In today’s clean label era, consumers are increasingly looking for food products that are free of artificial ingredients, particularly chemical preservatives, and that have undergone minimal processing. Satisfying these consumer demands, however, poses quite the challenge for food manufacturers.
If consumers don’t want the artificial preservatives or intensive processing techniques that the food industry currently relies on to keep food shelf-stable, safe, and appealing, what are the alternatives? Are there other ingredients or processes manufacturers can use to ensure that their products will still have a reasonable shelf life and be safe to eat?
Over the last decade or so, food producers have been intensively exploring this question. They have come up with a variety of possible answers, ranging from non-synthetic preservatives to natural methods like biopreservation. One of the most promising possibilities that many manufacturers are excited about is a relatively new technique known as high pressure processing.
As the name implies, this process relies on pressure, rather than high temperatures or synthetic ingredients, to neutralize the harmful microorganisms that can cause food to spoil quickly and make consumers sick. Read on to learn more about how high pressure processing works, and the benefits it can offer.
What is high pressure processing?
High pressure processing (HPP) is a food preservation method that inactivates harmful pathogens by using a special machine to apply extremely high pressures to foods. It is also known as cold pressure processing or Pascalization.
HPP can be used on all types of food products that naturally contain moisture. However, it is proving particularly useful for fresh, perishable products such as juice, hummus, fruits and vegetables, and even poultry and other meat products.
How do HPP machines work?
An HPP machine is about the size of a mini-van. Its main component is a thick tube of solid steel, similar to a torpedo tube. Foods to be processed are first carefully packaged, and then loaded into the tube. During processing, the central chamber of the tube is flooded with water, which is then compressed with an extremely powerful piston.
Incredibly, the pressure produced by an HPP machine can reach 87,000 PSI (pounds per square inch). To truly understand how high that is, consider the fact that at the deepest point in the ocean—the Mariana Trench, at about 36,000 feet below sea level—the massive volume of water creates pressure levels of about 16,000 PSI. This is over five times less than an HPP machine!
How does HPP actually kill bacteria?
It’s clear that HPP machines produce remarkable amounts of pressure, but how does that actually destroy food-borne pathogens like E. coli and listeria? Essentially, what happens is the external pressure outside the packaged food—that is, the pressure inside the tube—is transmitted inside the packaging to the food itself via the water molecules that the food contains.
While nutrients and biological cells have cell walls that are strong enough to withstand this pressure, the bacteria do not. As a result, the pressure forces water through the bacterial cell walls until they are so saturated that they can no longer function. This is why HPP requires foods with a minimum level of moisture content. Drier foods like nuts simply don’t contain enough water molecules to transmit the pressure effectively.
How is HPP different from current popular food preservation methods?
HPP uses pressure to destroy microorganisms and keep food safe. The two most popular preservation methods currently in use rely on heat and chemicals, respectively. Pasteurization is the name for the process that kills microbes in food through the application of heat.
Specific pasteurization methods are approved by the USDA for different types of food, but in all methods, food is heated to a minimum of 145 Fahrenheit and a maximum of 284 degrees Fahrenheit. This kills pathogens very effectively and efficiently. However, such high heat can also negatively impact a food’s texture, flavor, and nutrient content.
Preservatives, on the other hand, use natural or synthetic chemicals to either kill harmful microorganisms or prevent them from reproducing. Today’s commonly used preservatives are also very effective and can have only minor effects on a food’s other properties. Some consumers are concerned that artificial preservatives may contribute to health conditions such as cancer or neuro-degenerative diseases. They try to avoid these preservation methods as a result.
What are some of the advantages of HPP?
When compared with the two other main methods of food preservation, HPP offers some significant benefits. Because the process does not involve any high temperatures, the texture and flavor of foods that undergo HPP are not typically altered in any way. Their nutrient content is also unaffected.
And because no chemicals are involved, there are no health risks that may be linked to the use of synthetic additives. Furthermore, HPP also helps food keep its shape better than some other forms of preservation because pressure is applied to the food evenly from all directions. HPP preservation methods may also be better able to maintain the functionality of fresh foods.