Floral parts of Gomphrena globosa L. as a novel alternative source of betacyanins: Optimization of the extraction using response surface methodology
Introduction
Colour is often the first sensory quality by which we judge all the things that surrounds us including food and food products. Colorants have been used for a long time in the food industry, and the major reason is to improve the attractive and appetizing of foods for the final consumer (Chen, Mou, Hou, Riviello, & Ni, 1998). This kind of additives are also used to compensate the colour loss due to the conditions of manufacturing and storage, enhance natural colour, provide colour to a colourless food, but also to allow the consumers to identify some products by sight (González, Gallego, & Valcárcel, 2002).
Food dyes or colorants can be classified as natural (or nature-identical) or synthetic; natural dyes when compared with the synthetic ones have a lower tinctorial strength, and are more sensitive to environmental conditions such as light, temperature, pH, among others. Due to their potential harmful features, the usage of most synthetic pigments has been restricted, becoming extremely important the application of natural colorants in the food industry (Amchova et al., 2015, Martins et al., 2016). This relates not only to the restrictions in using synthetic dyes, but also to the need to satisfy consumers, which over time become more and more demanding about the quality of the products they are purchasing.
Today, most consumers prefer foods without additives or with natural additives in place of the synthetic ones, which have been associated with some toxic effects (Gengatharan, Dykes, & Choo, 2015). There are many natural dyes used in the food industry, in particular carotenoids, anthocyanins and betalains. The betalains are very similar to the anthocyanins, and include compounds having colours ranging from red-violet (betacyanins) to yellow-orange (betaxanthins) (Carocho, Morales, & Ferreira, 2015). Betacyanin structures have some variations in the acyl groups and sugar moieties; the basic structural unit of most of the betacyanins is betanidin, followed by its C15 epimer, so a considerable number of different betacyanins can be obtained by glycosylation of one of the hydroxyl groups (Delgado-Vargas, Jiménez, & Paredes-López, 2000).
Table 1 shows a bibliographic summary of betalains content from different plant materials. Among the various sources of betalains, the most explored one is red beet (Beta vulgaris L.), due to its very high concentration in these pigments (Nemzer et al., 2011), but there are less explored alternative sources, such as flowers from the amaranthaceae family, Gomphrena globose L. Native to Latin America and commonly known as globe amaranth, this plant contains a variety of compounds with biological activity, being betacyanins one of them. Therefore, this plant is a good candidate as an alternative source to obtain the mentioned pigments (Roriz, Barros, Carvalho, Santos-Buelga, & Ferreira, 2014).
Different solid-liquid systems (maceration, microwave, ultrasound, among many others) are available for the extraction of compounds. There is not a universal approach better than the others, focussing in reducing the time of extraction, amount of solvents, the energy costs and the degradation patterns (Alonso-Salces et al., 2001, Dai and Mumper, 2010, Ince et al., 2013). Betacyanins are generally extracted by maceration extraction technique with water as the main solvent, but aqueous organic solvent mixtures have shown certain improvements in the final extractions yields obtained. Maceration extraction is a conventional method easily transferable to industrial scale and traditionally used in the extraction of bioactive compounds. The main advantage is its simplicity, but if the variables are not properly optimized, very often requires long time periods and high temperatures resulting in high-energy costs and bioactive compounds degradation.
The maceration extraction depends on several process variables whose values cannot be generalized for all matrices due to their specificity in terms of composition and target compounds. Thus, the optimization of the variables involved in the process is needed to select the best conditions to ensure a maximum yield, minimum time, energy and solvent consumption, squeezing the utmost from the maceration system. Traditionally, optimization is achieved by monitoring the influence of one factor at a time. However, by using the response surface methodology (RSM), optimization is done simultaneously and in a more precise manner obtaining polynomial models able to describe within the experimental range tested the optimal conditions that maximize the response criteria used (Bezerra et al., 2008, Ferreira et al., 2007, Kalil and Maugeri, 2000).
Therefore, the aims of the present study were: 1) to develop a process in a pre-industrial form for the isolation of the floral parts (mainly bracts and bracteoles of G. globosa flowers); and 2) optimize the primary variable conditions of the maceration system (time, temperature, ethanol-water proportion and solid-liquid ratio) and maximize betacyanins extraction assisted by the statistical RSM technique, contributing to the understanding of the potential of betacyanins from G. globosa for industrial applications.
Section snippets
Reagents
Acetonitrile of HPLC grade and ethanol p.a. were purchased by Fisher Scientific (Lisbon, Portugal). Water was treated in a Milli-Q water purification system (TGI Pure Water Systems, Greenville, SC, USA). All other chemicals and solvents were of an analytical grade and purchased from common suppliers.
Sample collection
Gomphrena globosa L. plants were purchased by Ervital, a Portuguese company from Castro Daire, established in a mountain region full of diversity. This company markets different certified plant
Producing food colorants from the floral part of G. globosa
The pigmented portion of the plant is only a part of the inflorescence, so to not compromise the effectiveness of the process it is necessary to separate the parts of interest from the remaining plant material. This will increase the effectiveness of the pigment extraction, without the interference of other portions of the plant that are not pigmented. To overcome this problem a mechanical separation process was used for isolating the pigmented parts (bracts and bracteoles) from the flowers
Conclusions
Betacyanins are betalain pigments that display a red-violet colour that have been reported to be three times stronger than the red-purple-blue dye produced by anthocyanins. The applications of betacyanins cover a wide range of matrices, mainly as additives or supplements in the food industry, cosmetics, pharmaceuticals and livestock feed. Although being less commonly used than anthocyanins and carotenoids, betacyanins are stable between pH 3 and 7 and well suited for colouring low acid
Acknowledgements
The authors thank the Foundation for Science and Technology (FCT, Portugal) and FEDER under Programme PT2020 for financial support to CIMO (UID/AGR/00690/2013) and L. Barros (SFRH/BPD/107855/2015) grant. To POCI-01-0145-FEDER-006984 (LA LSRE-LCM) funded by ERDF through POCI-COMPETE2020 and FCT. To Xunta de Galicia for financial support for the post-doctoral researcher of M.A. Prieto. The authors also thank Ana Maria Carvalho for the plant donation and Celestino Santos-Buelga for the preparative
References (40)
- et al.
Pressurized liquid extraction for the determination of polyphenols in apple
Journal of Chromatography A
(2001) - et al.
Health safety issues of synthetic food colorants
Regulatory Toxicology and Pharmacology
(2015) - et al.
Response surface methodology (RSM) as a tool for optimization in analytical chemistry
Talanta
(2008) - et al.
Natural food additives: Quo vadis?
Trends in Food Science & Technology
(2015) - et al.
Determination of eight synthetic food colorants in drinks by high-performance ion chromatography
Journal of Chromatography A
(1998) - et al.
SOLVERSTAT: A new utility for multipurpose analysis. An application to the investigation of dioxygenated Co (II) complex formation in dimethylsulfoxide solution
Talanta
(2003) - et al.
Box-Behnken design: An alternative for the optimization of analytical methods
Analytica Chimica Acta
(2007) - et al.
Betalains: Natural plant pigments with potential application in functional foods
LWT – Food Science and Technology
(2015) - et al.
Automatic screening method for the rapid and simple discrimination between synthetic and natural colorants in foods
Analytica Chimica Acta
(2002) - et al.
Optimized microwave-assisted extraction of phenolic acids from citrus mandarin peels and evaluation of antioxidant activity in vitro
Separation and Purification Technology
(2009)
Optimization of ultrasound-assisted extraction to obtain mycosterols from Agaricus bisporus L. by response surface methodology and comparison with conventional Soxhlet extraction
Food Chemistry
Functional significance of betalain biosynthesis in leaves of Disphyma australe under salinity stress
Environmental and Experimental Botany
Separation of amaranthine-type betacyanins by ion-pair high-speed countercurrent chromatography
Journal of Chromatography A
Separation of betalains from berries of Phytolacca americana by ion-pair high-speed counter-current chromatography
Journal of Chromatography A
Response surface analysis and simulation as a tool for bioprocess design and optimization
Process Biochemistry
Characterization of phenolics, betacyanins and antioxidant activities of the seed, leaf, sprout, flower and stalk extracts of three Amaranthus species
Journal of Food Composition and Analysis
Food colorants: Challenges, opportunities and current desires of agro-industries to ensure consumer expectations and regulatory practices
Trends in Food Science and Technology
Genetic diversity of celosia variants in east java based on polyphenol oxidase-PPO genes
Procedia Chemistry
Betalainic and nutritional profiles of pigment-enriched red beet root (Beta vulgaris L.) dried extracts
Food Chemistry
Betalains biosynthesis by Beta vulgaris L. hairy root culture in a temporary immersion cultivation system
Process Biochemistry
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