Over-processing products can cause losses in taste, texture, and ultimately profit. Hurdle technology (also known as combination techniques or barrier technology) is a valuable tool in the fight against over-processing. It combines different preservation factors or techniques to achieve mild but reliable preservation.
Working together for food safety
Hurdle technology deliberately combines existing and new preservation techniques to establish a series of preservative factors that microorganisms are unable to overcome. These hurdles can include temperature, water activity, acidity, redox potential, preservatives, competitive organisms, vitamins, nutrients, and more.
How hurdles work
In order to thrive and multiply, microorganisms need to maintain homeostasis–a stable and balanced internal environment. Hurdles attempt to disturb one or more homeostasis mechanisms, causing the microbes to become inactive or even die. The best hurdles combine to disturb several homeostasis mechanisms simultaneously. This multi-targeted approach is more effective than single targeting and allows hurdles of lower intensity.
The following figure shows how hurdles work together to limit microbial growth.
Figure 1 shows several examples of combined processes. Each of the illustrations shows, by means of dotted lines and arrows, whether or not the processes are effective in stopping microbial growth. In number 3, for example, temperature alone wasn’t an effective control, but water activity plus temperature combined to prevent the growth of microorganisms. In example 4, the hurdles were not enough to prevent microbial growth. In this instance, the temperature hurdle would have needed to be increased by refrigeration.
Cooperation or competition
The effect of hurdles on each other must also be considered. Sometimes a second agent will simply add to the effectiveness of the first. Sometimes the agents act synergistically, making their combined effect even greater. However, one agent may also antagonize or negatively impact the effectiveness of the other, either partially or completely offsetting the effectiveness of one or both agents. These effects must be carefully researched before agents are used in combination.
Water activity as a hurdle
Water activity (aw) is one of the most useful hurdles, both alone or in combination with another hurdle. There are specific water activities below which certain microbes can’t grow and a water activity below which no microbes proliferate. These microbial growth limits apply to every type of food and, in fact, to every porous product.
Water activity and pH: synergistic hurdles
Water activity and pH work synergistically, allowing you to control microbial growth to a degree not possible using one of these factors alone. This synergistic effect is part of the FDA’s definition of potentially hazardous foods.
Table A can be used to determine if a food which is heat-treated and packaged is a potentially hazardous food (PHF), Non-PHF, or Requires Product Assessment. Food must meet cooking requirements of Food Code section 3-401.11 (no partial cooks) to eliminate vegetative pathogens. Spore forming pathogens are the only remaining biological hazards of concern. Food is packaged to prevent recontamination. Therefore, a higher pH & water activity can be safely tolerated.
|aw Values||pH: 4.6 or less||pH: >4.6 - 5.6||pH: >5.6|
|0.92 or less||Non-TCS food*||Non-TCS food||Non-TCS food|
|>0.92 - 0.95||Non-TCS food||Non-TCS food||PA**|