A series of scientific papers have addressed the quality of chia seeds since the crop's rediscovery. Most of them focus on fatty acids since chia oil has the highest concentration of ω-3 of all natural sources (Palma et al. 1947; Ayerza 1995; Ayerza and Coates 2011; Segura-Campos et al. 2014). Seeds are also a source of proteins, fiber, and nutraceuticals, and there is an increasing interest in those compounds in literature reports.
Also, no significant content of toxic compounds have been found in chia seeds, and there is no evidence of allergic responses (EFSA 2005, 2009) caused by the consumption of chia seeds. The omega-3 chia website (chiagrowers.com) reports laboratory analysis where no mycotoxins where found on tested chia samples.
The oil yield of mature chia seeds generally ranges from 29.36 to 33.50 %, depending on the areas of origin, climatic conditions, and on the technique used for oil extraction (Ayerza and Coates 2004, 2009a, b; Ixtaina et al. 2011; Marineli et al. 2014; Rocha Uribe et al. 2011; Silveira Coelho and de las Mercedes SalasMellado2014). Moreover, the seed's oil content tends to rise as altitudes of ecosystem in which the seeds are grown increase (Ayerza 2009). From a nutritional point of view, the concentration of fatty acids in chia seed oil ranks in the following order: α-linolenic acid > linoleic acid > oleic acid > palmitic acid > stearic acid. In particular, the content of α-linolenic acid (C18:3) is about 60 % of all fatty acids present in oil.
Medical and epidemiological studies have demonstrated that ω-3 fatty acids are essential nutrients and play a role in human health for the prevention of cardiovascular diseases, being antithrombotic, anti-inflammatory, antiarrhythmic, and favoring plaque stabilization. Therefore, the intake of foods containing high amounts of α-linolenic acid is recommended. Also, an important ratio of unsaturated fats to target in the human diet is that of ω-6:ω-3 fatty acids. The ideal ratio ranges from 1:1 to 3:1, but generally in the western diet, it is much higher, even in vegetable oils, where the content of ω-6 fatty acids is high. The ratio is lower than 1 in chia (Ixtaina et al. 2011; Silveira Coelho and de las Mercedes Salas-Mellado2014); therefore, chia seeds or extracted oil can be used as a means to balance the unsaturated fatty acid intake in diets.
However, genotype and environmental conditions can influence the fatty acid composition more than the total oil content in chia seeds (Ayerza 2009, 2011; Ayerza and Coates 2004, 2009a, b, 2011), and namely α-linolenic content of chia seeds varies under differing environmental conditions and ecosystems, even in the case of a common genetic source. In general, it has been observed that as elevation of the seed production location increases, oil saturation decreases since the levels of α-linolenic and linoleic fatty acid increase and palmitic and stearic fatty acids decrease (Ayerza and Coates 2011). The ratio of ω-6:ω-3 fatty acid ratio decreases and that of polyunsaturated fatty acid/saturated fatty acids ratio increases. Also cool temperatures can often positively affect the level of unsaturation of chia fatty acids as for other oil seed crops (Ayerza 2009; Ayerza and Coates 2004, 2011).
In addition to important fatty acid composition, chia seed and oil also represent a rich font of compounds which have beneficial effects on human health such as vitamin B (Bushway et al. 1984) and natural antioxidants such as tocopherols, phytosterols, carotenoids, and phenolic compounds, including chlorogenic acid, caffeic acid, myricetin, quercetin, and kaempferol (e.g., Reyes-Caudillo et al. 2008; Marineli et al. 2014; Amato et al. 2015), and do not represent a hazard for human health (Bresson et al. 2009).
Amato et al. (2015) report the first data on the quality of chia seeds produced in Europe, from an experiment conducted in Basilicata. They found that oil concentration from Basilicata seeds was not significantly different than that of commercially available seeds from Australia and Peru, but characterized by a higher concentration of pigments (chlorophyll and carotenoids) and α-linolenic acid.
Chia seeds are also a source of protein and fiber: Capitani et al. (2012) report that after oil extraction, chia meal contains 19–23 % of proteins and 33.9–39.9 % of dietary fiber. Proteins in whole seeds range from 12 to 26 % (Ayerza and Coates 2004, 2009a, b, 2011). Ayerza and Coates (2009a, b, 2011) report changes with environment of production, and, namely, a highly significant decrease in protein if elevation increases. Its amino acid profile is suitable for the adult diet (Weber et al. 1991).
One of the most promising features of chia seeds is the 5–6 % content of fiber, which can be used as dietary fiber (Ayerza and Coates 2001; Reyes-Caudillo et al. 2008) but are also very interesting for industrial and pharmaceutical uses because of the high content of soluble fiber forming a highly hydrophilic mucilage. A polysaccharide with a molecular weight of 0.8–2 x 106 Da has been identified by Lin et al. (1994) who proposed a tentative structure as a tetrasaccharide with 4-O-methyl-a-D-glucoronopyranosyl residues occurring as branches of b-Dxylopyranosyl on the main chain and yielding by acid hydrolysis the monosaccharides b-D-xylose, a-D-glucose, and 4-O-methyl-a-D-glucoronic acids in the proportion 2:1:1. The fiber is localized in the fruit exocarp (Capitani et al. 2013), namely, in the first three cell layers. After contact with water, hydrated filaments of the mucilage are partially extruded out of the seed and form a transparent “capsule” which remains strongly attached to the fruit outer layers (Mu~noz et al. 2012a, b).