Optimization of spray-drying conditions for microencapsulation of Citrus x paradisi L phenolics using maltodextrin and skim milk as wall materials

Abstract

Introduction: Spray drying is widely utilized for encapsulating biologically active compounds to enhance their stability and protection against environmental factors [1]. In this study, we aimed to investigate the effects of various conditions and optimize the composition of wall materials for the microencapsulation of phenolics extracted from Citrus x paradisi L fruit peels [2]. Maltodextrin and skim milk were employed as wall materials to encapsulate grapefruit extracts and naringin. Keywords: Spray drying, Microencapsulation, Citrus x paradisi L, Maltodextrin, Skim milk, Phenolics Methods: The preparation of the ethanolic extract from Citrus x paradisi L fruit peels involved the drying and grinding of peels, followed by extraction with 50% v/v ethanol. After centrifugation and filtration, the resulting flavanone extracts were used for further encapsulation. The wall material solution of maltodextrin and skim milk was mixed with the ethanolic extract to prepare the liquid for spray drying. The wall material solutions were designed by wetting the required amounts of maltodextrin 10 g and skim milk 10 g in purified water at 22–25°C for 12 hours, then dissolved using a magnetic stirrer hotplate for 30 minutes. Spray-drying was carried out using a Buchi B-291 Mini Spray-Dryer under varying experimental conditions, including inlet temperatures of 90, 120, and 160°C, outlet temperatures ranging from 25 to 80°C, a spray flow feed rate of 30 mL/min, air pressure in the range of 6-8 bar. The resulting spray-dried powders were collected and stored in a refrigerator at +4–7°C to prevent undesirable changes in material properties. Results: The analysis of the spray-dried powders revealed different yield percentages and moisture content under distinct spray-drying conditions. The following table summarizes the results: Table 1. [...]. Conclusion: Among the tested conditions, the spray-drying process conducted at an inlet temperature of 160°C, an outlet temperature of 80°C, a flow rate of 30 mL/min, and an air pressure of 6-8 bar yielded the highest percentage (52.95%) of microcapsules loaded with phenolics. Furthermore, this condition resulted in the lowest moisture content (5.97%) within the spray-dried product. Hence, these specific conditions are considered the most optimal for achieving successful microencapsulation of Citrus x paradisi L phenolics using maltodextrin and skim milk as wall materials.