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Should we be storing warmer for fresh market sectors?

Publication Date: 
2 September 2015

Should we be storing warmer for fresh market sectors?

Plant Pathologist, Dr Glyn Harper discusses how long term established practice in storage temperatures has recently been challenged in a three year AHDB levy-funded project.

“Every so often it’s important revisit and retest common practice,” says Glyn. “For the fresh market keeping commercial stores between 2 and 3.5°C is thought to provide the best control to maintain quality, skin finish, and to limit disease and weight loss.”

“However, maintaining low storage temperatures has a significant influence on energy costs. It also has a known trade off in eating quality, as lower temperatures also affect reducing sugar levels and the sweetness of the tubers.”

“Flavour and texture, is influenced by sugar formation in combination with amino acids, it also results in acrylamide production when certain preparation methods are employed,” adds Glyn.

A three year AHDB Potatoes funded trial supported by the Fresh Potato Suppliers Association (FPSA) recently concluded at Sutton Bridge Crop Storage Research (SBCSR). Four well-established varieties, Desiree, King Edward, Marfona and Maris Piper, were stored under controlled conditions at 2.5, 4 and 5.5°C.

“The highest temperature in the study, 5.5°C is very high compared to UK standard practice but is not uncommon across Europe,” explained Glyn.

Skin finish.

“Across all four varieties there was noticeable deterioration in bloom at two monthly intervals,” noted Glyn. “But it was hard to see any difference between the storage temperatures tested with each variety.”

Blemish diseases

Temperature also had no significant effects on Black dot, Silver scurf, and Skin spot over the six month storage period.

“We might have expected some temperature affect on disease development,” said Glyn. “This on reflection could be associated with the rapid pull down.

“Fresh market potatoes are typically pulled down at fast rates, 1°C a day, where possible. This requires good condensation control, with condensation especially aggravating to Silver scurf.

Sprout control

No chlorpropham (CIPC) was applied to the trials and unsurprisingly, some sprouting was apparent after two months and sprouting levels increased at every two month interval.

“Interestingly there was little differences in sprouting of the varieties between 2.5 and 4 °C but there were more significant increases at 5.5 °C,” noted Glyn.

Weight loss

“We’ve tended to assume that temperature has a significant effect on weight loss, however the trials did not find this across the varieties tested.”

“The respiration rate is a key component of energy demand and the amount we need to put into refrigeration. Respiration is an area that we will be exploring further.

Old research, used as an industry standard suggests that respiration rates would be enhanced a 2.5 °C. “This was not the case,” adds Glyn. “Although there was a variety difference, Desiree and King Edward respire a little more than Marfona on average and after six months the respiration rate creeps up in many but not all cases.”

Fry colour

As expected sweetening was more apparent at the lower temperatures for each variety.

Taste and Texture

Organoleptic taste panels tool place at the end of year 2 and 3 and concluded that there was a slight preference for warmer stored potatoes and that lower temperature stored potatoes tasted sweeter, as expected.

Energy costs

The assessment showed that the impact of lowering temperatures from 5.5 to 2.5°C increased energy costs by 11%.  

Further studies

“The research suggests that middle of the range temperatures in the trial provided a cost and taste benefit without dramatically increasing the level of sprouting. We are now doing further work at 3.5°C and results will be shared with our levy-payers,” ended Glyn.  

To watch Glyn’s presentation at AHDB Potatoes On-farm Storage Day, Shropshire in June 2015:

Glyn Harper will be on the SBCSR stand at BP2015 to discuss the work with levy-payers in Harrogate 12 – 13 November. To register go to

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