INCORPORATING COLD CHAIN
CONTRIBUTORS
Facts are stubborn things By Jan Lievens
I mentioned in one of my previous articles that the last 5 % of the timing in your product cycle is important . Fact .
There really seems to be a problem for many people to see and understand exactly what the importance of this statement is . Do you realise and understand that you ( the farmer ) produce blood , sweat , and tears , often with lots of stress as well , for over 8 to 9 months to produce the best possible products on the vine , orchard , bush , or field ?
In the process , nature too throws all kinds of curved cricket balls at you : pests , climate change , rain , often when you really do not need it , insects - the works !
Then you have all kinds of gurus that come and tell you what and what not to do , fancy products , of course only the ones that are allowed , plenty of myths , again : the ‘ Full Monty ’. And , yes , they all have their place in the preharvest scene , of course .
But if you really must start believing one thing - it is that when you grow the near perfect product , the last 5 percent of your efforts sit in the postharvest trajectory after you cut the umbilical cord of your fruit . Fact . Ninety-nine percent of the farm income depends not only solely on what you do in 24 to 48 hours after you did that ; I can tell you it starts within minutes after your harvest . Fact .
Now , I am really going to throw a battery of cats among the pigeons …
Fact , and for the last time , please take note : cold rooms DO NOT maintain RH levels . Cold room panels are usually made from a closed-cell structure steel plate glued on both sides of a closed-cell product that is the insulation .
It has no properties to enhance , create or maintain RH levels in your rooms and , the refrigeration systems get the moisture out of the atmosphere - and your product . Period . It is simple , basic physics .
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The effects of poor post-harvest practices generally only become evident down the line towards the end of the logistics process .
A lot has been said about the time that is needed to cool grapes down to the prescribed temperatures of + 0.8 ° C or even still -0.5 ° C . Everybody wants to cool down as fast as possible and looks at the clock to get the forced air-cooling tunnel time down to a sometimes ridiculously fast time .
Firstly , that is all good and well , but the rule of thumb seems to be forgotten here ; an uncooled table grape deteriorates in an hour at 32 ° C , as much as in a day at 4 ° C , or a week at 0 ° C . That means that the timing from harvest until it reaches the cold room is of utmost importance .
Secondly , what is the RH in your precoolers when you start without fruit inside ? Has this been accurately measured and recorded ? Where are the records kept ? What do you do with the readings ?
Thirdly , what is the core temperature of your product after precooling ? Is it even over the whole line ? Has this been accurately measured and recorded ? Where are the records kept ? What do you do with the readings ?
Fourthly , did you balance the temperature between the precooled product and the temperature in the packhouse ? Has this been accurately measured and recorded ? Where are the records kept ? What do you do with the readings ?
Fifthly , did you ever measure and do all your boxes get measured on the correct end temperature on every position in the tunnel during and at the so-called “ end of the cooling process ”? Or do you , or “ they ” - whoever that might be , only measure the outside boxes , ie the easiest cooling targets ? Has this been accurately measured and recorded ? Where are the records kept ? What do you do with the readings ?
That brings us to remarkably interesting discussion points in our industry .
Jan Lievens , born in Belgium , is a graduate civil engineering ( B ) and international senior consultant for engineered applied postharvest technology at Humiditas South Africa . With over 20 years of experience in this field , he is widely regarded as a specialist in the fruit- , vegetable- and flower industry with regards to humidity , airborne bacteria and ethylene removal , both locally and internationally . Furthermore , he also designed airflow-friendly packaging systems for the industry with proven results .
On the first issue , it is simple : You can talk all you want about the speed of your fast-forced air-cooling facility for as long as you want , if your delay and path between harvest and the cooling tunnel are too long , it does not really matter what the “ fast ” cooling time is . Your product is damaged , and that damage is irreversible .
Some farms still have > 7 hours , and far more in some instances , delay time between harvest and the arrival at the central cooling facilities , often not precooled correctly with too elevated temperatures , too high wind speeds with too low RH , often still not precooling at all .
Then the industry will have to start realising that you still cool like forty years ago with , at that stage , four to five cultivars and that you now have sixty-five cultivars to work with . To tell you the truth , the one-sided cooling regime is for many new varieties a death penalty .
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For decades there has been a disconnect between science and what happens out in the field , at farming level .
COLD LINK AFRICA • June 2022 www . coldlinkafrica . co . za 25