Encapsulation of stevia rebaudiana Bertoni aqueous crude extracts by ionic gelation – Effects of alginate blends and gelling solutions on the polyphenolic profile
Graphical abstract
Introduction
Encapsulation of polyphenolic-rich crude extracts constitutes a current research need since it can be incorporated in foods to act as a food additive, preventing or delaying food deterioration, as well as functioning as a nutritional supplement with health benefits, giving rise to innovative functional foods (Kurozawa & Hubinger, 2017). Encapsulation technologies have been extensively applied in the pharmaceutical, nutraceutical and food industries as an important tool to enhance the stability of bioactive compounds during processing and storage as well as to improve their bioavailability (McClements, 2015, Nedovic et al., 2011).
Ionic gelation through extrusion dripping represents a simple, efficient and low-cost encapsulation technique that does not require specialised equipment, high temperature, or organic solvents, making it suitable for both hydrophobic or hydrophilic compounds (Đorđević et al., 2015, Nedovic et al., 2011). Because of their ionic gelation properties and biocompatibility, sodium alginates are considered one of the most versatile, natural anionic polymers widely employed as an encapsulation agent of bioactive compounds, including plant extracts polyphenols (López-Córdoba et al., 2014, Lozano-Vazquez et al., 2015, Stojanovic et al., 2012). However, there are limitations commonly associated with hydrophilic bioactive compounds encapsulated with alginates, such as burst release mechanisms and loss by diffusion during gel formation and storage (Arriola et al., 2016, Gombotz and Wee, 2012).
Therefore, a current challenge in the design of carrier systems for water-soluble compounds, such as plant polyphenols, by ionic gelation is to increase encapsulation efficiency and enhance controlled release properties (Kurozawa & Hubinger, 2017). Current approaches include the use of filler materials within the polymer matrix, internal ionic gelation, coating as a barrier as well as the use of natural polymer mixtures (Kurozawa and Hubinger, 2017, Lozano-Vazquez et al., 2015).
Stevia rebaudiana Bertoni (stevia) is a perennial South American herb, also known as ka’a hee or sweet-leaf, originally native to the north-east region of Paraguay (Gaweł-Bȩben et al., 2015, Wölwer-Rieck, 2012). Besides its commercial application due to its foliar steviol glycosides with natural and intense sweetening properties, a growing body of research is pointing to stevia leaf extracts as a multifunctional source of natural bioactive compounds (Ruiz-Ruiz et al., 2015, Shivanna et al., 2013). Different therapeutic properties have been linked to stevia phytoconstituents that comprise vitamins, phytosterols, triterpenes, essential oil components, as well as polyphenols – mostly consisting of flavonoids and phenolic acids – associated with its anti-inflammatory and antioxidant properties (Gaweł-Bȩben et al., 2015, Karaköse et al., 2015, Molina-Calle et al., 2017, Wölwer-Rieck, 2012). Yet, despite the relevance of phenolic compounds, studies involving stevia crude extract characterisation are few and still emerging, especially compared to the extensive work published regarding its glycoside derivatives (Gaweł-Bȩben et al., 2015, Wölwer-Rieck, 2012).
In our previous study, the successful encapsulation of crude stevia extracts with alginates through ionic gelation was described for the first time in scientific literature (Arriola et al., 2016). However, both the alginate employed and the free and encapsulated polyphenolic profile of stevia lacked a thorough characterisation analysis. Furthermore, we observed a significant diffusional migration of phenolic compounds from stevia in and out of beads during both the ionic gelation process and during beads storage.
In this study, we hypothesise that the entrapment efficiency of stevia phenolic constituents by the formulated systems will be enhanced not only by employing alginate blends, but also by employing the extract in the crosslinking solution. Therefore, mixtures of sodium alginates with different molecular characteristics were formulated and characterised as carrier blends. The two blends were formed into plain alginate beads (no stevia in either the bead or the collecting solution) and two types of stevia-loaded beads which were either gelled in calcium chloride solution, or in calcium chloride dissolved in stevia extract. The structural and morphological differences between beads of the same blend and beads across blends were investigated using Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) analyses. Subsequently, secondary metabolites (phenolics and their derivatives) were identified through a comprehensive untargeted metabolomics profiling, an innovative approach in stevia publications.
Section snippets
Chemicals
The Folin–Ciocalteu reagent, gallic acid and calcium chloride dehydrate were purchased from Sigma-Aldrich (Poole, UK). Sodium alginates employed in this study were characterised using 1H nuclear magnetic resonance spectroscopy (ASTM F2259-12) (Chater et al., 2015, Wilcox et al., 2014). Alginates employed in the blend preparations included LFR 5/60, a low viscosity and low molecular weight (MW) (40,000) sodium alginate rich in guluronate Fg 0.64; SF120, a high viscosity and high MW (225,000)
Characterisation of alginate beads
In preliminary tests, all sodium alginates used as ingredients in the blends were assessed for their individual entrapment efficiency of total phenolic content of stevia extracts (data not shown). The alginate LFR5/60 (2% w/v) was selected as the main ingredient of both the blends since it showed the best encapsulation performance (data not shown).
Conclusions
Encapsulation of stevia crude extract within two alginate blends by ionic gelation has been assessed. The impact of carrier formulations and crosslinking conditions on the overall encapsulation performance was investigated aiming to overcome phenolic compound losses by diffusion and, thus, increase encapsulation efficiency. All the formulated stevia-loaded beads reached high encapsulation efficiency values (>60%), independent of the carrier combination or the crosslinking conditions.
Conflict of interest
The authors declare that they have no conflict of interest in this study.
Acknowledgements
This work was supported by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) through Programa de Doutorado Sanduíche no Exterior (PDSE) [99999.006878/2015-06].
References (35)
- et al.
Improving the controlled delivery formulations of caffeine in alginate hydrogel beads combined with pectin, carrageenan, chitosan and psyllium
Food Chemistry
(2015) - et al.
Alginate as a protease inhibitor in vitro and in a model gut system; selective inhibition of pepsin but not trypsin
Carbohydrate Polymers
(2015) - et al.
Comparison of spray, freeze and oven drying as a means of reducing bitter aftertaste of steviol glycosides (derived from Stevia rebaudiana Bertoni plant) - Evaluation of the final products
Food Chemistry
(2016) - et al.
Encapsulation of natural antioxidants extracted from Ilex paraguariensis
Carbohydrate Polymers
(2008) - et al.
Protein release from alginate matrices
Advanced Drug Delivery Reviews
(2012) - et al.
Hydrophilic food compounds encapsulation by ionic gelation
Current Opinion in Food Science
(2017) - et al.
Corn starch-calcium alginate matrices for the simultaneous carrying of zinc and yerba mate antioxidants
LWT – Food Science and Technology
(2014) - et al.
Effect of the weight ratio of alginate-modified tapioca starch on the physicochemical properties and release kinetics of chlorogenic acid containing beads
Food Hydrocolloids
(2015) - et al.
Trends in LC-MS and LC-HRMS analysis and characterization of polyphenols in food
TrAC Trends in Analytical Chemistry
(2017) Encapsulation, protection, and release of hydrophilic active components: Potential and limitations of colloidal delivery systems
Advances in Colloid and Interface Science
(2015)
Characterization of Stevia leaves by LC-QTOF MS/MS analysis of polar and non-polar extracts
Food Chemistry
Rapid and effective evaluation of the antioxidant capacity of propolis extracts using DPPH bleaching kinetic profiles, FT-IR and UV-vis spectroscopic data
Journal of Food Composition and Analysis
An overview of encapsulation technologies for food applications
Procedia Food Science
Alginate-based encapsulation of polyphenols from Clitoria ternatea petal flower extract enhances stability and biological activity under simulated gastrointestinal conditions
Food Hydrocolloids
Antidiabetic potential of bioactive molecules coated chitosan nanoparticles in experimental rats
International Journal of Biological Macromolecules
Antioxidant, anti-diabetic and renal protective properties of Stevia rebaudiana
Journal of Diabetes and Its Complications
The modulation of pancreatic lipase activity by alginates
Food Chemistry
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