Frying is a thermal process commonly used at homes and at the industrial level to create food with distinctively appetizing taste and texture. The process is used to cook and process food all across the globe. Its origins are found in ancient Egypt around 5th century BC. Donuts or fried cakes are believed to be the first among the deep-fried foods. In ancient times, it was also used as a means of preserving food for consumption at a later date. The invention of frying pans in ancient Mesopotamia also gave rise to different forms of fried food products. Tempura was first introduced in Japan in the 16th century. Another delicacy enjoyed globally today, the Fried Potato or French Fries became popular in France and Belgium around 1830s. With time, people came up with different types of fried food items which we enjoy in our meals today.
Frying is one of the most popular unit operations to process food. It provides the desirable sensory attributes; it is relatively fast and provides a secondary benefit, which is its better keeping quality. The preservative effect results from the thermal destruction of microorganisms and enzymes, in addition to a reduction of water activity on the food surface. Thus, there is a lot of economic potential to improve and innovate on different parameters involved in frying of food. Typical examples of frying technology that are still evolving include improving oil quality, the mechanism of oil absorption and engineering considerations of residence time and design.
The most common type of frying used commercially is the deep fat frying and shallow frying. Few more types of frying processes include Sauteing, Stir frying and Pan frying.
Deep Fat Frying:
It is defined as the process of cooking and dehydration of foods that is done by immersing them in hot oil, typically at 165–190◦C. During this time, various chemical and physical changes occur. Chemical structural changes occur in the form of starch gelatinization, protein denaturation and flavour development. Physical changes are manifested as a decrease in moisture content, increase in product temperature, oil content and uniform crust formation.
Shallow Frying:
Surface or Contact frying involves heat transfer that takes place to the food mainly by conduction of the hot surface of the frying pan through a thin layer of oil. This type of frying produces variable browning in the food, preventing standardization of the product. The uptake of oil by the product is comparatively lower than deep fat frying.
Nowadays, people have become more self-conscious about their diet and the intake of right kind of nutrients. The nutritional profile of fried food, the main issue which stands first in one’s mind is the high fat/oil content of fried food. The current challenge of the fried food industry is to process food with the least oil content and present it to the consumer with the same taste. Thus, different types of frying methods have been adopted over time to make food more nutritious, while keeping its typical fried sensory characteristics. Some of these are mentioned below:
Vacuum Frying:
Vacuum frying or pressure frying is done in a vacuum tank. The main advantage of frying in vacuum conditions is that it helps to reduce the boiling point of water and oil, which reduces the requirement of high temperatures which are used in normal atmospheric frying. The absence of air also helps to reduce the chances of lipid oxidation, acrylamide formation and better nutrient retention. It also has some drawbacks, such as high installing cost and is also a time-consuming process. The process has been proved to be beneficial for preparation of vegetable and fruit-based fried snacks.
Microwave Frying:
The use of microwave as a heating power source during frying can be defined as a new alternative frying way, which is not only the method of improving the fried products, but also helping to reduce the production cost at the industrial level. The range of electromagnetic wave is 300MHz–300GHz with 1mm–1 m wavelength. The process has the advantage of reduced processing time and lower uptake of oil in the final product.
Radiant Frying:
In the radiant heating systems, there is exposure of heat through the substance from an infrared source at the wavelength ranging from 0.78 to 1000 mm. The microwave also uses electromagnetic waves, but the infrared radiant heating system shows more thermal efficiency and responses with much faster heating ability. Nevertheless, there are very few works of frying using a radiant heating system.
Ultrasound-assisted Frying:
The range of acoustic waves used in this treatment ranges between 20 kHz and 10 MHz. Ultrasound is relatively a novel technology for the fried food industry that is currently in use. The on-going studies point out that the use of ultrasound treatment during vacuum frying helps to produce a better-quality product (low oil content and crispier) with high efficiency of production rate. The major disadvantage of the process is the production of unbearable amount of sound which may cause injuries to inline workers at the site of production. Thus, making the system sound proof adds in to the cost and makes the system expensive.
Air Frying:
Air Frying is a rapid cooking technology of food using a high velocity of blowing air. Instead of submerging into the heated oil in this frying system, the sprinkle of oil applies to the product with air circulation. The air-tight, compact design of air fryers ensures that all air is contained in the chamber and actively flows around the food, promoting the intensity and efficiency of cooking.
Conclusion:
The upcoming technologies have better scope of creating food with the popular sensory characteristics along with maintaining the nutrient profile of the fried food. Also, apart from the high starch processed food, fried snacks made from fruits and vegetables are gaining popularity. It seems to have much potential for producing snacks a lot faster and healthier.
References:
• Shoma Devi , Min Zhang , Ronghua Ju & Bhesh Bhandari (2020): Recent development of innovative methods for efficient frying technology, Critical Reviews in Food Science and Nutrition.
• https://www.esquire.com/food-drink/deep-fried-history/
• Pandey, Arun & Ravi, N. & Chauhan, Om. (2019). Use of Vacuum Frying Technology for the Development of Strawberry Chips. 37. 147-156.
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