Iota-carrageenan/casein micelles interactions: evidence at different scales

The effect of temperature on the behaviour of iota-carrageenan (CI) 0.1 wt.%/casein micelles (CM) 0–5 wt.% mixtures has been studied using three techniques: confocal laser scanning microscopy (CLSM), differential scanning calorimetry (DSC) and spectrophotometry. The microscopy clearly shows that those mixed systems separate in two phases, one being enriched in CM. It has been shown that the CM concentration seems to have an effect on the extent of the phase separation phenomenon. The DSC experiments show that addition of CM modifies the helix to coil transition temperature of carrageenan. The enthalpy of melting of helices decreases as the CM concentration increases, and the peak is shifted towards higher temperature. Local electrostatic interactions between carrageenan chains and CM have been studied by a spectrophotometric method using methylene blue (MB) properties of absorption. The absorption spectra of MB in presence of CI and CM were compared with the one of MB in presence of carrageenan alone at temperatures above and below the carrageenan coil to helix transition. The modifications of the spectrum by addition of CM are discussed in terms of interactions and rigidification of the carrageenan chains.     

Gamma radiation synthesis of rapid swelling superporous polyacrylamide hydrogels

In this report a simple route for gamma radiation induced synthesis of superporous hydrogel (SPH) is described. Conventional SPH synthesis requires foaming and cross-linking reactions to take place simultaneously. However, in radiation synthesis it is difficult to introduce foaming during the cross-linking reactions. In order to overcome this limitation, the foaming and radiation cross-linking reactions were decoupled and carried out in two stages. The polyacrylamide SPH synthesized by this approach has very fast swelling kinetics compared to the non-porous hydrogel.     

Molecular interactions of plant and algal polysaccharides

This article presents an overview of the interaction in solution of certain plant and algal polysaccharides with cations and also of their interaction in admixture with other polysaccharides and proteins. The mechanism of gelation of pectin and alginate in the presence of calcium ions is discussed together with the specific binding of potassium ions to kappa carrageenan and its influence on the coil–helix transition. The associative and segregative phase behaviour that is encountered in aqueous solutions of mixed polysaccharide systems is considered together with the formation of the soluble and insoluble complexes in mixtures of polysaccharides and proteins.     

Syneresis of Carrageenan Gels: NMR and Rheology

Abstract

A novel and quick method to predict the syneresis of carrageenan gels using ¹³³Cs NMR is proposed. Cesium ions in carrageenan undergo a sharp change in mobility while cooling. By correlating that to the mobility of the polymer chains, we can identify a transition from a mobile gel to a frozen “glassy state” as a function of temperature and ion concentration. The demarcation between gel and glass distinguishes between systems that synerese over long times and those that do not. This is supported by rheological measurements that show that the modulus remains constant over time at temperatures below the transition temperature.     

The effect of the linear charge density of carrageenan on the ion binding investigated by differential scanning calorimetry, dc conductivity, and kHz dielectric relaxation

The effect of the linear charge density of natural polyelectrolyte, carrageenan, on the ion binding to carrageenan molecules in relation to the gelation was investigated by using the dielectric relaxation spectroscopy, dc conductivity, optical rotation, and differential scanning calorimetry (DSC). Although carrageenan is an anionic polysaccharide, carrageenan molecules in the helix state at low temperatures can bind not only cation, such as potassium and cesium, but also anion, such as iodide. The dc conductivity steeply decreases just below the coil–helix transition temperature, which indicates the binding of ion to the carrageenan molecules in the helix state due to the increase of the linear charge density compared with that in the coil state. The addition of NaI promotes the helix formation, and prevents from aggregation of helices, which was suggested by the results of the dynamic shear modulus and the DSC, and resulted in an increase of the relaxation amplitude of the lowest frequency relaxation (kHz) attributed to the fluctuation of the tightly bound counter ions along the high charge density region (helix). It is concluded that binding of iodide induces (1) the increase in the amount of tightly bound counterions to carrageenan molecules and (2) the formation of non-aggregated helix.     

基于带强负电性物质作电极界面的电流型转铁蛋白免疫传感器的研究

将角叉胶、溶胶—凝胶与碳粉相结合,构成了一种具有强负电性可更新电极界面,用于静电吸附固定免疫材料,研制成一种安培型转铁蛋白免疫传感器。研究了电极膜组成、工作电位、底物pH、酶标转铁蛋白浓度及培育时间等实验条件对响应电流的影响。响应电流与转铁蛋白浓度在1．5～60mg／L范围呈线性关系：检出限为1．5mg／L。将传感器初步用于人血清中转铁蛋白的测定,结果良好。     

Application of Carrageenan extract from red seaweed (Rhodophyta) in cosmetic products: A review

Cosmetic industries have expanded globally and will continue to increase as there are consumers. Nowadays, the interest starts to incline towards cosmetics formulated using plant-based ingredients. Marine plants such as seaweed possess numerous natural polysaccharides. Carrageenan is one of the compounds that can be extracted from red seaweed (Rhodophyta). This natural polysaccharide is widely known to act as a thickener, stabilizer, and water-binding agent as well as have diverse biological activities that make it a suitable active ingredient in cosmetic products. The review paper is organized by starting with discussing the significant aspects related to carrageenan which are the source, structure, as well as general and biological properties of carrageenan that make it appropriate to be applied in cosmetics. This paper also highlighted the applications of carrageenan in cosmetics, followed by the extraction method and instrument used.     

κ-卡拉胶研究进展

结合作者的研究工作，综述了κ-卡拉胶(KC)的化学结构、性质、应用及热可逆凝胶化机理及金属离子促凝胶化的研究进展。     

Radiation effects on agar, alginates and carrageenan to be used as food additives

Agar, alginates and carrageenan are hydrocolloids that induce stabilization of physical properties of the food product during shelf life and prevention of undesirable changes such as moisture migration, gas cell coalescence or textural profile changes. In this work, agar, alginates and carrageenan was irradiated as powder with different doses (0–10 kGy) of Co-60 and the rheological functional performance of water solutions of these irradiated additives was studied. The results are analyzed taking in account the future applications of those additives in irradiated foods.     

Influence of the composition of milk-protein κ/ι-hybrid-carrageenan gels on product properties

κ/ι-Hybrid-types of carrageenan are often used for stabilisation of milk-based systems. However, real food systems vary in their composition, so it is of interest to investigate the influence of the product composition on the gel properties and storage stability. A response surface experimental design with four factors was analysed: casein:whey-protein ratio, concentration of carrageenan, KCl and CaCl₂ addition to the milk system. The characteristics of the gels were determined by oscillatory rheometry. In the statistical fitted model using all ingredients as parameters it was shown that the storage modulus G′ was linearly dependent on the minor ingredients KCl and CaCl₂. Non-linearity was seen for the influence of the concentration of carrageenan. As the total protein content was kept constant at 5%, the linear increase of G′ with higher casein amount can be explained by the known interactions between casein and carrageenan.