| Although the spicy strip industry started late,the development speed is increasingly.Because of good taste and suitable price,the spicy strip is popular among people of all ages,especially teenagers.With the development of society and the improvement of people's living standard,the food safety problem of spicy strip industry has attracted more and more attention.At present,the disqualification of microbiological indicators for low-salt spicy strip needs to be solved urgently.In this paper,the effects of polysaccharides on the quality of wheat flour and spicy strip were studied,the spoilage fungi of spicy strip were identified,the bacteriostatic activity of polysaccharides on spoilage fungi was evaluated,and the bacteriostatic mechanism of polysaccharides on spoilage fungi in spicy strip was investigated.This work can provide a theoretical basis for quality improvement of spicy strip as well as a reference for the study of the effect of polysaccharides on spoilage fungi,and thus expanding the application of polysaccharides in the field of food.The effects of polysaccharides on the properties of wheat flour,the secondary structure of protein in dough pieces and the microstructure of dough pi eces were studied by farinograph,extensograph and rapid viscosity analyzer(RVA),fourier transform infrared spectroscopy(FTIR),and scanning electron microscopy(SEM).The results showed that there was no significant difference in dough development time,stability time,degree of softening and extensibility after adding yeast ?-glucan,and the tensile area,tensile resistance and maximum tensile resistance were all reduced.When the addition of yeast ?-glucan was more than 0.3 wt%,with the increase of yeast?-glucan content,the water absorption increased significantly.With the increase of chitosan-oligosaccharide(COS)content,the water absorption and degree of softening decreased,and the development time and stability time increased significantly.When the content of COS added was not less than 0.8 wt%,the tensile resistance and maximum tensile resistance increased significantly.With the increase of the content of hyriopsis cumingii polysaccharide(HCP),the water absorption and extensibility of dough decreased significantly,the degree of softening of dough decreased slightly,and the tensile area,tensile resistance and maximum tensile resistance were all increased.Compared with the blank group,with the addition of yeast ?-glucan,COS or HCP,the peak viscosity decreased,the breakdown and setback viscosity decreased,the pasting temperature increased,the ?-helix content increased,the irregular curl content decreased,that is,the ordered structure(?-helix)increased.These results showed that the addition of polysaccharides could maintain the stability of starch structure,slow down the retrogradation process of starch,inhibit the gelatinization of starch,and strengthen the three-dimensional network structure of the dough.Moreover,the gluten protein network structure was more complete after the additio n of COS,and the degree of roughness was reduced,and no obvious pores and cracks were found,as well as the fracture of the gluten structure,and the gluten structure was denser.Taking color,the expansion ratio,hardness,oil absorption rate,water content,hardness and the mold counting of spicy strip as evaluation indicators to investigate the effects of polysaccharides on the quality of spicy strips.The results showed that with the increase of COS and HCP contents,the brightness(L*)was significantly reduced,whereas the redness(a*)and yellowness(b*)were increased significantly.But with the increase of yeast ?-glucan content,the brightness(L*)was not significantly different from that of the blank group,and the redness(a*)of spicy strip was increased slightly.When the content of yeast ?-glucan added was more than 0.9wt%,the yellowness(b*)increased.With the addition of COS and yeast ?-glucan,the expansion ratio,oil absorption rate and water content of spicy strip were increased,and the hardness of the sample was decreased.While the expansion ratio,oil absorption rate and water content were decreased,the hardness was decreased first and then increased after adding the HCP.The mold counting of spicy strip was decreased with the addition of COS,but after adding HCP or yeast ?-glucan,the mold counting was decreased first and then showed an increasing trend.Overall,the effect of adding COS on the mold counting in spicy strip was more significant than yeast ?-glucan.The bacterial phase of spoilage fungi in spicy strip was analyzed and identified.The results showed that the dominant spoilage phylum in spicy strip was Ascomycota,followed by Basidiomycota.The spicy strip samples were dominated by Aspergillus,more than 50% of the samples were tested.In this study,the bacteriostatic activity of COS and the bacteriostatic mechanism against spoilage fungi were further investigated.The results showed that the minimum inhibitory concentration(MIC)of COS on fungi was 15.6-31.2 mg/m L,the MIC of COS on Aspergillus fumigatus,Aspergillus ochraceous,Aspergillus versicolor was 15.6 mg/m L.While the MIC on Aspergillus niger and Aspergillus flavus was 31.2 mg/m L,different fungi have different sensitivity to COS.COS had inhibitory effects on the growth of these fungi,the growth curve experiment showed that it was mainly in the logarithmic phase,which can effectively inhibit the proliferation of spoilage fungi.The effect of COS on mycelial growth increased gradually with the increase of the concentration of COS,when the concentration of COS was MIC and 2MIC,the inhibition rates on mycelial growth were more than 30% and 55%,respectively.It also inhibited the spore germination of the five fungi,when the concentration of COS was 2MIC,the inhibition rate of spore germination was also above 36%.The chitin content of fungi treated with different concentrations of COS decreased significantly,in a concentration dependent manner.The activity of fungal chitinase increased with the increase of the concentration of COS,and showed a positive correlation.COS can destroy the integrity of the cell wall of several fungi.The degree of damage is positively correlated with the concentration of COS.After treatment with COS,the mycelia became wrinkled and dried up,and even appeared mycelia fracture and collapse phenomenon.With the increase of COS concentration,the absorptivity and conductivity increased,which was proportional to the concentration of COS,indicating that COS could destroy the membrane integrity of the fungi in a concentration-dependent manner.COS can also cause the accumulation of reactive oxygen species induced by oxidation(ROS).With the increase of COS concentration,the content of malondialdehyde(MDA)is concentration-dependent.In a word,COS has inhibitory effects on the activity of spoilage fungi,mainly through affecting cell wall,cell membrane and cell metabolism. |
PDF Full Text Request