Currently, the world has approximately 7.75 billion inhabitants, and it is forecast that, before 2050, it will reach 10 billion. Therefore, it is necessary to have products that have food and nutraceutical functionality for consumption (ONU 2019).
In Mexico, various studies have been carried out on seeds of pre-Columbian use, such as amaranth, quinoa, chia, and chan. These seeds were used as food and medicine by Mesoamerican inhabitants, and they present important potential for human consumption because they are a source of carbohydrates, fats and oils, proteins, oligosaccharides, and minerals among others (Acuña-Gutiérrez et al. 2019).
The chan (Hyptis suaveolens (L.) Poit) has a worldwide distribution in temperate zones, particularly in the Mediterranean and Central Asia. In Mexico it is distributed in mountainous areas and it belongs to the Lamiaceae family (Martínez-Gordillo et al. 2013). This family has economic importance because some species are used as condiments (Origanum, Thymus, Mentha) to obtain essential oils (Lavandula, Pogostemon, Salvia) and ornamental oils (Coleus, Salvia, Scutellaria). The most frequent genera in the country are Salvia, Scutellaria, Stachys, and Hyptis. Chan seeds have a significant oil content, and their extraction and characterization have not been fully studied. The predominant fatty acids in the seeds are unsaturated fatty acids (UFAs), such as oleic, linoleic, and linolenic acids (Acuña-Gutiérrez et al. 2019).
Oils of vegetable origin are essential in the human diet, due to their energy intake and fat-soluble vitamins, as well as nutritional and functional properties. Currently, there has been special interest in polyunsaturated fatty acids (PUFAs) due to their benefits for health, prevention of cardiovascular diseases, and anti-inflammatory properties (Zamani Ghaleshahi et al. 2020). Other studies have found that monounsaturated fatty acids (MUFAs) help improve insulin sensitivity; furthermore, their consumption is associated with healthier serum lipid profiles (Qiu et al. 2019).
Various diseases are related to the deficiency or imbalance of ω 3 and ω 6 fatty acids (Aremu et al. 2015). Seed oils are the main source of polyunsaturated fatty acids, especially α-linoleic and α-linolenic acids. Chan seeds oil is predominantly composed of PUFAs, 76–86%, and MUFAs, 6–13.6%. Therefore, this type of oil can be considered for food applications (Sahu et al. 2020).
Recently, to evaluate the nutritional quality of vegetable oils, various indices have been developed that allow different groups of fatty acids to be related to each other to determine their potential for the prevention of some diseases. The hypocholesterolemic/hypercholesterolemic (HH) ratio assesses the effect of fatty acid (FAs) composition on cholesterol, by the ratio between hypocholesterolemic FAs (cis-C18:1 and PUFA) and hypercholesterolemic FAs (C12:0, C14:0 and C16:0). The atherogenicity index (AI) provides information on the degree of atherogenicity of fatty acids. Low AI can reduce the levels of total cholesterol, phospholipids and esterified fatty acids and therefore reduce the incidence of coronary heart disease (Munhoz et al. 2018; Chen and Liu 2020). On the other hand, the thrombogenicity index (TI) refers to the tendency to form clots in the blood vessels.
Alternately, different physicochemical and rheological properties of vegetable oils are considered quality parameters that are important in industrial processing, stability, useful life of the product, and cost. Such is the case for the acidity, iodine and peroxide values, refractive index, and oxidative stability (Zahir et al. 2017). Physical properties such as surface tension, density, and viscosity are important in transportation, processing, food manufacturing, and heat transfer (Sahasrabudhe et al. 2017).
The specific extinction coefficients, K232 and K270, and the peroxide index are used to determine the degree of oxidation and degradation of the oils (Bordón et al. 2019; Muangrat and Jirarattanarangsri 2020). K232 is indicative of the formation of peroxides and hydroperoxides during the primary and intermediate oxidation process of the oil. Later, the secondary stage of fatty acid oxidation occurs with the formation of conjugated triene, aldehydes, ketones, and acids. These functional groups have the characteristic of absorbing at 268–274 nm, which allows them to be related to the specific extinction coefficient K270 (Timilsena et al. 2017).
Vegetables are a source of a wide variety of bioactive compounds, mixtures of triglycerides, fatty acids, flavonoids, terpenoids, phytosterols, fatty alcohols, and tocopherols. The extraction of these compounds from plant matrices, mainly seeds, leaves, roots, flowers, rhizomes, and bark represent important challenges in obtaining ingredients for food, cosmetics, and pharmaceutical products (Belbaki et al. 2017).
Supercritical fluids extraction (SFE) is friendly to the environment compared to conventional extraction methods; it maintains the quality and safety of the products, reduce energy consumption, toxic waste, and by-products. SFE uses fluids above its supercritical temperature and pressure as solvents. Under these conditions, the fluid has solvent properties typical of a liquid and a viscosity like that of a gas, which facilitates mass transfer (Mwaurah et al. 2020). Supercritical carbon dioxide (scCO2) is widely used in FAs because they are thermodynamically stable, non-flammable, non-carcinogenic or non-mutagenic effects, and is inexpensive, it has low toxicity and high availability (Knez et al. 2019). In addition, it has low viscosity and high diffusivity, which allows it to have a better ability to penetrate porous solid matrices than conventional solvents and can generate a much faster mass transfer, resulting in faster extractions (Kulazynski et al. 2016). The SFE process consists of pressurization, temperature adjustment, extraction, and separation. These extraction processes depend on factors such as particle size, mass flow rate, temperature, pressure, and extraction time. Industrial applications of SFE are increasing because it uses less process time, has high selectivity, and does not require a product recovery stage; among which are the extraction of antioxidants, spices, aromas, and nutraceutical components (Mwaurah et al. 2020). On the other hand, the extraction of vegetable oils through SFE processes has been studied in different materials (Sodeifina et al. 2018).
Currently, Fourier transformed infrared spectroscopy (FTIR) and Raman spectroscopy techniques have seen increased development in the food industry; in edible oils, they are used in characterization, detecting adulterations, quality analysis, degradation, and identifying oils (Rohman 2017; Zahir et al. 2017; Matwijczuk et al. 2019; Qiu et al. 2019). FTIR has been used as an alternative to conventional analytical methods, with the advantage of being a fast, nondestructive method (Wójcicki et al. 2015; Rohman 2017). Raman spectroscopy is used for the authentication of edible oils, determination of impurities, proportion of cis/trans isomers, and degree of unsaturation (Jiménez-Sanchidrián and Ruiz 2016); the technique is based on the change in polarization of the distribution of electrons in the molecule when it vibrates. The nonpolar groups present intense scattering bands, as is the case of multiple bonds (-C = C-) and the main chain of carbon atoms (-C-C-) of lipids. Alternately, the vibrational modes of the polar groups (C = O and OH-) are weaker, contrary to what happens in infrared spectroscopy. These two spectroscopies provide complementary information for the characterization of vegetable oils (Samyn et al. 2012).
The aim of the present study was the extraction of chan seed oil by supercritical fluids as a function of pressure, temperature, and extraction time, as well as evaluate its physicochemical characteristics and nutritional quality.