Research On The Rheological Properties And The Interactions Between Hydrolysis Peach GUM And Sodium Caseinate

Polysaccharides and proteins, as natural biological macromolecules, are two key components in both natural and processed foods. The interactions between them make the products with more excellent properties and determine the structure, properties and stability of products. Phase separation phenomenon such as flocculation and precipitation under acid condition can be effectively solved by complexes formed by polysaccharides and proteins. Peach gum has been chemically treated into a good soluble anionic polysaccharide, which is lack of corresponding theoretical research. Hydrolysis peach gum (HPG) and sodium caseinate (NaCN) are used as the research objects in this topic. The preparation methods, stability and rheological properties of HPG are studied primarily; Interactions between polysaccharides and proteins and conditions of improving stability of systems are emphasized, and properties of complex complex coacervates are also further analyzed. The main contents and results are as follows:Properties of HPG differed greatly at different hydrolysis time. The longer hydrolysis time was, the higher dissociation degrees were, the better the water-soluble and extraction yield were. Longer hydrolysis time meant higher potential value, smaller particle size and better stability of system. HPG was hydrolyzed completely in 2.5 hour, properties of HPG had no obvious difference at higher hydrolysis time. HPG solution was a typical pseudoplastic fluid, compared with pectin and gum arabic, the effect of shear thinned was more obvious at higher HPG concentration. Temperature effects on the rheological properties of HPG were obvious. Rising temperature led to lower apparent viscosity, but high concentration of salt and low pH reduced viscosity slightly. The results showed that HPG has good acid and salt resistance which could keep stable in acidic conditions.Unstable phenomenon of NaCN could be effectively improved by the addition of HPG. Complex system could be maintained stable at below the isoelectric point of NaCN while particles were tight and homogeneous. The results further demonstrated that HPG was an anionic polyelectrolyte which had excellent characteristics like as other anionic polysaccharides, and provided the peach gum more extensive application prospects. When the total concentration was constant, mixing ratio of HPG/NaCN varied from 1:6 to 6:land the isoelectric point of system varied from 4.42 to 2.74, while the critical pH and turbidity was turned into lower value. It was proved that the greater the proportion of HPG could more effectively improve the stability of the system in the acidic conditions. Under the condition of low ionic strength, electric charge shielding effect could reduce the electrostatic repulsion between the two kinds of electrolytes, accelerating the formation of the soluble compounds. As ionic strength rising, charge shielding effect could reduce the electrostatic interaction, decreasing the formation of complexes, making stronger acid stability.Rheological properties of HPG-NaCN complex coacervates were tested by using the Anton Paar rheometer after centrifugation. It was resulted that the storage modulus (G1) was found to be larger than the loss modulus (G") at all the ranges of frequency, where in the two modulus were almost independent of frequency. The much higher G’ indicated that HPG-NaCN complex coacervates had a highly interconnected gel-like network structure with mainly elastic behavior. The structure of coacervates formed under higher pH were relatively loose, the number of the coacervates and the storage modulus was the highest near the isoelectric point. Electric charge shielding effect could reduce formation of coacervates and the storage modulus, the storage modulus decreased more obviously when salt concentration was higher than 0.25 M. The structures of HPG-NaCN complex coacervates were loose when weak intermolecular interactions were weak, which had a direct impact on the rheological properties of the complex systems, led to the decrease of the apparent viscosity.