Research On Moisture Loss Of Fresh Vegetable And Fruit Stored In Cold Conditions

The moisture lose will influence the fruit quality of many fruits and vegetables. For low temperature preservation, one of its goals is try to reduce water loss. Combined with epidermis, the effects of temperature, humidity, air velocity on moisture loss of fruits and vegetables are researched.First, the tissues of apple, lettuce, pleurotus pulmonarius are observed and analyzed by biological microscope. The cell size and arrangement of different kinds of fruits and vegetables are different, so is the same individual, from centre to epidermis, cells become smaller and closer. Through the epidermis structure of comparative analysis, the skin of most fruits and vegetables can be divided into three kinds. Than,based on skin types, four skin models are built, the mathematical model of moisture loss is established. Using mathematical method, the relationship between the external factors such as temperature, air velocity and specific moisture loss has been deduced. Under steady condition, specific moisture loss increases as long as the air velocity increases. When the surface is wet surface covered by porous layer, the value of moisture loss has maximum. The moisture loss during cooling period of a wet body is proportional to the temperature drop. For the body with a wet surface does not depend on the air velocity and the length of the cooling period; for the body with surface covered by porous layer, the moisture lose is smaller when the cooling period is shorter and the air velocity is higher. And the moisture model is solved.The orthogonal and subsequent experiment with apple is conducted. There are interaction effects on moisture loss of fruits and vegetables between temperature, humidity and air velocity, and they play a bigger role than each factor alone. The biggest role is the interaction effect of humidity and air velocity; it is found from the subsequent experiment that for the fruits and vegetables such as apple with higher diffusional resistance, moisture loss is proportional to the temperature gradient; the effect from air velocity on moisture loss during cooling down is contrary to the steady condition,when the air velocity is higher,the moisture lose is smaller; it is also found that moisture loss is proportional to humidity during both steady condition and cooling down. The theoretical results were verified using the experimental results.