Study On Quality Change Mechanism Of Noodles With Different Gelatinization Degree During Frozen Storage

Frozen noodles is a kind of frozen noodle products based on traditional noodles and combined with freezing technology.Compared with the well-known hanging noodles,fresh noodles and fried instant noodles,frozen noodles combine the advantages of health,safety and long preservation time,and can be eaten by direct heating.The development of frozen noodles can better meet the needs of consumers for high quality,healthy and convenient food.But during the frozen storage process,the ice crystals formed by the freezing of moisture inside the noodles have a damaging effect on the gluten network of the noodles,resulting in product quality deterioration.However,the internal water distribution and the binding state of moisture to starch,gluten and other macromolecules of frozen noodles with different precooking time were different.In this study,frozen noodles with different precooking time were taken as the research object to explore the quality changes of noodles with different gelatinization degrees during frozen storage.The quality change mechanism of frozen noodles with different precooking time during frozen storage is discussed,which is expected to provide a theoretical basis for improving the frozen storage quality of frozen noodles.Firstly,the effects of different precooking time on the gelatinization degree,cooking quality,texture properties,tensile properties and sensory property of frozen noodle were studied.The results showed that that in the process of precooking,starch granules absorb water,expand and gelatinize,and protein cross-linking polymerization.The gelatinization degree of noodles elevated with the increasing in cooking time,and the noodles are almost completely gelatinized after being precooked for 5 minutes.With the increase of precooking time,the loss rate and water absorption rate of precooking increased significantly(P < 0.05).The optimum recooking time of frozen noodles decreased from 300 seconds to 60 seconds,and the loss rate of recooking decreased.The recooking water absorption of frozen raw noodles was 78.40%,which increased significantly to 92.34% when pre-cooked 5min.The increase of recooking water absorption led to the deterioration of noodle toughness and the decrease of sensory score.The hardness,chewiness and viscosity of frozen noodles decreased with the increase of precooking time.When the precooking time was increased to 1min,the tensile properties of noodles decreased significantly after recooking.Further increasing the precooking time had no significant effect on the tensile properties(P > 0.05).Then the noodles with different pre-cooking time were frozen for 1,30,60,90 and 120 days,and the quality changes of noodles with different gelatinization degrees during frozen storage were studied.The results showed that with the extension of frozen storage time,the loss rate of recooking of noodles with different gelatinization degree increased,the water absorption of recooking decreased,the hardness,chewiness and viscosity increased,and the tensile properties decreased.The sensory quality of raw noodles,pre-cooked 1min and 3min noodles decreased with the extension of frozen storage time,while the sensory quality of precooked 5min noodles maintained better.The quality of uncooked noodles deteriorated seriously in the process of frozen storage.Prolonging the precooking time can alleviate the quality deterioration caused by frozen storage,improve the surface stickiness of noodles and the sensory quality of noodles after frozen storage.Precooking for 5 minutes can achieve the optimum effect.At the same time,with the increase of precooking time,starch granules gradually decreased,gelatinization degree increased,and a more continuous starch-gluten matrix was formed.After 120 days of frozen storage,the continuity of gluten network structure decreased.Pre-cooking treatment can significantly enhance the thermal stability of frozen noodles,and pre-cooking 5min can reduce the damage of frozen storage to gluten network structure.Then the law of water migration of noodles with different gelatinization degrees during frozen storage was discussed.The results showed that compared with frozen raw noodles,the water content of frozen noodles increased significantly after pre-cooking.With the extension of frozen storage time,the moisture content of noodles with different gelatinization degrees decreased,the content of freezable water decreased,and the moisture loss rate increased.The water loss of noodles precooked for 1 minute and 3 minutes was the most serious during frozen storage.The noodles that were pre-cooked for 5 minutes had the highest content of freezable water,and the content of freezable water remained better after frozen storage.Magnetic resonance imaging showed that the high moisture area of raw noodles was in the center of noodles when frozen for 1 days.In contrast,the high moisture area of the pre-cooked noodles is close to the outside of the noodles.After frozen storage,the water loss in the high-moisture areas inside the raw noodles and precooked noodles for 1 or 3 minutes was serious,while precooked noodles for 5 minutes maintain a better level of moisture.The increased water mainly exists in the form of free water,and a small part of it forms deep bound water which is closely combined with macromolecules.Finally,the starch properties of frozen noodles with different gelatinization degrees during frozen storage were analyzed by X-ray diffractometer,Fourier transform infrared spectrometer and fast viscosity analyzer.The results showed that after precooking,noodle starch crystal structure changes from A-type to V-type,and the binding ability of starch and water is decreased.And the pre-cooking treatment can reduce the starch short-range and longrange order of noodles.With the extension of frozen storage time,the short-range order and relative crystallinity of noodle starch with different gelatinization degree increased.Frozen storage enhanced the association between starch chains,formed a more orderly molecular structure,and intensified starch retrogradation.With the increase of noodle gelatinization degree,the peak viscosity,valley viscosity and final viscosity decreased,the gelatinization temperature increased and the breakdown value decreased.Meanwhile,pre-cooking treatment can improve the short-term retrogradation of starch during noodle storage.