FRUIT COLD STORAGE: TECHNIQUES AND EQUIPMENT

Abstract

The cold storage of fruit has advanced noticeably in recent years, leading to better maintenance of organoleptic qualities, reduced spoilage and longer shelf-lives. These advances have resulted from joint action by physiologists to determine the requirements of fruit and by refrigerating specialists to design and run refrigerating machines accordingly. Refrigerating systems have developed rapidly in order to meet the provisions of the Montreal Protocol on ozone-depleting substances and of the Framework Convention of the United Nations on climate changes. There has thus been renewed interest in natural refrigerants like ammonia, and in indirect cooling systems. Pre-cooling is used less for fruit than for vegetables. Nevertheless, its advantages have been proven for some sensitive species and varieties having short shelf-lives, particularly prior to transport or storage. Cold rooms are now designed to cool down produce more rapidly and keep it within narrower temperature and humidity ranges. Among the specific developments: refrigerating capacity per unit volume has risen, cold rooms have becomc smaller but more numerous, screw compressors have gradually replaced reciprocating compressors, and installations run much more smoothly, thanks to more accurate and reliable sensors. There has also been renewed interest in controlled-atmosphere technology, which is making it possible to obtain the desired atmosphere more rapidly. The advent of ULO-type atmospheres requires greater room airtightness and better atmosphere control, since the limit of anoxia is being approached. In conclusion, there is no revolution occurring in fruit cold storage equipment and technology, but rather constant improvements that are raising the quality of produce.