Physicochemical Properties Of Quinoa Flour And Its Application In Extruded Noodles

Quinoa,which is nutritious and gluten-free,is an ideal food ingredient for patients suffering from celiac disease and gluten allergy.However,the gluten-free,non-formable properties limit its use in food processing.In this work,the physicochemical properties of quinoa and some kinds of common gluten-free cereals were compared and the following research direction of processing method for quinoa was determined.The effects of different processing methods on the formation and characteristics of quinoa noodles were compared,and the forming mechanism of quinoa noodles was explored.And the nutritional aspects of quinoa noodles before and after processing were evaluated in order to provide a theoretical basis for the development of pure quinoa food.Firstly,the physical and chemical properties of white,red and black quinoa flour were compared,and the white quinoa was chosen as the test material.The basic components,solubility,swelling property,freeze-thaw stability and gelatinization characteristics of the white quinoa were determined and compared with the common gluten-free cereals such as rice,millet,corn and oat.The results showed that the gelatinization temperature of quinoa is 83.2?,which shows convenience to processing,while the peak viscosity and final viscosity were lower.Other physical and chemical properties of quinoa were in the middle level in several gluten-free cereals.All results indicate that subsequent processing of quinoa needs targeted enhancement of those properties from the perspective of processing method and quality improvers.The freeze-thaw stability of quinoa flour was poor and it is not suitable for the development of frozen-cooked noodles.Secondly,the effects of pre-gelatinization,such as steaming and roasting,followed by the traditional physical extrusion method and twin-screw extrusion method on the forming characteristics of quinoa gluten-free noodles were compared,and the results showed that steaming,roasting and twin-screw all could make the quinoa gelatinized.And the highest degrees of gelatinization were reached under the conditions: steaming for 60 min: 87.64%;steaming for 80 min: 91.97%;roasting for 6 min: 86.03%;roasting for 12 min: 87.54%;extrusion: 92.53%.The viscosity of quinoa flour obtained by twin-screw extrusion was much higher than that prepared by pre-gelatinization treatment,and the gelatinization peak was obvious.Comparing the X-ray diffraction patterns of different processed quinoas,the original A-type diffraction peak in the raw material weakened or disappeared after processing for the gelatinized starch,and a new diffraction peak was produced at 20.03°,possibly due to the formation of the amylose-lipid complex.The quinoa noodle obtained by twin-screw extrusion got a good moldability and acceptable quality compared to the pre-gelatinization-conventional extrusion product,which was loose and not resistant to boiling.The results of the Fourier infrared spectroscopy showed that the degree of starch crystallization in quinoa decreasedafter extrusion.The results of low field NMR showed that the mobility of protons in quinoa noodles after twin-screw extrusion was lower than that of the other two methods,indicating that the combination of moisture and noodles was more tight after twin-screw extrusion.Thirdly,the effects of twin-screw extrusion process parameters,drying process and the addition of the hydrophilic colloid on the quality of twin-screw extruded quinoa noodles were investigated.The results showed that the extrusion temperature,water addition and screw speed all had an effect on the cooking properties,texture and microstructure of the extruded quinoa noodles,and the best process conditions were: twin-screw extruder temperatures for the four zones were 80?,80?,100?,100?,respectively;the water addition was 35 g/100 g,and the screw speed was 100 r/min.And the optimum hot air drying conditions were 40? for 140 min.The addition of hydrophilic colloid has a significant improvement on the quality of the noodles.The effects of hydrophilic colloids on the qualities of noodles followed the order that guar gum>xanthan gum>locust bean gum.When adding 0.3% guar gum,the quality of extruded quinoa noodles was the best.Finally,the nutritional characteristics of the extruded quinoa noodles prepared under the optimal conditions were evaluated.The results showed that the total amount of hydrolyzed amino acids in quinoa was undiminished after extrusion,and the loss of total polyphenols and flavonoids was very little.In addition,the starch and protein digestibility of the quinoa noodles significantly increased compared with that of the quinoa flour.And the mineral content of the extruded quinoa noodles was higher than that of the commercially available pasta,and the nutritional value was relatively higher.