Food Physics

dauswq

1) Dunking Biscuits


                       
Who will win and who will crumble in the Ultimate Biscuit Dunking Challenge? And what's physics got to do with it?                       
Which biscuit is the tastiest?
                       
Biscuits are made mostly from sugar, flour (which is 60% starch) and fats. When you dunk your biscuit into your drink, the liquid is drawn up through the tiny channels and holes in the biscuit by capillary action. The liquid starts to dissolve the sugar that is holding the biscuit together and makes the starch swell. If you continue to dunk your biscuit without taking a bite, it soon won't be able to hold itself together - leading to a dunking disaster.
                       
As all biscuits have a slightly different structure, they can survive a different number of dunks. Len Fisher from the University of Bristol found that you need to have a thin dry layer of biscuit within your dunked biscuit for it to stay in one piece. He also found that dunking your biscuit sideways gives you the most dunking opportunities as the drink takes longer to saturate the biscuit when soaking it from only one side.
                       
Len Fisher went on to discover that milk was the best beverage in which to dunk a biscuit if you want maximum taste. Dunking your biscuit in milk releases up to 11 times more flavour than eating a dry biscuit. Milk is full of fat droplets suspended in water and fat droplets are very good at absorbing the flavour molecules that excite your taste buds. They also hang around in your mouth so that the flavour and aroma chemicals can sit on your tongue and be released up your nose giving you a better taste sensation.
                       
So which biscuit is the tastiest? It's all down to personal preference, but the best beverage to use is a glass of milk!

dauswq

2) What's the difference between a cake and a biscuit?



A few years back the tax man was trying to add VAT to the Jaffa Cake claiming that it was not, as it said on the packet, a cake which is VAT exempt, but a luxury chocolate covered biscuit for which VAT has to be paid.
                       
The case went to court, so what is the technical difference between a cake and a biscuit?
                       
Biscuits are baked starch and fat held together by sugar, whereas cake has a structure like a sponge. During baking the bubbles in cake mix expand giving the cake a foam-like structure. As the cake continues baking this foam starts to set and form a sponge. If you open the oven door too soon, the bubbles in the delicate foam stage collapse, giving you a sunken cake!                       
Another difference between cakes and biscuits becomes evident when you leave the lid off the biscuit - or cake - tin. Because of the way they are made, biscuits are very dry (before they are dunked) and so absorb moisture from the air. Cake on the other hand is quite moist, so water is released into the atmosphere if it's left out, making the cake go hard.
                       
To solve the Jaffa Cake cake/biscuit conundrum, McVities made a giant Jaffa Cake to bring to the court's attention the sponge-like structure of Jaffa Cakes and the fact that they go hard when left out. The court ruled that Jaffa Cakes are indeed a cake and should, if you don't want hard cake, be kept in a tin.                       
                       
How to make reduced fat biscuits                       
Making lower fat foods is easier said than done. If you simply reduce the fat content of a food you change the structure, texture and flavour release of that food. Fats give us unique sensory stimuli which are very hard to mimic with non-fat ingredients.                       
So scientists at the Institute of Food Research have been researching how to make reduced fat foods, but without sacrificing the role that fats play. Many reduced fat foods rely on replacing the fats with a starch such as corn, potato or tapioca, or proteins such as egg white or gelatine. All of these ingredients bind with water to produce a thickened gel, recreating that creamy feel we associate with fats.
                       
However, this type of fat substitution doesn't work for all food stuffs, including biscuits and chocolate. Reduced fat biscuits depend on some clever engineering which reduces the overall fat content, whilst retaining the sensation of fat in the mouth. By taking a small amount of fat and wrapping it around a droplet of another liquid, then the overall surface area will be the same as a droplet made entirely of fat. This fools your tongue by mimicking the taste and texture of the fat in a normal biscuit, but the overall amount of fat is reduced.                       
This technique is called WOW (water-in-oil-in-water) and is currently being developed and due to be used in low fat products over the next few years.

dauswq

3) Physics of chocolate




Physics plays a part in everyone's favourite treat - chocolate. One of the reasons that chocolate is incredibly good to eat is that its melting point is just below body temperature. When you place a piece of chocolate on your tongue it immediately starts to melt, spreading the sweet, satisfyingly fatty taste across your mouth. Chocolate also contains chemicals such as caffeine and theobromine which are thought to contribute to that feel-good lift that keeps chocolate addicts coming back for more.                       
Chocolate can behave in a rather strange way when heated and cooled. If you've ever cooked with chocolate you may have found that once heated and then cooled it takes on a dull appearance rather than the glossy smooth texture that it started off with. This is because the structure of chocolate can change when heated.

adamh

nice info dauswq . now i know why i was addicted to choc