Elsevier

Journal of CO2 Utilization

Volume 63, September 2022, 102125
Journal of CO2 Utilization

Role of supercritical CO2 impregnation variables on β-carotene loading into corn starch aerogel particles

https://doi.org/10.1016/j.jcou.2022.102125Get rights and content

Highlights

  • Corn starch aerogels were impregnated with β-carotene using supercritical CO2.

  • The impregnation yields were measured at 15 & 30 MPa and 40 & 60 °C.

  • The impacts of depressurization rates and number of cycles were also examined.

  • The highest impregnation yield was 0.96 mg β-carotene/g aerogel.

Abstract

β-carotene is a natural dye with antioxidant and provitamin A activities, which has essential roles in human health. However, its direct use in food products is unviable since it is susceptible to oxidation, easily isomerization under light, heat or acids, and has low water solubility and oral bioavailability. To address this issue, this work reports, for the first time, the impregnation of β-carotene into corn starch aerogels using supercritical carbon dioxide (sc-CO2). The aerogel particles were produced by the emulsion-gelation method, dried by sc-CO2 and loaded with β-carotene by sc-CO2 impregnation. The impacts of pressure (15 and 30 MPa), temperature (40 and 60 °C), average depressurization rate (0.25–2.61 MPa/min), and cycles (1−4) were investigated on loading. Excepting depressurization rate, all variables played fundamental roles in loading, reaching a maximum of 0.96 mg β-carotene/g aerogel (30 MPa, 40 °C, 0.40 MPa/min, four cycles).

Introduction

β-carotene is a natural dye with bioactive attributes such as antioxidant and provitamin A activities. However, it is susceptible to oxidation due to the presence of unsaturated compounds in its structure, and it is easily isomerized when exposed to light, heat, and acids. Low oral bioavailability, low water solubility and high melting point of β-carotene also compromise its use in food systems, especially in high humidity products (beverages, sauces, and desserts) [1]. Therefore, several techniques have emerged to enhance the stability and functionality of poorly water-soluble dyes, like β-carotene, by synthesizing delivery systems such as nanoemulsions, solid lipid nanoparticles [2], [3], [4], [5], and supercritical impregnated aerogels [6].

Aerogels are solid materials with high porosity and surface area, produced by replacing the liquid in a gel with gas while keeping the gel structure unchanged. Recently, aerogels fabricated from natural polymers (bioaerogels) have been highlighted due to their bioavailability, safety, and biodegradability [7]. Considering food industries, starch is a promising and suitable alternative for aerogel formulation as it is cheap and generally recognized as a safe (GRAS) [8], [9], [10], [11], [12], [13]. Starch aerogels can be obtained from several sources, namely, potatoes, corn, cassava, peas, among others. Chemically, starch macromolecules are formed by two main components, amylose and amylopectin, which are alternately arranged to create a semi-crystalline structure. Amylose has a linear structure, while amylopectin is highly-branched, with a relative proportion of these components varying depending on the starch source [14], [15], [16]. Three main steps are described in the production of starch aerogels: (1) hydrogel formation based on gelatinization and retrogradation properties, (2) water replacement in the gel structure with an appropriate organic solvent such as ethanol, and (3) removal of the alcoholic phase using supercritical CO2 (sc-CO2) drying [17], [18]. The use of starch in the synthesis of aerogels allows creating solid networks with different geometric shapes, such as monoliths, microspheres and microparticles. Starch aerogels in form of microparticles are highly recommended when the objective is the incorporation of target compounds, such as β-carotene, which stands out for its bioactivity and wide distribution in the nature [19], [20].

Supercritical impregnation is an environmentally sustainable process that uses CO2 as a mean to incorporate active agents into solid materials through interactions, such as Van der Waals or hydrogen bindings, between functional groups of an active substance and polymer, or physical entrapment due to the depressurization step [21], [22], [23], [24]. This technique is able to impregnate solid matrices with high efficiency and without requiring toxic solvents, under high diffusion coefficient, and mild supercritical conditions [19], [25], [26], [27]. It has been widely reported in the literature that the impregnation of hydrophilic aerogels (such as starch aerogels) with poorly water-soluble drug enhances the drug solubility in water [28], [29]. The reason is that once the impregnated aerogel is subjected to aqueous solution, the carrier is dissolved and the drug is released in the form of small colloidal particles with high specific surface area, which therefore causes higher dissolution rate of the drug [30]. The impregnation of starch aerogels can also enhance the controlled release of β-carotene in foods and nutraceuticals. One of the main challenges in supercritical impregnation is finding the best process conditions for efficient impregnation without changing the physical properties of structured matrices, such as aerogels. Literature presents several hundred works on the use of this technique for the carriage of polymers with medicines [31], food packaging [32], [33], [34], [35], [36], [37], and functional compounds in pharmaceutical materials [38]. sc-CO2 was used to impregnate α-tocopherol and menadione in a maize starch aerogel [39]. The maximum impregnation for both components was obtained under 15 MPa and 60 °C, which was 19.99 wt% for α-tocopherol and 8.76 wt% for menadione. In another relevant work, a one-pot process was developed to fabricate starch aerogel and to impregnate it with green coffee oil [40]. The highest impregnation yield (39 wt%) was obtained under 30 MPa and 40 °C for 12 h.

Few works applied sc-CO2 impregnation in aerogels, and to the best of our knowledge, there are no works reporting the production of corn starch aerogel impregnated with β-carotene. Thus, the main objective of the presented work was to evaluate the effect of process variables (e.g. pressure, temperature, depressurization rate, and the number of impregnation cycles) on the β-carotene loading in corn starch aerogels using sc-CO2, as well as the morphological and physico-chemical properties of the aerogel.

Section snippets

Materials

Corn starch was kindly donated by Ingredion Ing. Ind. Ltda. (São Paulo, Brazil), commercial soybean oil (Soya, Bunge Brazil) was purchased in a local market (Campinas, Brazil), and Span® 80 was acquired from Sigma-Aldrich (St. Louis, USA). Absolute ethanol (≥99.5%, v/v) and carbon dioxide (≥99.0%) were, respectively, purchased from Synth (Diadema, Brazil) and White Martins (Campinas, Brazil). β-carotene standard (≥93.0%) was purchased from Merck Group (Darmstadt, Germany) and petroleum ether

Effects of depressurization rate, pressure, temperature and number of cycles on β-carotene loading

The effect of average depressurization rate (0.45 and 2.61 MPa/min) on the loading of β-carotene in corn starch aerogels was evaluated at 30 MPa and 60 °C. The average depressurization rates of 0.45 and 2.61 MPa/min were obtained by releasing the CO2 inside the vessel at constant flow rates of 1.79 and 10.43 g CO2/min, respectively. For better comprehension, Fig. 2 represents the exact pressure profile along the depressurization under two CO2 flow rates. These profiles, which are nonlinear,

Conclusions

This work investigated the production of corn starch aerogel particles by the integration of emulsion-gelation method with sc-CO2 drying, and sc-CO2 impregnation of aerogels with β-carotene. The highest β-carotene loading (0.96 ± 0.07 mg β-carotene/g aerogel) was obtained at 30 MPa, 40 °C, average depressurization rate of 0.40 MPa/min and four cycles.

Thermo-physical analyses confirm amorphous and polyamorphic states of corn starch aerogels. Nitrogen adsorption-desorption graphics showed the

CRediT authorship contribution statement

Arthur Luiz Baião Dias: Conceptualization, Methodology, Investigation, Writing – original draft, Writing – review & editing, Funding acquisition. Tahmasb Hatami: Software, Formal analysis, Investigation, Writing – original draft, Writing – review & editing, Funding acquisition. Juliane Viganó: Conceptualization, Methodology, Investigation, Writing – original draft, Writing – review & editing, Funding acquisition. Erick Jarles Santos de Araújo: Writing – original draft. Lucia Helena Innocentini

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments

The authors would like to thank Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) [grant numbers 151005/2019-2, 408285/2018-4, 303063/2018-1], Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) [grant number 2017/2367-2, 2018/18722-6, 2018/23769-1 and 2020/15774-5] for financial support. This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior – Brazil (CAPES) [Financial code 001].

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      The use of SFI to deliver nonpolar bioactive components in starch aerogels has only been reported a few times so far, mainly evaluating the loading of coffee oil, phytosterols, and fat-soluble vitamins (De Marco et al., 2018, 2019; Franco et al., 2018; Milovanovic et al., 2015; Ubeyitogullari and Ciftci, 2017; Villegas et al., 2019). Our research group has recently investigated the role of SFI variables in beta-carotene loading in corn starch aerogels (Dias et al., 2022). Currently, no studies report the SFI impregnation of phenolic compounds into starch aerogels.

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