This week DTP student Emma White is back giving us all another insight into the science of cooking, with one of everyone’s favourite foods.. pizza!
It may feel slightly gloomy at the moment, but something which might help us get through these long winter months is World Pizza Day, which is celebrated on the 9th of February every year! The word ‘pizza’ was first officially documented in 997 A.D. However, simple flatbreads topped with cheese that somewhat resembled modern-day pizza are likely to have been eaten hundreds of years before this date in various forms across the Mediterranean. In the simplest terms, the classic pizza which we are all familiar with consists of a bread-like base, topped with an often tomato-based sauce and plenty of cheese. Did you know that making both the base and the cheese would be difficult to do without the help of microbes?
The Dough: Yeast
For anyone who has made pizza from scratch, the dough used for the base is very similar to bread dough: it contains flour, yeast, salt and water. The main difference between bread and pizza dough is that olive oil is added to pizza dough. As with breadmaking, the yeast respires to release carbon dioxide which creates air bubbles that add to the texture of the base. The activity of the yeast is dependent on temperature: increasing the temperature to around 40oC will mean that the dough rises more rapidly, but too hot and it will kill the yeast.
For bread and pizza doughs, strong flour is often used as it contains the right combination of proteins compared with plain and self-raising flours. With strong flour, adding water and kneading will lead to the accumulation of more gluten, which is essential for the structure as it forms a scaffold for the air bubbles produced by the yeast. Contrary to popular belief, gluten is actually a combination of two proteins stuck together (gliadin and glutenin) as opposed to a single protein! For people who don’t really enjoy handling the dough, it is possible to extend the proving time to allow for the gluten to form naturally.
The Cheese: Bacteria
Quite basically, cheese is a lump of curdled milk which has been fermented by microbes. This doesn’t sound too appetising but, as I am sure most people can testify, the outcome tastes divine. It also has its health benefits, as a recent study carried out at Iowa State University suggests that UK adults between the ages of 47 and 77 who regularly eat cheese experience less cognitive decline than those who don’t! If you’re really interested in making pizza from scratch, then why not try your hand at cheesemaking?
In the process of making all types of cheese, rennet or acid is added to milk. This causes the proteins and fats to separate from the remaining liquid to form the curds. In most cases, this milk is pre-treated with bacteria (often varieties of Lactococcus and Lactobacillus). However, it can be curdled without the presence of additional bacteria as is the case with young cheeses like ricotta. The curds are then cut into pieces, drained and put in moulds for varying lengths of time depending on the type of cheese that is being made. The texture of the cheese is mainly dependent on the size into which the curds are cut, and whether they have been drained or pressed to remove moisture in the earlier stages of the process.
The key qualities for pizza cheeses are flavour and stringiness. Cheeses such as cheddar have the flavour, but due to their firm texture they form greasy lumps if heated. In younger, softer cheeses such as mozzarella, proteins called casein which are present in the curd are less tightly bound than in harder cheeses, causing them to soften much sooner into the heating process which means the cheese melts more easily. Cheeses which are curdled using acid will not melt as the acid causes irreversible binding between the proteins in the curd. Due to additional processes in the production of mozzarella, such as kneading and folding, it is widely considered a cheese of optimum stringiness. The flavour and texture combination of cheddar and mozzarella make them a classic combination for use in pizza making.
That’s all there is to it. Once you have added your cheese (or a vegan substitute), feel free to cover with your favourite toppings and enjoy World Pizza Day your way!