What Are Nonthermal Food Processing Technologies?

As a food processing expert, I have seen an increase over the last couple of decades in consumer demand for increased freshness, convenience and variety in their foods.

I believe this has been driven by the ways that the traditional methods of food processing alter the taste, texture, appearance and nutritional value of food, as well as a pushback against artificial preservatives.

In response, the food processing companies have worked with academia to develop alternative processes that reduce the effects of excessive heat. Processing foods at lower temperatures has a variety of benefits, including better taste and mouthfeel. This is because sugars are not caramelized, flavors are not destroyed, and proteins are not so denatured. Also, processing foods at lower temperatures can extend the shelf life of refrigerated foods. As an example, one of Fres-co’s customers is producing fruit juices using high-pressure pasteurization in our flexible packaging. This results in fresher taste and longer shelf life. These benefits are achieved without compromising food safety.

While there are many food processing technologies that are effective alternatives to high heat, here is a list of the most promising.

Pulsed Electric Field Processing

This is a high-intensity (15,000 V/cm2), pulsed electric field that passes through food. When combined with mild heating, pulse electric field processing enhances the inactivation of vegetative cells, extending shelf life. The pathogens are inactivated through the destruction of the cell membranes. This process works well with flexible packaging.

Ultraviolet (UV) Light

This process uses the ultraviolet region of the electromagnetic spectrum to disinfect food. The germicidal properties of this process are mainly the result of mutations that occur when UV light is absorbed into DNA molecules. Commercial applications of UV light include disinfection of water supplies and food contact surfaces. There is also growing interest in using UV light to reduce microbial loads in clear fruit juices. This process can extend the juices’ shelf life and make them fresher-tasting, compared to thermal food processing. UV light may also be used in combination with other technologies, including various powerful oxidizing agents such as ozone and hydrogen peroxide for package sterilization.

Pulsed Light

Like UV, pulsed light does not penetrate food. It is most useful for killing microorganisms on the surface of foods, a process for which it was approved by the FDA. Pulsed light is also effective for thin liquids, and it is finding its way into aseptic packaging to sterilize flexible packaging films. Pulsed light consists of very intense (20,000 x the power of sunlight) short flashes of light (between 0.1 sec. and 1msec.) with UV, visible light and IR wavelengths.

High Hydrostatic Pressure Processing (HPP)

HPP is a method in which foods are treated with extremely high pressure (up to 90,000 psi) to inactivate the microbes. Typically, the food product is packaged into flexible containers, allowing transmission of the pressure to the product. The flexible packages are then placed into a high-pressure chamber filled with a pressure-transmitting medium (usually water). The fluid-filled chamber is then pressurized with the pressure being transmitted through the package and into the food itself. Because this non-heating method does not cause thermal degradation, HPP retains the food’s nutrition, keeps its taste fresher, and maintains its appearance. While HPP is currently limited to pasteurization of food and beverages that must be kept refrigerated, there is much research underway to help us understand the inactivation of bacterial spores, leading to shelf stable products.

Cold Plasma

Plasma is the fourth state of energy; it is gas at a more excited level. Cold plasma is a novel non-thermal technology that uses gases such as air, nitrogen or CO2 to produce short-lived free radicals. This incapacitates the contaminating microbes not only on fruits and vegetables, but also dry products, such as nuts or powdered infant formula. While cold plasma is currently in the research and developmental stages, it holds great potential for surface treatment of many foods and even flexible packaging materials.

Irradiation

While gamma irradiation has been around for a long time and has generally not been accepted by consumers, electron beam irradiation has recently become widely accepted as a way to kill bacteria on the surface of meats and other food products. Also, I recently learned that cases of packaged foods can be passed through an electron beam process on a conveyor to produce shelf stable products. Again, flexible packaging lends itself well to this technology.

Traditional thermal food processing is a long-accepted method in the industry, but alternative methods are rising along with consumers’ desires for better, more natural-tasting foods. It’s true that the various technological methods I listed above are at different stages of development and are also the subjects of large amounts of research. However, they are becoming more accepted by industry, regulatory agencies and consumers, and they are finding their way into commercial food production.

For more than 40 years, Fres-co System USA, Inc. has manufactured high-performance flexible packaging systems and invented dozens of innovative breakthroughs including degassing valves, modified atmosphere technologies, and reclosure systems.

Topics: Flexible Packaging, Food Processing

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