Optimization of Encapsulation by Ionic Gelation Technique of Cryoconcentrated Solution: A Response Surface Methodology and Evaluation of Physicochemical Characteristics Study.

María Guerra-Valle,Guillermo Petzold,Patricio Orellana-Palma

doi:10.3390/polym14051031

María Guerra-Valle, Guillermo Petzold + Show 1 more

Open Access

https://doi.org/10.3390/polym14051031

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Abstract

The objective of this study was to evaluate the optimal conditions to encapsulate cryoconcentrate solutions via ionic gelation technique. Hydrogel beads were prepared using alginate (1%, 2% and 3% (w/w)) and cornstarch (0.5%, 1% and 2% (w/w)). Later, a sucrose/acid gallic solution was concentrated through block freeze concentration (BFC) at three cycles. Thus, each solution was a mixture with the respective combination of alginate/cornstarch. The final solution was added drop-wise on a CaCl2 solution, allowing the formation of calcium alginate-cornstarch hydrogel beads filled with sucrose/acid gallic solution or cryoconcentrated solution. The results showed that alginate at 2% (w/w) and cornstarch at 2% (w/w) had the best efficiency to encapsulate any solution, with values close to 63.3%, 90.2%, 97.7%, and 75.1%, and particle sizes of approximately 3.09, 2.82, 2.73, and 2.64 mm, for initial solution, cycle 1, cycle 2, and cycle 3, respectively. Moreover, all the samples presented spherical shape. Therefore, the appropriate content of alginate and cornstarch allows for increasing the amount of model cryoconcentrated solution inside of the hydrogel beads. Furthermore, the physicochemical and morphological characteristics of hydrogel beads can be focused for future food and/or pharmaceutical applications, utilizing juice or extract concentrated by BFC as the solution encapsulated.

Highlights

Many studies have shown the potential of block freeze concentration (BFC)to improve different physicochemical properties and bioactive compounds from fruit juices, such as total soluble solid content [1], color [2], polyphenols [3], anthocyanins [4], and flavonols [5], and antioxidant activity [6]
In the BFC process, the liquid solution is completely exposed to freezing temperatures, and as the temperature decreases below the freezing point, the water turns into ice crystals, and in turn, the unfrozen fraction remains between the ice crystals by a counter-diffusion phenomenon, and once the freezing stage has finished, the cryoconcentrated solution can be extracted from the ice fraction by gravitational methods [7] or by external forces such as centrifugation [8], vacuum [9], or centrifugation-filter [10]
The optimization process by response surface methodology (RSM) indicated that alginate at 2% (w/w) and cornstarch at 2% (w/w) allowed for better efficiency of encapsulation of sucrose/acid gallic concentrated by block freeze concentration assisted by centrifugation than other alginate/cornstarch mixtures, where cornstarch filled the empty space of the alginate beads

Summary

Introduction

Many studies have shown the potential of block freeze concentration (BFC)to improve different physicochemical properties and bioactive compounds from fruit juices, such as total soluble solid content [1], color [2], polyphenols [3], anthocyanins [4], and flavonols [5], and antioxidant activity [6]. It is important to protect the cryoconcentrated solutions against different factors through a simple, versatile, practical, and economical technology, avoiding the color degradation and the progressive loss of nutritional properties. In the last few decades, the encapsulation by ionic gelation has emerged as an effective technology to contain liquid samples in biopolymer matrices due to the low temperatures involved in the encapsulation process, and this method allows minimal modification of the quality properties in the encapsulated solution [13]. The hydrogel beads obtained by ionic gelation have been widely used for the immobilization of different food solution, protecting important bioactive compounds, such as betacyanins [16], betaxanthin [17], and ellagic acid, quercetin, kaempferol, and caffeic acid [18], anthocyanins [19,20], and polyphenols [21]. To the best of our knowledge, the encapsulation of any cryoconcentrated solution by ionic gelation technique has not been reported

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