Encapsulation of beetroot antioxidants by coacervation and optimization of the parameters using fractional factorial design

Most of the developed countries seek a solution against diseases of the modern life, e.g. cancer, allergies, obesity. Furthermore, the diets which supply fewer of certain nutrients such as the meals with the foods having high caloric content are held responsible for a range of illnesses. Accordingly, the consumers' interest in healthy eating is increasing day by day, as it is a well-known fact. This rising trend brings along the positive attitude of the consumer towards the dietary supplements, functional foods and nutraceuticals. While the dietary supplements gives the consumer to take the certain nutrients more, such as minerals, vitamins or essential amino acids whose recommended intake dosage the consumer can not reach with a regular diet; functional foods might be considered as the meals containing bioactive component. If a functional food is specialized for preventing or threating a disease then it is named as nutraceutical. The active component in these kinds of products are vitamins, minerals or in some cases it might be a fatty acid which have antioxidant activity. One of the limiting factors for the utilization of bioactive compounds in the formulation is the stability of the compound. Like most of the organic compounds, bioactive materials can keep theirselfs in the stable, especially during digestion. This instability problem results with very limited bioavailability of the active component. During degradation of bioactive compounds, they lose their biological activity and health benefits also. Another subject which is highly concerned about the bioactive compounds is their solubility and stability in the food matrix and the release rate and release mechanism during digestion. The solubility properties of materials can be related with the food quality, since it affects the texture and rheology of the food directly. The rate and mechanism of release are important parameters affecting the bioavailability of materials. Most of the bioactive components used in the products are derived from the plants, more specifically, from vegetables and fruits. Beetroot has been ranked among the most powerful vegetables due to its high antioxidant content. Beetroot contains high amounts of betalain which exhibits antioxidant activity. It is known that 55 different chemical structure of betalain is found in the nature. Betalains are classified in two groups; red-purple coloured betacyanins and yellow-orange coloured betaxanthins. The difference between the chemical structure of these two sub-classes is the chemical moiety combines with betalamic acid which is the main unit of the chemical structure of betalain. Betacyanins are formed of betalamic acid and cyclo-DOPA, while amino acids or amines takes the place oc cyclo-DOPA in the structure of betaxanthins. 95% of the total betacyanins in the beetroot is composed of betanin and isobetanin, and Vulgaxanthin I and Vulgaxanthin II are the betaxantins found in the beetroot. Besides its antioxidant function, betalains exhibit anticarcinogenic, antilipidemic and antimicrobial activities. Moreover beetroot is also the source of certain phenolic acids such as p-coumaric acid, protocatechuic acid, ferulic acid, vanillic acid, p-hydroxybenzoic acid and syringic acid. Phenolic acids represents one of the subclasses of phenolics – in other words, polyphenols. Phenolics are classified into two groups, i.e. flavonoids and phenolic acids which are non-flavonoid phenolic compounds. Phenolics acts as a antioxidants. Due to the hydroxyl moiety in phenolic structure, phenolic compounds donates hidrogen atom and reacts with reactive oxygen and nitrogen species. Thus, the free radical reactions are terminated. The aim of this study is to optimize the encapsulation parameters of antioxidants extracted from beetroot using maltodextrin, gum arabic and whey protein concentrate as wall materials. Encapsulation process variables were selected as extract ratio (%), pH and wall material composition. At the first and second part of this study, response surface methodology (RSM) and fractional factorial design were used for optimization of encapsulation, respectively. RSM was performed with encapsulation efficiency (%) responses on total phenolic content, DPPH and CUPRAC, size and zeta potential; however, the only response was taken into accont for KFT was encapsulation efficiency (%) on total phenolic content. The study was started by extracting antioxidant from the fresh beetroot samples purchased from local markets in Turkey. Afterwards, an experimental design was prepared with the help of Response Surface Methodology, which is one of the powerful optimization tools in order to optimize the encapsulation processes. According to the experimental design, fifteen different sample were prepared with different pH, core material ratio (%) and wall material composition. The homogenization process and drying process were conducted by ultrasound and spray dryer, respectively. The total phenolic content and the antioxidant capacity (CUPRAC and DPPH) of the powdered samples were measured and encapsulation efficiencies (%) were calculated on phenolic content and antioxidant activity for each sample. The encapsulation efficiency data was used as response with Response Surface Methodology. It was found that the results are not statistically significant (p>0.05). It can not be proved that independent variables; pH (X1), the core material ratio (%) (X2) and the wall material composition (X3) on the encapsulation efficiency, the particle size (X4) and the zeta potential (X5) of samples have a significant impact on the encapsulation process (p>0.05). A second experimental design was prepared and this time Fractional Factorial Design was used. The same parameters pH, core material ratio and the wall material composition analyzed with Response Surface Methodology were taken as the independent variables and the variables were the encapsulation efficiency on the total phenolic content. The range of pH and the core material ratio was extended from pH 3-5 to pH 3-8 and 0.2 % - 1% to 1% - 5%, respectively. For wall material composition only 2 alternatives of Maltodextrin: Whey protein concentrate:Gum Arabic at varying ratios were selected to be analyzed; one has Maltodextrin and Gum arabic at the ratio of 5:5 and the second mixture has Maltodextrin, Whey protein concentrate and Gum arabic at the ratio of 5:1:4. According to Fractional Factorial Design, eight samples were prepared. During sample preparation, the drying process was conducted by Ultrasound and Spray dryer, respectively, the same as previous design. The zeta potential and particle size of the samples were measured. Encapsulation efficiencies (%) were calculated according to the results of total phenolic content of the samples. It is found that the factors analyzed have no significant impact on encapsulation efficiency (p>0.05).