Development of CA Storage Facilities for Vegetables
Although controlled atmosphere (CA) storage is used for apples, the technique has not been applied to the commercial storage of vegetables yet in Japan due to the high storage cost. Two types of modified air system CA (MASCA) storage facilities were developed which are economical and can be applied to vegetables. The construction and operation cost of MASCA storage facilities is low and the system consists of a simple structure with easy maintenance. MASCA facility is composed of a modified air generator, gas-tight CA room, O2 and CO2 monitors and sequence program. Two types of modified air generators, pressure swing adsorption (PSA) type and gas separation membrane (GSM) type, were developed. Both were designed to obtain the modified air (N2-rich air which contains desired O2 concentration) by improving the PSA-N2 generator or GSM-N2 generator. The O2 concentration in modified air is regulated by controlling the pressure of the air compressor of PSA or GSM. The sequence programs were developed to operate these modified air generators for the rapid reduction of the O2 concentration in the CA room and for the control of the atmosphere. As neither propane gas nor a CO2 scrubber is required, fire hazard is reduced and the structure simplified, which is one of the features of MASCA storage facility. Storage tests of shiitake mushroom, broccoli, cabbage and mature-green Japanese apricot revealed that MASCA facility can be used widely for the storage of various fruits and vegetables.