Dr Hector Perera London

There are a few ways of cooking such as baking, roasting, broiling and grilling, frying, boiling, simmering, and steaming.

Baking is a food method of cooking food by using prolonged dry heat acting by convection, rather than by thermal radiation, normally in an oven, the most common baked item is bread but many other types of foods are baked. Heat is gradually transferred “from the surface of cakes, cookies and breads to their centre. As heat travels through it transforms batters and dough into baked goods with a firm dry crust and a softer centre”.

The word baking usually refers to the cooking of foods made from a batter or dough. Food is baked by cooking it in an oven as mentioned above are bread, cakes, pizzas, biscuits pies and pastries. However, casseroles, a few vegetables and fruits, and some cuts of meats can also be baked. In most cases, the oven temperature ranges from 300 to 450 ƒÆ’-¡ƒ”š‚°F (149 to 232 ƒÆ’-¡ƒ”š‚°C). Simply because there is an energy lost in this type of cooking baking, that does not mean no one should use the oven for making bread, cakes, pasties, pies, pizzas and biscuits. Here I am trying to point out which method uses most, least energy and which one wastes energy.

When we cook on the hob or on the cooker by gas or electric, the cooking vessel is in direct contact with the fire where as in an oven or in a grill the fire is not directly in contact with the food so there is a huge loss of energy in cooking by oven and the grill.

Roasting is cooking food uncovered in hot air. The term usually refers to the cooking of meat. For example, a turkey or a leg of lamb is roasted. In roasting, the meat is usually placed on a rack in a shallow pan and cooked uncovered in an oven. The temperature usually ranges from 300 to 350 ƒÆ’-¡ƒ”š‚°F (149 to 177 ƒÆ’-¡ƒ”š‚°C).

Broiling and grilling are methods of cooking by the application of direct heat. In broiling, the food lies directly under a continuous heat source. Meat can be broiled by placing it on a rack in a shallow broiler pan. The surface of the meat lies 3 to 5 inches (8 to 13 centimetres) under the flames in a gas range broiler or below the broiler heating unit in an electric oven. Leave the door open slightly when broiling in an electric oven to prevent the air in the oven from becoming too hot.

Grilling is sometimes referred to as barbecuing but that word can also mean a different cooking technique. Cooks sometimes grill sandwiches in a skillet on the stove. This is a fast method of cooking by radiant heat and is also known as broiling.

Frying. This research paper covers the discussion on the rheological properties and the correlation between the viscosity and the frying cycles, correlation of viscosity with different temperatures on the 3 frying oils such as cooking oil, Sunflower and Palm Olean oil.

Rheological behaviour is particularly readily observed in materials containing polymer molecules which typically contain thousands of atoms per molecule, although such properties are also exhibited in some experiments on metals, glasses, and gases. Thus rheology is of interest not only to mathematicians and physicists, who consider it to be a part of continuum mechanics, but also to chemists and engineers who have to deal with these materials.

As for the viscosity of oils and temperature, the viscosity decreases when temperature rises. In the food industry, viscosity is a simple measurement that is being applied to determine the behaviour of solutions, suspensions and mixtures. For example, in frying process, fats and oils are repeatedly used at elevated temperatures in the presence of air and moisture. This caused partial conversion of fats and oils to oxidized derivatives, and dimeric, polymeric, or cyclic substances which will affect the viscosity of the solutions. In addition, these undesirable constituents produced may also pose health hazards. This is simple to understand when we think about car engine oils. Why do we change it? That is because it is too viscous and the engine does not work properly with blackened thick oils. When food is fried in these oils which are repeatedly fried, frying foods absorb these denatured oils, would you not agree its bad for health? At the takeaways they fry fish, chips, chicken and many more things repeatedly on the same oil. As I asked before are they healthy to eat, the best thing is you decide.

ƒÆ’‚¢ƒ¢-¡‚¬ƒ”¹…”Cooking fumesƒÆ’‚¢ƒ¢-¡‚¬ƒ¢-¾‚¢ or ƒÆ’‚¢ƒ¢-¡‚¬ƒ”¹…”cooking oil fumesƒÆ’‚¢ƒ¢-¡‚¬ƒ¢-¾‚¢ is the term commonly used to describe the visible emissions generated during cooking by frying with oil. However, these emissions are not technically ƒÆ’‚¢ƒ¢-¡‚¬ƒ”¹…”fumesƒÆ’‚¢ƒ¢-¡‚¬ƒ¢-¾‚¢. In occupational and environmental hygiene, ƒÆ’‚¢ƒ¢-¡‚¬ƒ”¹…”fumesƒÆ’‚¢ƒ¢-¡‚¬ƒ¢-¾‚¢ are defined as submicron-sized solid particles (particulate matter) created by the cooling of hot vapour. During cooking, such vapour is formed when the cooking oil is heated above its boiling point. The fumes are so dangerous because itƒÆ’‚¢ƒ¢-¡‚¬ƒ¢-¾‚¢s possible to catch fire. In TV some cooks purposely set fire to these fumes to excite the viewers. How many takeaway shops in America caught fire because of these dangerous volatile fumes? In addition to this ultra fine particulate matter, cooking, especially frying and grilling, generates aerosol oil droplets, combustion products, organic gaseous pollutants, and steam from the water contents of the food being cooked. Now please tell me who would argue it is healthy to breathe these fumes? Invariably one has to breathe these fumes if you are frying things in the kitchen such as fish, meat or even dry fish. Sure the extractor removes some of it but still is the air fresh and safe to breathe? In Sri Lanka this is not quite a problem because they always leave the kitchen windows wide open for adequate ventilation. Anyone is cared to fry some dry or fresh prawns? Please remember that if you are not careful the volatile vapour that comes out has a strong odour and very likely to deposit on you. Due to careless cooking, this kind of odour and the other types of cooking odours from curries might get deposited on your clothes and on your body. ItƒÆ’‚¢ƒ¢-¡‚¬ƒ¢-¾‚¢s no problem but would you like to walk about like a mobile kitchen?

Boiling. All liquids, at any temperature, exert a certain vapour pressure. The vapour pressure can be thought of as the degree to which the liquid molecules are escaping into the vapour phase. The vapour pressure increases with temperature, because at higher temperature the molecules are moving faster and more able to overcome the attractive intermolecular forces that tend to bind them together. In water each molecule of water is bound or attracted to each other by a force called hydrogen bonding. If there was no hydrogen bonding then all water become so volatile say for example in methane or cooking gas no hydrogen bonding from one molecule to the other. That is why methane is a gas and due to hydrogen bonding water is a liquid. Boiling occurs when the vapour pressure reaches or exceeds the surrounding pressure from the atmosphere or whatever else is in contact with the liquid.

At standard atmospheric pressure (1 atmosphere = 0.101325 MPa), water boils at approximately 100 degrees Celsius. That is simply another way of saying that the vapour pressure of water at that temperature is 1 atmosphere. At higher pressures (such as the pressure generated in a pressure cooker), the temperature must be higher before the vapour pressure reaches the surrounding pressure, so water under pressure boils at a higher temperature. If rice or curries are cooked at higher pressures, they cook faster than without pressure. When the lid is closed it creates a high pressure, how did our clever servants knew it creates high pressure? According to thermodynamic equilibrium condition a higher pressure can be created that helps cooking things faster that means less energy is required in cooking things by boiling. Less energy is required means some of the energy can be saved or less energy is spent on cooking. This principle can be applied in energy saving in cooking rice, pasta, spaghetti, boiling sweet potatoes, chick peas or even cooking curries. How do I say this principle helps in cooking because I practice what I preach? Now I would like to help the general public how to apply this principle in the energy saving and time saving cooking. Comments welcome perera6@hotmail.co.uk

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