Abstract
Abstract Study of protein stability depending on the various technological factors allows to directionally adjust the physicochemical properties of raw meat and the quality of finished meat products. The paper investigates the possibility of using the DSC to study the influence of monovalent and divalent salts on protein thermal stability. In order to determine the effect of sodium chloride and its substitutes, potassium and calcium salts, on the thermal stability of proteins, the studies were carried out with grinded pork longissimus muscle samples salted with sodium chloride at level of 2.0% and with salt compositions containing reduced by 50% level of sodium chloride (a mixture of sodium and potassium chlorides; a mixture of sodium, potassium, and calcium chlorides) using the differential scanning calorimeter DSC Q 2000 in the temperature range of 5 °C to 100 °C and the temperature change rate of 1 K/min. It was found that the addition of potassium chloride instead of 50% of sodium chloride had no significant effect on actin and myosin resistance to thermal denaturation. Meat salting using the mixture of sodium, potassium, and calcium chlorides resulted in decrease of myofibrillar proteins stability indicating the destabilizing effect of calcium on actin and myosin. A negative correlation between the magnitude of the ionic strength and the temperature of myosin and actin denaturation has been found. The correlation coefficients were minus 0.99 and minus 0.95 for myosin and actin respectively. Reduction of denaturation temperature for myofibrillar proteins in the presence of calcium chloride opens perspectives to study the possibility of heat treatment at lower temperatures for meat products with reduced sodium content.
Highlights
Many scientific works of national and foreign scientists studied the properties of protein components in meat raw materials
According to thermogram obtained under study (Figure 1), in pork salted with sodium chloride at level of 2.0% there were three peaks - 30.98 °C (I), 48,85 °C (II), and 66.24 °C (III) corresponding to fat melting point (I), temperature of myosin denaturation (II) and actin denaturation (III) respectively
Partial replacement of sodium chloride with potassium chloride did not lead to significant change in fat melting point, as well as in the values of temperature peaks typical for myosin and actin denaturation
Summary
Many scientific works of national and foreign scientists studied the properties of protein components in meat raw materials. Most of the methods used to study the physical and chemical changes of proteins during meat ageing and processing are based on preliminary extraction of proteins with various solvents, which considerably complicates the research and increases labor input. In this context, it is interesting to study the possibility of thermal analysis (calorimetry) usage to determine physical and chemical changes in biological components of meat, i.e. protein and fat. Исследования термодинамических характеристик различных видов мяса, проведенные зарубежными учеными, позволили установить пики термограмм, соответствующие температуре денатурации миозина (54-58 °С), актина (71-83 °С) и коллагена (67 °С) с помощью дифференциальной сканирующей калориметрии (ДСК) [2,3,4,5]. Схожие данные были получены Kijowski и др., которые зафиксировали смещение температуры денатурации миозина с 58,4 до 53,6 °С и актина от 80,7 до 64,0 °С, в результате внесения хлорида натрия в количестве до 40 г/л в экстракт мышечных белков [3]
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