基于内外协同的荔枝保鲜包装微环境多目标调控机理研究

Litchi fruit is difficult to be stored after being harvested, since it is easy to loss moisture and cause browning during preservation. Package can delay the moisture loss on account of the air flow produced by the process of environment regulation. However, easy condensation and the difficulty of regulation on the environment multi-objective parameters are the most common problems in the storage package of litchi fruit at present. Thus, it is necessary to conduct research about the effects on the micro-environment of litchi storage package by environment regulation as well as gas permeability of the package and respiration characteristic of litchi fruit. First, the effects of different harvest maturity and ambient temperature on the respiratory intensity of litchi were studied, and the Michaelis-Menten enzyme kinetics and Arrhenius' law of litchi respiration was established, from which the respiratory characteristics of litchi was obtained. Secondly, the influence mechanism of environmental parameters fluctuation on the dew point in the package was clarified base on the characteristics of moisture permeability and moisture loss rate of litchi fruit. Then, according to the multi-source information, a heat and mass exchange model of packaging inside and outside environment was built, and the coupling relationship between environment control, packaging air permeability and litchi respiratory characteristics was obtained. Finally, the effect of perforation distribution and placement of the package on process about internal and external heat and mass exchange was investigated by aerodynamic method, by which the heat and mass transfer model was improved. The research stated above will provide theoretical foundation for the selection on porosity of litchi fruit package for storage and transportation as well as the improvement of precision on multiple target regulation in micro-environment, by which the shelf life of litchi fruit after harvested can be extended.

荔枝采后不耐贮藏，易失水褐变。气调保鲜可延长荔枝保鲜周期，包装可减缓因空气流动导致的果皮失水；然而包装在气调保鲜中应用，还存在着包装内易结露、微环境多参数难调控等问题。因此，有必要研究保鲜外环境调控、包装透气特性和荔枝生理特性对微环境参数调控的协同作用机理。首先，研究不同采收成熟度和环境温度对荔枝呼吸强度的影响，建立荔枝呼吸动力学方程，获得荔枝呼吸特性。其次，结合包装透湿透气特性和荔枝果实水分流失速率特性，阐明保鲜环境参数波动对荔枝包装微环境结露的影响机制，优化湿度调控。接着，融合多源信息，构建包装内外环境热质交换模型，获得保鲜外环境调控、包装透气性和荔枝呼吸特性的耦合关系。最后，采用空气动力学方法，研究开孔分布和摆放方式对内外热质交换过程的影响，完善热质交换模型。研究结果将为荔枝贮运包装开孔参数的选择和微环境多目标精准调控提供理论依据。

荔枝生产于高温高湿的夏季，采后易腐烂褐变，不耐贮运。气调保鲜通过调节温度、相对湿度和气体成分等多目标参数，可延长荔枝保鲜周期。然而，通过气调保鲜试验发现，在无包装的情况下，环境参数波动或制冷风机高风速易导致荔枝加速失水褐变；生产上广泛使用的荔枝包装形式，则包装内保鲜环境易产生结露，且其阻隔性导致内外保鲜环境存在差异，使得包装内外环境多目标参数难以精准调控。而气调参数不准确，可能会导致果蔬保鲜品质严重下降。因此，建立荔枝生理、包装微环境结露与保鲜环境的相互作用关系，实现保鲜环境多目标精准调控，对延长荔枝保鲜周期有重要作用。. 本项目以实现荔枝气调保鲜环境多目标精准调控为目标，借助包装外环境参数调控，结合荔枝生理特性和包装透湿透气特性，探索外环境调节-包装透湿透气特性-荔枝生理特性的耦合作用关系，为荔枝气调保鲜环境多目标精准调控提供依据，延长荔枝保鲜周期。取得的主要研究成果如下：①获得了荔枝果实失水速率对包装内环境空气湿度变化和结露的影响关系，建立荔枝果实失水速率随环境参数变化的关联关系。②构建了环境参数变化与包装内环境空气露点的关系，阐明包装内环境结露产生机理。③考虑外环境调节、包装透湿透气特性、荔枝生理特性的相互作用，建立基于多目标参数约束的荔枝气调包装内外协同调控模型。. 我国是荔枝的主要产区，产量占世界1/5以上。因此，项目的研究成果具有巨大的应用前景。同时，随着人们对新鲜农产品品质的需求不断提高，过往的粗放式处理，已难以符合社会的需求。项目组所研究的荔枝包装微环境精准调控机理在环境热质传递规律获取等工作的基础上，提高荔枝保鲜环境参数的调控精度，从而延长荔枝保鲜周期。研究结果既能够满足消费者对农产品品质要求的，也能降低荔枝在采后流通的损耗，具有较好的科学意义。