Numerical investigation of Marangoni effect during precooling of fruits and vegetables

Abstract

Precooling is widely adopted to weaken respiration and remove field heat of postharvest fruit and vegetables. Temperature and gas composition are two main factors that affect respiration. However, the interaction mechanism between them has not been clearly studied. In addition, for the mechanism of gas transport, existing models lack consideration of interaction of gas-liquid two phases. This paper is dedicated to present the Marangoni effect during precooling of fruit and vegetables. The theory explanation and numerical method of the volume of fluid (VOF) model was firstly set up. Parameters investigation including temperature difference, bubble diameter, aspect ratio, and fluid type were then conducted to illustrate this phenomenon and reveal the mechanism. Finally, the synergetic regulation of temperature and gas composition based on Marangoni effect was proposed. It contributes not only maintain high quality of fruit and vegetables, but also reduce energy consumption, which will have a great significance on environment. Practical applications Marangoni effect induced by temperature difference would weaken the respiration during precooling, and thus reduce the decay of quality. It was found that low precooling temperature could enhance the Marangoni effect. In addition, for the bubble in the wide channel of fruits and vegetables with low concentration, the Marangoni effect is relatively strong. Furthermore, the bigger the bubble diameter is, the more obvious the Marangoni effect is. Thus, the most suitable regulation strategies of temperature and gas composition differ between cultivars and also between positions in the parenchyma tissue of the same object. In addition, gas composition could be controlled by changing the temperature, which indicated that precooling can also play the role of controlled atmosphere storage. Therefore, the synergetic regulation of temperature and gas composition has a beneficial effect on preservation of fruits and vegetables, which is far more than a single factor. Thus, it can not only maintain high quality of fruits and vegetables, but also reduce the energy consumption, which will have a profound significance on environment.