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Rate Constant and Activation Energy for Formation of a Nitrosoascorbic Acid Intermediate Compound
Kenjiro Izumi1, Robert G Cassens1, Marion L Greaser1
1Department of Meat and Animal Science, University of Wisconsin, Madison, Wisconsin 53706.
Journal of Food Protection
|April 5, 2019
Summary
The reaction between nitrite and ascorbic acid forms nitrosoascorbic acid, with its rate influenced by pH and temperature. This study reveals insights into the kinetics of this reaction, crucial for understanding cured meat products.
Area of Science:
- Food Chemistry
- Chemical Kinetics
Background:
- Nitrite is used in meat curing, and its reaction with ascorbic acid is significant.
- Understanding the decomposition kinetics of nitrite is essential for food safety and quality.
Purpose of the Study:
- To determine the rate of nitrite decomposition by ascorbic acid.
- To investigate the influence of pH and temperature on this reaction.
- To elucidate the reaction mechanism and activation energies involved.
Main Methods:
- Spectrophotometric measurements were employed to monitor the reaction rate.
- Experiments were conducted across various pH values and temperatures.
- Kinetic analysis was performed to determine reaction order and rate constants.
Main Results:
- The reaction initially followed second-order kinetics, forming nitrosoascorbic acid.
- The rate constant increased as pH decreased.
- Deviations from second-order kinetics at low pH and high temperatures indicated the formation of 2,3-dinitrosoascorbic acid.
- Activation energy decreased with increasing pH, suggesting two reaction pathways.
Conclusions:
- The reaction mechanism involves both undissociated and dissociated forms of ascorbic acid.
- The findings are significant for understanding nitrite-ascorbate reactions in cured meats.
- Low activation energy and heating enhance the reaction rate constant in cured meat products.
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