Popcorn – nutrition and gelatinisation NEA 1

Popcorn makes a fun lesson for food science and you can explore lots of food knowledge.

I know it’s not a healthy food, but that’s the point – let students discover its nutrition – mostly starch.

Here’s some activities you can investigate

  • For teachers – what is the value of a lesson with popcorn?
  • Find 20 popular products made from maize. Now plan a day’s meals and snacks with foods made from maize.
  • Find the nutritional value of plain popcorn and then find health claims people are making
  • What is the science behind popped corn? Look at popping kernels then look at popped corn and work it out!
  • How much does it cost? Compare supermarket sites for cost 100g. Where does it come from?
  • Get hold of a bag of cinema popcorn and fill it with popcorn you have made – work out how much it has cost.

Nutrition of cinema popcorn

I can’t find the weight of Cinema popcorn but here’s some nutrition data from The Odeon – fascinating reading.

How much popcorn in a box?

How much popcorn in a box?

Sweet popcorn – small 318 kcal 15g sugar 3.5 tsp sugar

Sweet popcorn – medium 522 kcal 26g sugar 6 tsp

How many teaspoons of sugar in sweet popcorn

How many teaspoons of sugar in sweet popcorn

Sweet popcorn  – large 816 kcal 40g sugar 9 teaspoons sugar

Salt popcorn – small 357 kcal 0.48g sugar 0.7g salt

Salt popcorn – medium 609 kcal 1.2g salt

Salt popcorn – large 812 kcal 1.6 g salt

Small coke 195 kcal, 48g sugar (11 tsp)

Small fanta 195 kcal, 48g sugar (11 tsp)

Large coke 390 kcal, 97g sugar (22 tsp)

World Health Organisation suggests we cut sugar to 5% daily intake.

That’s about 25g (around six teaspoons) for an adult of normal weight every day.

A teaspoon of sugar weighs 4.4g so

The large popcorn bags are intended for sharing but are often eaten by just one person.

Make your own popcorn in a microwave

Ingredients

10g popping corn

Equipment – clear plastic food container with lid, plate

Method

Put the popping corn in the food container and put lid on top.

Cook in the microwave for 1 minute. Some kernels may begin to pop. Removed the popped ones and microwave for a further minute.

Remove the popped kernels and heat the remaining ones again. You will find that some do not pop – this is because they are too hard and dry.

Take care when you open the lid as the steam is hot.

Now think of the science – the kernel is heated and the water in the kernel heats and turns to steam.

The starch in the kernel gelatinises with the water and expands and the steam and the cooked starch explode outside the kernel.

popcorn cooked

Cooked popcorn gelatinisation

This bursts the grain and the starchy gooe turns inside out and the protein in the maize coagulates forming the popcorn.

  1. Heat the oil in a large, thick bottom saucepan.
  2. Put 4-5 popping corns into the oil and when they pop, add the remaining corns.
  3. Cover with a tight fitting lid and remove from the heat. Count to 30 – this brings all the corns to the right temperature ready for popping.
  4. Put the pan back on the heat with the lid on – you can hear the corns popping.
  5. Leave the lid slightly open to allow steam to escape.
  6. When the popping begins to stop, remove from the heat and put the popped corn into a bowl.
  7. Remove any unpopped corn – these are very hard and can break your teeth.
  8. Popcorn needs to be eaten soon after it is made – or store in a closed plastic bag for a short time.

Flavour the corn with salt mixed with finely ground spices such as smoked paprika, cumin and coriander.

popcorn kernels and cooked

Unpopped corn and the cooked amount

Sweet popcorn can be tossed with icing sugar and cinnamon.

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Pink pickled turnips

Pink pickled turnips are a favourite ingredient in falafel wraps and mezze in the Middle East.

Pink pickled turnips - done!!

Pink pickled turnips – done!!

The science of making them is amazing – osmosis transfer of the colour from the beetroot to the white turnips.

Ingredients

500g small white turnips

1 small red beetroot 25g

25g salt

300ml white distilled vinegar

300ml water

1 teaspoon sugar

1 red chilli

Method

  1. Peel the turnips and the beetroot to remove outside skin.
  2. Cut into 1 cm chip sized shapes. Put in a bowl and sprinkle over 1 tablespoon of salt. Leave for 15 minutes so that the turnips soften.
  3. Heat the vinegar, water and sugar in a saucepan
  4. Wash the turnip chips by placing in a sieve and running cold water through them. Dry with paper towel
  5. Place turnip chips into a glass jar and cover with the slices of beetroot.
  6. Pour over the vinegar mixture – you can add chilli for flavour.
  7. Cover and store for a week to allow the turnips have turned pink. Leave for longer and they will turn pinker. They can be stored for up to 6 weeks in the refrigerator.
  8. The pickled turnip strips can be used as dips for hummus or rolled up with falafel in pitta bread with some tahini dip. I like to remove the beetroot strips as they lose their colour in the pickling.

Pink pickled turnipspickled turnipsturnip3Pink turnips after week

Pink pickled turnips - done!!

Pink pickled turnips – done!!

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Pickled onions – the science

Pickled onions with star anise, mustard seeds and peppercorns

Pickled onions with star anise, mustard seeds and peppercorns

Seal in jars and leave for 6 weeks to infuse

Seal in jars and leave for 6 weeks to infuse

Ingredients

600ml brown malt vinegar

500g small pickling onions

25g table salt

100g brown sugar

10 peppercorns

2tsp mustard seeds

4 star anise
(You can swap spices to your own taste so use coriander or cumin seeds, chillies and bay leaves.)

Method

  1. Put the unpeeled onions in a large bowl and pour over some very hot water water. Leave for a minute then pour into a colander or sieve to remove the water.
  2. The onion skins should peel off very easily! But watch out they can make you cry.
  3. Put the peeled onions a bowl and sprinkle with salt. Turn the onions with your hands to coat each one with salt.
  4. Cover and leave overnight or up to 24hrs.
  5. Pour the vinegar and sugar into a large saucepan with the peppercorns, mustard seeds and star anise. Boil then remove from the heat, cover with a lid and leave to let the vinegar absorb the flavour of the spices.
  6. Next day rinse the onions well to remove the salt and dry with a paper towel.
Pack the onions into sterilised jars.
  7. Pour over the vinegar, including the mustard, peppercorns and star anise, to cover the onions. Seal and allow to mature for 6 weeks.

The science bit

Adding salt to the onions before they are pickled, removes some of the water in the onion cells by osmosis. Removal of water helps the onions keep longer as bacteria, yeasts and moulds cannot multiply so quickly.

The onions are pickled in a sugar, spice and vinegar solution.

The vinegar changes the pH and prevents the enzymes and the microorganisms from working so the onions are preserved and keep for a long time.

My blog on Cooking in the 1970s

Here is the link to my pickled onion lesson of 1972.

Pickled onions

It made the boys cry but the room had wonderful smells of pickling!

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Making kefir from kefir grains

Kefir is the latest super food so I’m having a go at fermenting water kefir grains to ‘make an alternative to fizzy drink’ and that doesn’t mean champagne

Kefir is a fermented pro-biotic food made from fermenting micro-organisms. Water kefir is made from fermenting the kefir grains in sugar and water.

So the science on the website says:

The beneficial bacteria and yeasts present in the kefir grains metabolise the sugar and turn it into acetic acid.

The grains look like clear, colourless jelly and they are made of ‘lactobacillus hilgardii’.kefir

Method

Dissolve 60g of sugar in 750ml water.

Add the grains and some fruit flavours such as lemon and raisins or chopped ginger root.

Let it ferment in a glass jar for 24-72 hours with a J cloth as a soft lid.

strain the grains and put the strained liquid into smaller jars.

Leave 24-48 hours to ferment then chill and enjoy as a drink.

What the scientists think about kefir and probiotics.

‘There is no benefit to probiotics to repopulate gut bacteria – ref European Food Safety Authority.

Nutrition for 100ml

Typical Values per 100ml
Energy kJ 243
Energy kcal 58
Fat (g) 3.0
of which saturates (g) 2.0
Carbohydrates (g) 4.6
of which sugars (g) 2.8
Fibre (g) 0.5
Protein (g) 3.2
Salt (g) 0.1

Milk kefir

Milk kefir is a natural probiotic, living culture and the grains look like small cauliflower florets. As the culture ferments the milk, these grains grow, creating new grains in the process.

Add a tablespoon of grains to about two cups of raw organic milk in a glass container and cover loosely to allow fermentation gases to escape. A piece of cheesecloth secured with an elastic band works very well.

After 24 hours strain with a plastic strainer into a container– do not use metal utensils. Place the grains that were caught in the strainer into another container with 2 cups of milk to make a fresh batch of kefir. The strained milk can be used or refrigerated until required. Repeat this process about every 18 – 24 hours.

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Don’t put these foods in the fridge – the science!

  1. Bread – it dries and goes stale faster than in a bread bin. Use a bread bag and store in bread bin.

This is why the bread in chilled sandwiches sold in supermarkets is often dry and feels stale.

The science – Moisture is lost during storage which dries out the bread. But there is retrogradation and recrystallisation of starch which makes the bread harden. The bread in the fridge is stored in a cold environment and recrystallisation happens much faster than in the warm.

Experiment – take some slices of bread and share into 4 portions. Pack one portion in a paper bag, pack one in foil, pack one in plastic bag and store in fridge, pack one in plastic bag and store in freezer.  Hope you find the best way is to wrap, store in freezer, then reheat when you need it!

2. Tomatoes – they lose their taste when stored in the fridge so keep at room temperature.

The science – the flavour of tomatoes comes from sugars, acids and volatile compounds. If a tomato is stored at room temperature it keeps its volatiles but in the fridge the volatiles break down, the tomato changes texture and breaks down quicker.

3. Garlic Keep at room temperature in the dry as the fridge does not help it keep longer.

4. Avocados Keep in a brown bag but to speed up ripening, keep next to a ripe banana.

The science – avocados will not ripen in cold conditions and the cold fridge can break the fruit cells and the enzymes will react and turn the fruit black. If the avocado is cut, the flesh must be tossed in lemon juice to stop the enzymes from working and changing the colour from green to brown.

5. Onions – keep in dark to avoid sprouting – in the fridge their aroma can spread to other foods.

6. Honey It never goes off so store in food cupboard.

The science – honey is so high in sugar that it is not affected by bacteria, yeasts or enzymes so does not change.

7. Cake – like bread, cakes go stale quickly in the fridge. Fresh cream cakes need to go in the fridge though.

The science -the mixture dries out and the starch in the cake retrogrades and the starch crystallises and makes the cake mixture drier.

8. Melons – uncut melons are stored at room temperature, but once cut put in the fridge.

9. Coffee – best kept in an airtight container, not in the fridge as it absorbs smells of other foods.

The science – the cold causes condensation of water in the coffee grains and this changes the flavour.

Click here for more

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