Bactericidal Effect of Ultra-high Pressure on the Spoilage Mold of Wet Starch Vermicelli and Its Induced Quality Changes
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Abstract:
The effects of different UHP conditions on the inactivation of the spoilage molds, Aspergillus niger (Aspergillus 305.01 and Aspergillus 305.02), in wet starch vermicelli and the cooking characteristics of wet starch vermicelli were studied. The experimental results showed that the inactivation effect of UHP on Aspergillus niger increased as the treatment pressure and time increased. After the UHP treatment at 400 MPa/10 min, both the Aspergillus 305.01 and Aspergillus 305.02 of the vermicelli decreased by 6.01 log10 CFU/mL. Compared with the untreated bacterial suspensions, the nucleic acid absorbance values corresponding to Aspergillus 305.01 and Aspergillus 305.02 increased from 0.03 and 0.04 to 0.56 and 0.48, respectively, the protein absorbance values increased from 0.04 and 0.08 to 0.70 and 0.44, respectively, and the conductivity increased from 0.04 mS/cm and 0.06 mS/cm to 0.12 mS/cm and 0.20 mS/cm, respectively. Under the 400 MPa treatment, increasing the UHP treatment time led to increases of conductivity, nucleic acid loss and protein loss. The results showed that UHP could induce the outflow of intracellular substances such as nucleic acids, proteins and electrolytes, thereby causing cells death, through altering partial function of the cell membrane. In addition, as the processing time prolonged, the boiling loss and swelling degree of the vermicelli increased, whilst the breakage rate changed insignificantly. Based on the effect of UHP on the sterilization effect and cooking characteristics of wet starch vermicelli, the treatment at 400 MPa for 10 min was a better approach for sterilizing wet starch vermicelli, which provides a theoretical basis for UHP to improve the sterilization effect and quality of wet starch vermicelli.
