Who does not like a freshly fried food or a snack made by deep fat frying? Most humans have a weakness for preparations made by using high levels of oil and higher the oil content more tasty would be the product though health wise such foods many pose dangers in the long run. Interestingly foods with high moisture content, if fried at lower temperatures for a shorter time, may not contain too much adsorbed oil while dry products during frying process have a tendency to get infused with the frying oil thereby raising the oil content in the end product. Scientific basis for such an explanation is that in high moisture foods during frying the water gets evaporated high temperatures creating an internal pressure by the steam which comes out in force and oil has no chance get into the product if the residence time in the fryer is not too long. In contrast dry foods already have cavities pre-existing within their matrix where oil can get in fast and easy. This is the reason why most snack making plants deploy centrifuges to extract free oil from inside the product.
The debate regarding the importance of fat as a calorie source in preference to carbohydrates is a never ending one but one thing that is certain is that high levels of fat in every day diet can lead to increased body weight and eventuality to obesity. Of course if heavy physical activity is practiced every day, body fat can get burned and it is nothing but common sense to understand the basic principle of eating and its consequences. If calorie intake is more than calorie expenditure, the body has to store the excess calories through fat deposited in different parts of the body. Sadly the food manufacturing industry has discovered that most human beings cannot resist the temptation of foods containing high sugar and fat and very little control can be exercised while choosing foods. Besides psychologists are unanimous in their opinion that fat, sugar and salt are addictive food components like alcohol and tobacco.
One of the reasons for frequent visits to restaurants by people is the number of choice of tasty fried foods available which are not made at home regularly. Many kitchens in western world shun frying in their kitchen because of the mess that is created by the hot and smoky oils during frying. If fast food chains have become landmarks in developed countries, the reason is the same that their foods are palate tingling and irresistible to avoid. Even young kids ought to be brought up in a healthy eating environment but fall for the unhealthy products from the fast food joints and the processed food industry because of their easy availability and often at low prices. It is next to impossible to make them eat nutritious foods like fruits, vegetables, wholegrain foods, milk, etc in their every day diet. One of the reasons health pundits advocate reducing intake of fried foods is that most frying oils tend to cause atherosclerosis and consequently heart disease and stroke with tragic consequences over a period of time. Except some oils like that extracted from Mustard, Palm fruits and kernels, Coconuts, Peanut, Safflower, almost all others are not fry-stable causing generation of undesirable artifacts at high temperatures and repeated heating.
Frying is an interesting process in food technology where the temperature of the oil is raised to high levels around 200C for fully frying the product to get the desired texture and flavor. If the heat stability of the oil is low, temperatures as low as 165C can also be used to get a fully cooked end product. It is always the dilemma of a Chef as to what temperature he must use to prepare a product to reduce as much as possible oil uptake by the end product, considering that the market price of oils can vary enormously. Ideally every Chef would like to use an oil like Olive oil but it is not practical because of the high cost of this fancy oil. Many choose Palm Oil which is considered the cheapest oil in the global market thanks to the tremendous production in countries like Indonesia and Malaysia. Oils derived from Soybean, Rape seed, Maize germ, Sunflower seed, Safflower, Sesame and rice bran are also widely used. In some cultures Coconut oil is the preferred choice though its peculiar flavor is not liked in most countries.
The oil used in frying process can degrade in quality, the rate spoilage being proportional to the extent of unsaturated fats present in it and the severity of the temperature deployed for frying. Common fryers like deep fryer, pan fryer, Chip fryer etc can have no control over the heating process and oils can deteriorate rapidly. To some extent these undesirable changes can be prevented by using modern equipment like Vacuum Fryers or Pressure Fryers which, of course need higher investment. The deterioration will be more severe if the oil is repeatedly heated and cooled over a period of time. Oxygen present in the air reacts with the unsaturated fatty acids creating highly reactive oxy radicals and other undesirable artifacts, some of which have been proved to be toxic. High frying temperatures can also break down fats into smaller molecules which cause many other problems like excessive foaming. Polar compounds and polymerized products of oxidation have been proved to be injurious to human health. Frying of starch containing foods is known to produce the carcinogenic artifact Acrylamide. In view of these evidences, oils are not allowed to be used repeatedly for frying and discarding them after using it in the fryer is always considered a wise policy. Many high class restaurants and snack food industry dispose off the heated oils which are supposed to end up as a waste. In reality this does not happen as oil is a high value material in great demand and used oil invariably finds new users who smell money in this "waste" !
When oil is subjected to repeated heating, it becomes dark in color, starts smoking, foaming, generates unpleasant smell, creates undesirable rancid taste, increases viscosity etc, unacceptable to the consumer. While large scale manufacturers of snack foods deploy fryers with multiple controls to regulate the temperature and the frying time, it is the unorganized sector where small scale, semi skilled and illiterate cooks make the products using their "experience" and "hunch" and who unknowingly contribute to very significant damage to the oil. Emergence of oil protectants like antioxidants, chelating agents and a variety of adsorbents of polar chemicals formed during frying prolong the life of frying oils very significantly but even here its life is not eternal, requiring replacement at regular intervals. In countries like the US or the European Union fried oils are never reused for food preparations, invariably ending up ass a biofuel. Recently there were reports that fried oil is fetching a higher price in the market than that commanded by its virgin counterpart! Fryer oil is also used extensively in power generation, household heating during the winter season as it burns clean without any significant carbon foot print and as automobile fuel with no pollution. Carbon monoxide is virtually nil when it is burned. No wonder recycling of fried oil has become a become business world over.
In India and China the recycled oil business is almost a parallel industry gnawing at the seams of the main stream edible oil industry. Of course it can be more aptly called an underground operation being carried out under the very nose of the food laws authorities and it has patrons, millions in number spread all over the country who are food artisans, vending their foods on the road side and small scale unlicensed eateries. These clients find it extremely convenient to buy the used oil supplied to them by unscrupulous processors who buy their raw material from large restaurants for reprocessing. Basically reprocessing involves filtration and decolorization in rare cases. If reports are to be believed recycled oil can be sourced at half the price of virgin oil which presently sells at around Rs 80 per liter in India! Those who use the recycled oil justify their action because oil constitutes a large chunk of the cost of the food they make and according to them if they are forced to shun these oils, they will have no alternative but to raise the prices of their preparations to levels unaffordable to most of their clients! What a justification for demolishing the population through slow poisoning!
Take the case of China where it is reported that recycled oil use is more rampant than that in India. It is a shocking revelation that one out of ten low end restaurants in China uses "Gutter Oil" for preparing their foods, a form of recycled oil which is the worse form of oil one can imagine. Most Chinese dishes are heavy in oil content and imagine the long term consequences for a population fed on such products! Gutter oil is made from discarded restaurant oils from the organized sector, drains, grease taps, slaughter house wastes, discarded animal parts, low grade animal fat. internal organs, skin portions of animals etc. The process of making it includes filtration, boiling, refining, removing adulterants and packing. As the major raw material viz, "the Fryer discarded oil" costs less than $ 900 a ton, the business is indeed fantastic as the reprocessed oil is in demand for prices beyond $ 1500 a ton! It is a mystery as to why an autocratic government like that in China where punishments can be severe and swift is allowing such criminal activities by a section of the industry which jeopardize the health of its citizens.
How can such despicable acts by the fraudulent oil trade be minimized if not curtailed in absolute terms? As some observers believe, it may be difficult to control these nefarious actors unless there is massive vigilance deploying thousands of personnel and severe punishments are given swiftly without allowing the fraud cases to linger on for years in the judiciary. On a long term basis Government will have to address the problem of critical edible oil shortage in the country during the last 3 decades on a war footing by shifting its focus from cereals to oil seeds production.