Effects Of Low-moisture Potato Starch On The Gel Properties Of Silver Carp Surimi

As a widely used ingredient in food industry, starch is often added to improve the gel properties of surimi products. To date, most of the researches on starch using were focused on chemically modified starch. However, the existing of limits of chemical raw material, residues of by-products and the amount of substituent groups make a certain security risk once there is a fluctuation during the process of production. Regarded as a physical modification starch with less safety risk, low-moisture potato starch was selected to investigate its adding effects on surimi products compared with native ones after ascertaining the basic physicochemical properties and did a preliminary research work on the interaction mechanisms. The main contents and conclusions are as follows:(1) The physicochemical properties of low-moisture potato starchCompared with native potato starch, the morphology, microscopic morphology, crystal structure, pasting and thermal properties of low-moisture potato starch were investigated by Scanning Electron Microscope(SEM), X-Ray Diffraction(XRD), Rapid Viscosity Analyzer(RVA), Different Scanning Calorimetry(DSC) and Thermogravimetric Analyzer(TG). It was found that the water content of low-moisture potato starch was not more than 8%. The modification treatment caused a certain degree of damage to the starch granule, resulting in shrinkage and crack observed on the surface. Due to that, low-moisture potato starch has a lager amorphous region with the relative degree of crystallinity decreased from 35.02% to 14.15%. The results of RVA and DSC showed that the pasting temperature and gelatinization of low-moisture potato starch were both lower than native ones, indicating an easier gelatinization property of low-moisture potato starch. In addition, according to the research of gel consistency, solubility, swelling power, expressible moisture and transparency, the low-moisture potato starch had higher swelling power and better freeze-thaw stability. The gel consistency is lower than native starch, indicating a better gel forming ability.(2) Effects of low-moisture potato starch on surimi gel propertiesTo investigate the effects of low-moisture potato starch on surimi gel properties, gel strength, whiteness and water retention ability were used as the evaluation index. It showed that both native and low-moisture potato starch could improve the properties of surimi gel, increasing gel strength and enhancing water retention ability and low-moisture potato starch had more significant effects. Optimum addition of starch was about 8%. The gel strength of surimi products with 8% low-moisture potato starch increased by 75% compared with surimi gel with no starch and the water retention ability were promoted from 50.52% to 61.49%. After the treatment of different freeze-thaw cycles, surimi gel with 8% low-moisture potato starch could better maintain the gel strength and water retention ability, which means a more stable quality. The results of gel strength determination and sensory evaluation of surimi products with industrial formula indicated that the addition of 8% low-moisture potato starch significantly enhanced the gel strength and could maintain the elasticity at the same time. Also, it could bring the surimi products a better texture and taste, making it the most acceptable.(3) Preliminary study on the mechanisms of the interactions between low-moisture potato starch and surimi proteinTo inquiry the mechanisms of the interactions between low-moisture potato starch and surimi protein, the microscopic morphology, thermodynamic properties, chemical interactions and protein conformation of surimi gel with 8% low-moisture potato starch were investigated by SEM, DSC, TG and Raman Spectrometer. The results showed that some low-moisture potato starch performed a partly gelatinized and swelled state in surimi gel, having a packing and compression effect on protein gel matrix due to the internal pressure, bringing the surimi gel a more compact structure with higher gel strength. Some of the low-moisture potato starch completely gelatinized in surimi gel, filling and covering the protein gel matrix, bringing it a partly smooth and uniform interior, thus improved the gel properties of surimi. The addition of low-moisture potato starch negatively affected the formation of disulfide bond and hydrophobic interaction, making a certain impediment of surimi gel formation. However, it enhanced the thermal stability of gel system. In addition, the increase of the content of hydrogen bond and non-disulfide covalent bond and reduction of ionic bond were conducive to stabilize the network structure of protein gel. The analysis of Raman Spectroscopy showed that with the addition of low-moisture potato starch, more α-helices turned into random coin structure. At the same time, it enhanced the combination and retention ability of water of surimi gel. All these effects helped to form a surimi product with higher strength and water retention ability.