Microwave Heating Characteristics Of Minced Antarctic Krill (Euphausia Superba)

Antarctic krill is a key species in the Antarctic Ecosystem and has a huge yield,known as the world's largest protein pool.Because of its unique physiological structure,not easy to human direct consumption,must be deep processing of Antarctic krill.Compared with air heating,solvent extraction and steam heating,microwave heating has the advantages of low energy consumption,low cost,low consumption of solvents and no environmental pollution.However,microwave heating also has the phenomenon of uneven heating and local overheating,in which the key factor is the dielectric properties of food.So,the change of the basic food components affects the microwave heating and further changes the quality of the food.Based on the above problems,this study mainly from the two kinds of carbohydrates and amino acids on the impact of the dielectric properties of minced shrimp,and the introduction of Debye formula to establish the corresponding prediction model;the GC-MS analysis of Maillard reaction products after microwave heating and the effects of added to minced shrimp on the temperature distribution and temperature history.The temperature distribution and temperature history during microwave heating was simulated and validated by COMSOL Multiphysics software.1.The Antarctic krill and two sugars(sucrose and glucose)were studied in this study,the open-ended coaxial probe technique was used to study the dielectric properties of sucrose and glucose powder at 25 °C,and the effects of concentrations of sucrose and glucose(0% ~ 5%),temperature(20 ~ 80 °C)and frequency(300 ~ 3000MHz)on dielectric properties of Antarctic krill.The results showed that the dielectric constant and dielectric loss factor of sucrose and glucose powder were 1.70 ± 0.15 and0.03 ± 0.11 at the frequency of 300~3000 MHz.The dielectric constant of Antarctic krill decreased as temperature increased.When the frequency was lower than 2300 MHz,dielectric loss factor increased as temperature increased,and when the frequency washigher than 2300 MHz,it was contrary.At the same temperature and sugar content,the values of dielectric properties and penetration depth at 915 MHz were higher than 2450 MHz.At the same temperature,frequency and sugar content,the penetration depth of adding glucose to minced Antarctic krill were higher than adding sucrose to minced Antarctic krill.Sucrose addition had no significant influence on the dielectric properties of minced Antarctic krill compound(p > 0.05).With the content of glucose increasing,the dielectric constant of minced Antarctic krill compound increased,however,the dielectric loss factor decreased.With the temperature increasing,the dielectric loss factor of adding sugars to minced Antarctic krill increased at 915 MHz and decreased at2450 MHz.At 915 and 2450 MHz,the regression equations between temperature(20 °C~ 80 °C)and dielectric properties of minced shrimp compound were established,the regression coefficients were greater than 0.90.2.The open-ended coaxial technique and network analyzer were used to determined the dielectric properties of ten solid amino acids,namely,glycine,proline,cysteine,glutamine,lysine,methionine,histidine,arginine,tyrosine,and tryptophan,and the effects of amino acid concentrations(0,1,3 and 5 %)on the dielectric properties of minced Antarctic krill(Euphausia superba)were studied within a frequency range of 300~3000 MHz at 20.0 ± 0.5 °C.The results show that: The dielectric constants and dielectric loss factor of amino acids were 2.0 ± 0.4 and 0.2 ± 0.3,respectively,(moisture contents: 0.05 ~ 0.33 %),except those of lysine(5.5 ± 0.5 and1.5 ± 1.0,respectively)(moisture content: 4.5 %).The dielectric properties of non-polar,neutral-polar,alkaline amino acids added to Antarctic krill were affected by the frequency and moisture contents,molecular weight,and isoelectric points(pI)of amino acids.As the molecular weight and pI values increased,the critical frequencies of aliphatic amino acid additives in Antarctic krill decreased,whereas heterocyclic amino acid additives in Antarctic krill increased.Quantitative relationships between parameters that define both the real and the imaginary parts of the Debye relations and the weight fraction of amino acid contents in Antarctic krill were determined.Moreover,glycine(at5 %)or lysine(at 5 %)significantly influenced the dielectric constants and dielectric loss factor of minced Antarctic krill(p < 0.05).3.In this study,the GC-MS analysis of Maillard reaction products between lysine and glucose was investigated in the microwave heating time(1,3 and 5 min),and the effect of surface color and microwave heating characteristics(temperature distributionand temperature profile)of Maillard reaction product was added to the minced Antarctic krill shrimp after microwave heating.The results showed that with the increase of microwave heating time,the pH of Maillard reaction products decreased,the color difference value increased,the content of ether components increased and the main substances were pyrazines and furans.The longer the microwave heating time,Maillard reaction product added to the minced shrimp,minced shrimp surface color difference smaller change,Maillard reaction product was added to minced shrimp can increase microwave heating rate.The prediction model of minced shrimp temperature distribution established by COMSOL Multiphysics software is consistent with the measured values.