96-7 |
Respiration of fresh produce using closed systems and the need for correction factors |
L. CISNEROS-ZEVALLOS and J. G. Loaiza. Department of Horticultural Sciences, Texas A&M University, College Station, TX 77843 Respiration of fresh produce is an important factor in modified atmosphere packaging (MAP) design. Respiration can be determined using containers with gas flow through systems or closed systems. The latter is commonly used for evaluating respiration at normal air conditions, and has been proposed for evaluating respiration at different O2 levels as the tissue depletes the O2 inside the container. However, appropriate use of closed systems may require correction factors to compensate for CO2 solubility within the tissue as respiration takes place. The objective of this study was to evaluate closed systems for measuring respiration as the tissue depletes O2 inside the container, and to determine the contribution of CO2 solubility effects. Carrots were used in this study and stored in closed jars at temperatures ranging from 0 to 15°C and monitoring O2 depletion and CO2 production throughout time using an oxygen analyzer S-3A/I and a Horiba PIR2000 infrared CO2 analyzer. Respiration was calculated using a Michaelis Menten enzyme kinetics approach. Results indicate that errors in CO2 quantification can range from ~ 0 to 14% due to CO2 solubility. At lower temperatures error will increase due to a higher solubility factor of CO2. The CO2 calculation error will also increase as the ratio (volume container: tissue weight) decreases. With an appropriate correction factor involving CO2 solubility, volume container, tissue weight, and temperature we can obtain reliable respiration values at different O2 levels. Additionally, we can calculate respiration quotient and the lower oxygen limit values of the tissue which indicate the O2 level under which anaerobic respiration takes place. Closed systems are very convenient to determine O2 uptake and CO2 production at different O2 concentrations. Correction of CO2 solubility effects will allow obtaining reliable and accurate results for appropriate MAP design of fresh produce.
Session 96, Fruit & Vegetable Products
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