Studies On Effects Of Calcium Chloride Injection On Color And Color Stability Of Chilled Pork

Meat color is one extremely important character of meat and the primary consideration for consumers. Chilled pork, which color stability is essential to both producers and consumers, is on behalf of the development direction for fresh pork production and consumption. Few study for the internal biological factors which influence color stability, such as myoglobin oxidation, Metmyoglobin (MetMb) reductase activity, lactate dehydrogenase activity (LDH), lipid oxidation and mitochondrial oxygen consumption has been conducted in our country.Calcium chloride (CaCl2) injection can significantly improve the tenderness of pork, but its impact on meat color is still in dispute. The purpose of this study is to determine the influence of CaCl2injection on chilled pork longissimus dorsi color and color stability during storage time, analyze the function of internal biological factors on meat color maintenance and discuss the possible reasons for color changes due to CaCl2injection, in order to provide a theoretical basis for the research in post-mortem chilled pork color stability.1. CaCl2injection on color stability of post-mortem chilled porkThe study was designed to compare the changes of pH、 surface color features (L*、a*、 b*、Chroa、 Hue angle)、 total pigments content、 relative MetMb and Oxymyoglobin (OxyMb) percentage、 water changes of post-mortem chilled pork longissimus dorsi, which were injected with water (5%of meat weight) and200mM CaCl2(5%of meat weight)1.5h postmortem. The results showed:compared with the control group, CaCl2injection accelerated pH decrease, reduced a*values, total pigment content and the initial T21peak area, increased Hue angle values, relative MetMb percentage and the initial L*values; Water injection increased relative MetMb percentage, Hue angle values and reduced total pigment content in meat. Both Cacl2and water injection induced a negative effect on post-mortem chilled pork longissimus dorsi color stability and accelerated meat discoloration. 2. CaCl2injection on post-mortem chilled pork longissimus dorsi ultrastructure, energy metabolism and activities of color-related enzymesThe study was conducted to investigate the influence of water and CaCl2injection on Malondialdehyde (MDA) values, MetMb reductase activity, LDH-B activity, muscle fiber ultrastructure and energy metabolism of post-mortem chilled pork longissimus dorsi during storage time. The results showed that:aging reduced chilled pork MetMb reductase activity, LDH-B activity and increased MDA values. Compared with the control group, CaCl2injection increased pork MDA values, reduced MetMb reductase activity, LDH-B activity and muscle fiber diameter, accelerated the decrease of post-mortem ATP and ADP content; Water injection reduced MetMb reductase activity and muscle fiber diameter.3. CaCl2injection on post-mortem chilled pork mitochondria functionPost-mortem chilled pork longissimus dorsi were injected with water (5%of meat weight) and CaCl2(5%of meat weight) at1.5h postmortem, mitochondria of different treatments were isolated during storage time. The study was conducted to study the mitochondria state3respiration rate, state4respiration rate, respiration control rate, membrane potential, electron transport chain related MetMb reduction and MDA values in vitro. The results showed:CaCl2injection had a negative effect on post-mortem mitochondria respiratory function. Aging reduced mitochondria electron transport chain related MetMb reduction and accelerated MDA values. Compared with the control group, CaCl2injection decreased mitochondria’s state4respiration rate, which was to some extent conducive to the stability of myoglobin, but also decreased mitochondria electron transport chain related MetMb reduction and increased MDA values, which promoted the oxidation of myoglobin. Water injection had no significant effect on mitochondria’s state4respiration rate, electron transport chain related MetMb reduction and MDA values.4. Partial least square analysis and discussionFrom the Partial least square analysis we can find that the relative MetMb percentage, b*value and Hue angle value are very important to indicate the change of postmortem meat color. There were also significant positive correlations between MetMb reductase activity, LDH-B activity, mitochondria state4activity and mitochondria electron transport chain related MetMb reduction. Water and CaCl2injection accelerated the relative MetMb percentage, which have a negative effect on color stability. The color stability of chilled pork in the early post-mortem time is probably determined by mitochondria, MetMb reductase activity and some other factors, but MetMb reductase activity may play a major role in maintaining color stability with the extension of post-mortem aging.