Studies On Effect Of Freezing And Refrigerated Storage On Noodles Quality

This paper mainly studied changes in the quality of frozen dough during frozing,refrigerated storage, defrosting and freeze-thaw cycles. The effect of core-temperature,refrigerated storage time, defrost temperature and defrost time on variations in fermentativeactivity, tensile properties, TTA, pH, baking properties and protein properties, the bestfrozing condition, defrosting condition and the optimal refrigerated storage time wasexplored.The results showed that: when the freezing temperature was below－40℃, thefermentation activity, pH and extension resistance of frozen dough decreased, but extensionreduced slightly, the specific volume of bread was also reduced. The TPA and the sensoryevaluation of bread baked by frozen dough which was frozen at－40℃was better thanthat of dough frozen at other Temperature.As the core-temperature of dough decreased, the indicators of frozen dough, such asfermentation activity, extension resistance, tensile distance and TTA, increased at first andthen decreased. And all of the indicators were of good degree when the core-temperature ofdough was at about－18℃. The volume, TPA and the sensory evaluation of bread bakedby frozen dough which was frozen to－18℃was better than that of dough frozen to otherTemperature.The quality of frozen dough decreased quickly in the first four weeks, and it declinedfastest in the first week. It tended to stability after four weeks’ refrigerated storage; and thepictures of scanning electron microscopy(SEM) showed that: the gluten network wasincreasingly worse as the refrigerated storage time prolonged. And it can be observedobviously that the gluten network was destroyed seriously when the refrigerated storagetime was up to8weeks. The refrigerated storage time could also influence the secondarystructure of gluten protein. Data from FTIR indicated that the sum of β-turn had decreasedand β-sheet had increased and the other had no significant change as the refrigerated storagetime prolonged.Frozen dough can be of good quality when thawing at5℃, and it needs a long time. Thequality of frozen dough thawing at20℃and30℃is slightly poorer than that of5℃.Frozen dough thawing at38℃take less time, but it can’t be thawed symmetrical becausethe thawing temperature is too high. The results showed that the change of thawing temperature had no significant influence on the SEM structure of dough and the secondarystructure of gluten protein.As the times of freeze-thaw cycles increased, the quality of frozen dough became worse.And the quality decreased serious after three times’ freeze-thaw cycles. The pictures ofscanning electron microscopy(SEM) showed that: freeze-thaw cycles has significantinfluence on the SEM structure of dough. And the gluten network was destroyed seriouslyafter three times’ freeze-thaw cycles. The gluten network was increasingly worse as therefrigerated storage time prolonged. And it can be observed obviously that the glutennetwork was destroyed seriously. Data from FTIR indicated that the sum of β-turn haddecreased and β-sheet had increased as the times of freeze-thaw cycles increased.