www . refrigerationandaircon . co . za RACA Journal I April 2024 37
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GRANT LAIDLAW
Grant Laidlaw is currently the owner of the Air Conditioning and Refrigeration Academy ( ACRA ) in Edenvale . He holds a Bachelor of Business Administration and an associate degree in educational administration . He has a National Technical Diploma and completed an apprenticeship with Transnet . He has dual-trades status : refrigeration and electrical . He has been involved with SAIRAC for over two decades and served on the Johannesburg committee as chairman and was also president between 2015 and 2018 . Currently he is the SAIRAC national treasurer .
WELCOME TO THE SOLUTIONS PAGE
By Grant Laidlaw
Many people ask for assistance in the understanding of theoretical and practical aspects of the industry . I will endeavour to enlighten . We are going back to basics as I have questions coming in that indicate that the basic understanding necessary to work in industry is not in place .
Joshua asks : I am looking into refrigeration to store foods : what should we consider for refrigeration when we want to store foods ? Temperatures are important but what more should I know ? For example , time .
Hi Joshua , thanks for the question . When dealing with refrigerated storage , for the purposes of food preservation , we find that food products are generally grouped into two categories : a . Products in which the living processes continue and on which low temperature exposure has only a retarding effect . The degree of retardation depends on the temperature level . Fruits and vegetables are examples of foods in this category . b . Non-living substances such as meats , meat products , fish and dairy products . These products are highly susceptible to the activity of spoilage agents . They lack any means of self-preservation and deteriorate rapidly unless drastic preventative measures are taken .
The initial cold storage conditions are determined by firstly looking at the type of food to be stored and secondly , by the length of time such foods are to be kept .
Refrigerated storage may be divided into three general categories : a . Short-term storage – 1 to 15 days b . Long-term storage – 15 to 150 days c . Frozen storage – in excess of 150 days
The storage period in all cases depends on the type of product stored and the condition of the product when it enters the cold store . Some fresh food , such as tomatoes , are damaged by the freezing process and cannot be successfully frozen . To preserve these types of products for longer periods , other methods of preservation must be used .
For short- and long-term storage , products are chilled and stored at a temperature above the product freezing point .
Frozen storage takes place at temperatures far below the product freezing point ; usually temperatures between -12 ° C and -23 ° C are employed , -18 ° C is the temperature most frequently used . Optimum storage conditions depend on :
• the nature of the product
• the length of time it is stored
• whether it is packaged or unpackaged
Whether products are to be stored in a frozen or unfrozen state depends mainly on the length of time they are to be kept , which may be for either short or prolonged periods . There are exceptions to this rule as not all uncooked products can be frozen without irreparable damage – apples and potatoes being good examples .
Some fruits and vegetables are susceptible to cold storage diseases when stored at temperatures above or below their critical storage temperature . Prolonged storage periods necessitate freezing of most commodities in which state they can be held indefinitely . Temperatures in this case are maintained considerably below freezing ( -12 ° C to -25 ° C or lower ).
Meats and other non-living substances as a rule present few problems in their preparation for freezer storage , whereas fruits and vegetables often require considerable processing before they can be frozen in order to safeguard them against deterioration while in storage .
STORAGE CONDITIONS Joshua , with regards to storage conditions , we find that the main cause of deterioration of products such as meat , poultry ,
www . refrigerationandaircon . co . za RACA Journal I April 2024 37