Heating, chilling, and freezing of food are the methods of food processing, preservation, and storage. These methods are developed in recent years to improve the quality of food products and to increase its shelf life.
The main reason behind emerging technologies is the comfort and easiness of life, safety, and quality of food. This article covers the latest technologies of heating, freezing, and chilling.
Emerging heat processing technologies of food
- Radiofrequency heating
- Ohmic heating
Innovative freezing technologies for food
- Impingement freezing
- Hydro-fluidization freezing
- High pressure-assisted freezing
- Ultrasonic assisted freezing
- Electrostatic assisted freezing
- Microwave-assisted freezing
- Dehydro freezing
- Antifreeze protein
- Ice-nucleation protein
Methods of food chilling
- Air chilling
- Chilling with liquid secondary agents
- Ice –Chilling
- Chilling in heat exchangers
Details of these topics are:
Emerging heat technologies:
Heating technology is used to inactivate microorganisms in different types of foods. Heating technology is used to preserve food and maximize product safety and quality of food.
Radiofrequency is a novel technique used for drying, baking as well as the thawing of frozen food.
Principle of radiofrequency heating:
Dielectric heating is used by radiofrequency heating to thermally process using electromagnetic waves. The wavelength range of RF (3 kHz to 300 MHz) covers the electromagnetic spectrum. During the RF method, the dielectric is placed in an alternating electric field uses a triode valve to generate energy. Molecular friction in food produces dielectric heating. Dielectric heating is considered fast and volumetric. water is a polar component of food, the molecules of water produces dipole moments (positive and negative charges), when placed in an electric field the polar molecules rotates to align with the electric field .friction is produced between molecules which created electromagnetic energy into heat energy.
Electromagnetic properties like permeability and permittivity are used to determine process parameters .however permeability has a little contribution to dielectric heating permittivity helps to define the dielectric properties of food.
Commercial application of Radiofrequency heating:
Baking and drying In snack food manufacturing post-baking RF drying plays an essential role .to To avoid cracking after traditional drying RF drying is used because energy penetrates evenly, the RF drying also prevents discoloration and flavor damage.
RF baking reduces the baking time for the bread loaves, In RF baking balls from the dough of brad are placed inside heat resistant RF compatible food graded polymer and introduced in the RF baking oven with controlled temperature and airflow.
Due to RF, the heat is generated rapidly and a product can be defrosted in minutes rather than hours like the traditional defrosting method. The RF heating process helps in a significant reduction of drip losses and the safety of products from bacterial growth.
Pasteurization and sterilization
RF generates heat rapidly and volumetrically and saves the product from deterioration. The RF equipment uses less space than the conventional thermal technologies equipment used for pasteurization and sterilization.
Ohmic heating is a novel technology for heating of food it is based on the principle of converting electric energy into thermal energy. Due to ohmic heating, better nutritional quality and organoleptic qualities are possible as compared to conventional in-can sterilization.
Ohmic heating is defined as a process in which electric current is passed through food material to heat them .ohmic heating is different from the traditional electrical heating process because of the presence of electrodes contacting the food and waveform.
Innovative freezing technologies
Freezing is an important food storage process used to store the food for a longer period .some innovative freezing technologies are introduced to improve existing methods.
These methods are:
This technology is used for freezing, the very high-velocity impingement air jets break the static surface boundary layer of gas that surrounds food. Impingement freezing is useful for high surface area to weight ratio.
It is an improved version of immersion freezing, HF freezing is used to circulate the refrigerating liquid upward through orifices or nozzles in a refrigerating vessel. Bed highly turbulent liquid and stirring products and thus provide enormously high surface heat transfer coefficients that enable fast freezing.
This type of freezing helps to tackle the problem of tissue damage during freezing. In the traditional way of freezing the volume increases which causes tissue damage in food .however when freezing assisted with high pressure is applied the ice being formed has a greater density than water and does not expand in volume upon freezing.
Ultrasonic radiations produce cavitation in the food product which promotes more even ice nucleation and fragment ice crystals already present into minor crystals. This process accelerates the convective heat transfer in the cooling media and speeds up the freezing process.
Applying an electric field to food will turn the polar molecules like water thus controlling supercooling and ice –crystallization.
During microwave assisted freezing water dipole rotation is exploited by microwaves to disorder ice nucleation and ice crystallization formation during freezing.
The principal of dehydro freezing is to dehydrate the food before freezing because dehydration will remove moisture content and due to this freezing time will be reduced.
Antifreeze proteins help in reducing the freezing temperature. Preventing the growth of ice nuclei altering ice crystals growth and delaying recrystallization on frozen storage. The application of antifreeze proteins in the food industry is in low-fat ice cream and frozen yogurts.
Ice-nucleation proteins are opposite to antifreeze proteins they raise the freezing temperature of ice-nucleation and reduce the degree of supercooling, this process shortens the freezing time and aids the nucleation of ice throughout the product.
Methods of food chilling
Chilled foods gained popularity due to its good quality and microbiological safety at the time of serving .some methods of food chilling following by the food industries are:
The air chilling is performed in chilling rooms or chilling tunnels, chilling room functions in batch processing while the tunnels work in a continuous process.
Air chillers used convection methods to circulate the chill air through the tunnel or room at high speed which helps in reducing the thickness of the boundary layer and the heat transfer rate is increased.
Chilling with liquid agents
A secondary liquid agent is sprayed or the food material is immersed into the liquid .the secondary agents have a higher value of convective coefficients and this thing helps in rapid chilling than air chilling. Poultry, fish, and some vegetables are suspected of this method of chilling.
Fish is stored in ice blocks while shipping the ice helps to remove heat from the surrounding structure of the box. Thus reducing the chances of fish spoilage.
Chilling in heat exchangers
This type of chilling method is used for liquid products like milk, juices, beer, and wine. Refrigerants are used on the cold side of the devices to chill and protect the liquid food from spoilage.
The food industry is rapidly growing old and traditional methods of food processing, storage, and distribution are replacing to enhance the quality of food and provide easiness not just for the consumer but also for the industries.
Food industries are on the mission to research new heating, cooling, and chilling technologies for food to produce a healthy, nutritious product for consumer’s convenience.