What happens when we cook the food?

Cooking is an important part of our daily life. We all love and enjoy cooked food, whether prepared in a home kitchen or by professional chefs in a restaurant kitchen. We are often puzzled by the changes happening in the foods while cooking. Some of the questions come to our mind: Why do potatoes become softer when we heat them, and runny, liquid eggs become solid after heating? Ice creams are made up of milk which is liquid then why are they so soft and solid that they are so pleasurable to eat? By typical definition, “Cooking is an art, craft, and science that makes food palatable, digestible, nutritious, and safe.” The term also includes a full range of culinary techniques: Preparing raw and cooked foods, final dressing of meats, fish and fowl, cleaning and cutting fruits and vegetables, preparing salads, garnishing dishes, decorating desserts and planning meals (1).

Every step in the process of cooking has some purpose and changes are happening in the physical/chemical structure of the basic ingredients. Understanding these changes will be fascinating and make us even more excited while we cook food and eat cooked foods at home or outside.

Before we cook food, some pre-treatments are to be given to food. All fruits and vegetables and agricultural commodities like cereals and legumes are grown in soil and will carry a lot of microorganisms which can be hazardous to our health. Simple steps like cleaning and washing are quite preliminary but very important as they are responsible for the reduction of microbial load helping to have safe food.

Any food ingredients used for cooking are from plants and animals which are living things, they constitute basic nutrients: Carbohydrates, Proteins, Fats (Oils), Vitamins, Minerals, and water. The food we eat not only satisfies our hunger but also gives us nutrition from these basic nutrients. When food is cooked, complex chemical and physical changes occur in the food constituents that alter its colour, texture, flavour and even nutritional values.

It is a common observation that soaking pulses and cereals help to reduce cooking time. This is because when they are soaked in water, they absorb water which softens them, and that helps them to cook faster. In the soaking process, some chemicals like phytates and tannins get reduced. These chemicals are called antinutrients because they do not allow the absorption of important minerals like zinc and iron. Therefore, this simple step makes food cook faster and makes it healthy as well. Some of the beans like faba beans which are otherwise difficult to cook are allowed to sprout by soaking them for longer periods. This helps cooking time to reduce further. Sprouting activates the chemical processes by producing some biochemicals like enzymes. There is an increase in Vitamin C and some B group vitamins. This also reduces antinutrients like phytic acid.

Cooking in water: When the cereals, legumes, and vegetables are heated with water they are cooked and become palatable and easier to digest. This is basically because of the changes happening in constituents like carbohydrates and proteins. Raising the temperature of the food to 100 deg C is responsible for these changes. It is a common observation that when rice and legumes are cooked in a pressure cooker, they cook faster. This is because when the water is boiled under pressure, its temperature is higher than its boiling point. Starch which is a carbohydrate is the main constituent of potatoes. Potatoes become softer after they are cooked. After cooking the potatoes, the starch in the potato swells, and heat causes physical changes making it softer.

Frying: This is another method used in cooking. The boiling point of oils is higher than water. Generally, the frying is carried out at temperatures higher than 170 deg C. Therefore, cooking is much faster than in water. Also because of a sudden loss of moisture, the products become crispy. Different kinds of frying methods are; stir-frying, deep frying, and shallow frying and are employed depending on the product requirement. Frying is also responsible for changes in colour and flavour. Sugars in the foods undergo chemical changes while frying which are responsible for the flavour and colour changes in these products. Thus, we enjoy fried chips and a variety of Indian snacks which are crispier with typical flavours. When eggs are fried, the structure of proteins in eggs change because of exposure to high temperatures and are solidified. This is because of a change in the physical nature of proteins, which causes liquid eggs to solidify. This change is called denaturation of the proteins.

Baking is cooking by the dry heat of an oven. The moisture within the food is converted to steam which helps to cook the food. Baking also brings in many changes in starch and proteins, the surface becomes brown. All products like bread, biscuits, pastry, and cakes are prepared by baking.

Roasting is also a cooking method where dry heat is used. It is done in an oven or over an open flame. The high heat causes browning of the surface and a typical flavour is developed. Meats and vegetables are typically roasted.

Some of the interesting facts to know:

Tadaka is an Indian cooking method that is given to vegetables during cooking. In this process, the spices used for the food are heated in a small quantity of hot oil. This gives a typical flavour and aroma to the food. The reason is that the essential oils in the spices responsible for the aroma and flavour, are soluble in the oil. They get carried in oil when heated and distributed throughout the curry or vegetable cooked. We get the oil-soluble yellow colour called curcumin from turmeric to the food prepared. Curcumin is also known for its medicinal uses like antiseptic and antioxidant properties.

Ice cream is very soft to texture and we love it. During the process of making ice cream, there is continuous cooling to freeze it and churning. Air is incorporated into the process along with the freezing of the ice cream mix. In a technical language, this incorporation of air is called overrun. Most of the ice creams will have an overrun of about 50 %. That means for one litre of ice cream mix there will be 500 ml of air incorporated. This is responsible for the texture of the ice cream we enjoy.

Lemon juice enhances the taste and flavour of food. Generally, lemon juice is added at the end of cooking. This is a healthy way of adding vitamins like vitamin C, which will not degrade.

Some chocolates are found to have white spots when we open the wrapper. This makes the appearance of the product very unappealing. However, these chocolates are safe to eat. These spots on the chocolate are of sugar and fat in the chocolate. When during storage if there is temperature fluctuation, moisture from the environment gets condensed on the surface. This will dissolve some sugar from the product in the moisture. When the moisture is evaporated, the sugar will appear as white crystals. The temperature variation in the storage of chocolate will cause some fat from the chocolate to melt and come to the surface. This fat appears as white spots when the chocolate is again kept in the refrigerator for storage.

The food is delicious and we all enjoy it. Knowledge of the science behind the cooking is even more exciting.