Study On Quality Changes And Hyperspectral Visualization Detection Of Penaeus Vannamei During Hot Air Drying

Penaeus vannamei is native to the Pacific waters of South America and has become one of the most important farmed shrimp species in China.Penaeus vannamei is popular because of its rich protein content.Dried shrimp is rich in nutrients and unique flavor,and it is easy to store and carry,so drying has become an important processing means to extend the storage period of shrimp.Hot air drying process of shrimp protein denaturation is very easy,improper control will seriously affect the color,texture and other quality of dried shrimp products.At present,the intrinsic relationship between drying-induced protein changes and physical quality changes of shrimp is not clear,and the detection methods of physical quality of shrimp need to be improved.In this paper,we take Penaeus vannamei as the research object and study its physical quality and protein changes during hot air drying,using Pearson correlation analysis to clarify the intrinsic effect of protein changes on physical quality changes.At the same time,the prediction model of shrimp physical quality indexes was established based on hyperspectral imaging technology to realize the spatial visualization of the dynamic changes of shrimp quality during drying.The study clarified the deep-seated causes of the physical quality changes of shrimp,and provided technical support for online real-time monitoring of shrimp quality during the drying process.The main findings are as follows:1.The change of physical quality during hot air drying of Penaeus vannamei was clarified.The changes in moisture content,moisture distribution state,shrinkage,rehydration rate,color,texture and microstructure were used as evaluation indicators to analyze the physical quality of shrimp during hot air drying.The results showed that the moisture content reached 35.02%at the end of drying.The relaxation times of the relaxation signal T21 for bound water and T22 for fixed water decreased to 1.52 ms and 14.17 ms,respectively,and the relaxation times of the relaxation signal T23 for free water became 0 ms after 9 h of drying.The shrinkage rate was 37.51%and the rehydration rate was 43.60%at the end of drying.With the hot air drying,the L*,a*and b*values of shrimp gradually decreased,while the hardness,stickiness and chewiness increased significantly.Microstructural results showed that the structure of muscle fibers was damaged during drying,and muscle fiber breakage occurred at 12 h of drying.2.The changes of protein during hot air drying of Penaeus vannamei were clarified.The changes of amino acids,total sulfhydryl groups,carbonyl groups,trichloroacetic acid(TCA)-soluble peptides,SDS-PAGE,chemical interaction,secondary and tertiary structure were used as evaluation indexes to analyze the protein changes of shrimp during hot air drying.The amino acid content of shrimp increased to 52.15 g/100g during drying,and the total sulfhydryl content gradually decreased to 0.36 μmol/g,while the carbonyl content increased to 2.03 nmol/mg protein,indicating that the protein was oxidized during drying.The trichloroacetic acid(TCA)-soluble peptide content increased to 0.91 μmol/g,and the SDS-PAGE results showed that the myosin heavy chain and αactin bands disappeared,and the troponin bands became significantly shallower,indicating that the protein was degraded during the drying process.In addition,the ionic and hydrogen bonds were broken and their relative contents were significantly reduced,and the hydrophobic and disulfide bonds were significantly increased,and Raman spectroscopy analysis showed that the α-helical content was decreasing and the β-turned structure and random curl content were increasing during the drying process,indicating that the protein molecular structure was transformed from regular to loose during the drying process.3.The correlation between protein changes and physical quality during hot air drying of Penaeus vannamei was revealed.A Pearson correlation analysis was conducted to determine the correlation between protein changes and color and texture characteristics of shrimp during hot air drying.The Pearson correlation coefficient(R)analysis showed that there was a high correlation between protein changes and color and texture.Among them,total sulfhydryl value,hydrogen bond and color(L*,a*,b*)had a significant negative correlation(P<0.05),and disulfide bond and β-turn angle had a significant positive correlation(P<0.05)with L*,a*and b*.There was a significant positive correlation(P<0.05)between protein carbonyl values and hardness,stickiness and chewiness with R 0.884,0.924 and 0.877,respectively,and a significant positive correlation(R=0.865)between TCA-soluble peptides and hardness.The results of correlation analysis proved that protein oxidation was associated with color change and protein degradation denaturation significantly affected the texture properties of shrimp.4.A model based on hyperspectral imaging technology was developed to detect the physical quality of Penaeus vannamei during the drying process.In HSI experiment,a hyperspectral imaging system was used to monitor the changes of moisture contentαL*,a*,b*,hardness and elasticity of Penaeus vannamei during hot air drying.The modeling process used competitive adaptive reweighted sampling(CARS)to screen the characteristic bands of spectral information,principal component analysis(PCA)and grayscale co-occurrence matrix method(GLCM)to extract color and texture information from the images,and finally fused the spectral information with the image information to build the partial least squares regression(PLSR)and least squares support vector machine(LSSVM)models.The model results show that the LSSVM model constructed by fused information has strong and accurate prediction ability for L*,a*,b*,hardness and elasticity.For each index,the residual predictive deviation(RPD)of the LSSVM model constructed by fused information were>2.5,and the prediction performance was better than that of the PLSR model.Therefore,hyperspectral imaging technology can evaluate the quality changes during shrimp drying,and fusion mapping feature information modeling can improve the performance of predicting shrimp quality.