Tribo-rheometry behaviour and gel strength of K-carrageenan and gelatin solutions at concentrations, pH and ionic conditions used in dairy products

摘要

Understanding the flow and lubrication properties of hydrocolloids, commonly used to enhance the mouthfeel properties of various dairy products can provide valuable information to manufacturers. The current study examined the lubrication (tribology) and rheological properties of gelatin (0.2-3.0%, w/w) and carrageenan (0.01-0.7%, w/w) in the concentrations ideally added in dairy products in the presence of KCl (0-0.3%, w/w) and CaCl2 (0-3.0%, w/w) within the pH range of 4.0-8.0. Additionally, the hardness and fracturability of the corresponding gels formed at various pH, ionic and concentration of gelatin and kappa-carrageenan conditions were determined using a texture analyser. Both the flow and tribological behaviors depended on the pH, addition of salts and dosage of hydrocolloids. Near its isoelectric point, gelatin solution had the lowest viscosity, gel strength, lubrication property and poor visual aspect of formed gel. Carrageenan solution had the highest viscosity and best lubrication property at neutral pH. The strength of formed gels from carrageenan solution was low in acid condition, and the formed gels had unchanged visual aspect. Adding salts improved the viscosity and tribology property, and to some extent increased the gel strength while lower gel strength was obtained when the addition of CaCl2 was beyond 0.8% for carrageenan formed gel. kappa-carrageenan increased the viscosity more significantly than gelatin. However, the gelatin solution exhibited good lubrication property during low and medium sliding speed, which is good for soft dairy products that do not require much chewing.