Hurdle technology

Hurdle technology refers to the selective combination of multiple preservation and pathogen control methods to improve food quality and extend its shelf life. The technology takes its name from the various individual methods used by the strategy, each of which presents a “hurdle” that a pathogen must clear to maintain its continued active presence in the food item. Hurdle technology is also known by several other names, including combined method technology, combined preservation, and combination technology.

The individual preservation and pathogen control methods used in hurdle technology each have a long, well-established history of safety and efficacy. Scientific reviews of combined method technology note that it was used empirically for many years before being specifically developed, refined, and purposefully applied through intelligent design. Hurdle technology is both mild and effective and is widely used in both developed and developing countries as a food safety strategy.

Brief History

Prior to the development of food preservation methods, human populations were constantly mobile and traveled from place to place to locate fresh food sources. Archeological evidence shows that ancient Middle Eastern and Oriental cultures used sun-drying food preservation methods as far back as 12,000 BCE. These advancements are believed to pre-date organized agriculture by at least two thousand years. The ability to extend the life-length of food was a key catalyst for the development of permanent human settlements and their eventual expansion across the globe.

Drying methods were originally applied to fruits and vegetables, later expanding to fish, game, and other animal-based food sources. Early civilizations also preserved foods using honey and sugar and applied various types of salt to desiccate savory nourishments. Cultures based in climates with cold winters also developed freezing techniques at relatively early stages, while another preservation technique known as fermentation was discovered around 10,000 BCE. Fermentation destroys toxins while enhancing food’s vitamin content, extending its life, and facilitating the production of appetizing foods and beverages from relatively bland raw materials. Smoking also has a precedent extending back to the ancient world, when it was used as both a preserving and flavoring technique.

Food preservation technology began to mature and accelerate as the result of cross-cultural contact and trade, with histories noting that many advancements occurred in sixteenth-century Europe. Pickling became a widely used technique around this time, while progressions arising in the post-Industrial Revolution (ca. 1760–ca. 1840) era enabled innovations such as canning and mechanical refrigeration and freezing.

Premodern civilizations applied these methods individually and in varying combinations intuitively and empirically. In many cases, their underlying scientific principles were understood at only a very basic level, if at all. As a targeted area of research inquiry, food science developed during the nineteenth century, with some sources crediting the French inventor Nicholas Appert as the field’s originator. As scientific understanding of food preservation advanced during the twentieth century, food scientists began to apply multiple techniques in targeted ways. The origins of the term “hurdle technology” date to 1976, when the term was first used by renowned German researcher Lothar Leistner.

Overview

Leistner is widely credited with developing modern hurdle technology and promoting its intelligent, purposeful application to manufactured and mass-distributed food products. Since Leistner’s pioneering research in the field began in the 1970s, food scientists have since identified more than sixty specific hurdles for plant- and animal-based foods, which generally work to prevent the growth of dangerous pathogens, improve the microbial stability of foods, and maintain their palatability over extended periods of time. In broad terms, the most important of such hurdles include controls on temperature, pH level and acidity, water activity, and reduction-oxidation potential. The application of specific preservative agents, such as nitrites, sorbates, and sulfites, also ranks among the most commonly used hurdles, as does the active cultivation of microorganisms that compete with those capable of accelerating food spoilage.

The exact combination of hurdles used in a given foodstuff varies, depending on its specific characteristics and degeneration potential. Food scientists thus use multiple models to describe the ways in which various hurdles interact. Three such models include grouping hurdles by their primary functions, types, and applications.

Primary functions include four main classes of hurdles: microbiocidal controls that neutralize pathogen growth; microbiostatic hurdles that use biochemical methods of inhibiting or preventing pathogen growth; microbiostatic hurdles that use physical methods of inhibiting or preventing pathogen growth; and hurdles designed to prevent contamination and cross-contamination.

Classification systems that group hurdles according to their typology separate them into three categories: physical hurdles, physicochemical hurdles, and microbial hurdles. Examples of physical hurdles include sterile packaging, exposure to high or low temperatures, ultra-high pressurization, and various forms of radiation exposure. Physicochemical hurdles cover food preservation strategies such as curing, smoking, and applying nitrates, nitrites, sulfites, surface treatments, herbs, and/or spices. Microbial hurdles encompass antibiotics and the introduction of competitive microbes or flora to food products.

Hurdle applications include physical and biochemical methods of extending food life and removing pathogens. These are the most familiar to consumers and include techniques such as heating, chilling, freezing, curing, drying, conserving with sugar, adding chemical preservatives, and removing oxygen from food packaging via vacuum sealing or adding nitrogen.

Hurdle technology facilitates the delivery of high-quality, nutritious, fresh-like foods to consumers with minimal additional processing. In addition to extending the shelf life of commercially available food products, hurdle technology can also improve its nutritional content, reduce storage costs and transportation distances, and boost the economic feasibility of certain food items. It also makes packaged foods shelf-stable at standard room temperatures for long periods of time.

Notably, hurdle technology also enables food manufacturers to realize its benefits through relatively modest technique applications. By selectively and intelligently applying multiple hurdles, food producers are able to reduce their reliance on certain preservatives known or suspected to have adverse effects on human health. Examples of such preservative agents include nitrates and nitrites, both of which have been linked to cancer in humans when consumed in high quantities over long periods of time.

Bibliography

Abdullahi, Nura and Munir Abba Dandago. “Hurdle Technology: Principles and Recent Applications in Foods.” Indonesian Food and Nutrition Progress, Vol. 17, No. 1 (Jan. 2021): pp. 6–11.

Chauhan, O.P. Nonthermal Processing of Foods. CRC Press, 2019.

Khan, K.A., Megh R. Goyal, and Abhimannyu A. Kalne. Processing of Fruits and Vegetables: From Farm to Fork. CNC Press, 2019.

Leistner, L.”"Basic Aspects of Food Preservation by Hurdle Technology.” International Journal of Food Microbiology, Vol. 55 (2000): pp. 181–186.

Leistner, L. “Hurdle Technology.” Encyclopedia of Life Support Systems, 2009, www.eolss.net/sample-chapters/c10/E5-10-04-12.pdf. Accessed 17 Jun. 2021.

Neeha, V.S. and Subhash B. Kakade. “Use of Hurdle Technology in Food Preservation.” International Journal of Engineering and Management Research, Vol. 4, No. 5 (Oct. 2014): pp. 204–212.

Rahman, Mohammad Shafiur. Handbook of Food Preservation. CRC Press, 2020.

Singh, Shiv and Rachana Shalini. “Effect of Hurdle Technology in Food Preservation: A Review.” Critical Reviews in Food Science and Nutrition, Vol. 56, No. 4 (2016): pp. 641–649.