In 1974 Kimpton installed a heat pump at Walkers Crisps in Leicester that played a key part in the development of the UK crisp industry. It has always been difficult to store potatoes and stop them from sprouting or rotting, but this innovation allowed them to buy in bulk, when prices were cheap and store them for longer than ever before and benefit from a stable and consistently priced supply of their main staple ingredient.
So, how did this come about and what happened before our involvement?
First, a little about about potatoes themselves.
Potatoes were initially cultivated by the Andean people as long as 7-10,000 years ago. They were know for their hardiness and ability to grow in harsh mountain conditions. These early farmers developed many different varieties of potatoes, each suited to different climates and altitudes.
The potato was introduced to Europe by Spanish explorers in the late 16th century. It was initially viewed with suspicion and was not widely adopted as a food crop. However, its ability to grow in poor soil and its high nutritional content eventually led to its widespread acceptance.
In the early days of potato cultivation, potatoes were typically consumed soon after they were harvested. However, as the potato became a more important food crop, farmers began to look for ways to store potatoes for longer periods of time.
One of the earliest techniques for long-term storage was to bury potatoes in pits or cellars. This method helped to keep the potatoes cool and dry, which prevented them from sprouting or rotting. However, this was unreliable. In the 19th century, Potato Clamps became the norm. In a clamp, the potatoes are stacked in layers, with straw between each layer to help absorb moisture and prevent rotting. Commercial-sized clamps were used for storing large quantities of potatoes.
As refrigeration became more common, cold storage became the new norm, replacing the almost agricultural methods of years gone by, but this was still prone to problems with moisture causing rot.
When the commercial production of crisps began in 1913 in the UK, by Frank Smith of Smiths Crisps, potato storage became an industrial scale problem. During World War II, crisps became even more popular in the UK due to rationing and the need for portable, non-perishable snacks. The popularity of crisps continued to grow even further after the war, with new flavours and varieties quickly making them the nations favourite.
Walkers entered the scene in 1948 when a man named Henry Walker first established the business and started out as a small potato-crisp making operation in Leicester. When they introduced new flavours, including salt and vinegar, cheese and onion, and prawn cocktail they quickly grew to become one of the largest crisp manufacturers in the UK.
But the issue of storage still hadn’t been solved.
Prices for potatoes were dependent on the size and quality of the harvest in any given year and for any business, that level of uncertainty is hard to cope with, let alone trade through. But enter Kimpton in 1974 and things were set to change.
Having worked with Walkers and Golden Wonder for some years already on their refrigeration, we worked together with their own technical team to apply the relatively new heat pump technology that we had already been working with, to the issue of long term potato husbandry.
The solution was a careful balance of temperature, humidity, and ventilation to deliver year round stable conditions, whatever the weather, whatever the humidity outside. Finding this sweet spot allowed potatoes to be stored almost indefinitely, without significant degradation. It meant prices became much more stable as they could ride out supply fluctuations and quality could be maintained year round.
The way the system worked
In order to reduce the moisture content of air (dehumidification) the air is cooled and the moisture particles gathered as condensation. This is done by passing the warm moisture laden air at around 20 deg C and 55% Relative Humidity (RH) through a refrigerated coil. The air off the coil is colder and dryer at 5 degrees C and 45% RH
In a conventional system, the cold air would be reintroduced to the space. This would then drop the ambient air temperature, which would mean that the room would have needed significant heating due to the drop in temperature. You can see the original installation here.
Within the Kimpton designed potato drying scheme, the air was cooled and dried and then partially reheated (by approx 10 deg C) using the spent heat from the condensing coil. This is normally a wasted bi-product of the refrigeration cycle. The air would then only need ‘trimming’ where a small temperature increase was required – typically 5 degrees, so as to have a neutral affect on the room temperature. The trimming energy would be a fraction of the energy needed to reheat the space in a conventional system.
You can see some original images of the system here:
We will try and improve these 🙂
We continued to work with Walkers and Golden Wonder for many years in developing and improving the system, that is the worldwide norm today.
Next time you’re wincing at your Worcester Sauce Crisps or sucking on a salt and vinegar, think. Without our work back in the early 1970’s and our early adoption of (h)eat pump technology, it may not taste quite as good as it does today. We’re not trying to claim that we revolutionised the UK potato crisp industry, but we certainly had our hands all over its development.