Potatoes come in all sorts of shapes and sizes, even colours! For our needs we want a nice round or oval shape to make it easy for them to be peeled in the potato peeler or rumbler.
You need a floury potato rather than a waxy variety. Some varieties are not good for chipping and are better suited to being boiled, we want potatoes with a higher dry matter of around 22%. Dry matter is quite complicated to calculate but your potato merchant should be able to tell you what the drymatter of a particular sample is.
We want shallow eyes as if the eyes are deep you will have to do more work by hand on the potatoes to remove blemishes.
The potatoes should be firm when you touch them, potatoes can get dehydrated in storage or when they start to grow and become very soft on the outside, making them difficult to peel.
The ideal size range of potatoes would be 60-80mm but the processing industry need these tight graded raw materials as they are processing at a rate of many tonnes per hour. We can handle a bit more variation but it is better they are above 40mm and below 100-120mm. Larger potatoes are difficult to fit in the chipper and can also be hollow in the middle. Smaller potatoes tend to get stuck at the bottom of the peeler and get over peeled.
Check the Potato Sack
The back of the sack should have the variety clearly marked.
Ideally the bag should be printed with the growers name or brand so they can be traced back to source.
The sacks should show no sign of moisture coming through, if you can see wet patches it could be a sign of damaged or rotten potatoes.
Potatoes store energy as starch and convert it to sugar when they need to use it. This can be when they are growing, when the are fighting disease or mechanical damage but most often when they are exposed to cold temperatures.
You can test the sugar content by using Sugar Testing Strips. We recommend the ones produced by Drywite as they are designed for use with potatoes.
If you select a small potato and cut it in half you can then place the testing strip between the two halves of the potato and press them together on it for around 15 seconds. The pad on the testing strip should change colour and you can compare it against the colour chart on the side of the pack of testing strips to determine if the sugar is low enough to accept the delivery.
If potatoes are harvested in rainy or wet conditions you can find there is a lot of soil stuck to the tubers. Sometimes there maybe no alternative as all potatoes on the market may have the same issue but it is something you can raise with your merchant.
To calculate the weight of soil you can weigh a 5kg sample, wash the potatoes and then re-weigh them. If you divide 100 by the first weight and multiply it by the second you get the weight of the actual potatoes, subtract this from 100 and you have you percentage of soil.
Damage and Disease
When potatoes are damaged or diseased they convert their starch to sugar, this will cause the chips to cook dark resulting in a mixed fry colour in your chips. It is a good idea to visually inspect the potatoes to ensure they are firm and have no sign of damage on the surface.
Pre Prepared Chips
When you receive a delivery of preprepared chips you should check there is a label with the best before date . It is also best practice to know the variety and the farm the potatoes were grown.
Give the bags a visual check for eyes and green potatoes. There should also be as little water in the bag as possible, on loose bags this will fall to the bottom and over treat the chips it is in contact with. If the chips are vacuum packed then the water will surround all the chips and over treat them. To check for water in a vacuum packed bag you will need to pop the bag and hold it so that all the water runs to a bottom corner.
Pre-prepared chips should be refrigerated and it is important to preserve the cool chain by storing them in a fridge. Ensure they do not freeze where they come into contact with the back of the refrigerator. You can store chips as low as 2 degrees without any issue as starch will not turn into sugar once chipped and treated.