Determination of subfreezing temperature and gel retrogradation characteristics of potato starch gel

The freezing properties and retrogradation of potato starch gels were studied. The freezing points of the starch gels decreased with increasing starch concentration and ranged from −0.7 °C to −1.4 °C. The water in the gel was partially frozen at −3 °C and was essentially frozen at −6 °C. The glass transition temperatures of potato starch gels increased with the increase of starch concentration and ranged from −3.69 °C to −3.23 °C. Therefore, −3 °C was selected as the subfreezing temperature for potato starch gel, and the retrogradation characteristics of gel with 8% potato starch concentration (w/w) were investigated at this temperature. The results showed that the hardness of starch gel stored at −3 °C was stronger than that at other temperatures, and the relaxation times T23 and T24 were shorter. Potato starch gel stored −3 °C had better rheological properties and higher relative crystallinity than those of the other gels, and still exhibited B-type crystallinity according to X-ray diffraction analysis. Thus, potato starch gel has a higher retrogradation rate and better gel-related properties at subfreezing temperatures than those at other temperatures, which represents a new approach for the aging of potato starch products.