Double (iron and zinc) fortified black tea : assessing the bioaccessibility and bioavailability using spray drying microencapsulation technology

Fortification of black tea with iron and zinc has the potential to reduce the prevalence of iron and zinc deficiency in the developing world. Tea is an ideal vehicle for food fortification because it is the second most consumed beverage globally, aside from water, and is consumed throughout the world independent of socioeconomic strata. Unfortunately, polyphenolic compounds present in tea form complexes with iron, which cause colour changes. The formation of this intensely blue-purple non-bioavailable iron-polyphenol complex is a barrier to consumer acceptance and the public health effectiveness of iron-fortified tea. The objective of this study was to develop and assess the fortification of tea with microencapsulated iron and zinc to increase their absorption, and that could prevent the formation of the iron-polyphenol complex in tea. Whey protein isolate and Eudraguard® that either provide gastric and intestinal protection and increase bioaccessibility of iron and zinc in the human body, were used as coating materials for the development of the microencapsulated iron and zinc. A response surface design was used to optimize the encapsulation efficiency of iron and zinc in the microcapsules. The microcapsules were subjected through a simulated gastric and intestinal digestion, whereas the microcapsules showed higher resistance to intestinal conditions. Absorption studies performed using a Caco-2 cell model revealed that the iron delivered through the microcapsules increased cellular absorption by 73%. Zinc from the microcapsules also increased cellular absorption by 81%. The iron-polyphenol complex is dependent on the pH, therefore, the use of MES and PIPES buffers was investigated for the measurement of the iron-polyphenol complex formation. The results show that MES buffer at 0.2M and pH 5.5 can be used to quantify the iron-polyphenol complex in a polyphenolic model system (gallic acid), closely resembling tea. The prevention of the iron-polyphenol complex formation was further investigated with the microencapsulated iron and zinc using a gallic acid and brewed tea. The microcapsules slowed down the formation of iron-polyphenol complex in tea by 60% within 30 minutes of tea brewing. The results of this thesis have the potential to guide the path to reduce micronutrient deficiencies, through fortification of commonly consumed tea with iron and zinc.Land and Food Systems, Faculty ofGraduat