Study on physicochemical properties of Quinoa flour of three different varieties and the effect of pH on their functional characteristics

Grains are important food sources for human diet because of high protein content. There are different kinds of grains used as food worldwide. Today herbal proteins play an important role as food sources in societies. Herbal protein sources are actually strategic points for improving national dietary all over the world. (Mashayekh et al, 2008). Food experts are becoming more open to Quinoa, because of high protein content, (Dallagnol et al., 2013). FAO compares Quinoa grain with concentered milk powder considering high nutritional facts, and called grains as multi vitamin (FAO, quinoa, 2011). According to scientific reports quinoa grain can be replaced with rice in national dietary (Ferreira et al, 2015. Oelk et al., 1992). Quinoa originally cultivated in South America (barazil, Chile, Peru etc.) and known as semi-cereals (Schoenlechner&Berghofe2010).Furthermore, Quinoa flour is a highly nutritional alternative to feed animals as well as in the production of foods which are suitable for patients with celiac disease and gluten-sensitive patient worldwide. (Dallagnol et al, 2013). From the technological point of view, functional properties hold an important position, Water and oil absorption capacity, protein solubility, gelatinization capacity, foam ability and foam stability are the most important functional properties. (Kaur and Singh, 2007. Ameri shahrabi, 1390). Functional properties are affected by different parameters such as protein network structure, lipid, carbohydrate, temperature and pH, respectively. (Alukoand Yada, 1995). This study proposed to investigate the physicochemical properties of Quinoa flour of three different varieties and monitor the effect of pH on their functional characteristics
 
three different variety of Quinoa grain, originated and cultivated in Peru, were used for experiments, varieties were black (BLACK COLLANA), white (SALCEDO INIA) and red (PASANKALLA), respectively. Grains were grind by 75 degree in mesh and refrigerated during storage. Carbohydrate, fat, ash, moisture content and protein were measured by AACC, (2003) methods. Functional properties were also measured using scientific methods, Owusu-Apenten, (2002), Kaur and Singh (2007) and customized Adebowale et al, (2005) method which used to measure protein solubility, Water and oil absorption capacity, foam ability and foam stability, respectively. Emulsion capacity and emulsion stability were measured using majzoobi et al, (2012) method.
 
chemical properties are important in both technological and nutritional aspects, chemical characteristics were observed and reported for three studied varieties. Protein solubility known as the first criteria in protein functional properties (Asadpour et al., 2010), this parameter is influenced by pH and the least value were observed in pH=4.5 (protein isoelectric point). Water and oil absorption capacity is one of the most important characteristics in flours (Kinsella, 1979), this parameter is a physical phenomenon which is known as oil or water confined in non-polar protein chains that is dependent on protein spatial shape. (Kinsella, 1979؛ Kaur and Singh, 2007؛ Trayunham et al., 2007) responses led to 1.285, 1.475 and 1.295 for white, red and black varieties, respectively. Foam ability and foamstability, actually known as volume increase caused by fast stirring and usually results in convenient rheological properties in products texture like ice cream and bread.this parameter refers to the ability of protein to make stable foam aginst mechanical and Gravitational stresses and measured in a 90 min. period of time (Oladela & Aina,2007) (Kinsella,1979).  Least responses in this case were observed in pH=4.5 which is an isoelectric range of pH for protein chains. Results were corresponded by responses of El Nasri and El Tinay (2007), Lawal) 2004(, Taghizadeh et al, (2017) and Asadpour et al (2010) about other semi-cereal grains. Last metered parameter was emulsifying ability and emulsion stability, emulsifying in protein structure is an equilibrium between hydrophilic and hydrophobic parts of protein and affected by alkaline range of pH (Ragab et al., 2003(this parameter is influenced by protein solubility which is in the least measures in isoelectric point (Feizi et al., 2013). Results had shown that foam stability would decrease during time passes. This may be due to the coupling of dispersed phase particles (oil droplets) over time. Concerning the effect of pH on emulsion stability, the results showed that the stability values at alkaline pH were higher than that of acidic pH, so that this stability at pH = 9 was significantly different from other pHs. Among the three varieties of quinoa, the amount of protein in the black variety (16.81%) was higher than the other varieties, which could be further investigated as a potential protein source. In addition, results indicate functional properties are influenced by pH, which means out of iso electric point, protein solubility increase and other fictional properties were improve followed.