DR. PREETI BIRWAL *
Food is the necessity of all the creatures on earth but the human body cannot digest many raw foods. The processing and preservation of food is done for long storage and convenience. Processing involves drying, dehydration, heating, cooking, solutes addition, concentration and freezing. Somehow all the processing affects the texture, nutrition and sensory characteristics of the food. The heating depletes the nutrition of the food. The impact on protein and texture is reported. The state of food is changed in drying and dehydration. Though drying is one of the best ways to preserve food for the longest time, the impact is great on the food structure and nutrition. Consequences of thermal processing and increase in health concern from consumer fetched the researchers concern towards the novel processing where the preservation can be done without affecting the food quality. Several new food processing and preservation technologies have been investigated by the researchers which have expected potential to inactivate micro-organisms named as non-thermal processing technologies.
Pulsed Electric Field
Pulsed electric field (PEF) is a novel emergent technology which was first reported in the early 90s. High voltage pulses are utilized with voltages up to 20-80 kV/cm for a very short duration i.e. 10-100 µs. The exposure of bacterial cells to high voltage leads to irreversible permeation in the cell wall due to decrease in resistance and increase in conduction. This is called electroporation. The permeability leads to swelling of the cell and helps in degrading the microbes. Many reports have been reported on the application of PEF. Recently processing of liquid, semi-liquid and to some extent solids, have been reported for juices, yogurt, cheese, soups, egg, water treatment, potato, purees. Also an application on drying enhancement, modification of enzymes, improvement in extraction are reported by a large number of groups. A tremendous application can be forecasted in liquid commodities like milk. Milk is a complete food and milk treated with PEF, definitely preserves all the nutrients required for the growth of children.
High-pressure processing (HPP) is known as one of the best innovative technologies in the last 50 years. HPP showed a positive response towards the production of safer food and longer shelf life. HPP processed foods is reported to be better in texture, fresher in taste, better in appearance and to have better nutrient retention in comparison with conventional thermal processing. The first application was reported in 1899 by Hite. The food is subjected to a very high pressure of 300-1000 MPa which is almost 6000 times higher than the atmospheric pressure. Major application is found in fish, oyster, juices, guacamole, meat, jams and yogurt. Many products are already present worldwide. Also, in India companies are coming up with HPP treated juice. Products can be treated in batches, in a semi-continuous and continuous type of mode. Le-Chatelier is the predominant principle for the HPP, which says the on application of isostatic pressure the reduction in volume will be promoted, which results into reactions which cause inactivation of the micro-organism. HPP is very rapid technique which is very good for low pH foods.
A different innovation has happened when research after taking the concept of PEF undertaken the research on the wide light spectrum. The light wave has its own germicidal effects in particular ranges. Due to photochemical and photothermal effect the decontamination is done in the food processing industry. Pulsed light is a very rapid processing technique. The decontamination occurs due to high-power, short-duration light pulse, which is emitted by inert gas flash lamps. This technology has one drawback, which is penetration depth. Pulsed light has a great application in food surface, equipment surface and packaging material surface. It has shown a good effect on the enzymes present in and on the surface of foods and it damages the DNA, cellular material and prevents the replication of the microbes.
Ultrasound or Ultrasonic Processing is one of the highly used novel technologies in all the sectors of the food processing industry. The high intensity vibrations are generated due to sound waves which lead to rise in the temperature due to friction. This is one of the fastest and most versatile technologies which has its applications in extraction, mixing, drying, emulsification, homogenization, spraying, crystallization, cleaning, filtration, heating etc. Ultrasonic treatment has four categories according to operating temperature ranges namely Ultrasonication, Thermosonication, Manosonication, and Manothermosonication.
Ozone treatment is also one of the most emergent non-thermal food preservation techniques, which is that it has a potential application in the beverage (food) industry. Ozone is a very powerful spectrum for antimicrobial activity. The major application is for surface decontamination of fruits and vegetables, juice and water purification. It inactivates with bacteria, viruses, fungi, spores and protozoa present in liquid or on the surface of food. The principle behind the inactivation is still complex. Many reasons have been investigated and stated. The Ozone has a capability to interact with proteins, enzymes, unsaturated lipids and cytoplasm and leads to breakdown or decomposition and produce the radicals like ?OH, ?O2-, and HO?3.
Non-thermal processing is a promising alternative to conventional heat processing for better quality. Industries are showing progress towards its adoption on a commercial scale in processing. Pulsed light, sonication and ozonation may require further understanding related to effect on the food and also development of refined equipment.
* Assistant professor – Department of Food Technology, School of Engineering and Technology, JAIN (Deemed-to-be University), Bangalore.