Rocket seed (Eruca sativa Mill) gum: physicochemical and comprehensive rheological characterization

Gums are complex polysaccharides with high molecular weight and lots of hydrophilic groups that dissolve in water providing viscosity to aqueous systems (Dabestani et al., 2018). Starch and its derivatives, galactomannans, carrageenans, pectin, gum arabic, and cellulose are mostly preferable gums that are used as a thickening and gelling agent, texture modifier, emulsifiers, and stabilizers in the food industry (Wang et al., 2019). Besides, new plant-based gum obtained from different seeds such as flaxseed, white mustard seed, yellow mustard seed, fenugreek seed, sage seed, and cress seed has been introduced by researchers in the last years (Balke & Diosady, 2000; Brummer et al., 2003; Cui et al., 1993; Cui et al., 1994; Karazhiyan et al., 2009). Knowledge of the physicochemical, functional, and rheological properties of a new gum source is useful for the evaluation of gum’s behavior in a large number of food products and their processing (Koocheki & Razavi, 2009). Many studies have been conducted on the rheological properties of seed gum solutions such as fenugreek seed gum, basil seed gum, and locust bean seed gum (Dakia et al., 2008; Farahmandfar et al., 2019; Gadkari et al., 2018). Polysaccharides, the main components of natural gums, consist of more than one type of monosaccharide (Dickinson, 2003). The difference in the monosaccharide compositions of gums affects the rheological properties and solubility of gums. Therefore, the monosaccharide compositions should be determined in the evaluation of rheological properties and solubility. Eruca sativa (‘rocket’ in English) is a lifelong herb of the family Brassicaceae grown in Southern Europe and India. For many years, rocket plants have been used as a food ingredient, especially in a salad. Rocket plants contain a wide range of health-promoting phytochemical compounds such as polyphenols, fibers, and glucosinolates (Koubaa et al., 2016; Miyazawa et al., 2002; Perry & Metzger, 1980). The seeds of rocket plants have been used for oil production in the industry because of their high oil contents (20.0%) and Erucic acid contents, one of the most sought-after fatty acids (Koubaa et al., 2016). Also, the rocket seed has a significant amount of total carbohydrate (23.1%), crude fibers (20.4%), and crude protein (31.0%)-rich (Nail et al., 2017). Thanks to their chemical composition, rocket seeds may have reasonable gum content with functional properties. The effect of extraction parameters on some technological properties and extraction yield of Eruca sativa seed mucilage was studied (Koocheki et al., 2011). However, there is no published study on the comprehensive rheological characterization of RSG.