) can be an alternative to mammalian counterpart [4]. Fish gelatin is advantageous due to the lack of BSE outbreaks. It is acceptable for Islam and can be used with minimal restrictions in Judaism and Hinduism. Moreover, the production of gelatin from byproduct of the fish-processing industry could reduce waste and pollution.

Cuttlefish is one of major seafood products of Thailand. During processing, the skin is removed and becomes the by-product with the low market value. Recently, Aewsiri et al. [5] successfully extracted the gelatin from cuttlefish skin. However, gelatin from cuttlefish skin had the poorer surface activity due to the lower hydrophobic amino acids content (proline and leucine) and a large portion of hydrophilic amino acids (lysine, serine, arginine, hydroxyproline, aspartic acid and glutamic acid) [5], [6]. Gelatin with a higher hydrophilic region generally has the limited ability to function as a surface active agent [7].

Attachment of hydrophobic domain to protein may lead to the increase in its hydrophobicity, causing the changes in the surface activity and functional properties of protein [7], [8]. Lipid oxidation products, including lipid hydroperoxides and reactive aldehyde derivatives, could modify amino acids of proteins [9]. Alkyl and peroxyl radical decomposed from hydroperoxide can directly interact with side chains of proteins [10]. The secondary lipid oxidation products, such as aldehydes, react mainly with amino acids via condensation reaction to form Schiff's bases or by Michael addition reactions [9], [11]. Therefore, the introduction of lipid oxidation products to gelatin might provide the hydrophobic domain for gelatin, thereby facilitating the migration of gelatin to the interface. Therefore, the objectives of this work were to study the improvement of surface activity of cuttlefish skin gelatin via the modification with oxidized linoleic acid as affected by reaction time and temperature and to investigate the effect of modified cuttlefish skin gelatin on the stability of emulsion under different harsh conditions.

Section snippets

Chemicals

Linoleic acid, o-phthalic dialdehyde (OPA), 2-(dimethylamino)ethanethiol hydrochloride (DMA), cumene hydroperoxide and 1-anilinonaphthalene-8-sulfonic acid (ANS) were purchased from Sigma Chemical Co. (St. Louis, MO, USA). Hydrogen peroxide (H₂O₂), sodium hydroxide, ethanol, sodium dodecyl sulfate (SDS), dimethyl sulfoxide (DMSO), sodium chloride, sodium hydroxide, sodium sulfite, ammonium thiocyanate (NH₄SCN), barium chloride (BaCl₂), ferrous sulfate (FeSO₄) and boric acid were procured from

Oxidation of linoleic acid as affected by temperature and time

The oxidation of linoleic acid during incubation at different temperatures for various times was monitored as shown in Fig. 1. Generally, PV and TBARS of linoleic acid increased with increasing incubation times, except PV of samples incubated for 9 and 12 h, which had the similar value (p > 0.05) (Fig. 1A). At the same incubation time, the higher temperature yielded the higher PV and TBARS (p < 0.05). The result suggested that the oxidation of linoleic acid proceeded to a higher extent at higher

Conclusion

Modification of gelatin with OLA could improve surface activity of obtained gelatin as indicated by the decrease in surface tension and the increase in foaming and emulsifying properties. Gelatin modified with OLA prepared at 70 °C for 9 h showed the highest surface activity, especially at high molar ratio used. The increases in hydrophobic region at surface of gelatin play a key role in enhancing surface activity, foaming and emulsifying properties of modified gelatin. Gelatin modified with OLA

Acknowledgement

The authors would like to thank Prince of Songkla University and the Office of the Higher Education Commission, Thailand, for supporting by grant fund under the program Strategic Scholarships for Frontier Research Network for the Join Ph.D. Program Thai Doctoral degree for this research.

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Surface activity and molecular characteristics of cuttlefish skin gelatin modified by oxidized linoleic acid

Abstract

Introduction

Section snippets

Chemicals

Oxidation of linoleic acid as affected by temperature and time

Conclusion

Acknowledgement

Food Hydrocolloids

Food Hydrocolloids

Food Chem.

J. Food Eng.

J. Colloid Interface Sci.

Biochim. Biophys. Acta

J. Biol. Chem.

Food Chem.

Methods Enzymol.

J. Biol. Chem.

J. Dairy Sci.

Methods Enzymol.

Food Chem.

LWT-Food Sci. Technol.

J. Lipid Res.

Food Chem.

Biomaterials

Biochim. Biophys. Acta: Protein Struct. Mol. Enzymol.

Polymer

Colloids Surf. A

Food Hydrocolloids

Food Hydrocolloids