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! Today, you will learn how to make cheese and the science behind this thousand-year-old treat. Cheesemaking is fairly simple as long as you know the chemical processes deployed in creameries. Cheesemaking is the process of controlled spoiling of milk by removing the water and then concentrating its protein, fats, and other nutrients to increase its shelf life. This process is thought to have been accidentally discovered and made by nomadic herdsmen who stored their milk in vessels made from their livestock’s stomachs. These stomach linings contains a mix of lactic acid, bacteria as milk contaminants and rennet, which would sour the milk and coagulate and ferment. Cheese could made from a variety of animal milks like goat and buffalo milk, but cow milk is by far the most popular. Cow milk consists of mostly water (86.5%), lactose (milk sugar) (4.8%), fat (4.5%), proteins (caseins and whey) (3.5%), and several other vitamins and minerals (0.7%). During the process, the liquid containing whey proteins, other major milk proteins, and lactose are all removed in the cheese whey. This is why cheese barely contains any water, which explains why 10 liters of milk only yields 1 kg of cheese.
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Curdling the milk Separating they whey (liquid) and curds (solids) Pressing down the curds Ripening / aging 2
: Milk is curdled by using acids, bacteria, and enzymes, such as rennet, lemon juice, or vinegar. After adding any of those the casein protein in the milk will start to destabilize and coagulate to form curds. This also helps to control the growth of any unwanted bacteria in the cheese. A special type of bacteria is usually added to start the cheesemaking process by converting lactose into lactic acid which decreases the milk’s pH. Different types of acids, bacteria, and enzymes is added into the milk that depends on the type of cheese being made. •
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Mesophilic bacteria → used to make mellow cheeses such as cottage cheese, cheddar, and gouda, since they can only thrive at room temperature and die at higher temperatures. Thermophilic bacteria → used to make sharp tasting cheeses such as parmesan and Romano, since they can still thrive at higher temperatures (~ 55 °C)
Rennet is a mixture that contains an active enzyme called chymosin, and is used as a starter bacterium for making most cheeses. Rennet speeds up the casein protein coagulation process and produces a stronger and firmer curd. Rennet is also used to lower the acidity in some types of cheese. Rennet originally came from the stomachs of any young mammal that has a diet mostly made up of milk, but most of the rennet we use today is GM (genetically modified). Casein proteins are called micelles in milk, because their molecular structure is ball-like shaped. Casein molecules contains both a hydrophilic (attracted to water)
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and hydrophobic (repels water) part. The hydrophobic parts sit in the middle of the micelle, while the hydrophilic parts sit on the outside. Chymosin breaks down the kappa casein found on the surface of these micelles and convert them from being hydrophilic to hydrophobic, which causes them to trap fat and water in the curds. These micelles could be as large as 0.1 mm but are limited in their size, because the κ-casein will grow larger when this protein is neutralized. When the protein is finally neutralized it can’t prevent their growth of these micelles anymore → curds.
: After curdling the milk, you remove they whey or the liquid part using a cheese cloth or a fine mesh cloth. After removing the water and whey proteins from milk the fats, casein proteins, and lactose are left behind. Sometimes the curds are reheated and have salt added to them to drain any excess water left and make them firmer. When heating the curds, the protein within the curds will start to denature (the protein bond and links are broken down). 4
: This is an optional step that depends on the type of cheese being made. Soft and moist cheeses such as ricotta won’t require to go through this step. This process is just pressing any excess water from the cheese to tighten the curd texture which will result in a more solid product. The cheese is then pressed and molded into the desired shape.
: Ripening or more commonly known as aging, is a process where several types of firm or moldy cheeses go through this step-in order to develop flavor and lose more water. The cheese is left in a humidity and temperaturecontrolled environment which depends on the cheese type. During this time bacteria will start to break down the cheese proteins will will alter and affect the final flavor and texture of the cheese. Sometimes cheesemakers introduce different types of fungi to produce a specific desired characteristic, such as flavor and texture. In camembert and brie cheeses its’s on the surface, while for blue cheese its internally. These fungi will produce digestive enzymes that will break down the large protein molecules present in the cheese, which makes the cheese softer, runnier, or maybe even blue. Sources: 5
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