Frequently asked questions
1. Why do potatoes go green?
Greening is caused when potatoes are exposed to light. The greening is due to the presence of a substance called solanine, which is poisonous. If there is only a small portion of the potato that is green, cut it off and discard.
2. Why do some potatoes go grey when they are cooked?
This is related to the iron content of the potato. At certain times in the year the iron content of the soil varies – when the iron content of the soil is low the potatoes tend to grey if they are cut open and/or cooked and left at high temperatures. To stop this, add some lemon juice to the water and this will reduce the greying.
3. Why do potatoes vary?
The growing conditions of a potato greatly influence the characteristics of a particular potato. A similar potato which is grown in different conditions, e.g.amount of rain, frost, soil type, can show different qualities in terms of cooking attributes and flavour.
4. If I select a potato variety I really like, why does it cook, and sometimes taste, differently from time to time?
This is the nature of the potato and it is why the industry is reticent to make a claim about a particular potato variety and its performance. See seasonal changes.
5. I have heard potatoes described as waxy and floury – what does this mean?
There are two main parts of a potato – water and starch. The more starch in the potato the more ‘floury’ it is, and the more water, the waxier its texture is. The amount of water and starch affects how potatoes cook. A potato with lots of starch goes really fluffy and soft when cooked -so it is ideal to mash or bake. A potato with less starch has a waxy, more solid, texture when cooked making it ideal for boiling or to use in salads. Some potatoes have moderate amounts of starch. These potatoes fall into the ‘general purpose’ category and will tend to perform most tasks, although perhaps with not as good results as potatoes which clearly fall into the floury or waxy category. Look for the label and purchase potatoes for end use.
Download the ‘Potato varieties and how they cook’ poster from the Download section to the right.
6. Why do some potatoes fall apart when boiling?
Some potatoes retain their shape better than others. This depends on the structure of the potato. Potatoes which disintegrate when boiling tend to be floury – which are better suited to mashing. It is also sometimes due to the cooking technique being too aggressive – i.e. boiling too hard or for too long.
7. Why do some potatoes brown better when making them into chips or wedges?
This is due to the sugar level in the potatoes. Potatoes with a naturally high sugar level will brown a lot faster that those with a low sugar level. This is why processing manufacturers are particularly careful to monitor sugar levels. Sugar levels are higher in new potatoes before the sugar is converted to starch.
8. Why do some potatoes have a hole in the centre?
This is called hollow heart. This may be seen in small potatoes but it is more likely in large or over-mature potatoes. They are safe to eat.
9. Can I eat raw potatoes?
Potatoes.co.nz recommends cooking potatoes and to avoid eating them raw.
Cooking potatoes breaks down the starch in the potato and makes it easier for the body to digest. The resistant starch in uncooked potatoes is harder for the body to digest and can cause abdominal cramps, fever, diarrhoea or vomiting.
Regular consumption of raw potatoes may lead to a fatty liver which can cause pain in the abdomen, fatigue and weight loss.
Eating a raw potato occasionally maybe OK, however always remove the skin. As potatoes are grown in the ground they are susceptible to naturally occurring pathogens and other residues that may reside on the skin, cooking however kills these pathogens.
10. Is the Carisma variety of potato available in New Zealand?
This variety has a low GI rating that may be suitable for diabetics.
Currently the Carisma variety is not available in New Zealand.
With the media commentary around low GI foods, Potatoes New Zealand Inc.’s viewpoint is that despite potatoes having a higher GI rating than other foods, we very rarely eat them in isolation. Instead we choose to consume them as part of a whole meal and the cumulative effect of other foods lowers the GI of the entire meal.
We have more information available for you to read about Glycaemic Index on our website here: /nutrition/glycaemic-index.asp
11. Are Kipfler potatoes available in New Zealand?
We do not currently have this variety on the market in New Zealand.
Characteristics of Kipfler potatoes are small and finger like, with yellow skin and yellow flesh. They are waxy or smooth in texture so are best for boiling and use in salads.
Despite not having the Kipfler variety we have a wide range of other varieties available here in New Zealand.
Waxy textured potatoes or those specified for boiling or salads would be suitable to use in place of Kipfler’s as they hold together when cooked (unlike fluffy/floury textured potatoes).
More information about cooking and the varieties is available on our website: /Potato_know_how/end_use.asp