Abstract:Gellan gum is commonly used as a food ingredient because of its gelling and thickening properties. Application of high intensity ultrasound (HIUS) in food industry is currently attracting much attention because it can be used to alter food physical or chemical properties with a low impact on the environment. Gellan gum solution was subjected to high intensity ultrasound at 55℃ (above the sol-gel transition temperature) before acdification to determine the effectes of HIUS on glucono-δ-lactone (GDL) induced gelation properties of low acyl gellan gels (LA). The results showed that with the increase of gellan concentration, fracture stress, initial Youngs modulus, the opacity index and water holding capacity were increased, but fracture strain was decreased. With the increase of ultrasonic time and ultrasonic power, the fracture stress and initial Youngs modulus were decreased, while the fracture strain was increased. The fracture stress and initial Youngs modulus were firstly increased and then decreased with the increase of GDL/LA weight ratio. The optimum GDL/LA weight ratio to the gel strength for the acid gels was about 1. As the GDL/LA weight ratio was increased, fracture strain and the water holding capacity were decreased while the opacity index was increased. The reduction in gel strength was attributed to the reduced chain length of the gellan polymer molecules and the gel network may include dangling chains which did not contribute to elasticity. The higher the gellan concentration was, the more dense microstructures were. The results indicated that high intensity ultrasound could be used for modifying gellan gum to improve its gelling properties.
