Encapsulation of aqueous extract of Arctium lappa L. root and study its effect on physicochemical and functional properties of Synbiotic orange-carrot juice

Nowadays, there is a great tendency to consume functional foods, with special medicinal and extranutritional value in addition to basic nutritional properties. Foods containing probiotics and prebiotic compounds are classified in this category. Inulin is a water soluble storage polysaccharide and belongs to a group of non-digestible carbohydrates called fructans. Inulin is naturally present in some flowering plant species such as chicory and burdock root. The amount of inulin in these plants is in the range of 1 to 20% of the weight of the fresh plant. Pharmacological studies report that Burdock root contains significant amounts of the inulin as a prebiotic compounds, also exhibits a wide range of biological activities, specifically antioxidative, anti-inflammatory, and free radical scavenging activities. The aim of this study was to encapsulate the aqueous extract of burdock root and use it in a probiotic drink based on orange-carrot juice. 

The Burdock roots were obtained from the local medical plant market, Tehran, Iran. Orange and carrot juice were purchased from Nooshin and Tandis (Food Company, Tehran, Iran) respectively. Maltodextrin and gum Arabic were prepared from Merck, Germany. First, the plant roots were dried to 5.2% moisture and then its aqueous extract was extracted with the help of ultrasonication. Then burdock roots extracts were encapsulated by spray drying (microencapsulation) and freeze drying (nanocapsulation) using maltodextrin and gum Arabic as wall coating agents. Capsule properties including encapsulation efficiency, particle size distribution, moisture, density, structural properties, TPC and antioxidant were determined. Then the encapsulated extracts (at levels of 0.5 and 1%) and free extract were used in the formulation of probiotic orange-carrot juice and its effect on the survival of probiotic bacteria as well as physicochemical and sensory properties of the final product during 30 days in refrigerator (4±0.5 °C) were investigated. All experiments were carried out based on complete randomized design and the results represent the mean of at least three replicates. The data obtained were analyzed by the analysis of variance (ANOVA) using Minitab 16.0 statistical software. Significant differences between means were determined by Duncan’s multiple range test at a probability levels of P≤0.05. 

The results of encapsulation phase showed that Nanocapsules had higher efficiency and phenolic compounds content than microcapsules. The highest level of efficiency (92.75%) and phenolic compounds (0.385 mg GAE/g) and the smallest capsule particle size (14.33±0.22 µm) were observed in Nanocapsules prepared with gum Arabic. The SEM images showed that the produced capsules in terms of microstructure, had flaky/glassy and angular surfaces and did not have a regular shape. By adding different forms of the extract (free/micro/Nano) to the orange-carrot juice, it was found that its characteristics including viability of probiotics, formalin index, turbidity, viscosity and antioxidant activity were significantly enhanced during cold storage compared to the control (p<0.05). During refrigeration, turbidity, acidity and IC50 increased in all treatments, especially in the control sample, while other characteristics (including the viability of probiotic bacteria), showed a decreasing trend. Addition of different forms of burdock root extract did not have an adverse effect on the flavor and odor of the samples, so that, all treatments were acceptable. Therefore, based on the results of this study, it can be stated that encapsulated burdock root extracts, especially in the form of nanocapsulation, can be used to increase the viability of probiotics and enhancement the antioxidant activity of functional foods