Food safety remains a significant issue especially in developing countries, since the application of food additives continues to increase. However, it is impossible to avoid the application of food colours in food industry, since colour is an important sensory attribute. Natural colorants came into consideration as soon as consumers showed more interest in organic pigments. Nevertheless, their high level of sensitivity to heat, pH, and light, high cost, and low stability are drawbacks for their use.
Common plant pigments, such as betalains, carotenoids, anthocyanins, and carminic acids, are commonly used as natural colourants in medicinal and food applications (Stintzing & Carle, 2004). Among them, betalain, a water soluble compound, is prominent for its biological properties such as antioxidant, anticancer, antiradical, and antimicrobial activities (Georgiev et al., 2010). This kind of compound is present in 37 species of 8 genera in the Amaranthaceae family, which is one of the 17 families of the order Caryophyllales (to date) (Slimen et al., 2017; Cai et al., 2005b) and is noticeably found in the beetroot crops, which represent an important source of bioavailable compounds. Nowadays, red beetroots are receiving significant attention from consumers due to their prominent antioxidant activity and high oxygen radical absorbance capacity (Georgiev et al., 2010).
Betalain is composed of a nitrogenous core structure, betalamic acid, which combines with amino acid and derives red violet betacyanin (betanin 75–95%) and yellow betaxanthin (vulgaxanthin I ∼ 95%) (Cai et al., 2005a). Owing to their hydrophilic nature, betalain compounds can be extracted with pure water, aqueous methanol, or ethanol. However, the extraction method and choice of solvents affect noticeably the content of individual compounds in the extract. In addition, extracted beetroots are susceptible to pH, water activity, temperature, light, oxygen, metal ions, and enzymatic activities (Ravichandran et al., 2013).
Extraction of valuable compounds has recently been realised by ultrasonic extraction method (Sivakumar et al., 2009), microwave assisted extraction method (Singh et al., 2017), and pulse electric field extraction method (López et al., 2009). Undoubtedly, these methods have high efficiency; however, some of them are rather costly compared to traditional extraction methods.
Many observations have been made for the extraction of betalain compounds and phytochemicals from the whole tuber of beetroot. Moreover, there are some accessible investigations of bioactive antioxidants and colour-giving compounds, which are present in the waste part of beetroot such as peel (Singh et al., 2017), pomace (Kushwaha et al., 2018), and stalk (Maran & Priya, 2016). Nevertheless, there is still need to do further investigations of important colour compounds extraction from waste parts of beetroots. The aim of this study was to determine the effects of process variables (solvent ratio, temperature, and extraction time) on the quantities of betalain compounds in beetroot peel extracts.
The project is supported by the European Union and co-financed by the European Social Fund (grant agreement no. EFOP-3.6.3-VEKOP-16-2017-00005) and the Tempus Public Foundation under the Stipendium Hungaricum Scholarship Program.
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)| false ( , Aguirre-Joya, J. , De La Garza-Toledo, H. , Zugasti-Cruz, A. & Belmares-Cerda, R. Aguilar, C.N. 2013): The optimization of phenolic compounds extraction from cactus pear (. , Opuntia ficus-indica) skin in a reflux system using response surface methodology 3( 6), 436- 442. 10.1016/S2221-1691(13)60093-3
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