PSI Bulletin: January 2024
HAPPY NEW YEAR TO ALL OUR SUBSCRIBERS
No. 1/24 SUBSCRIBER EDITION: please go to potatostorageinsight.com/subscribe to sign up as a Synopsis subscriber. Most of our bulletins are fully accessible only to our subscribers.
Welcome to the January subscribers' edition of our Synopsis bulletin. Synopsis is PSI's monthly update on key news and developments in the world of potato storage.
It's been a quiet month since our last bulletin with holidays dominating for many, but it's important to remember that crops in store still need to be monitored closely. The recent change in the weather to a colder air stream from the Arctic brought its own threats for crops in store. Please see our January Best Practice piece below.
Feedback from stores suggests that crops which went in early and dry are keeping well, those from later, stickier harvests less so. That said, there are starting to be a few indications of variable quality around, so it is important to be sampling your crop to assess how its matching up to market requirements so that you can act accordingly. Far better than getting an unwanted surprise in a month or two's time!
POTATO STORAGE INSIGHT (PSI) ACTIVITY
2024 Store Managers' Course now full
After little more than 6 weeks since our launch at BP2023, the 2024 Potato Store Managers' Course is already fully booked and we are taking names for the reserve list just in case any places come free.
SPoT storage demonstration store project
We are continuing to collect data for this project, being co-ordinated by Potato Storage Insight, SDF Agriculture and GB Potatoes, in conjunction with our partner organisations at the two south Lincolnshire storage sites which include:
Winters Lane Storage S & S Pugh
Produce Quality Centre (Greenwich University) Potato Storage Treatments
NFU Energy Cornerstone Systems
Biofresh/Safestore Certis Belchim
Hutchinsons Restrain
Crop Systems
A date for the Open Day for dissemination of the work has now been set: Tuesday 14 May. Please keep this free. It will be a free-to-attend event and open to all. We will have much more information about our plans for the day in the coming weeks.
There is still capacity for other partners to come on board with the project and organisations making a commitment will receive stand space at Long Sutton at the Open Day event. Please contact Adrian Cunnington on 07970 072260 if this is of interest.
Finally, my thanks to huge number of people who have sent me messages after I was given the British Potato Industry Award at Harrogate; I very much appreciate all of your kind words and thank you once again.
BEST PRACTICE for January/February
Frost protection
Given that we've just had quite a cold period and are moving into deeper January and February, I thought it worthwhile running through some key points on cold weather management in stores as part of this month's best practice guidance.
All potato stores are environments which, as store managers, we need to protect from the effects of the weather as these can be quite damaging to the crops we are storing irrespective of the target market.
Storage buildings are designed to try to isolate the storage environment from the variable climate outside. We do this with a structure which needs to maintain its integrity to keep the crop dry and to offer sufficient insulation to allow the temperature of the crop to be impacted as little as possible by the vagaries of the weather. We also need to avoid the problem of condensation which can become a very big risk if the external temperature plummets.
The thickness of insulation is not something we can alter during the course of a season but it needs to be sufficient to prevent loss of temperature in the stack due to frost or, perhaps more difficult to minimise, a penetrating gale of freezing air. Typically, we need at least 75mm of good quality insulation in a processing store and up to 100mm in a fresh market or seed storage facility. Roofs on the most modern stores could be as thick as 120mm nowadays. And don't forget the store door itself can be the weakest element of the store; many stores have just a 40mm panel door, especially if they are older installations.
Sealing gaps is another crucial part of making sure the 'insulation envelope' is intact to make sure the crop is protected from wind chill. This means attention to detail around doors using rubber seals (the biggest gaps are often across the top of the door) whilst a can of spray-foam from a local DIY store can go a long way to seal up defective panel joints or cable ports; poor-fitting gutters or the occasional bit of forklift damage to the structure. Without sealing gaps, there is always the risk of cold air penetration which can quickly become sites of condensation, either on the structure (where it drips on to crop) or directly onto the potatoes.
Heaters must be used very carefully in stores. They are clearly of advantage if they can be used to dry or warm ventilating air to increase its drying capacity. But don't go mad! A small amount of heat is often more beneficial than a lot. Using air which is too warm creates a temperature difference in the store and anything more than a 2°C difference is likely to cause condensation somewhere, quite often where it is out of sight. Wet potatoes promote rotting and sprouting.
If the added warmth is to try to preserve fry quality, proceed cautiously. Again, crops will respond best to steady changes rather than abrupt, sharp shots of heat. Try to use dry heat sources rather than anything which is going to have an exhaust laden with carbon dioxide, carbon monoxide and water which might affect quality. And always be aware of the risk of fire from ignition sources or wet/overheated electrical inputs.
Disease
Whilst dealing with cold weather risk, the other key factor that must be remembered for crops stored in a season such as his one is disease.
Any later harvested, less-well-cured material could be susceptible to soft rot but, beyond that, might also be susceptible to skin spot (pictured, top) or even, in damaged crops, gangrene (bottom).
Here are a couple of photos to remind you of the symptoms of these two diseases which tend to favour cooler storage conditions and/or poorer curing. The skin spot lesions tend to become expressed almost without warning at this time of year, whilst the first signs of gangrene may a 'thumbprint' size indentation in the tuber which shows a sharp border against healthy tissue when cut open.
TECHNICAL INSIGHT
This month's Technical Insight is covering temperature measurement. Did you know there are four distinct types of temperature measurement device commonly in use in potato stores?
I thought it might be useful background for store managers and other users to provide some information on each of the types and their respective pros and cons.
So what are they? The devices you use will likely be one or a combination of thermocouples, resistance temperature detectors (RTD), thermistors or infrared sensors. Here's a summary of each one:
Thermocouples: these generally measure temperatures over a very wide temperature range. There are inexpensive and rugged, but lack accuracy and stability so are not ideal for potato stores. However, because they are low cost, I still find many in use in storage buildings.
Thermocouples have two wires composed of dissimilar metals. If these are joined at both ends and one end is heated (the measurement junction), a continuous current is generated in the circuit. The voltage across the two metals (at the reference junction) correlates to temperature.
Resistance temperature detectors (RTDs): an RTD is very simply a piece of metal wire, very often platinum or nickel, that has a known electrical resistance at 0°C. When such a metal wire is heated the resistance increases. This means a temperature can be measured using the resistance of the wire.
Often the sensing wire is wrapped around a ceramic or glass core. As the wire is usually quite fragile, so it is often placed inside a sheathed probe to protect it. By using specific metals whose resistance at various temperatures has been documented, there is a predictable change in resistance as the temperature changes which can be used to determine temperature.
Pt100 sensors are perhaps the best known RTDs and they can be highly accurate. We commonly used them for experimentation at Sutton Bridge. There is a European standard, also known as the DIN or IEC standard, that is considered the world-wide benchmark for platinum RTDs. It requires the RTD to have an electrical resistance of 100.00 ohms (O) at 0°C and a temperature coefficient of resistance (TCR) of 0.00385 O/O/°C between 0 and 100°C.
The downside of RTDs is that they can be subject to 'self-heating' as they have to be energised to operate.
Thermistors: Thermistors are thermally sensitive resistors. They are made from a type of semiconductor. Semiconductors have a greater electrical resistance than conducting materials, but lower resistance than insulating materials. For thermistors, a material is chosen which has a resistance that changes significantly with a small change in temperature; this gives them high accuracy but over a relatively small range of temperature.
For potatoes held in store, this is ideal. We don't need to read a wide range of temperatures so many dedicated control systems used for storage ventilation systems are fitted with thermistors.
Thermistors are often chosen for use in places where ruggedness, reliability, and stability are important. They’re well suited for use in environments with extreme conditions, or where electronic noise is present (such as a potato store!). Many have a 'bead' type of construction that can be used inside a protective sheath that protects the sensor from any effect of disinfectants or sprout control chemicals.
Infrared Sensors: these are suited to many hand-held applications and will measure temperature without any direct contact with the crop simply by pulling the trigger.
IR thermometers are available at very low prices and - providing you accept their limitations - can be a handy addition for any store manager's toolkit.
I find IR thermometers useful in box stores to read temperatures without needing to access high locations or for measurements in pallet slots.
However, there is a price to pay for this convenience in terms of accuracy and readings can often be skewed by any surface which affects surface radiation so it is important to use these devices carefully.
SNIPPETS
New physiological age research in Holland focuses on storage phase of seed potato tubers
Potato News Today reports: ' In new research conducted over three production cycles, focused primarily on the storage phase, researchers selected four potato varieties, each with different physiological characteristics, and subjected them to different storage temperatures. The aim was to introduce variations in physiological age within the same variety. Throughout the 3 storage seasons, the sprouting behaviour of these tubers was periodically evaluated. This provided valuable data on aspects such as the number and weight of sprouts and tuber weight.'
Results showed that seed tubers stored at higher temperatures began to germinate earlier, signalling an accelerated end to ecodormancy. But, over time, those tubers stored at cooler temperatures caught up in terms of the number of sprouts produced. Specifically, tubers stored at the lowest temperature of 4˚C, remained largely in ecodormancy and exhibited minimal sprouting by the end of the storage period. The work concluded that this variation in sprouting behaviour across temperatures and cultivars necessitated a dynamic method to quantify physiological ageing.
A novel mathematical model was therefore developed by the research team: the model effectively described the different sprouting patterns across the range of varieties and storage conditions. It not only accurately captured sprouting behaviour, but also provided information on key parameters relevant for analysing the behaviour trends specific to each variety.
Full article at:
CIPC residue data: a reminder
The CIPC Residues Management Group (CRMG) is the independent industry body now accepting data on CIPC (chlorpropham) residues. These can be from any stores that were previously-treated with the chemical prior to its ban in 2020. If you can help provide residues, which are needed to meet a request from CRD to enable the new temporary MRL of 0.35 mg/kg to be supported, please provide your data. It will be submitted anonymously. Contact CRMG Chair, Adrian Cunnington in the first instance (or call 07970 072260) and he'll advise on how to easily get the data submission organised. See the article first published in our October bulletin for further details.
FORTHCOMING EVENTS
Potato events in the coming months include:
January
Wed 24 SACAPP Conference, Apex Hotel, Dundee
February
It has been announced that there will be consultation meetings about the new National Potato Innovation Centre held on Mondays 5th (JHI, Dundee), 12th (Sandburn Hall, York) and 19th (NIAB, Cambridge) February. Information and booking at Eventbrite.co.uk
Wed 28 - Thu 29 PSI Potato Store Managers' Course, Boroughbridge, Yorkshire.
May
Tue 14 GB Potatoes/PSI/SDF SPot Storage Day, south Lincolnshire.
Save the date. Details to follow.
August
Thu 8 Potatoes in Practce 2024, Dundee
September
Wed 4 - Thu 5 Potato Days UK hosted by Dyson Farming,
Other 2024 International Potato Events
23-26 Jun WORLD POTATO CONGRESS, Adelaide, Australia
7-12 Jul EAPR 22nd TRIENNIAL CONFERENCE, Oslo, Norway
including the 1st European Wireworm Workshop
11-12 Sep POTATO EUROPE, Villers St Christophe, Picardie, France
24-26 Nov INTERPOM '24 Kortrijk, Belgium
Remember you, or a colleague, can subscribe to Synopsis at any time by going to potatostorageinsight.com and clicking on SUBSCRIBE. We can also now take payments by credit card. Call Adrian on 01406 364795 or 07970 072260 if you have any questions.
Subscriptions: we issue invoices as individual subscribers reach the anniversary of their payment. A full year's subs is great value at just £9/month (£108 + VAT per annum), so please renew promptly. Unpaid subscriptions will be closed within 8 weeks of invoice issue. Thank you.
Synopsis is published by Potato Storage Insight Ltd., 45 Main Street, Gedney Dyke, Spalding, PE12 0AJ. UK.
© Potato Storage Insight Ltd. 2024
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