There are typically a myriad of unknowns associated with the safe use of novel preservation technologies in the production of foods and beverages intended for human consumption. Chief among these are concerns for food safety and regulatory acceptance. Confirming food safety is a daunting undertaking. Validating food safety involves every element of the manufacturing process. Consideration must be given to microbial stability, toxicology, product and packaging interactions, process capability and product stability and chemistry, as well as possible harmful effects of the stabilization process. In most cases, there will also be the need to provide objective data that confirm, with a high degree of confidence, that the product meets the safety expectations of the various regulatory agencies. Under certain circumstances, the rigor demanded for confirming safety and regulatory compliance, when joined with the high associated cost, has served to slow or deter commercialization and therefore the uptake of novel processing and preservation methods.

According to Gustavo V. Barbosa,[1] “As interest in the development and use of novel thermal and nonthermal technologies to process foods increases worldwide, special attention must be paid to identifying the key goals for these new technologies. While a technology itself may prove successful in its operation, the more significant goal is that the technology is actually useful in the industry for which it is intended. For the food manufacturing industry, this means that the use of novel technologies ultimately must result in the production of nutritious, safe and high-quality foods at a reasonable cost for the consumer.” Likewise, a 2007 survey[2] and overview of the status of novel and emerging technologies showed that considerable work had been done to validate safety and efficacy of many of the novel technologies, but at that time, only high pressure, irradiation and pulsed electric field had been used commercially.

Food Processing Basics
Food processing and preservation methods have been traditionally associated with four fundamental concepts:

1.    Application of thermal energy to elevate product temperatures to achieve long-term or extended stability or preservation

2.    Removal of thermal energy to reduce product temperature and extend shelf life  

3.    Removal of water from product structure, thus achieving extended shelf life

4.    Packaging or the step required to maintain product properties achieved during processing  

Over the last few decades, a fifth alternative processing concept called “novel processing technologies” began to emerge globally in food production. In the history of technology, novel or emerging technologies are those contemporary technical innovations that represent progressive developments within a field for competitive advantage. In the food industry, as a result of modern demands for foods that are fresher, more natural or minimally processed and additive-free, novel processing techniques are currently in broad development. The use of novel technologies ultimately produces higher-quality foods due to reduced thermal and chemical abuse, plus higher safety attributes during extended shelf life and at a reasonable cost for the consumer. Food safety is one of the important components driving the development of novel microbial-intervention technologies to reduce, control or eliminate foodborne pathogens from food products and contact surfaces. Additionally, novel processing technologies might be used as tools to tailor foods with added or enhanced functional and nutritional values, to lower carbon footprint and substantially reduce water volumes used in heat-transfer processes. As an example, novel processing methods are being explored to potentially create hypoallergenic products and have been tested to alter allergen reactivity of components of food matrices.

This fifth novel processing concept includes advanced thermal and nonthermal technology that uses mechanical, electrical and electromagnetic energy, and combined-applications approaches. So-called novel foods with no history of consumption that can be produced by novel processes have started to emerge in the market and often can replace traditional-style foods. For example, old-style ham treated by high pressure or fresh apple cider pasteurized using ultraviolet (UV) light become novel foods.

Processing Interventions
Processing techniques that can be used to reduce microbial loads include removal and inactivation. Removal unit operations include filtration, centrifugation and separation, which belong to the group of hydrodynamic processes that are driven by a hydrostatic or hydrodynamic pressure gradient. Inactivation unit operations include a number of physical methods and chemical agents capable of pronounced bactericidal and/or sporicidal effects. A summary of different techniques that have been explored and their fundamental mechanisms of delivering a lethal treatment is presented in Table 1.

Since introducing preservation principles in food processing in the beginning of the 19th century, the food industry along with the scientific community accumulated critical knowledge for establishment of thermal and other traditional processes that include:

•    Established organisms of public health concern

•    Well-understood and known kinetics of microbial destruction

•    Knowledge of product heating in given processing systems

•    Establishment of equivalent safety of different processing systems expressed in lethality

Due to different fundamental principles, the performance capabilities of novel technologies and processes differ from traditional processing in terms of the types of food categories that can be treated, microbial efficacy and destruction models, desired and undesired effects on food quality and their economic and environmental impact.

Before a novel process can be used and product can be sold, food industry professionals and regulatory agencies must review its impact on quality and nutrition, and evaluate the safety of a novel process and its resultant novel foods. Hence, the incremental developments of novel technologies for a variety of food applications led to significant accumulation of new scientific and engineering information. However, the technology readiness level is assessed by its suitability for the actual application in its final form. Recently, a few novel intervention technologies were successfully developed, approved by regulatory agencies and applied as inactivation steps to enhance food safety.

High Hydrostatic Pressure Processing
High hydrostatic pressure processing (HPP) has been commercialized since the mid-1990s and successfully applied to inactivate microbes in heat-sensitive drinks and solid foods such as guacamole, jams and jellies, fruit juices, tomato salsas and applesauce. HPP has also been applied to ham, cooked ready-to-eat meat products and seafood products such as oysters. Based on the growing scientific evidence and fast commercialization, HPP is an example of alternative technologies that can be used for in-package pasteurization to control postprocess contamination.

An automated HPP system involves placing a flexibly packaged product into a handling basket that is set inside a vessel in which ultrahigh hydrostatic pressure of between 80,000 and 130,000 psi is uniformly applied to both pre- and postpackaged foods. Food samples are pressurized between 2 and 5 minutes, taken out of the pressure chamber and stored or distributed as usual.

HPP inactivates most vegetative microorganisms that grow in foods under normal storage conditions. Studies showed that water activity and pH are critical process factors in the inactivation of microbes by HPP. HPP is particularly effective when applied to high-acid foods to extend shelf life or improve food safety. For foods where thermal treatment is not an option (due to flavor, texture or color changes), HPP can extend the shelf life by two- to threefold over a nonpasteurized counterpart and improve food safety. As commercial products are developed, shelf life can be established based on microbiological and sensory testing.

Recently, low-acid products that are meant to be shelf stable, such as vegetables or soups, were not considered good candidates for the HPP process due to its inability to kill spores without added heat. Low-acid refrigerated products fare better when processed with high pressure, both in terms of extended shelf life and pathogen reduction.

In 2009, the U.S. Food and Drug Administration (FDA) approved the commercial use of a pressure-assisted thermal sterilization process (PATS) for application in the production of low-acid foods. To achieve a commercially sterile food product, PATS utilizes a combination of HPP and temperature over a short hold time. The rapid temperature increase during compression and temperature decrease upon decompression are unique technology benefits to produce superior quality products. While there are currently no PATS-processed, shelf-stable foods on the market, PATS holds promise to provide a route for novel processing of products such as soup, stews and mashed potatoes that would see a severe loss in quality by traditional thermal processing.

Microwaves
Although industrial microwave pasteurization and sterilization systems have been used for three decades, commercial radio frequency heating systems for the purpose of food pasteurization or sterilization are not yet fully commercialized. In 2011, FDA approved another novel sterilization process using 915 MHz microwave energy called a microwave-assisted thermal sterilization process (MATS).[3] As reported, the technology immerses packaged food in pressurized hot water while simultaneously heating it further with microwaves at a frequency of 915 MHz. This combination eliminates food pathogens and spoilage microorganisms in just 5 to 8 minutes and produces safe foods with much higher quality than conventionally processed, ready-to-eat products.

High-Intensity Pulsed Electric Fields
High-intensity pulsed electric fields (PEFs) have been used in the U.S. for the commercial pasteurization of juice products in compliance with the mandates of FDA’s juice HACCP regulations (21 C.F.R. 120). PEFs have also been used successfully to treat salsa, yogurt and milk. One of the main drawbacks to using the technology is the requirement for aseptic filling and packaging. To overcome this challenge, a company in Yverdon-les-Bains, Switzerland, is seeking to confirm the efficacy of its in-bottle pasteurization system that combines microwave heating and high-intensity PEFs. Using these combined technologies, filled and sealed bottles are rapidly heated by microwaves and immediately exposed to high-intensity PEFs. The company has conducted a number of microbial challenge studies using an assortment of microorganisms in acidic beverages. The results of the challenge studies are reported to show microbial inactivation at levels consistent with requirements for pasteurizing high-acid or acidified liquids.[4]

UV Light
UV light has been used for the decontamination of air in food factories, treatment of drinking water, water for food and beverage formulation, wash water and wastewater, and surface treatment of contact surfaces and products in the bakery industry. FDA approval of UV light emitted by low-pressure mercury lamps as a safe alternative to thermal treatments of juice products, along with recent engineering developments, led to the growing interest in research and commercialization of UV technology. Despite the challenge of low UV light penetration, a few designs of continuous-flow UV apparatuses have been developed for processing various types of fluids. UV systems that used flow patterns such as thin-film laminar, annular turbulent and Dean flow in coiled tubes were validated for a variety of preservation applications to treat raw and finished products. However, the current 21 C.F.R. 179 Food Additive Regulation recognizes distinctions between flow patterns and stipulates the use of turbulent flow for UV systems for fresh juices. The overall quality of UV-treated products is superior to that of untreated raw or thermally treated products.

Summary
Worldwide, interest is growing in the development and use of novel thermal and nonthermal food processing technologies as tools that can be applied successfully throughout the food supply chain from ingredients to finished products. The main driver for companies implementing some of these emerging food safety technologies is the assurance of microbial reduction on their products at different steps of production but also the resulting higher quality of the foods produced. In general, the approach is that the novel process should demonstrate equivalency with traditional processes (e.g., pasteurization). High investments are generally required to carry out tailor-made research on these new processing methods, but the results of fundamental research are promising. The recent commercial successes of novel processes demonstrated a need to summarize and reestablish scientific knowledge, including the fundamental aspects of novel processing and preservation methods as an interdisciplinary subject involving topics from microbiology, chemistry, engineering operations and technological processes. Applications of the technologies for uses beyond preservation or safety have been studied to develop high value-added processes or to identify other saving opportunities.

Tatiana Koutchma, Ph.D., is a research scientist in novel food processing at Agriculture and Agri-Food Canada (AAFC), graduate faculty at the University of Guelph and a member of the board of directors of Ontario Food Protection Association. She can be reached at Tatiana.Koutchma@agr.gc.ca.

Larry Keener, CFS, is the president and general manager of International Product Safety Consultants (IPSC). He is an adjunct professor of food science and technology at Tuskegee University and serves on the Editorial Advisory Board of Food Safety Magazine. He can be reached at lkeener@aol.com.

References
1. www.food-safety.com/magazine-archive1/augustseptember-2002/key-goals-of-emerging-technologies-for-inactivating-bacteria/.
2. www.food-safety.com/magazine-archive1/aprilmay-2007/innovations-in-technology-promising-food-safety-technologies/.
3. www.foodengineeringmag.com/articles/91312-microwave-sterilization-for-packaged-meals.
4. Personal correspondence with Opus Industries S.A. Switzerland. 2014.