Study On Rapid Freshness Detection Of Cyprinidae

Cyprinidae was popular with consumers because of its delicious taste, high nutritional value. At present, the detection for freshness of Cyprinidae and other aquatic products only focued on conventional method, such as sensory scores, physical and chemical indicators and microbial detection, which was unable to meet the needs of convenient and rapid freshness detection of Cyprinidae. The quick freshness detection of Cyprinidae was emphasized. With the freshness change of Cyprinidae, its smell, color and texture changed. Therefore this paper measured the fresh degree changes of Cyprinidae, like odor, color and texture, respectively using electronic nose, color difference meter and texture analyzer; The correlation was analyzed between these freshness indicators and total volatile base nitrogen(TVBN); A model was built to predict Cyprinidae freshness and the quality of Cyprinidae was estimated. The main work was as follows:1. Sensory scores of Cyprinidae, respectively be stored at 4℃, 0℃and-18℃, were all declining and total volatile base nitrogen were all rising. The sensory score of samples, stored at 4℃, was below 60 point and TVBN value exceeded the critical value of corruption at the forth day. At the twenty-sixth day, samples stored at 0℃ was unedible for its TVBN value exceeded the critical value. The TVBN value of samples stored at-18℃ rose to the critical value at the seventieth day.2. The hardness, adhesion, elasticity, viscosity and chewiness of samples under three storage temperature declined compared with fresh samples. The TVBN value of samples stored at 0℃ was up to the national standard limit, and its hardness value was less than 225 g, glue viscosity was less than 154.1g and chewiness was less than 80.1. TVBN value of samples stored at 4℃ was up to the national standard limit and sensory score was below 60 points, and its hardness value was less than 723 g, adhesiveness was less than-22 g.s, glue viscosity was less than 388.9g and chewiness was less than 288.5. At-18℃, TVBN value of cyprinidae samples was up to the national standard limit,and its hardness value was less than 225 g, the adhesiveness was more than-45 g.s, the glue viscosity was less than 154.1g and chewiness was less than 80.1.3. With the extension of storage time, the color of samples changed under different storage temperatures. Under the three storage temperature, the change of a* value was not obvious but the changes of L*, b* and ΔE* were obvious. The color change of samples was small compared with fresh samples during early storage. there was no obvious color change when the sample was stored at-18℃. Therefore, the low temperature storage could better maintain the color of the samples.4. As the extension of storage time, complex changes occured in the nutrients of fish and volatile substances was produced, which gave rise to different sensor output value. Under three storage temperatures, the output value change of sensors 1 and sensor 3 was small, the output signal of sensor, sensor 4, sensor 5 and sensor 6 presented different change rule. As a whole, the output signal of samples under different storage temperature fluctuated, but the signal strength was enhanced gradually. The output signal strength was enhanced with the decline of the fish freshness.5. It was analyzed that the correlation between the smell index, texture index, color difference index and TVBN value during the process of storage. With total volatile base nitrogen value, odour index, texture index and color difference index, a model was established to evaluate the fish quality with the multivariate linear regression analysis method. The accuracy rate of the model was 90.4%.