Research And Application Of Micro-perforated Film On The Packaging Of Vegetables

At present, modified atmosphere packaging is the most common way for the preservation of fruits and vegetables at home and abroad. However, common preservative film is difficult to provide the optimum gas conditions for fruits and vegetables, which have different requirements for gas concentrations. But micro-perforated preservation film attracts people’s attention by the controllable gas permeability and a wide range of CO2/O2 permeability coefficient ratio. The objective of this paper is to study the permeability of the micro-perforated film, and to put forward the theory design method of micro-perforated packaging parameters of fruits and vegetables and the experimental screening method, and to study the fresh-keeping effect of micro-perforated packaging on three kinds of common fruits and vegetables. The detailed research contents are as follows:(1) The influence of perforation edge effect on the gas permeability of the micro-perforated. A simple packaging device with perforations was designed. CO2 was used as experimental gas. Dynamic CO2 concentration with time in the micro-perforated packaging was theoretically analyzed and practically measured. Results showed that the theoretical values of CO2 concentration were much lower than the practical measurement values. The results were explicated as perforation end effect, and the corrective formula of effective length of perforation which was prepared by laser was put forward.(2) The theoretical design and the experimental screening method of micro-perforated packaging parameters. According to the corrective formula of effective length of perforation, we put forward the basic equations of micro-perforated packaging design and the determining method of perforation parameters of certain fruits and vegetables. In view of the limitation of the theory, we put forward the two steps experiment screening method of micro-perforated packaging parameters.(3) The application research of micro-perforated packaging of lettuces, romaine lettuces and celeries. According to the two steps experiment screening method of micro-perforated packaging parameters, we put the three kinds of vegetables into PE packagings with different perforations for 70 days under 0℃. The concentrations of O2 and CO2 in the packages were measured regularly, and weight loss rate, TSS content, Vc content, Chlorophyll content, MDA content, ethanol content and sensory quality of vegetables were measured and analyzed regularly. At last, the micro-perforated packaging parameters and preservation periods of vegetables were gained.(4) The fresh-keeping effect of micro-perforated packaging of three kinds of vegetables. The results showed that:PE packages (45×50 cm) of 50 μm thickness with 1,3,6,50 perforations (0.18 mm) all were suitable for lettuces storage with fine quality up to 50 days; PE packages (40×65 cm) of 50 μm thickness with 1,3,6 perforations all were suitable for romaine lettuces storage with fine quality up to 50 days; PE packages (30×95 cm) of 20～30 μm thickness can provide appropriate gas conditions for celeries, while the advantage of micro-perforated packaging on celery preservation is not obvious. PE packages of 50 μm thickness with 50 perforations were suitable for celeries storage with fine quality up to 40～55 days.