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Function of potatoes

Potatoes are a very important ingredient for many cold and hot dishes. The many uses and the different cooking techniques of the species the potato can be served in many different ways with dishes.

Potatoes can be used in various menu courses:

  • In cold starters, as a part of a composed potato salad or as a potato terrine
  • As a part of a farce, quenelles, panade or gnocchi
  • In soups, as a base or with the preparation of puree soups
  • In main courses, as accompaniment of the main course, either hot or cold, as boiled/steamed (with or without the skin) or deep fried/bakes or as a potato salad
roast potatoes

Also the starch in the potato that consists of carbohydrates is a very important binding agent in soups and sauces. Next to that potato starch is used as sago, tapioca or glucose syrup in de food industry

The nutritional value of potatoes

The kind of soil that potatoes grow on determines the amount of starch the potato contains. Potatoes that grow on clay contain more starch. We say that these potatoes cook mealy. Potatoes that grow on a sandy soil contain little starch. These potatoes cook not to medium mealy.

Potatoes are an important part of our daily food and they don’t contain a lot of calories. The potato is built up in the following way:

  • Water              77%
  • Starch             17% (2% egg white, 98% carbohydrates)
  • Vitamin B1
  • Vitamin B2
  • Vitamin C
  • Calcium
  • Kalium
  • Iron
  • Phosphor

Especially new potatoes contain a lot of vitamin C. The longer the potatoes are kept, the lower the amount of vitamin C becomes.

Purchasing potatoes

When purchasing potatoes you have to pay attention to the following things:

  1. The species
  2. The physical condition
  3. The quality
  4. The price
  1. The species
    Depending on the race potatoes have certain characteristics. Some species like the eersteling (the firstling) cook not mealy at all while the “eigenheimer”cooks very mealy. A potato like the Dore is perfect for scraping by machines. Eigenheimers are not very suitable to be peeled by a machine because their eyes lie very deep. In certain conditions new plants can grow from the eyes of the potato. Some species like the Irene can be kept for a long time. The “alpha “then again is very perishable

Clay potatoes have high starch content. Sand potatoes have very low starch content. Depending on the method of preparation en the final product we can make a choice between potatoes that cook very mealy or potatoes that don’t cook mealy

Very mealy:  

  • Eigenheimer
  • Irene

Medium mealy

  • Bildtstar
  • Bintje
  • Sante

Not mealy

  • Accent
  • Nicola
  • Oppperdoezer
  • Timate

Not all potatoes are available throughout the whole year. We can make a distinction between.

  • Early potatoes that are harvested in Holland in June and July
  • Midd early potatoes that are harvested in august and September
  • Midd late/ late species, that are harvested between half September and the end of October

What are new potatoes?
New potatoes (from the new harvest) are mainly suitable for direct use. They are harvested when they haven’t completely grown and have a very thin peel. These potatoes are mostly imported because Dutch potatoes are still in the ground. As we have seen above, the first Dutch new potatoes from Dutch soil come on the market in June. The first harvested new potatoes in March origin from south European and North African countries such as Egypt, Israel, Greece and Algeria. These potatoes are still a bit Dutch because they are grown from Dutch seed potatoes that have been exported to these countries.

The Dutch potato race “alpha “is grown on the island Malta in the Mediterranean Sea. The potatoes that come out of the ground there come on to the market in February or march as “alphas “or “maltas “. When these potatoes are subjected to light, they quickly turn green. That is why they have to be kept in a dark place. That also counts for all potatoes that can be kept for a long or short time. New potatoes have a very fine taste and should not be peeled because of their thin peel. They should be scraped, they are available until august.
N.B: do not confuse new potatoes with “small potatoes”. These are potatoes that have been selected for their smallness and are available throughout the year. You can get both early small potatoes and late small potatoes

  1. The physical condition

We can buy potatoes in three conditions

  1. Fresh potatoes
  2. Pre treated potatoes
  3. Potato products
  1. Fresh potatoes

Fresh potatoes can be bought loose at any greengrocer and wholesaler in packages varying from 2,5 kg to 25 kg. Both loose and packaged potatoes have mostly been washed when you buy them

  1. Pre treated potatoes

With pre treated potatoes you have to know in what way the peel has been taken off. We know:

  • Scraped potatoes. These are scraped by a machine and then pipped, where they deep lying eyes are cut out. There is a chance that these potatoes are broozed by the machine that scrapes them. These brooses can shorten the shelf life of the potatoes. Unpackaged scrapes potatoes have to be kept in water and in a dark environment to prevent discolouring. These potatoes have to be processed as quickly as possible
  • Peeled potatoes. These are always peels by hand. Therefore the chance of bruising the potatoes is very small and they can be kept for a longer period. Unpackaged peeled potatoes have to be kept in water and in a dark place to prevent discolouring
  • Chilled, peeled and vacuumed potatoes

  1. Potato products

Next to fresh or pre treated potatoes there are also potato products. We know:

  • Pre fried and chilled or frozen French fries, potato croquettes and rosti
  • Fried products that have been packaged with flavourings such as crisps
  • Sterilized pommes pariesienne that have been canned or blocks and slices of potato that have been vacuumed

These products are sold packaged. Therefore you have to carefully check the expiry date, the method of preparation and that kind of information that is always displayed on the label

The following products that come from potatoes can be used as a binding agent:

  • Potato-starch. This is a powder that is used to bind soups, sauces and watery vegetables so that the liquid binds clear. When it is used in large quantities it binds like glue. It is often used in the food-industry. It is a glistening powder that has a blue-white colour. To prevent lumps you have to dissolve the starch in cold water before you mix it with a hot fluid
  • Potato-sago. This is a potato starch in granulated form. The granules lose their shape when we mix them with fluids. Sago binds clear aswell
  • Tapioca. This is granulated potato starch
  • Glucose-syrup. This is heavy, sweet and blank syrup. This syrup is not as sweet as sugar syrup. Glucose-syrup is used in products such as ice cream, jams, confit of fruits, lemonades, chocolate, liquors, meat products, dairy products, sauces, baby and dietary products. Glucose-syrup in solid form is called “masse”

  1. The quality

To purchase potatoes of a good quality, you have to be aware of the characteristics of a good potato

The government of the country where the potatoes are purchased always regulates the minimal standards that potatoes should have. In Holland this is done in the “landbouwkwaliteitsverorderding consumptie-aardappelen 1987 “. This document describes the quality and sorting requirements for consumption potatoes. These requirements concern the trading criteria. Although they are not the prime responsibility of a chef it can enable him or her to see if the potatoes comply with these criteria

Next to the minimum requirements good quality potatoes should:

  1. Have a Blanc peel. No green discolouring or blue/black marks may be visible
  2. They may not have any internal harts or rust marks
  3. They may not have any growing-cracks or any sprouting
  4. They have to be even and smooth and may have as little eyes and pips as possible

When you have to purchase large quantities of potatoes, ask the supplier for a sample of the potato at the beginning of the season. Check if the potatoes of the new harvest are good enough to boil. Then you know for sure that you always work with the right quality potato. For long term storage (a month) it is best to purchase potatoes that are harvested around September or later.

  1. The price

The price of potatoes is determined through the manor of growing and the availability. Biologically grown potatoes are due to a small-scale production and smaller revenue per hectare more expensive than normal grown potatoes. The same goes for species that are less popular and therefore a not produced on a high scale. In general you can say that potatoes from the new harvest are more expensive than old potatoes because of the high demand and the limited supply.

The handling of mushrooms in the kitchen

When treating potatoes in the kitchen we make a distinction in freshness. We speak of the following

  1. The treatment of fresh potatoes
  2. The treatment of pre-treated potatoes
  3. The treatment of potato products

There are two golden rules for a good treatment of potatoes’

Golden rule 1:            pay attention to correct storage

Potatoes have to be stored in a frost-free, dry, cool and dark environment where the air can easily be refreshed. The ideal temperature for storing potatoes is between 6º and 10º Celsius. If potatoes are kept below a temperature of 5º Celsius they will get a sweet taste

Golden rule 2:            pay attention to signs of decay

Check the potatoes on arrival in the kitchen on signs of decay and diseases. Moulds and bacteria cause most diseases
The most common diseases are:

  • Potato disease. This field disease causes browny, sometimes sunken spots on the potato that develop till deep in the flesh. This could also be called “rot”
  • Dry-rot. A fungus causes this storage disease. The fungus can develop really fast when the potatoes are stored in a temperature that is too high. The species “bintje “and “primura “are very sensitive to this disease. The potatoes go wrinkly and soft
  • Scabs. This is deterioration in quality that is caused by a fungus. This causes harmless mouldy spots on the peel. Mostly after peeling the potato the problem is solved

Be careful that the potatoes don’t show any green discolouring. This change in colour is caused by the toxic substance “solanine “. This toxic substance exists in all green parts of the potato plant, but also in parts of the potato that have turned green. Solanine causes a bitter taste. When the green parts are cut of, the potato can be used for consumption again.
You also have to pay attention to blue-sensitivity, that is caused by broosing or falling during the transport, underlying discolouring that is caused by broosing during transport or harvesting and glazy ness due to a growing stop. Sampling and peeling potatoes at random can discover glazy ness and underlying discolouring.

  1. The treatment of fresh potatoes

The treatment of fresh potatoes can differ in various situations but in every company you have to pay attention to

    1. The transport
    2. The receiving of the goods in the kitchen
    3. The storage
  1. The transport

When potatoes are transported you have to pay attention to the following things:
The temperature during transport and delivery
The packaging
The humidity level

The temperature during transport must preferably be at least 12ºC. During the transport the potatoes will bump into each other a lot. Especially when potatoes are transported in a low temperature, the bruising can cause blue spots. The blue sensitivity will be lower when the temperature during transportation is above 12ºC. Fresh potatoes are packaged in bags that contain holes. A potato is a living product that needs air to breath. If these holes would not be in there the potatoes could choke and start to rot

  1. Receiving in the kitchen

When receiving the potatoes in the kitchen you have to pay attention to a number of characteristics. Potatoes definitely have to qualify to the following:
They have to have a Blanc peel
They have to be of the desired species
They have to equally sized
No sand, clay or loose sprouting may be in between the potatoes

  1. Storage

The best storage temperature for consumption potatoes lies between 5-8ºC. If potatoes are stored below 5ºC the starch is turned into sugar. The potatoes then will get a sweet taste. If potatoes are kept at a temperature below zero the cells in the potato break. After and during defrosting the potato looses fluids out of the broken cells. The potato becomes week, soft and will rot very quickly. Potatoes that are stored to dry and warm can, during the winter months, start to sprout. Then the potatoes will also become weak and wrinkly. The potato will lose a lot of its vitamin C content

When you have to store potatoes for a long period (3 to 6 moths) they have to be stored in a dark place. Light causes the forming of solanine and that process shows in the form of green spots. This mainly counts for the new harvested potatoes.
New potatoes can only be kept for a short period. The time between harvesting and eating cannot be much longer than 4 weeks. Potatoes that can be kept for a longer period are available around September and can be kept till 6 months after purchasing them when stored in the right manor

Potatoes that are stored for a longer period can be treated with a substance that slows down the sprouting process. The amount of this substance is not allowed to be over 0.5 percent of the amount of potatoes that you want to treat with it. A thousand kilograms of potatoes are treated with 5 kg of the substance that is added gradually. Potatoes that have been treated can only be used 3 months after treatment

  1. The treatment of pre-treated fresh potatoes

Scraped potatoes are not allowed to have green peeling spots. That identifies a high content of solanine. Directly store them in water. Scraped potatoes that are not stored in water discolour under the influence of light to a blue/black colour
Peeled or scraped potatoes have to be kept in water at a temperature of +/- 8ºC. Then they can be kept for a maximum of one day

Pay attention to the use of sulphite
Peeled potatoes that can be bought dry, without being stored in water contain the substance sulphite. Sulphite influences the colour and the nutritional content in a negative way. When sulphite is used the potatoes will keep their Blanc colour. 50 mg of sulphite per kg of potatoes is allowed to be used

Sulphite can cause allergic reactions. For example tightness of the chest. The amounts of sulphite that can be used in other potato products are
Potato puree: max 100 mg/kilo
Peeled potatoes: max 50 mg /kilo

  1. Treatment of potato-products

Pre-treated potatoes are categorized in the following manor

    1. Chilled potato products
    2. Deep-frozen potato products
    3. Dried potato products
    4. Deriveries of potatoes
  1. Chilled potato products

Chilled potato products can be raw, blanched or pre-fried. Raw and blanched products are supplied vacuumed which influences the nutritional content and the shelf life in a positive way. They have to be kept at a temperature of 3ºC in the fridge.
Pre-fried chips are depending on the weight supplied in vacuum bags or in boxes of 10 kg.

  1. Deep frozen potato products

Deep frozen potato products are always pre-fried. They have to be kept at a temperature of -18ºC. These products can be kept for 3 months without them losing any flavour. There is a big assortment in frozen potato products available. They have to be fried in a frozen state in the deep fryer.

  1. Dried potato products

Dried potato products are products based on puree. By adding liquid, herbs, spices to the powder you can make certain potato products yourself

  1. Potato deriveries

These are products such as binding agents that have come from potatoes. These are always sold packaged. On delivery pay attention if the package is intact. Store these products in a coo land dry spot

Cultivation of potatoes

Potato species are grown especially so that they can grow on different kinds of soil and the yield is as big as possible. There are also species that can grow both on sand and clay. The prime example being the “bintje “.

In the Netherlands the potatoes are grown in 3 manors:

  1. Traditionally
  2. Integrated
  3. Biological
  1. Traditional

When potatoes are grown in a traditional manor the primary goal is to have the biggest yield per hectare as possible, the potatoes are of a good quality and often cheap. The traditional growing of potatoes is not very friendly for the environment because a lot of chemicals are used to protect the plants

  1. Integrated

Integrated growing of potatoes is in between biological and traditional growing. The goal is to get the highest yield possible while damaging the environment as little as possible

  1. Biological

When potatoes are biologically grown no chemical substances or artificial manor is used at all. Specially selected races like the “sante “ or “Nicola “ are grown in this manor. Potatoes that are grown biologically are not available throughout the year are mostly more expensive than the other potatoes