Study On The Effect Of Irradiation Combined With Alkaline Salts On Quality Characteristics Of Fresh Wet Noodles

As a traditional food in many countries and regions in Asia,noodles have a large audience and a huge consumer market.With the gradual transformation of dietary concepts to"green,healthy and convenient",fresh wet noodle products are favored by more people due to the attractive noodle aroma and balanced nutrition.However,fresh wet noodles are more susceptible to corrosion by microorganisms due to higher moisture content and sufficient nutrients.Therefore,it is extremely important to further explore and develop new and efficient preservation techniques.This dissertation focused on extending the shelf life of fresh wet noodles by studying p H control technology,namely the application of alkaline salts,and to detect the properties and storage stability of fresh wet noodles with different kinds of alkali salts.At the same time,the effects and mechanism of different alkaline salts on the physical and chemical properties and structural changes of fresh wet noodles were explored during storage.Finally,the effects of irradiation treatment on the processing quality of wheat flour and the combined influences of irradiation and alkaline salts treatment on the shelf life and quality characteristics of fresh wet noodles were investigated.Firstly,five alkaline salts that can inhibit the growth of microorganisms were initially selected from many alkaline salt food additives by using the total plate count in the noodles stored at 25°C for 24 hours as an indicator.And the five kinds of alkaline salts were sodium carbonate,potassium carbonate,trisodium phosphate,potassium phosphate tribasic,and sodium bicarbonate.Next,the inhibitory effect of different additional amounts of alkaline salts on the microorganisms in noodles was explored.The results showed that the application of five kinds of alkaline salts can prolong the shelf life of fresh wet noodles.The best performance was when sodium carbonate was added at 2.0%and the shelf life of fresh wet noodles was extended from 24 h to 60 h.Then combined with the influence of alkaline salts on the L*value and apparent state of the fresh wet noodles,the addition level of the five alkaline salts were screened to ensure the rational use of alkaline salts.And then,the additional amount of sodium carbonate was selected as 1.0%,and the additional amount of potassium carbonate,trisodium phosphate,potassium phosphate tribasic,and sodium bicarbonate was1.5%,and the following research and exploration were carried out on this basis.Secondly,the influences of the optimal addition amount of five alkaline salts on the storage stability of fresh wet noodles during the storage period（0-48 h）were studied.The research results showed that during storage,the application of alkaline salts could significantly improve the hardness,chewiness and maximum tensile strength of fresh wet noodles,and also slow down the rate of decline of various quality indicators,indicating that alkaline salts can effectively reduce fresh wet noodles of the rate of quality deterioration during storage.In addition,the addition of alkaline salts could improve the organoleptic properties of cooked noodles,especially in the evaluation scores of elasticity,viscosity,palatability and taste.Compared with other test groups,sodium carbonate induced noodles to show lower cooking loss and higher water absorption on the basis of improving the quality,and the effect of improving the quality of fresh wet noodles was better.Thirdly,the effects of alkaline salts on the physic-chemical properties and structural changes of fresh wet noodles during storage was investigated.Studies found that the improvement of the shelf life and storage stability of fresh wet noodles by alkaline salt were mainly due to the influences of alkaline salts on the regulation of the noodle matrix environment and the improvement of molecular structure.The five kinds of alkaline salts could effectively control the substrate environment of the fresh wet noodles and could also be kept in the alkaline range during storage.Sodium carbonate,potassium carbonate and trisodium phosphate induced the relatively higher p H value of the fresh wet noodle substrate,and remained more stable during that period.In addition,alkaline salts could strengthen the interaction between the main components of fresh wet noodles,inducing the increase of disulfide bond content,gluten macromer content and gliadin ratio,as well as the starch swelling power and gelatinization temperature,peak viscosity.Observed from scanning electron microscope（SEM）and relaxation time（T₂）,alkaline salts were beneficial to the formation of gluten network,strengthened the degree of binding between water and non-aqueous components,and slowed down the exposure of starch granules and the migration of free water.Among these results,carbonate salts had a more obvious effect on protein cross-linking and polymerization,while phosphate salts had a greater impact on the interaction between starch molecules in the early storage period.Finally,⁶⁰Co-γray irradiation as a kind of cold sterilization technology was used to explore the effects of irradiation on the processing quality of wheat flour and harmonized with sodium carbonate on the shelf life and quality characteristics of fresh wet noodles.The results showed thatγ-ray treatment with an irradiation dose of 0-5 k Gy could effectively reduce the initial bacterial content and polyphenol oxidase activity of wheat flour,and would not significantly reduce the nutritional value and processing quality of flour.Irradiation combined with sodium carbonate treatment could significantly increase the light value and water absorption of fresh wet noodles,increase the color appeal and taste of fresh wet noodles,and also improve the quality of fresh wet noodles to a certain extent.In addition,when the irradiation dose was 4 k Gy,the synergistic addition of 1.0%sodium carbonate could extend the shelf life of fresh wet noodles under 25℃storage conditions to 144 h,and would not cause a significant decrease in sensory quality.In other words,the processed fresh wet noodles had a 6-fold longer shelf life.