Study On Enzyme-assisted Fermentation To Improve Anticorrosion Capacity And Drying Characteristics Of Potato Pulp

As a main by-product obtained after the extraction of starch from potatoes,potato pulp was a good source of pectin and dietary fiber,which possessed a high utilization value.Potato pulp is difficult to be dried and utilized due to its high production rate,complex microbial content and high water holding capacity(WHC).Based on the effects of compositions removal on WHC and microstructure,enzyme-assisted fermentation with Lactobacillus plantarum was used to improve the anticorrosion capacity and drying characteristics of potato pulp by increasing organic acids content and reducing the WHC.After fermentation,the application feasibility of potato pulp was evaluated.The main contents of this paper are as follows:Firstly,the effects of hemicellulose,cellulose or pectin removal on the WHC and microstructure of potato pulp were investigated,which indicated that the hemicellulose had the minimal content and removal rate resulting in the minimal effect on WHC.Pectin contributed to the high WHC.The removal rate of pectin treated with 15 U/g pectinase could be up to 90%,while 35 U/g cellulase could only remove 33.72% of cellulose in the potato pulp.The WHC of potato pulp was reduced by removing compositions and destroying the network of cell wall polysaccharides.The effect of compositions removal on the structure of potato pulp was analyzed by scanning electron microscopy.Because the cellulose acted as the skeleton in the cell wall,while the pectin severed as the linkage,the potato pulp appeared a layer structure after effective pectic polysaccharides removal,while it exhibited a debris structure with removal of cellulose.Secondly,cellulase and pectinase were chosen to assist the fermentation of potato pulp with Lactobacillus plantarum.The growth curve and antibacterial capacity indicated that Lactobacillus plantarum had higher fermentative activity,survival rate and could inhibit the growth of Escherichia coli and Staphylococcus aureus when growing for 14 h.The conditions for fermentation with Lactobacillus plantarum,with or without enzymes were optimized based on titrate acidity(TTA),pH and WHC.The optimal conditions for fermentation of potato pulp with Lactobacillus plantarum were as follows: a proper inoculation amount of 8%(v/w),a temperature of 37°C and a processing time of 48 h,under these conditions,the TTA and WHC were 2.31%(w/w)and 17.68 g/g,respectively.The differences between the potato pulp fermented with Lactobacillus plantarum and untreated control were not obvious.The optimal conditions for pectinase-assisted fermentation with Lactobacillus plantarum of potato pulp were as follows: proper pectinase doses of 0.01%(v/w,0.38 U/g),a proper inoculation amount of 2%(v/w),a temperature of 37°C and a processing time of 60 h,under these conditions,the TTA and WHC were 5.28%(w/w)and 6.72 g/g,respectively.The WHC decreased by 64.14% in comparison with the untreated control.The optimal conditions for cellulase as-sisted fermentation with Lactobacillus plantarum of potato pulp were as follows: a proper pectinase dose of 0.30%(v/w,2.52U/g),a proper inoculation amount of 2%(v/w),a temperature of 37°C and a processing time of 60 h;under these conditions,the TTA and WHC were 8.56%(w/w)and 9.30 g/g,respectively.The WHC decreased by 50.74% in comparison with the untreated control.Finally,the effects of fermentation conditions on the antibacterial capacity and drying characteristics of potato pulp were studied.The organic acids contents,TTA,the clump count of lactic acid bacteria and species colony structure of fermented potato pulp were determined.The results indicated that the antibacterial capacity of potato pulp treated by enzyme-assisted fermentation could be improved due to the increase of TTA and organic acids content.The relevance among drying characteristics,water transverse relaxation time,viscosity,microstructure and texture of potato pulp fermented with enzymes was investigated.The drying time of potato pulp treated by pectinase-assisted fermentation was shortened by 33.33%,due to the increased water mobility,decreased viscosity and loosened structure.The layer structure and enlarged cell wall space of potato pulp,resulting from pectin removal,formed a micro passage helping drain out the water in potato pulp.Potato pulp with cellulose removal exhibited a gelatinous characteristic,increased the proportion of weakly-bound water and had high viscosity,thus prolonged the drying time.After fermentation with pectinase,potato pulp had low mycotoxins content,high glucose dialysis retardation index(GDRI)and could be easily dried by pneumatic drying.It might be indicated that pectinase-assisted fermentation could prevent potato pulp from decomposition,shorten dying time of potato pulp and simultaneously enhance the safety and application advantages.