| ObjectiveIn this study,one strain of Lactobacillus paracasei with high flocculation activity was isolated from natural fermented sweet potato sour pulp.Lactobacillus paracaseicould accelerate the sedimentation and shorten the production time.In order to determine the effection of the strain on the physical and chemical properties of starch and vermicelli.The starch was prepared by natural sedimentation method and the acid pulp method.In this study,the starch prepared by acid preparation method and natural sedimentation method.The physical and chemical properties of starch and the processing properties of starch were compared.Besides,the time of action of Lactobacillus paracasei starch was extended to 5 days and 10 days.The effects of Lactobacillus paracasei on the physical and chemical properties of starch and the processing properties of starch were studied.Provid theoretical basis and practical guidance for vermicelli.MethodsUsing uniform test design,the extraction process of sweet potato starch was optimized.In this study,the starch prepared by the acid pulp method and the natural sedimentation as the control group,compared physical and chemical properties of starch and vermicelli which prepared by Lactobacillus paracasei.Besides,the time of action of Lactobacillus paracasei starch was extended to 5 days and 10 days.The effects on the physical and chemical properties of starch and the vermicelliprocessing were definited.The physical and chemical properties of starch and vermicelli are determined as followed.Determination of starch content by enzymatic hydrolysis.Determination of protein content in Starch by kjeldahl method.Determination of viscosity of starch by brabender viscometer.The surface structure of starch granules was observed by scanning electron microscopy.Determination of X-ray diffraction of starch by Ultima Type X-ray diffractometer.TMS-PRO high-precision texture analyzer to determine the texture of the quality of the method.ResultsThrough the uniform test design.The extraction process of sweet potato starch with Lactobacillus paracasei as flocculant was optimized.The optimal extraction process was as followed: the ratio of material to water was 1: 6,the beating time was 74 s,and the amount of liquid fermentation of Lactobacillus paracaseiwas8% of the slurry and allowed to stand for 23 min.Starch extraction rate of up to 65.4%.Lactobacillus paracasei as a flocculant and fermentation on the physical and chemical properties of starch as follows.(1)Lactobacillus paracasei as a flocculant can improve the protein content of starch,aging rate of starch,amylose content,and the transparency of starch paste.Protein content increased by 0.4%,amylose content increased by 5.85%,the aging rate increased by 17.6%,starch paste transparency increased by 2.64%.But when the starch was fermented by Lactobacillus paracasei for a long time.Protein content decreased by 3.1%,amylose content decreased by 2.69%,the aging rate decreased by 13.6%,starch paste transparency decreased by 2.07%.(2)Lactobacillus paracasei as a flocculant can reduce the solubility and swelling force,the collapse of viscosity,the viscosity of the return.Among them,the solubility decreased by 2.5%,the swelling force decreased by 2.2%,starch collapse viscosity decreased by 54 cp,and the viscosity decreased by 21 cp.When the starch was fermented by Lactobacillus paracasei for a long time.The solubility increased by 1.4%,swelling force decreased by 0.5%,the crash viscosity increased by 35 cp,and the viscosity of the increase was 12 cp.The effect of Lactobacillus paracasei as a flocculant on the processing properties of the vermicelli was as followed.Lactobacillus paracasei as a flocculant can improve theaging rate,expansion coefficient and shear stress of vermicelli,reduce the cooking loss rate and tensile strength.The expansion coefficient of vermicelli decreased by 61%,the shear stress increased by 24 g/mm2,the aging rate was increased by 21.4%,the cooking loss rate was reduced by 1% and the tensile strength was reduced by 4.4 g/mm2.The starchwhichfermentatedfor a long time was produced to vermicelli.The aging rate decreased by 14.3%,the shear stress decreased by 8.2g,and the tensile strength was increased by 2.1 g/mm2.ConclusionsThrough the uniform test design.The extraction process of sweet potato starch with Lactobacillus paracasei as flocculant was optimized.The optimal extraction process was as followed: the ratio of material to water was 1: 6,the beating time was 74 s,and the amount of liquid fermentation of Lactobacillus paracaseiwas8% of the slurry and allowed to stand for 23 min.Starch extraction rate of up to 65.4%.The protein content of starch extracted from Lactobacillus paracasei was increased by 0.4%,theaging rate increased by 17.6%,the solubility decreased by 2.5%,the swelling force decreased by 2.2%,the amylose content increased by 5.85%,the transparency of starch paste increased by 2.64%,the breakdown viscositydecreased by 54 cp,the setback viscosity decreased by 21 cp.When the starch was fermented by Lactobacillus paracasei for a long time.Protein content,amylose content,aging rate,starch paste transparency began to decline,the collapse of viscosity,solubility,swelling force,the return viscosity began to rise.When the Lactobacillus paracasei was used as a flocculant,the shear stress of the vermicelli was increased by 24 g/mm2,the tensile strength was reduced by 4.4 g/mm2,and the cooking loss was reduced by 1%,thus improving the chewiness of the vermicelli.However,with the extension of starch fermentation time,the shear stress of vermicelli began to decline,the tensile strength began to rise,vermiculite chewiness was decreased.Prolong the fermentation time can not improve the quality of vermicelli. |
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