Cold Link Africa May 2024 | Page 32

TECHNICAL

Supplied by Grant Laidlaw

STORAGE CONDITIONS FOR PERISHABLE PRODUCTS

Both vegetables and fruit must be cleaned and washed to remove dirt , insects , juices and any other foreign matters before chilling or freezing . Vegetables are then blanched . Most micro-organisms are destroyed by this process . However , some bacteria may survive and to prevent spoilage by these bacteria , the product should be chilled in cold water ( about 10 ° C ) immediately after blanching and then dried thoroughly before packing . Blanching of fruit is not practiced . To do so would destroy its fresh quality , a characteristic that is highly valued .

As a general rule , meat products do not require special processing prior to freezing . Pork and fish must be frozen immediately after chilling . This is because of the instability of the fatty tissues . Beef is often allowed to hang in a chiller room for a couple of days before freezing . During the ‘ hanging ’ period , the beef is tenderised by enzymic activity .

Beef carcasses must not be aged or ‘ hung ’ for excessive periods as this will affect their storage life . Poultry must be aged for 12 – 24 hours before freezing . Ageing makes its meat more tender than if it were frozen immediately after slaughtering .

FROZEN STORAGE

The exact temperature for frozen storage is not critical , provided it is low enough and does not fluctuate . About -18 ° C for short term and -21 ° C for long term is recommended . The temperature should remain as constant as possible during the whole period of storage . Some products are particularly sensitive to temperature changes . The accuracy of automatic equipment is generally in the range of 1 – 1.5 ° C , which is acceptable . As many packaging materials do not offer complete protection against dehydration , the relative humidity should be kept at 85 to 90 % in frozen storage rooms . This is particularly important for long-term storage .

Proper stacking of products is also important . Adequate air circulation must be maintained around the product . Space must also be left between the stored product and the walls of the storage room in order to eliminate the possibility of the product gaining heat directly from the walls . CLA

High velocities also greatly increase the heat transfer rate . The humidity should be high when chilling to prevent excessive moisture loss .