However, high energy consumption and high cost cause
limited application of freeze dried lychees. Therefore, a
novel drying method should be applied to dry lychees.
Microwave vacuum drying (MVD) was already used
to dry many foods, like green tea[6], papaya[7] and
mangosteen[8] due to the lower energy consumption and
the higher quality retention. In previous studies, authors
studied the MVD process for lychees and obtained the
optimal technical condition and drying characteristics of
whole lychee[9]. Generally, drying time, energy
consumption and quality of materials are used to describe
the drying process[10-12], and good quality is judged by
freshness, expected appearance, flavor and texture[13].
Drying causes many changes in the structure of plant
material, including shrinkage, increased porosity,
decreased ability to imbibe water, and damage to
microscopic structure[14]. At present, microstructure of
samples was tested in many researches because
microstructure of food could reflect the macroscopic
quality of food. Therefore, it is the most needed method
for food processing to formulate new food products and
to preserve original nutrient[15].