Research On Quality Improvement Of Machine-made Dried Hollow Noodles

Dried hollow noodle is hollow inside,smooth,easy to cook and digest and full of fermented flavor,which has a good market development prospect.The manufacturing process of handmade dried hollow noodle is complicated,and it consists of more than a dozen processes.After a long period of natural fermentation,manual drawing for many times,and finally drying under the sun,it is time-consuming and laborious,and the quality is easily affected by experience and weather,so it is difficult to maintain stability and industrial mass production.In order to maintain the stability of quality and adapt to the industrial production,this study used yeast,Lactobacillus plantarum and Koji to produce machine-made dried hollow noodle(HN),studied the effects of crumbly dough fermentation and noodle fermentation on its edible quality,and analyzed its physical and chemical properties,nutritional flavor properties,etc.Finally,the texture quality of HN after cooking was improved by using hydrophilic colloid in order to explore the suitable production process of HN.Firstly,the effects of the addition of yeast,lactobacillus plantarum and Koji,the fermentation time of crumbly dough and the noodle on the apparent state of cross section,cooking quality and texture properties of HN were studied.With the increase of yeast addition and the extension of noodle fermentation time,the pore structure of HN became clearer and the optimal cooking time gradually shortened.On this basis,the optimal cooking time of HN was further shortened by introducing LP crumbly dough fermentation,but the hole distribution properties were not obviously improved.Besides,the introduction of Koji crumbly dough fermentation improved the distribution of hole structure in the cross section of HN and further shortened the optimal cooking time.The final results showed that the cross-sectional holes of HN were clearly visible,dense and evenly distributed under the conditions of 1.0% yeast addition,90 min noodle fermentation,1.5% Koji addition and 24 h crumbly dough fermentation,and the optimal cooking time was significantly reduced(from 450 s to 255 s).However,the hardness and tensile properties were obviously lower than those of unfermented ones.Secondly,the fermentation methods(HN1,noodle fermentation;HN2,crumbly dough fermentation+noodle fermentation;KJHN,Koji crumbly dough fermentation+noodle fermentation;LPHN,LP crumbly dough fermentation+noodle fermentation;Control,unfermented noodle)on the physicochemical properties(p H,TTA,reducing sugar,amylase and protease),starch and protein-related properties of HN and its influence on the cross-sectional microstructure of HN were analyzed by SEM.Among them,the fermented dough of KJHN had relatively low p H value,high acidity value,high reducing sugar content,high β-amylase and high protease content,which provided sufficient possibility for the hydrolysis of starch and protein.In addition,the surface of starch extracted from KJHN had obvious erosion-like pore structure,which showed lower amylose content,higher relative crystallinity and enthalpy,lower peak viscosity and retrogradation value.As for the protein properties of KJHN,it was found that it had higher free sulfhydryl content,higher SDS extractable protein content,and the low molecular weight protein bands in the electrophoresis map were obviously deepened,and the gluten network density of cooked noodle was obviously reduced.The reasons for these changes might be that the hydrolysis of microorganisms and the rapid water absorption and expansion of starch during cooking inhibited the cross-linking of gluten network,which might eventually lead to the increase of protein digestibility and the decrease of hardness and tensile properties of cooked HN.Finally,it was observed by SEM that the pore structure of the dried noodles in KJHN was compact and uniform,and the erosion properties of starch surface were obvious.Then the effects of fermentation methods on the nutrition and flavor properties of HN were studied.The KJHN tended to release a relatively high glucose content during the digestion process,resulting in a relatively high digestibility of the starch;at the same time,the Koji fermentation increased the content of free amino acids,especially the essential amino acid lysine,from 5.3 mg/100 g protein to 12.14 mg/100 g protein.The results of the peptide analysis showed that the extractable peptide content of KJHN increased significantly.In addition,based on the increased free amino acid content and extractable polypeptide content,the KJHN also showed an increase in vitro protein digestibility,mainly due to the hydrolysis of microorganisms on the one hand and the low cross-linking of proteins during the cooking process on the other;combined with the results of electron nose and GC-MS analysis,the KJHN was significantly different from those produced by other fermentation methods in the flavour analysis,mainly due to the high content of esters,including ethyl linoleate with a sweet and mellow flavour,ethyl palmitate with a creamy flavour and ethyl nonanoate with an apple and rose flavour.As a result,the flavour property of the HN was significantly improved.Finally,hydrophilic colloid was used to improve the quality of HN.Compared with the unmodified KJHN,the hardness and tensile properties of dried noodles during soaking were obviously improved by 0.3% curdlan,so that noodles still had good texture properties after soaking for 30 min.Therefore,under the conditions of 0.3% curdlan gum,1.0% yeast addition,90 min noodle fermentation,1.5% Koji addition and 24 h crumbly dough fermentation,the cross-sectional holes of HN were clearly visible,densely and evenly distributed,the optimal cooking time was significantly reduced,the texture properties were obviously improved,the nutrition and flavor properties were better,and the edible quality was obviously improved.