不同CO2浓度下鸡蛋呼吸仿真分析及验证

贮存环境中CO_2浓度对鸡蛋呼吸作用及新鲜度变化具有重要影响,为了进一步考察在不同CO_2浓度下鸡蛋呼吸释放CO_2的扩散及新鲜度变化情况,该研究测定贮存在温度为25℃、相对湿度为65%、CO_2体积分数分别为1.5%、3.0%、4.5%及空气(对照组)环境下鸡蛋呼吸和新鲜度,利用FLUENT软件完成不同CO_2浓度下鸡蛋第1天呼吸释放CO_2的扩散过程仿真。结果表明,利用Fluent软件计算所得气体速度值和试验值基本一致,模拟值与实测值相对误差在4%～9%。不同CO_2浓度下鸡蛋释放CO_2的扩散过程符合重气扩散的特点,其扩散方向受到CO_2浓度的影响,且随着贮存环境中CO_2浓度的增加,鸡蛋呼吸释放CO_2的扩散量和扩散速度逐渐变小,呼吸得到抑制。再通过分析贮存过程中不同CO_2体积分数下鸡蛋呼吸强度和新鲜度变化得出,对照组1.5%CO_2与3.0%CO_2下的鸡蛋呼吸强度和新鲜度具有显著差异(P0.05),当贮存环境中CO_2体积分数达到3.0%时,对鸡蛋呼吸强度的抑制效果不再明显,且新鲜度变化保持不变。3.0%CO_2和4.5%CO_2体积分数下贮存鸡蛋20 d,其新鲜度等级仍在AA级以上,综合经济因素,3.0%CO_2保鲜鸡蛋效果较优。该研究可为鸡蛋呼吸和气调保鲜技术提供理论及数据基础。

Simulation analysis and verification of egg respiration under different CO2 concentrations

Abstract: Egg quality depends strictly on the storage environment after acquisition. The concentration of CO2 has an important influence on the respiration and freshness of eggs during storage. This study aims to further observe the diffusion and freshness changes of CO2 released from egg respiration under different CO2 concentrations. The respiration intensity and freshness of stored eggs were measured at the temperature of 25°C, the relative humidity of 65%, the CO2 volume fraction of 1.5%, 3.0%, 4.5%, and air (control group). The egg model was built by UG software. An ICEM CFD software was utilized to establish the fluid domain of the egg released carbon dioxide diffusion, and then divide it into a structural grid. A FLUENT software was selected to complete the diffusion simulation of the first day breathing release CO2 from eggs with different CO2 concentrations. The results show that the law of heavy gas diffusion was followed by the diffusion process of CO2 released from eggs with different CO2 volume fractions. Four stages were divided into: the initial, descending, mixing, and turbulent flow. The diffusion time in each stage was affected by the concentration of external CO2. Specifically, the diffusion amount and speed of CO2 released by egg respiration gradually decreased, with the increase of CO2 concentration in the storage environment. Egg respiration was inhibited, as the outside CO2 concentration increased. There was a significant difference in the respiration intensity and freshness of eggs stored in the external environment with the CO2 volume fraction of 1.5%, 3.0%, and 4.5% (P<0.05) during the entire storage. The inhibitory effect on the respiration intensity of the egg was no longer obvious, and the freshness remained unchanged (P>0.05) when the CO2 volume fraction reached 3.0%. The freshness level of eggs was still above the AA level, when stored under the environment of CO2 volume fraction of 3.0%, and 4.5% for 20 d. Taking economic factors into account, the CO2 volume fraction of 3.0% was better to achieve the optimal freshness of eggs during storage. This study provides new ideas and data support for modified atmosphere preservation of eggs.