ABSTRACT
The effects of freeze-thawed cycles (FTs) and a new antifreeze protein from Sabina chinensis (Linn.) Ant. cv. Kaizuca leaves (ScAFP) on the structure and physicochemical characteristics of wheat starch were studied. The mechanical breaking exerted by ice crystals on starch granules during FTs gradually deepened, sequentially squeezing the surface (2-6 FTs), amorphous region (8 FTs) and crystalline region (10 FTs) of starch granules. These changes led to reduced thermal stability, increased retrogradation tendency, and weakened gel network structure. The addition of ScAFP retarded the damage of ice crystals on starch granule structure and crystal structure during FTs, and significantly reduced the retrogradation tendency. Compared with native starch, the hardness of freeze-thawed starch without and with added ScAFP after 10 FTs decreased by 17.85% and 9.22%, respectively, indicating ScAFP improved the gel texture properties of freeze-thawed starch. This study provides new strategies for improving the quality of frozen starch-based foods.
ABSTRACT
BiSnSbO6-ZnO composite photocatalytic material with type II heterojunction structure was synthesized by a simple solid-phase sintering method, it was characterized by XRD, UV-vis, and PT methods. The photocatalytic antibacterial experiments were carried out under LED light irradiation. The experimental results showed that the photocatalytic antibacterial properties of BiSnSbO6-ZnO composites against bacteria and fungi were significantly stronger than those of single BiSnSbO6 and ZnO. Under light conditions, the antibacterial efficiencies of 500 mg/L BiSnSbO6-ZnO composites against E. coli, S. aureus, and P. aeruginosa reached 99.63%, 100%, and 100% for 6 h, 4 h, and 4 h, respectively. The best antibacterial concentration of BiSnSbO6-ZnO composite against the eukaryotic microorganism Candida albicans was 250 mg/L, and the antibacterial efficiency reached the highest 63.8% at 6 h. Antibacterial experiments were carried out on domestic livestock and poultry wastewater, which showed that the BiSnSbO6-ZnO composite photocatalytic material has broad-spectrum antibacterial activity against bacteria, and the antibacterial effect has species differences. Through the MTT experiment, it is proved that the prepared BiSnSbO6-ZnO composite photocatalytic material has no toxicity at the experimental concentration. According to the free radical scavenging experiment and SEM observation of the morphological changes of the bacteria after light treatment, the prepared BiSnSbO6-ZnO composite photocatalytic material can generate active species OH, h+, and e- through light irradiation to achieve the purpose of sterilization, where e- play a major role, indicating that the BiSnSbO6-ZnO composite photocatalytic material has broad application prospects in the actual antibacterial field.
