Learning Journey: Food Technology

Day 1 - 20 June 2017

Salts – all sodium chloride. You can taste the difference and they have different uses (for seasoning whilst cooking or after cooking etc.)

Salts.jpg

Looking at bread – every world culture has some kind of bread. Bread involves many processes and examples of food science.

Make bread with strong flour – made from a different variety of wheat which contains more protein and the protein is what makes gluten. Gluten is made of 2 types of protein called glutenins and gliadins. It is stretchy so gives bread its chewy, not crumbly, structure. Kneading the dough develops the gluten and the proteins coagulate when heated, so the bread stays risen.

White flour has had the wheatgerm removed, so that what is left is the starch. Experiment for observing the amount of gluten vs starch in different flours:

Gluten pg1.jpg

Gluten pg2.jpg

Gluten experiment 1.jpg

Gluten experiment 2.jpg

Some of the little balls of dough with the starch washed out rose (or blew up like balloons) because the water within was turned to steam, thus expanding when baked. The strong wholemeal flours may have had a similar level of gluten in the unprocessed grain as the strong white, but are unable to rise as well because the wheatgerm disrupts (literally gets in the way of) the gluten's development (and there is less gluten by weight because more of the flour is made up of wheatgerm).

We set up some test tubes containing yeast to see under what circumstances it would become active and create gas (CO2). One was left as simply yeast; to one we added warm water; the next warm water and sugar; the next boiling water; the last cold water and put it in the fridge. Each had a balloon over the top to collect any gas. Of course, the one with sugar and warm water showed plenty of activity, with the balloon partially inflated by the end of the day. Yeast and warm water was a little bit frothy but not very gassy. The others didn't do much, if anything.

Beverley made some sourdough (but added some dried yeast) to demonstrate how fermentation creates other microorganisms that produce gas to make bread rise.

Beverley also set up the experiment below to demonstrate why industrial bread manufacturing uses soya. The soya loaf did not taste good but it did stay fresher longer!

Soya experiment.jpg

Our main baking activity was an investigation into why you need salt in bread. In “Food Science” by Fox and Cameron, it is suggested that the best amount of salt is 1.5-2% compared to the amount of flour. Salt tightens the structure of the gluten, meaning it can hold more gas more firmly, so gives an airier, less flabby texture. But with too much salt the flavour is effected (and loads too much salt kills the yeast – but it would have to be a lot to kill dried yeast).

We each made rolls to the same recipe but used the precision scales to vary the amount of salt we included.

Rolls in the oven.jpg

Salt in bread investigation.jpg

It did seem to be the case that my saltless bread was a bit dense, the 2.5% tasted too salty and the ones in the middle were pretty nice. I'd say anything over 0.5% made a difference.

Bread recipe.jpg

(Competencies: C.1, C.3, C.7, C.9, C.10, C.13, C.14, F.D.3.3, F.D.3.4, F.M.3.2, F.M.3.3, F.K.3.2, F.K.3.4, F.K.3.5, F.K.3.6, F.K.3.8, F.K.3.19)

Day 2 - Mon 10th July

Our students need to be able to: use words to describe food; discriminate between products; evaluate/compare food's sensory qualities; taste food against a design specification.

Sensory characteristics: Flavour/taste; texture; appearance (colour, shape, size); smell/aroma; sounds.
Taste vs flavour: Taste involves the areas of the tongue (bitter, sour, salty, sweet), flavour involves the mix of these into an identifiable element (lemon, tomato, chips).

Sensory tests are used throughout the design, development, production, packaging and storage of food products. Food companies identify their “super-tasters” and use them to test whether packaging is having an effect on the taste of food, whether changes to a recipe are noticeable, whether products lose flavour over time, etc.

Using sensory tests at the design stage is good for making a comparison to competitor's products, improvements to recipes, differences between batches.

Our first taste test was a simple preference test. There's no real description, it's just a choice. The answers are hedonic (linked to pleasure) and can be scored from “like” to “dislike” but don't tell you anything else. Our test was blind, with 3 digit random numbers to identify our samples, which were presented in identical bowls. We tallied our choices and found that 6 people preferred Walkers ordinary ready salted crisps, compared with 2 people preferring Walkers Light ready salted.

A triangle test puts 2 samples of a product against 1 of another to find out whether the difference is discernible. We tried 3 part-baked baguettes, 2 were ordinary and one was gluten free. There was a visible difference between the two types – in industrial trials this could be mitigated by coloured lighting – but it would have been easy to tell the them apart based on taste anyway, although we all agreed the gluten free one was better than we would have expected it to be!

Incidentally, the gluten free bread browned more than the other bread because it contains more sugar, which caramelises when cooked. A fun tip can be to use the golden brown end of DIY shop paint colour charts to make a chart that pupils can use to decide whether their food is cooked (or overcooked).

Triangle testing.jpg

For a third test, we tried three tomato pasta sauces and ranked them in order of “tomatoiness”. So this wasn't about preference, but our judgements on a particular flavour. The results were more split than expected (the homemade sauce usually wins, apparently, but was a bit bitter and over-spicy this time. The premium Loyd Grossman sauce did come out as the most “tomatoey” and the Sainsbury's Basics fell in the middle – whereas usually it loses!)

The final product we analysed was a Sainsbury's individual apple pie. We made a star diagram to rate the attributes we look for in a perfect apple pie. We then tasted the apple pie and marked our judgements of it on the points of the star. The star is a good tool for designing, evaluating and comparing people's sensory perceptions of the different attributes of a product. The thing is, you have to mark them all on one star in different colours, otherwise there is no meaningful way of analysing the data you have collected – I have seen stars used to allow multiple evaluations but they don't mean anything on their own: the stars have to be compared to one another.

Apple pie analysis.jpg

Moving onto fats: animal and vegetable. Suet (cow), lard (pig), butter (from milk), dripping (by-product of cooking any animal), fish oils. Coconut, rape seed, olive, linseed, sunflower, grape seed, avocado, etc.

Fat is one of the macronutients (along with carbohydrates and proteins – measured in grams) rather than a micronutrient (vitamins, minerals – measured in milligrams).

Fat molecules are made of carbon, hydrogen and oxygen atoms and the arrangement of the atoms defines whether the fat is saturated or unsaturated. Each molecule contains fatty acids and glycerol – digestion separates these parts to break the fat down and reassemble it into the fat our bodies store. Unsaturated fats have gaps where a hydrogen atom is missing so the carbons have to form a double bond. This cause a “kink” in the structure of the molecule and this goes some way to causing the fat to be a solid or a liquid. Adding hydrogen back into the gaps in unsaturated fat by an industrial process gives us transfats.

So, we all made egg custard tarts using different types or combinations of fat to make our pastry.

Making pastry.jpg

Egg custards.jpg

Grilling my egg custard oops.jpg

Trying them once cooked and discussing the tastes and textures was really interesting because the differences were really noticeable.

Pastry testing.jpg

Fats in pastry.jpg

Our final bake today was scones. We used different raising agents and a variety of combinations. We made the height of our scones uniform before baking and measured the risen scones to compare the effects of the raising agents.

Wholemeal scones.jpg

Bicarbonate of soda is an alkali that reacts with water producing CO2 and sodium carbonate. Sodium carbonate is very bitter and leaves a yellow residue (so can be used just fine in parkin or gingerbread type things because it doesn't effect the colour). An acidic ingredient can help to counteract the bitterness, for example buttermilk, sour milk or cream of tartar. The bitterness was very noticeable in the scones without enough acid to counteract the bicarbonate, and the buttermilk ones were the tastiest.

Scone recipe and alternatives.jpg

Ooh scones and tarts.jpg

(Competencies: C.1, C.3, C.7, C.9, F.D.3.4, F.D.3.8, F.M.3.2, F.M.3.3, F.K.3.1, F.K.3.2, F.K.3.5, F.K.3.6, F.K.3.9, F.K.3.10, F.K.3.19)

Day 3 - Tues 11th July

Right: macronutrients. Carbohydrates, fats, proteins (and dietary fibre). We had a go at matching up the pairs. I have left the picture sideways because this is how I felt this morning.

Macronutrients.jpg

After much discussion, later on in the day, I had an argument about semantics with Beverley, relating to her saying the chemical formulae for sugars were all the same, even though the elements of the molecule are arranged in different ways. I believed that the chemical formula would reflect the arrangement of the formula for each one, to accurately describe how they differ from each other. After a bit of Googling, I must concede that I was wrong. It is correct to say that the formulae are the same, but the chemical structure must be described to show the difference. I figured I'd do a cut-and-paste of what I found, rather than writing it out again, so here it is:

“The monomer of a carbohydrate is a monosaccharide. Monosaccharides include glucose, fructose, and galactose. Notice that each of these end in the Latin suffix –ose. The suffix means “full of” and is used in chemistry when naming sugars. The structures of glucose, fructose, and galactose are shown below. Under each structure is the chemical formula of the compound.

Glucose fructose galactose.jpg

“If you look closely at the molecular formulas, you will notice they are all the same. Glucose, fructose, and galactose are what chemists refer to as isomers. Isomers have the same chemical formula, but the atoms in the molecule are attached differently.

“You know that glucose is a product of photosynthesis. Glucose is often referred to as blood sugar because it is the immediate source of energy during cellular respiration. All carbohydrates are broken down into glucose for transport via the bloodstream and used by the cells of the body. Galactose is the sugar in milk and yogurt while fructose is a sugar commonly found in fruit.”

Source: https://ontrack-media.net/gateway/biology/g_bm1l1rs2.html

Pairs of monosaccharides join (with water as the bond) to make disaccharides, which are the common simple sugars we find naturally occurring:

1 glucose + 1 fructose = sucrose (sugar from beet, cane, etc.)

1 glucose + 1 galactose = lactose (in milk)

1 glucose + 1 glucose = maltose (by-product of starch breaking down in fermentation process)

Then we move on to polysaccharides, otherwise known as carbohydrates. These molecules are too big to dissolve in water. Starch is one of these polysaccharides which can be broken down by our bodies into its component sugars and reassembled into the substance needed.

Starch in particular is made of strings of glucose molecules. Cellulose is a non-starch polysaccharide (as are gums and pectins). It is also made of glucose but our bodies cannot digest it. The bonds in cellulose are twisted, or alternating, and our bodies do not produce the enzymes (or bacteria, as in animals) to break these kind of bonds. Cellulose contributes to dietary fibre.

Amylopectin is a part of starch (amylose is the other, lesser, part). Amylopectin is made from strings of glucose molecules that branch off frequently into more strings. We did an investigation into different kinds of starch, mixing 5g of each with 100ml water and heating it in a pan whilst stirring until it thickened.

Wheat flour – the starch is not pure at all so the mixture is cloudy. It only thickens to the point where it still runs off the spoon – carbohydrates here are long and straight. Thickened at high temperature – 80-90 C.

Cornflour – or ordinary maize starch. Still not very pure starch but clearer than wheat flour. Thicker. Thickened at high temperature – 90 C.

Arrowroot – or tapioca. Made from cassava. Clear, clingy but stretchy. Used to glaze fruit flans and tarts. Thickened at medium temperature – 72 C.

Waxy maize starch – clearer but really gloopy. The strands of carbohydrate are really branched and tangly to make it thicken like this. Thickens at low temperature – 63 C.

Modified maize starch – Shiny, smooth, doesn't congeal when cool. Slides but doesn't run off the spoon, because the structure of the carbohydrates has been modified to give thickness but not jelly. Thickens at low temperature – 60 C.

You can also get pre-gelatinised starch, which is used in cold products like Angel Delight.

Looking at proteins, we established that they are built from amino acids and these contain nitrogen in addition to hydrogen, carbon and oxygen. Chains of amino acids make peptides. Chains of peptides make polypeptides – or if there are more than 50 amino acids, a protein.

Liquid proteins (like egg) are little balled up spirals that can be agitated to uncurl and trap air. If the protein of egg white is aerated and not interrupted by fats, as in a Swiss roll, once cooked, the proteins solidify and hold their structure well, giving a flexible sponge that can be rolled.

Solid proteins (like meat) respond to heat by getting closer together and losing the water that bonds the amino acids together, making the food harder and drier.

Heating food changes it. Some changes are just physical – like lard melting to oil then solidifying again once cool. Some changes are chemical – protein is changed by heating because the water bonding the components is released, etc.

We grilled a variety of foods to see what happened.

Investigating heat.jpg

All done.jpg

On analysis, there was quite a lot going on here, so I'm photographing my notes rather than copying everything out.

Heating observations 1.jpg

Heating observations 2.jpg

These were grilled, so that was dry heat. Boiling and steaming are moist heat. Frying is dry heat because we're talking about the presence or absence of water, not any other liquid. Dextrinisation, or starch being broken down into dextrins which are sugars that are brown in colour, only happens in dry heat.

We grilled some sugar too – icing, caster and granulated. They melted then went brown – caramelising and going hard once cooled. The smaller the granule, the faster they caramelised.

Grilling sugars.jpg

When starch is heated in water, the structures break open and absorb the water, leading to gelatinisation (thickening) and softening. We cooked a potato for 5 mins and compared the cooked outer edge to the raw middle under the microscope. We could see that the starch “bubbles” had popped.

5 minute potato.jpg

Popcorn is an example of starch bursting in dry heat, which does not usually happen. The explosive pressure of the tiny amount of water inside the kernel being turned to steam very quickly cause the starch to break apart and allow air in.

Our final experiments related to eggs. We heated egg white and whole egg to see what effect the fatty yolk has on the white's protein. Whole egg requires a higher temperature to cook and coagulate because the fat gets in the way.

We used an egg and milk mixture to look at the effect of stirring whilst heating, and the effect of direct or diffuse heat. Without stirring, you can get the egg mixture to burn when it is over direct heat – this is the Maillard reaction (proteins and sugars reacting and causing a colour change). If you stir the mixture, this distributes the heat, so you don't get browning but the mixture is still a little lumpy in texture. In a bain marie, the heat is able to surround the mixture more broadly and evenly. The heat is diffuse and limited, and is just convecting and not conducting – this produces a smooth, even custard.

So, for a perfect custard tart or quiche, it's a good idea to blind bake the crust at a high temperature then use a low temperature bain marie to cook the filling.

We observed that some water separated out of the cooked egg mixture. This is called syneresis and can also happen when a product has been frozen and then thawed.

Eggs and heat.jpg

As if that wasn't enough, we ended the day trying out a food CAD programme, Focus on Food 2. With it, you can build up a recipe by listing the ingredients and quantities and it will produce a nutritional analysis, like the one below. You can also produce labels and it's a great tool for quickly seeing how an addition or modification will change the nutritional content of a product. We started with a recipe for white bread rolls and tried to increase the fibre content to make a healthier option.

White rolls Food in Focus.jpg

(Competencies: C.1, C.6, C.7, C.12, F.D.3.1, F.D.3.6, F.D.3.7, F.M.3.1, F.M.3.2, F.M.3.3, F.K.3.2, F.K.3.4, F.K.3.6, F.K.3.10, F.K.3.15)

Day 4 - Tues 18th July

Eggs are very useful. They do all sorts of things. It's a kind of magic.

We all made different recipes that use eggs in different ways:

Mayonnaise – the egg yolk emulsifies the lemon juice and/or vinegar with the oil. This was double-whipped because it began to separate whilst waiting in the fridge, so I think that's what caused it to be very think/solid. But it tasted good.

Veggie Burgers – the egg binds the ingredients together, coagulating when cooked. This was a very tasty recipe with fresh coriander and chilli. Yum.

Veggie Burgers.jpg

Fish Cakes – the egg forms a later around the fish and potato which is then sticky enough to hold breadcrumbs but also forms a barrier when heated that stops the inside soaking up lots of oil. These were really nice, but with 3 types of fish in them, not the cheapest. And they could take a bit more seasoning and perhaps some herbs.

Fishcakes.jpg

Scotch Eggs – the egg is the main event. These were surrounded by a beetroot and chick pea mix. Other people thought these were delicious. I thought they tasted really vegetarian. I wouldn't put the effort into making this myself.

Beetroot Scotch Eggs.jpg

Courgette and Cheese Muffins – the egg adds structure and richness to the batter. These seemed overly cheesy to me and not very muffiny.

Raspberry Cold “Soufflé” - more like a fool with gelatine, I'd say. The egg whites hold air and create volume and lightness. I made this (vegetarian gelatine doesn't work) but I didn't really like it. With a baked soufflé you get a variety of textures; this was just like soft blancmange. The flavour was good to start with but I felt it was too sickly after half a portion. I didn't take any pictures!

Swiss Roll – the eggs are the raising agent and make a cake that can be bent without cracking. I don't like this kind of chewy, fatless cake. It is so dry and clagging, like a cake with all the joy taken out of it.

Swiss roll and Scotch Eggs.jpg

Lemon Meringue Pie – the eggs yolks contribute to the thickening and colour of the cornflour custard, the egg whites trap air and coagulate around it when cooked to make meringue.

Lemon Meringue Pies.jpg

Because there was water left from the chick pea cans, we had a go at some vegan meringues. They held the air when whipped and went crisp when cooked, but they were completely hollow and stuck to the tray by solid caramel, as though the sugar had sunk to the bottom.

Feasting.jpg

After the feasting, our afternoon Ready, Steady, Cook challenge was a lot of fun. Mollie and I were lucky to get the sweet potatoes and made this delicious starter from Yottam Ottolenghi:

Sweet potato and orange.jpg

We got ourselves a lot of Mediterranean vegetables in the draw and decided to make a layered stack of fried/grilled stuff with a chunky bean tomato sauce. It was all pretty tasty but we could have done with 10 minutes more just to get our vegetables completely cooked.