Quality preservation of fruits and vegetables by simple spotted cooling system and/or by packaging using new plastic films

A simple spotted cooling unit (SCU) and micro-perforated plastic films with a high gas permeability were developed in order to improve the distribution system of fruits and vegetables practically. SCU with a bellows structure was designed to maintain the air temperature at about 15 deg C. When spinach which had been pre-cooled and transported at near 15 deg C to a collection and delivery center in summer, was stored within SCU, less than 10% of the L-ascorbic acid content decreased for about 10 h. On the other hand, nearly 50% of the L-ascorbic acid content decreased when spinach was left in open-air without any remarkable changes in appearance. Micro-perforated (MP) films were produced by processing the surface of the films by passing through press-perforating rollers with a good reproducibility. The use of MP films, which were laminated with oriented polypropylene and polyethylene and showed a gas permeability of O2 19,000 and CO2 28,000 mL/ (square m / 24 h / 101.325 kPa) at 15 deg C, respectively, and thickness of about 40 micro m, enabled to obtain practical and effective hermetic packaging for the preservation of broccoli for 14 days at 15 deg C without appreciable changes in appearance. Utilization of SCU and MP film packaging or the combination of the two was found to be suitable for freshness preservation in the distribution of fruits and vegetables.