The development and application of microencapsulation for enhanced retention of ascorbic acid during fortification of foods

Nizori, A 2013, The development and application of microencapsulation for enhanced retention of ascorbic acid during fortification of foods, Doctor of Philosophy (PhD), Applied Sciences, RMIT University.

Document type: Thesis
Collection: Theses

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Title The development and application of microencapsulation for enhanced retention of ascorbic acid during fortification of foods
Author(s) Nizori, A
Year 2013
Abstract Ascorbic acid (AA) is an essential nutrient that is extremely reactive and readily lost during processing of foods. Microencapsulation technology provides a potential strategy for enhancing the stability and retention of AA in food. The aims of the current study have been to investigate: the microencapsulation of AA, the optimum loading rates of AA, varying loading rates of hydrocolloids, optimal condition of spray drying process and the resultant microcapsules have been characterized. In addition, the incorporation of the resultant capsules into baked bread has been evaluated. Spray drying on a pilot scale was used to produce the microcapsules and capillary electrophoresis has been applied to analysis of AA. Structure of microcapsules was investigated using environmental scanning electron microscopy. In addition, central composite designs were developed for optimal conditions spray drying. A preliminary investigation was carried out on the use of various loading rates of AA on preparation of hydrocolloids for spray drying. Also the characteristics of microcapsules and loss of AA during processing by spray drying was analysed and it was found that microcapsules had good structure and integrity when loading rates were within the range of the designed model (6-54%). At levels beyond this, capsules appeared to lack integrity. Loading rates also had a significant effect on loss of AA, increasing the loading rates tended to decrease the loss of AA until optimum loading rates were reached (9-18%) and from then the loss of AA increased dramatically with increasing loading rates. The impact of varying hydrocolloid proportions was also studied, particularly the effect of core loading and binding agent rates. There were significant influences of core loading and binding agent rates on yield, AA retention, moisture content, water activity and particle size distribution of microcapsules. The optimal combinations of hydrocolloid proportions were established by varying the inlet air temperature (100 - 120 °C) and feed flowrate (within the range of 7-14 mL/min).

The results demonstrated the potential of microencapsulation by spray drying as a means to enhance AA retention. Vitamin retention, moisture content, water activity and process yield were influenced positively by increasing inlet air temperature and negatively as feed flow rate were decreased. Finally, using the best combination of hydrocolloids and optimum conditions of spray drying, microcapsules have been incorporated into baked products. The different loading rates of encapsulated AA on retention during different step of bread-making were evaluated. It was found that high recovery retention of AA in white bread loaf was achieved when rice starch, alginic acid and low methoxyl pectin were used as wall materials. In summary, a promising application of microencapsulation technology for encapsulated AA was found for bread loaves with high retention of AA. Spray drying also has been found to provide a convenient approach where high yields of microcapsules were produced. These findings provide an effective way to enhance the stability of AA used in fortifying loaf breads. Accordingly further studies are warranted and it is recommended to encompass a wider range of food products.

Degree Doctor of Philosophy (PhD)
Institution RMIT University
School, Department or Centre Applied Sciences
Keyword(s) ascorbic acid
vitamin retention
vitamin stability
wall materials
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Created: Fri, 01 Aug 2014, 10:40:25 EST by Denise Paciocco
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