Research On Freshness Evaluation Of Fresh Food Based On Spectral Analysis

The safety and quality of fresh food has always been an urgent concern of the people,and freshness is the core of the safety and quality of fresh food.Therefore,it is urgent to carry out research on the freshness evaluation of fresh food.In this paper,pork,spinach,baby cabbage,and lettuce,which have the highest sales among fresh foods,were selected as the research objects.They were stored at room temperature 20°C,refrigerated-4°C,and frozen-18°C(pork),and collected the spectral information of the samples,phone photos,the moisture content of vegetables,and sensory evaluation methods are used to evaluate the freshness of the samples during storage.Finally,the color spectrum of the mobile phone is constructed,and the color spectrum freshness recognition model of the mobile phone is established.Pork contains myoglobin.Due to direct or indirect contact with oxygen in the air during storage,its content is gradually reduced due to oxidization.The quality of pork gradually changes from freshness,and the content of myoglobin determines the color change of pork.Therefore,the pork freshness spectral index(FI)was constructed in the760 nm band of myoglobin absorption band,and combined with the sensory evaluation results of pork freshness,the freshness of pork samples was comprehensively evaluated.The analysis shows that with the increase of the sample storage time,the FI index of pork under different storage conditions shows a downward trend.When FI?0.5,the freshness grade of pork is fresh,and when 0.3?FI<0.5,the freshness grade of pork is sub-fresh.When FI<0.3,the freshness grade of pork is spoiled.Moisture content is an important factor in the freshness of vegetables.Based on the partial least squares method(PLS),the correlation analysis between vegetable spectrum and relative moisture content(RMC)shows that the RMC value and spectral reflectance of vegetables are very high in the moisture sensitive band.The absolute value of the correlation coefficient is above 0.85.Combined with the sensory evaluation results of vegetables,a comprehensive evaluation of the freshness of the vegetable samples was carried out.The analysis shows that when RMC?65%,the freshness grade of spinach is fresh;when 65%>RMC?40%,the freshness grade of spinach is sub-fresh;when RMC<40%,the freshness grade of spinach is rotted;when RMC? When 80%,the baby cabbage freshness grade is fresh,when 80%>RMC?60%,the baby cabbage freshness grade is sub-fresh,when RMC<60%,the baby cabbage freshness grade is rotted;when RMC?70%,Lettuce freshness grade is fresh,when 70%>RMC?45%,lettuce freshness grade is sub-fresh,when RMC<45%,lettuce freshness grade is rotted.Through the color quantization model method,the RGB quantization value of the mobile phone photo is obtained,and the relationship is established with the FI index and the RMC value to find the best color channel.At the same time,based on the ASD spectrum data of the sample and the RGB quantization value of the mobile phone photo and gray scale.The color spectrum model of the mobile phone is constructed,and the measured value of the color spectrum and the fitted value of the model are obtained.The measured value and fitted value of the best color channel of the sample were analyzed by linear fitting with FI index and RMC value,respectively,to construct a mobile phone color spectrum freshness recognition model.The results show that the measured and fitted values of the best color channel all satisfy a certain functional relationship with the FI index and RMC value,and the correlation coefficients are all above 0.8.