Handbook of Vitamin C Research

198Magdalena Stevanović and Dragan UskokovićCheng et al. introduced a new method with practical value of intercalating and stabilizingvitamin C within an inorganic layered material montmorillonite (MMT) [123]. Toxicityassessment pointed out the margin of safety and toxicity rankings for feasibility of L-ascorbicacid-montmorillonite (LAA-MMT) composites in practical applications.Production of methacrylate microparticles for the delivery of ascorbic acid via the oralroute was described by Esposito et. al.[71] . As polymers different acrylic compounds wereconsidered, namely Eudragit® RL, L and RS [71]. Results indicates that the release pattern ofthe vitamin C is slowly influenced by Eudragit® type or mixture used for microparticleproduction. Differently from other studies [124] were the release kinetics of the encapsulateddrug is clearly dependendent from the different solubility of the polymers at the pH of thereceiving buffer, in this case the release rate of the drug does not seem to be heavily affectedby the nature of the polymer.Carnauba wax was used in melt dispersion method of microencapsulation. Results showspherical particles with encapsulated ascorbic acid of approximately 50 μm in size [96, 125].Hydrated zinc oxide has high biocompatibility and skin affinity, so it can be applicable asthe cosmetic ingredient [87, 114]. It was very often used as an inorganic matrix forimmobilization anionic L-ascorbate species, since it has positive surface charge. Theimmobilizedated vitamin C shows superior storage stability in aqueous medium compared tothe pure sodium L-ascorbate, and an excellent time-controlled releasing behavior [87].7. Characteristics of Ascorbic Acid Nano andMicroparticles Prepared by Different MethodsEncapsulation efficiency, release rate, size distribution of particles with encapsulatedascorbic acid, are some of the parameters which are used for evaluating encapsulation systemcharacteristics.Uddin et al. studied the effect of process variables on ascorbic acid characteristics [96].They chose four different encapsulation techniques – thermal phase separation, meltdispersion, solvent evaporation and spray drying.Ascorbic acid is highly oxidative which can cause a problem in food systems. In theprocessing stage, it can change colour from white to yellow which affects food colours. Also,it can react with other ingredients and bring about undesirable changes in the colour and tasteof the food. The results show that microencapsulated ascorbic acid could prevent the ascorbicacid color change, retard its core release rate, and generally mask its acid taste [96]. In thethermal phase separation, molecular weight of ethyl cellulose and the addition ofpolyisobutylene significantly influenced the aggregation and release rate of microcapsules.Results show that there is a significant difference in release ratios with different molecularweights of ethyl cellulose. The higher the molecular weight, the lower is the initial releaserate. Molecular rate was not a factor for complete release as high or low molecular weightgave a release rate of ~1.0 in 20 minutes. This compares favourably to free ascorbic acid,which achieved a release ratio of 1.0 after only 20 seconds of dissolution.In the melt dispersion method, spherical particles were prepared by using carnauba wax[96]. The ascorbic acid release rate was found to be slower in the case of carnauba-