Submitted to: Food Science and Technology International
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/5/2006
Publication Date: 5/1/2007
Citation: Higiro, J., Herald, T.J., Alavi, S., Bean, S. Rheological study of xanthan and locust bean gum interaction in dilute solution: effect of salt. Food Research Int. 40:435-447. Interpretive Summary: It is currently estimated that there are between 3 and 5 million people in the U. S. that suffer from celiac disease. Celiac disease is an intolerance to gluten proteins which can cause damage to the lining of the small intestine and malnutrition. There is no cure for celiac disease, people with this disease must avoid all foods made from wheat, barley, rye, and possibly oats. Gluten-free foods, while safe for celiac patients, are often low in quality due to the absence of gluten. To overcome this problem, glucose based gums such as xanthan and locust bean gum are often used as gluten replacements. In order to produce higher quality gluten-free food products, such as those made from sorghum, the functionality of gums needs to be better understood. We found that addition of three common salts to a solution of these gums decreased their elasticity and thinned the solution. This research was conducted to better understand the effect of salt on gums to help improve their use in wheat-free food products.
Technical Abstract: An oscillatory capillary rheometer was used to investigate the effects of NaCl, KCl, and CaCl2 on visco-elastic properties of xanthan and locust bean gum (LBG) blends in dilute solution. Gums were evaluated for intrinsic viscosity and elastic component. Molecular conformation of the xanthan-LBG complex was assessed by the power-law and Huggins equations. Addition of any of the three salts reduced significantly the intrinsic viscosity and elastic component of the gum blends, with a pronounced effect from divalent ions, compared with monovalent ions. The 60% xanthan-40% LBG blend exhibited the strongest attraction between xanthan and LBG. For the three salts, the attraction weakened when 5-mM salt was added and vanished with the addition of 50-mM salt. The strongest attraction between xanthan and LBG molecules was also evidenced by a positive Huggins miscibility coefficient Km, and a positive attraction-repulsion coefficient '. With addition of 50 mM of any of the three salts, the coefficient ' became negative, suggesting a strong repulsion between the two gums. The power-law coefficient b increased as salt concentration and LBG fraction increased in the blends for the three salts, suggesting a more flexible xanthan-LBG complex dependent on salt concentrations and LBG.