Encapsulation of propolis with different methods: Investigation of optimum process conditions, storage stability, usability in model food systems and the effect on probiotic microorganisms

Objectives: The objectives of this study were to protect the contents of antioxidants and phenolic substances of propolis, allow the use of propolis as a component in food systems, and mask the bitter and unpleasant taste of propolis by microencapsulation. Propolis was microencapsulated by freeze-drying (FD) and spray cooling (SC) to suppress its unpleasant taste. Besides its use as a component in food systems, the project's objectives were to ensure its storage stability, inhibit its release in the mouth and stomach model systems, and maximize its release in the model intestine system. In addition, it was among the aims to investigate the usability of microencapsulated propolis particles obtained under optimum conditions by spray drying, freeze drying and spray chilling methods by adding them to model food systems (jelly, ice cream, buttermilk and cake). It also aimed to examine the effect of encapsulated and unencapsulated propolis on probiotics and on the lipid oxidation mechanism in peanut butter, a food product with high-fat content. Material and Methods: Propolis was microencapsulated by two different methods, freeze drying and spray chilling. The first step was determining the appropriate coating material combination specific to both approaches. After deciding the coating material combination specific to each encapsulation method, independent mixing and process variables (coating material mixing ratios, homogenization speed, as well as product thickness for the freeze drying method; air inlet temperature for the spray chilling) were selected. The freeze-drying method was targeted to maximize the encapsulation efficiency and maximum antioxidant content and minimize propolis powders' release in the mouth in the in vitro model gastrointestinal tract. For the spray chilling method, the optimization process was carried out by targeting the product yield of the powder particles, the encapsulation efficiency, the maximum amount of antioxidants, and the minimum release of propolis powders in the in vitro model oral gastrointestinal tract. Confirmation experiments were carried out at this point, determining optimum points for each encapsulation method. In the storage phase of the study, encapsulated propolis samples obtained by three different methods (spray drying (PK), freeze drying (DK) and spray chiling (PS) were stored for three months at 4°C and 25°C. In order to determine the storage stability, the changes in the physical and chemical properties and encapsulation efficiency were examined. The usability of microencapsulated propolis particles obtained under optimum conditions by spray drying, freeze drying and spray cooling methods was investigated by adding them into model food systems (jelly, ice cream, buttermilk and cake). The effect of the addition of encapsulated and unencapsulated propolis samples into peanut butter, a food product with high fat content, on the lipid oxidation mechanism was investigated by determining the peroxide value and induction time. Lactobacillus acidophilus DSM20079 was used to examine the effect of encapsulated and unencapsulated propolis on probiotics. Results: As a result of examining the powder product's physical and chemical properties and its emulsion properties, maltodextrin (MD)+whey protein isolate (WPI)+PGPR and WPI+PGPR were determined as coating materials for freeze-drying and spray cooling methods, respectively. The optimum processing conditions for the freeze-drying were 46.3% MD, 53.7% WPI, 11024 rpm homogenization speed, and 0.6 cm of product thickness. For the optimum spray cooling, the palm oil I ratio was 93.30%, palm oil II ratio was 6.70%, homogenization speed was 15000 rpm, and air inlet temperature was 10°C. As a result of the validation trials performed at the optimum point, there was no significant difference between the experimental results and the predicted results from the model. To determine the storage stability, the physical/chemical properties and encapsulation efficiency of the samples were evaluated. The stability of the encapsulated propolis powders was preserved during the 3-month. It was determined that microencapsulated propolis powders obtained under optimum conditions by spray drying, freeze-drying and spray cooling can be applied in a wide range of model food systems (jelly, ice cream, buttermilk and cake). As a result of the storage of peanut butter samples at 60°C to examine the effect of propolis powders on lipid oxidation, it was determined that the change in peroxide value of each of the peanut butter samples during storage was compatible with the 2nd order kinetic model. It was determined that each encapsulated sample had higher induction period values and lower peroxide values compared to the control samples. Lactobacillus acidophilus DSM20079 was used to examine the effect of encapsulated and unencapsulated propolis on probiotics. The inhibitory effect of unencapsulated propolis extract on L. acidophilus DSM20079, seen in both solid and liquid media, was determined. However, the impact of encapsulated propolis powders remained limited; thus, probiotic viability was effectively preserved. Conclusion: In this study, it was determined that the microencapsulation prevented propolis's beneficial components and suppressed its unpleasant taste. Therefore, it would be possible to add the microencapsulated propolis to various food items due to its ease of use compared to product forms available in the market.