Effect of bacterial cellulose on freeze-thaw stability of rice starch gels

The effect of bacterial cellulose (BC) on the freeze-thaw stability of rice starch gels during 5 freeze-thaw cycles were investigated, using scanning electron microscopy (SEM), rapid visco analyzer (RVA), X-ray diffractometry (XRD), differential scanning calorimetry (DSC) and textural analyzer (TA). SEM micrographs of freeze-thaw gels showed that smaller pore size and a thicker surrounding matrix corresponded with increasing bacterial cellulose concentration. RVA results showed that supplementation with bacterial cellulose could significantly decrease the breakdown and setback values, which meant that the short-term retrogradation of rice starch was inhibited. The freeze-thawed starch gels showed a typical B-type crystal structure in the XRD, significantly different from native starch (A-type crystal structure). The recrystallinity of rice starch was reduced from 7.22% to 5.61% with increasing bacterial cellulose concentration after five freeze-thaw cycles. DSC results showed that bacterial cellulose could significantly reduce the retrogradation enthalpy of rice starch, which was consistent with the XRD results. The textural properties of the rice starch gels during freeze-thaw cycles were improved with increasing bacterial cellulose concentration. This study showed that bacterial cellulose was an effective agent in preserving the quality of freeze-thawed rice starch based products.