Abstract
Thermal conductivity factor and specific isobaric heat capacity of food products are currently the most important parameters in the development of mathematical models for food freezing and thawing and in improving production technology. There is significant variance among the existing experimental data for the thermal conductivity factor in meat. Most of the modern calculated relationships are based on the nutritional approach, which favorably differs by the ability to calculate the thermophysical characteristics of any food products. However, the calculation error at the subcryoscopic temperatures may be 15% to 20%. The development of superchilling as a way of storing meat requires high accuracy of freezing time calculation, including vacuumpacked boneless meat. In the presented article, the authors investigated hydrogen index, cryoscopic temperature, frozen moisture proportion and thermal conductivity factor for beef M. longissimus dorsi samples of NOR and DFD grades. It was found that DFD beef is characterized by 10% to 12% higher values of thermal conductivity factor in comparison with NOR grade. Using the method of regression analysis, the authors developed empirical relationships for calculating the thermal conductivity factor of meat depending on its temperature and pH level. Unlike cryoscopic temperature and frozen moisture proportion, pH is easy to measure and may be easily used on a conveyor belt for more accurate assessment of meat thermophysical properties. With an increase in pH from 5.3 to 7, an increase in cryoscopic temperature is observed from minus 0.94 °C to minus 0.72 °C. It has been shown that one of the factors for the higher cryoscopic temperature and higher pH level of DFD beef is higher water-holding capacity with less strongly bound moisture.
Highlights
Simulation and control of food refrigeration and heat treatment processes based on the calculation of temperature profiles inside the food product, as well as the determination and justification of points for thermal control are inexorably associated with the need to know the thermophysical properties
Frozen moisture proportion analysis was confirmed by other authors showing that one of the reasons for the higher cryoscopic temperature and pH of DFD beef is higher water holding capacity with less strongly bound moisture
For meat of different grades, there is a difference in the values of thermal conductivity by 10% to 12%
Summary
Simulation and control of food refrigeration and heat treatment processes based on the calculation of temperature profiles inside the food product, as well as the determination and justification of points for thermal control are inexorably associated with the need to know the thermophysical properties. According to the results of studies [1,2,3], the accuracy of food technology processes simulation is determined primarily by the availability and reliability of the initial data on the thermophysical properties of food products, local heat transfer coefficients, intensity of chemical processes, rather than by the computing power and principles of the numerical models used. The main problem in introducing this technology is to determine the required time of meat freezing, as well as the development of appropriate calculation methods for various linear dimensions of samples and their thermophysical properties [7]
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