| The quality of beef depends largely on its water-holding capacity(WHC).WHC not only plays an important role in the food industry in terms of technology and economy,but also is an important factor affecting consumers'purchase intention.Poor WHC quality of beef will not only produce a lot of water loss,but also weaken its quality and appearance characteristics,resulting in economic losses.Therefore,it is of great significance to study the rapid detection method of WHC and improve the WHC quality of beef for the production and sale of modern food industry.The main contents and conclusions of this paper are as follows:(1)Developed a test paper for detection of beef WHC quality.Based on the property that cobalt chloride changed from blue to red when it contact with water,a kind of color change test paper was developed,so that the color of the test paper can reflect the ability of beef to maintain water.Based on the comprehensive analysis of color distribution,color rendering effect and flexibility of test paper,medium-speed qualitative filter paper was selected as the optimum test paper type.Taking cobalt chloride solution concentration,test paper soaking time,test paper drying time and test paper area size as test factors,and color change time of test paper as the index,orthogonal optimization experiment was carried out.The optimum conditions for making the test paper were obtained as follows:0.3 g/mL cobalt chloride solution,20 min soaking time,25 min drying time,and 10 cm~2 test paper areas.The factors affecting the discolored test paper were as follows:concentration of cobalt chloride solution>area of test paper>drying time>soaking time.The optimized test paper is sensitive to water,stable,portable and low cost.It was prepared for the research of rapid detection method of WHC based on color sensor.(2)Developed a color sensor for color change test paper to detect WHC quality of beef.Based on TCS34725 color sensor and Arduino controller,a color sensor was constructed to collect the color parameters of color change test paper.The optical signal was converted into electrical signal and returned to the computer through serial communication in the form of real-time data.In order to improve the detection accuracy,two hexagonal columns with length of 0.5 cm were installed at the bottom of TCS34725 color sensor.The vertical distance between TCS34725 color sensor and discolored test paper is 0.5 cm,which avoided the systematic errors caused by different measuring distances.The map function was used to adjust the code parameters,and the white balance of TCS34725 color sensor was adjusted,so that the color sensor met the RGB color model standard.Thirty sets of international standard colors were randomly selected.The color parameters collected by the color sensor were compared with the corresponding international standard colors.The accuracy of the color sensor was 96.67%.The color sensor could distinguish the subtle color difference,which laid the hardware foundation for the rapid detection of the WHC quality of beef.(3)Study on rapid detection method of beef WHC quality.In order to optimize the attachment time of test paper,a single factor experiment was conducted on the attachment time of test paper(10 s,20 s,30 s,40 s,50 s)with the coefficient of variation of color parameters as the index.The optimal test paper attachment time is 20 s.Based on BP artificial neural network,a prediction model of beef WHC quality rank was constructed,and genetic algorithm was used to optimize the prediction accuracy of the model.60 groups of beef samples were randomly selected as training samples.The BP artificial neural network prediction model was constructed by taking the color parameters R,G and B as input set and the beef WHC measured by pressure method as output set.Genetic algorithm was used to optimize the threshold and weight of artificial neural network.Another 20groups of beef samples were randomly selected as predictive samples to test the accuracy of the model,which predicted the WHC quality rank of beef.The results showed that the BP artificial neural network model optimized by genetic algorithm had better fitting effect.The regression linear correlation coefficient R~2 between the predicted value and the measured value is 0.987,which improved the accuracy of prediction of WHC quality rank of beef from 90%to 95%.It realized the rapid detection of the WHC quality of beef.(4)Improved the WHC quality of freezing-thawing beef based on ultrasound.The effects of ultrasonic power on the WHC quality of beef were studied.Single factor experiments were carried out with ultrasonic power(0 w,160 w,240 w,320 w,400 w)on the WHC quality of fresh beef.The WHC of beef samples was 0.72 when no ultrasound was applied,and the WHC was 0.80 when the ultrasonic power was 400 w.This indicated that ultrasound could improve the beef samples WHC(P<0.05).The WHC in freezing-thawing beef samples was 0.69 without ultrasound.In different stages of freezing and thawing(before freezing,during freezing,during thawing and after thawing),the application of ultrasound could improve the WHC quality of beef to some degrees.In the process of thawing,the effect of applying ultrasound to improve the WHC quality of beef was the best,which could reach 0.78.The effect of ultrasound on the texture of freezing-thawing beef was studied as well.Ultrasound could reduce hardness and improve elasticity(P<0.05),but had little effect on cohesion and resilience(P>0.05).The mechanism of improving the WHC quality of freezing-thawing beef by ultrasound was analyzed.Ultrasound could improve the pH value of beef samples in freezing-thawing process to a certain extent,and the increase of pH value was helpful to increase the ability of muscle to maintain moisture.Scanning electron microscopy(SEM)was used to observe the effect of ultrasound on the microstructure of freezing-thawing beef.It was concluded that the spacing of myofibrils increased and the protein spatial network became more complex after ultrasound treatment,which indicated that the structure of ultrasound could help to maintain more water molecules and improve the WHC quality of freezing-thawing beef. |
PDF Full Text Request