FREEZE-DRYING OF COFFEE Whilst it may be pertinent to describe the principles of freeze-drying coffee, it is a high capital investment project, spearheaded originally by General Foods Corp in the USA in 1964. Subsequently, production was extended in he States and Nestle entered the field and developed the process in Brazil, in the USA. whilst it i as a premium priced product, on account of the relatively high operating costs compared with spray dried coffee, freeze-dried coffee will undoubtedly hold its share of the market but it is not an area into which many newcomers may venture, as the market has been cultivated by the multi-nationals who were in from the beginning and have dominated the trade by expensive advertising and marketing devices which only massive organisations can sustain Technically, the first stages of the processes are similar to those applying to spray drying: blending, roasting, extracting and concentration. At this point the 30 percent solids extract is sometimes freeze-concentrated to 40 percent solids, and then frozen to about minus 50"C. The product is hen granulated, transferred into trays and dried in a vacuum chamber in an 10 hour cycle to about 2 percent moisture. End temperatures in the granules range from 37 to 40C A two stage compressor is needed to maintain a temperature of minus 50C in the condenser coils of the freeze dryer, and either ammonia or Freon is used as a ref A standard batch chamber dryer has a tray space of 93sq m and requires a 66ton two stage recirculating installation to operate it. Most commercial units operating on the batch system have at least 4 chambers of 93sq m in service, which today could involve a capital outlay of some $3m for equipment alone, not including installation. This is only a modest percentage of the total investment involved. Some plants are completely automatic, adding considerably to the investment cost but not always saving much on the operating costs per kg of coffee produced PACKAGING This is invariably in retail or catering glass packs, hermetically sealed and nitrogen-flushed, as the product is extremely hygroscopic