Physicochemical properties of a fibrous fraction from chia (Salvia hispanica L.)
Introduction
The beneficial aspects of dietary fiber depend on its physicochemical properties, which group into four categories: (1) hydration properties (solubility, swelling, water-holding and absorption capacity, viscosity and gelling); (2) cationic exchange capacity; (3) particle size, density and surface characteristics (porosity and oil-holding capacity); and (4) organic molecule adsorption capacity (López et al., 1997). The principal physiological effect of fiber is its ability to swell when absorbing water, which occurs due to the presence of carbohydrates with free polar groups, interaction with hydrophilic links or retention within the matrix (López et al., 1997). These lead to formation of gel and a consequent increase in feces volume, which provokes more frequent peristaltic movements of the intestine. This in turn facilitates transit of the fecal bolus and intestinal distention, and thus aids in reducing the probability of intestinal tract disorders and constipation (Oliveira, Reyes, Sgarbieri, Areas, & Ramalho, 1991).
Fiber extracted from some grains and seeds exhibits physiological and functional properties that make it promising for use in food industry and health applications. This promise has led researcher to search for novel raw materials that meet needs in these areas, with a particular focus on the co-products of protein extraction or other components from raw materials such as legumes (Betancur-Ancona et al., 2004, Goff et al., 2001). There is a parallel interest in new sources of dietary fiber that contain concentrations comparable to those in cereal and legume subproducts such as wheat, rice and oat bran, lupine, etc. (Villarroel, Acevedo, Yánez, & Biolley, 2003).
Fiber source research has focused on tubers, cereals, vegetables, fruit and algae, all of which are characterized by high dietary fiber content with low digestibility and low caloric content. The fiber fraction from chia (Salvia hispanica L.) seed has similar characteristics. A native of southern Mexico, chia has been under cultivation in the region for thousands of years. Chia (Salvia hispanica, L.) was among the principal crops grown by ancient Mesoamerican cultures. Recent evaluation of chia's properties and possible uses has shown that it has a high content of oil (32%) and 60% of this, is linolenic acid, a fatty acid denominate omega-3 associated with various benefits to consumer health (Rosamond, 2002). However, after extracting the oil to the seeds, defatted chia has fiber (22 g/100 g) and protein (17 g/100 g) contents similar to those of other oilseeds currently used in the food industry (Ayerza & Coates, 1999). This product has not been object of great interest in the investigation. Also, they have been carried out a good number of investigations on the composition in fatty acids of the oil (Bushway, Wilson, Houston, & Bushway, 1984), the benefits that it contributes their consumption to the health and the inclusion of seeds in animal feeding (Ayerza & Coates, 1999).
Its high unsaturated oil content has gained its attention as a dietary component (Ayerza, 1995). Oil extraction in chia, however, produces a subfraction with relatively high dietary fiber content (33.9 g/100 g) (Craig & Sons, 2004), which also contains polyphenols (Taga, Miller, & Pratt, 1984), possibly involved in high antioxidant activity, and compounds conferring functional characteristics with food system applications. As part of an effort to determine possible applications for this fraction, an evaluation was done of the physicochemical and physiological properties of a high dietary fiber content fraction produced by dry processing of defatted chia (S. hispanica) flour.
Section snippets
Seeds and chemicals
Chia (S. hispanica L.) seeds were obtained from the February 2000 harvest at Tapachula, Chiapas, Mexico (14°54′N, 92°56′W). All chemicals were reagent grade from J.T. Baker (Phillipsburg, NJ), and enzymes were from Sigma (Sigma Co., St. Louis, MO, USA).
Flours
The flours were produced with 10 kg seed. All impurities and damaged seeds were removed and the remaining sound seeds milled (Thomas-Wiley®, Model 4, Thomas Scientific, USA). Oil extraction from the milled seeds was done with hexane in a Friedrich
Proximate composition
Proximate composition analysis showed fiber content to increase from 26.5 g/100 g in the chia flour to 29.56 g/100 g in the chia fiber-rich fraction (FRF) (Table 1), an increase that could be reflected more in TDF than crude fiber content. This increase may not seem substantive, but the FRF fiber content is appropriate for a fibrous product. The FRF also had a higher fiber content than Canavalia ensiformis fibrous residue (22.68 g/100 g) extracted by wet milling (Betancur-Ancona et al., 2004),
Conclusion
The fiber-rich fraction of chia (S. hispanica) had a high proportion of TDF (56.46 g/100 g), composed mainly of IDF (53.45 g/100 g) with a low SDF content (3.01 g/100 g). Its water-holding capacity (15.41 g/g), water absorption capacity (11.73 g/g) and organic molecule absorption capacity (1.09 g/g) were all high. In contrast, its oil-holding capacity (2.02 g/g) and water adsorption capacity (0.3 g/g) were low. Its emulsifying activity was 53.26 mL/100 mL with high emulsion stability (94.84 mL/100 mL). The
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