Bioactivity of Encapsulated Lemon Peel Phenolics as Affected by Maltodextrin and Foam Mat Drying

Lemon peel constitutes a cheap potential resource for bioactive phenolics with antioxidant, antihypertensive, and antidiabetic activities. However, phenolic compounds are sensitive to environmental conditions and lose their activity during processing and storage without protection. In this study, a phenolic extract obtained from lemon peel was encapsulated to protect its bioactivity. For this purpose, two maltodextrins with 6- and 19-dextrose equivalent (6DE, 19DE) and whey protein concentrate were used along with foam mat drying (FMD) and foam mat freeze-drying (FMFD). The effects of maltodextrins and drying method were evaluated by determination of encapsulation efficiency, physicochemical properties, in vitro antihypertensive, and antidiabetic activities of the encapsulated extracts. In addition, encapsulated extracts were stored under adverse conditions to determine storage stability. All the encapsulated extracts were found to be in a glassy state. Maltodextrin with 6DE was the best wall material protecting the phenolic content. FMD with maltodextrin 6DE provided the highest encapsulation efficiency (97.6%) and hesperidin content (45 mg/100 g dm). On the other hand, FMFD with maltodextrin 6DE resulted in the highest glass transition temperature (97.1°C), total phenolic content (6.63 mg GAE/g), and antioxidant activity (17.6 mg TE/g). ACE inhibitory activities of the encapsulated extracts were above 75% but reduced to less than 50% after storage regardless of maltodextrin DE and the drying method. FMFD with maltodextrin 19DE yielded 71% α-amylase inhibitory activity, which was higher than those of the other samples. α-amylase inhibition increased up to 83% after storage with no significant effect of maltodextrin DE and drying method. Results showed that the wall materials used in encapsulation also have an influence on the bioactivities besides the lemon peel extract. Both FMD and FMFD along with maltodextrin 6DE can be used for encapsulation. However, FMD can be preferred as a practical method with low equipment and energy costs and short processing time.