Study On Quality Change And Regulation Of Frozen Cooked Noodles During Storage

Noodle,consumed as a staple food in many Asian countries,has been very popular among people.As the life pace accelerated and the living standard improved in modern society,the frozen cooked noodles?FCN?exhibited great market potential as a new instant noodle.However,FCN faces the problem of“frozen deterioration”in industrial production,which will affect the quality of noodles and the acceptance of consumers.Therefore,the study of the quality changes together with the internal mechanisms of FCN during frozen storage and the corresponding improvement methods can provide a theoretical basis for industrial production.Firstly,the quality changes of FCN during frozen storage?-18??were studied and the internal mechanisms were discussed.The results showed the cooking properties of FCN decreased during the frozen storage.It was found that the quality of FCN decreased slowly in the first 6 weeks but it declined significantly?P<0.05?from 6 weeks to 12 weeks.The texture quality decreased obviously and the sensory quality deteriorated with overall acceptance of consumers declined.Moreover,the freezable water content in FCN increased by 10.63%within 12 weeks.Nuclear magnetic resonance further indicated the deep bound water ratio(A₂₁)decreased,while the weakly bound water and free water ratio(A₂₂)increased.The high performance liquid chromatography showed the SDS extractable protein increased during the frozen storage.Besides,the fourier transform infrared spectroscopy detected the peak intensity 1045 cm^-1/1022 cm^-1 went up,indicating the starch crystallinity increased.The microcosmic conformation revealed the microstructure of FCN lost its original smoothness and compactness as the frozen time extended,and the protein network was destroyed.Secondly,the quality changes and internal mechanisms of FCN during freeze-thaw cycles were studied.With the increase of freeze-thaw cycles,hardness,chewiness and tensile properties of FCN decreased.The cooking loss ratio increased significantly?P<0.05?after two freeze-thaw cycles,and the water absorption ratio decreased significantly?P<0.05?.In addition,the total sensory score continued to decrease and it decreased by 42%after 6freeze-thaw cycles.The differential scanning calorimeter found the freezeable water content increased significantly?P<0.05?during the freeze-thaw cycles.The water bounding status study revealed the FCN gradually lost its water gradient and the water mobility increased with T₂₁ and T₂₂ extended.SDS extractable protein and the short-range order of starch molecules also increased during the freeze-thaw cycles.Microscopic studies found the structure of FCN was severely damaged by ice crystals with the increased big pores and a rough microstructure meanwhile the protein network was broken and discontinuous.Thirdly,three improvers?xanthan gum,potato hydroxypropyl starch?PHS?,monoglyceride?were selected to improve the quality of FCN.The rheological test showed improvers could increase the elastic modulus?G'?and viscous modulus?G"?of the dough.Moreover,PHS and monoglyceride could enhance the brightness of noodles.Three improvers could also promote the eating quality of FCN during frozen storage?-18??.Xanthan gum could significantly?P<0.05?reduce the cooking loss.PHS could increase water uptake rate from 95.30%to 97.23%,and it decreased the least during frozen storage.The addition of monoglyceride could improve chewiness and tensile distance of noodles.Water distribution and migration study showed three improvers could reduce the freezeable water and maintain the water gradient,which could help to reduce large ice crystals.The scanning electron microscope revealed improvers could protect the integrity and tightness of the microstructure,among them,xanthan gum and PHS exhibited good effects.Finally,the effects of three improvers on the quality of FCN during the freeze-thaw cycles were also investigated.The results showed all the improvers could reduce the cooking loss rate during freeze-thaw cycles,and xanthan gum performed the best with cooking loss rate as low as 1.39%after 6 freeze-thaw cycles.PHS significantly?P<0.05?improved the water absorption rate and the monoglyceride could also increase the water absorption rate on a small scale.The improvers could promote the texture and sensory quality of FCN,and PHS has the best freeze-thaw resistance with chewiness,tensile properties and sensory score ranking the highest after 6 cycles.Apart from these,it was found that the improvers could also reduce the freezeable water content.PHS presented the best effect,whose freezable water was6.72%less than control after 6 cycles.Microscopic studies indicated three improvers could protect the microstructures of FCN during the freeze-thaw cycles and could contribute to the maintenance of the internal moisture gradient.