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Crisp making

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Assignment 1

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Crisp making

Potato crisps are made from fresh potatoes, vegetable oil and flavourings. It takes about 4 tonnes of potatoes to make 1 tonne of crisps. Specific varieties are grown for crisp production, e.g. Saturna, Lady Rosetta. The potatoes must have a high dry matter content and must have a low level of reducing sugars (glucose) in order to ensure the crisps produced have a light golden yellow colour.

Storage
As there is only one potato crop per year across Europe, potatoes have to be stored after harvest (Sep-Oct) until the next new crop arrives (Jun-Jul). Potatoes are stored either in bulk or in wooden slatted boxes. During their time in store it is very important to ensure that they are held at the right temperature and humidity in order to keep them in good condition.
As the industry in Europe uses millions of tonnes of potatoes annually, potatoes which are harvested in the autumn are stored on the farm or in potato stores close to the factory.

Washing
The potatoes are washed to remove any adhering soil and separated from any debris or field material (e.g. stones, sticks, etc.) before moving on to the next stage of the process.

Peeling
Once washed the potatoes are peeled in a rotating drum which has rough surfaces to remove the skin. After peeling, the potatoes pass along a conveyor belt and are visually inspected. Any substandard potatoes are removed by hand.

Grading
The potatoes may also be graded to produce a consistent size. In this process potatoes which are too large are cut in half either manually and/or by automated sizer halvers. Pieces which are too large may cause serious blocking problems later on when the product reaches the packaging stage.

Slicing
The potatoes are then cut into very thin slices, about 1.27mm (0.050 inches) thick. The blades in the slicing machine have to be changed regularly (as much as every hour) to keep them sharp and accurate. Specially shaped slicer blades are needed to produce crinkle, ripple or ridged potato crisps.

Cooking 
The potato slices move on a conveyor belt to large cookers which can fry up to 4000 kg of crisps per hour. The frying operation is normally continuous with fresh oil being added as it is used up in the cooking process. Control of temperatures along the cooker are important as is ensuring that the final moisture content of the product is less than 2%. It is equally important not to overcook the product.

Quality check
After cooking, the product is inspected to ensure it meets the specification. Traditionally this was a manual operation but nowadays it is normally done by an inline sorting machine. This optical sorting machine utilises an array of cameras (UV, laser, visual, etc.) to check for crisp colour and product defects and blemishes.

Flavouring  
The crisps pass through a rotating flavour drum where they are lightly sprinkled with salt or other flavours. The rotating drum makes sure the flavouring is evenly distributed over all the crisps.  

Packaging
The flavoured crisps are fed from a conveyor belt onto the multi-head weigher sitting above the packaging machine. Here the 8 - 14 head weighers select the 'best' combination of heads to give the packet weight desired. That is the end of the process. The crisps are then transported to the shops. Then millions of us buy and enjoy them every day.

 

Assignment 2

Questions

  1. Which variety of potato do you need to make crisps?
  2. What is important when potatoes are stored after harvest?
  3. What is the first thing that happens to potatoes in the factory?
  4. How are potatoes peeled in the factory?
  5. Why are potatoes graded?
  6. What part of the slicing machine has to be changed regularly?
  7. What is important for the cooking process?
  8. What happens after the crisps are cooked?
  9. What is sprinkled on the crisps to flavour them?
  10. What does the multi-head weigher do?