| Water plays a crucial role in the quality and stability of food. Characterizing the features of the water in food is an effective method to explore the mechanisms that affect quality, acceptability and stability of food. Nuclear magnetic resonance (NMR) technology is one kind of high techniques featuring non-destructive and noninvasive. It has incomparable advantages in analyzing water distribution and migration of food. Using the NMR and magnetic resonance imaging (MRI) as the main methods and combining them with texture analysis and environment scanning electron microscope (ESEM) to monitor the changes of water status during kneading dough, dough resting and cooking. The effect of interaction between water and macromolecules on the quality of kelp fresh noodles was discussed and the process parameters of kelp fresh noodles were optimized. Then the correlation between relaxation behavior and texture properties was analyzed and the regression equation was obtained. Meanwhile, several kinds of typical noodle quality improver were added to the kelp fresh noodles and how they affected the quality of kelp fresh noodles was analyzed. Then, response surface analysis was used to determine the optimum addition level. Finally, the water distribution and migration of kelp fresh noodles stored in room temperature,4℃ and-18℃ were monitored. Their texture properties, acidity and colonies number were determined and the correlation between relaxation behavior and texture properties was analyzed. The mechanism of quality changes during storage process was explored. The results show that:1. Using the NMR as the main method and combining it with MRI, texture analysis and ESEM to optimize the process parameters of kelp fresh noodles as follows:1) The optimum mixing ratio of kelp and water was 1:3 to make kelp thick liquid.2) The optimum addition level of kelp thick liquid was 50%(flour weight was the total weight) to make kelp dough. The optimum mixing speed was 190 r/min and mixng time was 18 min.3) The appropriate resting temperature was 35℃ and resting time was 30 min when the resting humidity was 85%.4) The appropriate cooking temperature was 95℃ and cooking time was 120 s.2. Using the single factor experiment to optimize the addition of noodle quality improvers as follows:salt 2.00%, modified starch 3.00%, transglutaminase 0.30%, konjac glucomannan 1.50%, monoglyceride 1.50%. Salt, modified starch and transglutaminase have better effects on the quality of kelp fresh noodles. Choosing the T21, M21, elasticity and tensile force as indicators to optimize the improvers addition by response surface analysis. The optimum formula was 2.29% salt,0.30% transglutaminase,2.95% modified starch. The T21 was 0.0624 ms, M21 was 15123.1, elasticity was 1.466 and tensile force was 27.863 g under the optimum condition.3. The relaxtion time T22 of kelp fresh noodles stored in room temperature,4℃ and -18℃ increased with the extension of storage time. The proton density M22 decreased with the storage time increased. While the proton density M23 increased with the storage time extended. The crucial period to control the quality of kelp fresh noodles stored in room temperature was 28-35 day. The crucial period for the noodles stored in 4℃ and -18℃ was 35-42 day and 49-56 day respectively. |
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