Sterilization vs pasteurization

Sterilization vs pasteurization

We’ve performed a direct comparison of sterilization vs pasteurization using TERRA Food-Tech® autoclaves

Both pasteurization and sterilization are thermal processing methods for preserving food with heat. Both techniques are based on the application of high temperatures to food for a certain time to achieve inactivation of microorganisms and enzymes.

However, despite their similarties, there are differences between them. In the following post we will present a detailed comparison of sterilization vs. pasteurization using TERRA Food-Tech® autoclaves.

Sterilization vs pasteurization

Foodstuff that is usually sterilized or pasteurized

Illustration of foods for to compare sterilization and pasteurization

In reality, all food products can be sterilized or pasteurized in the TERRA Food-Tech® autoclaves provided that there is a medium to transmit heat, such as water or oil. If we are treating a dry product, or the package contains air, heat transfer is more troublesome and achieving a proper sterilization is tricky, products may not end tasting well. These products should be preserved with other techniques.

We could say that they must be pasteurized, that is, subjected to milder treatments at lower temperatures and for shorter periods of time:

  • Foods with delicate textures or products clear in color.
  • And also products that have been cooked, passed through the blast chiller and refrigerated before packaging, or products cooked and packaged directly while hot.

Instead, they must be sterilized or submitted to more aggressive treatments at higher temperatures:

  • Raw foods, especially vegetables that have been in contact with the soil.
  • Legumes, because they contain sporulated microorganisms that can survive milder heat treatments.
  • When hygienic conditions are not entirely optimal.
  • To eliminate the “fresh” taste, such as with canned tuna or sardines.
  • If the ambient temperature at which the product is going to be marketed is high (30-40ºC), such as in tropical countries.

But in short, the most usual technique for preserving meat, fish, vegetables and fruits is sterilization, whether the final product form are jams, syrups, pickles, creams, soups, sauces or stews, among others. On the other hand, the following products tend to be pasteurized: milk and its derivatives, flavored juices and beers, but also some ready meals and sauces. Although in the case of animal milk, vegetable milk and certain juices, they will not be completely good if we pasteurize them using an autoclave. Other technological approaches are more appropiate for pasteurizing those products.

Food safety: elimination of microorganisms and spores

While sterilization destroys all the microorganisms and spores present in the food, in pasteurization, a part of the most resistant microorganisms, a part of enzymes and bacteria spores survive.

Not carrying out these processes correctly can lead to enormous dangers both for public health and for your canning business. At first, it may seem trivial or almost impossible, due to its unusual nature these days, but you should bear in mind that incorrect pasteurization or sterilization of food can lead to serious risks, such as those caused by the consumption of food contaminated with Clostridium botulinum. This is one of the most dangerous pathogens because it produces the botulinum toxin, which causes botulism, a disease that can block nerve functions and cause respiratory and muscle paralysis and even death.

Storage and distribution temperature

Sterilized foods are perfectly preserved at room temperature. Pasteurized foods, on the other hand, require a refrigerator both during transport and storage, at a temperature of between 3ºC and 6ºC, to delay the proliferation of microorganisms and spores present in the food.

Likewise, pasteurized foods require trucks and refrigerated shelves for their distribution and sale. Unlike traditional preserves made by sterilization, which can be kept in perfect condition for much longer at room temperature and are easier to transport and market.

Best before date

In sterilization, the best before date of the products can be much more than four months or even, depending on the type of food and the treatment applied, it can be extended up to 2 or 5 years. The best before date for pasteurized preserves is much shorter. It could be two to three weeks or in best scenarios one to two months, depending on the product, and they must always be kept refrigerated at all times.

Once opened, both sterilized and pasteurized foods should be consumed quickly and stored in the refrigerator.

Organoleptic properties

One of the pros of pasteurization is the maintenance of the organoleptic and nutritional properties of the food thanks to the application of low processing temperatures.

This is one of the drawbacks of sterilization, since the use of high temperatures may affect the final food properties, reducing the value of the processed product by destroying some vitamins and changing its aromas. Likewise, it could produce a change in the food organoleptic properties, such as changes in color and the appearance of overcooked flavors.

There are various tricks used to prevent gourmet preserves or prepared dishes from undergoing changes when sterilized and make these variations almost imperceptible.

If you don’t want your products to taste overcooked, you can let it finish cooking, partially or totally, in the autoclave. And as for the color of the vegetables, if you see that they are a little dull, you can add a little baking soda or some type of natural dye that does not add any flavor and helps preserve color.

Food pH and acidity

The level of food acidity (pH) determines the growth of different types of pathogens. This determines the time and temperature our preserves should be subjected to and, therefore, the preservation method to be used. Foods with a higher pH require higher temperatures, and vice versa.

To be marketed at room temperature, neutral pH foods are usually sterilized, so more heat is applied to them, temperatures above 100ºC, for a specific period of time to destroy all microorganisms and spores.

On the other hand, foods with an acid pH (4.5) if to be used at temperatures below 100ºC, are not sterilized. They are pasteurized and must be marketed cold.

And what about foods with a pH between 4.2 and 4.5? Well, we must decide on a case-by-case basis. It is advisable to have a calibrated pH meter to correctly measure the pH of the food before subjecting it to any heat treatment. We should insert a core probe into one of the containers to collect all the parameters used in pasteurization/sterilization and then check if the initial flora has changed. Several analyses must be carried out on the products to confirm the ideal temperature and time required to eradicate possible microorganisms and while not altering the smell, color, taste and texture.

Fo-Po thermal values

Fo and Po are thermal values determined by the combination of time and temperature, used to ensure the effectiveness of the conservation treatment and to minimize changes in the color, texture, aroma and nutritional values of a preserved food product.

Fo es el valor de la esterilización, es decir, cuando se utiliza una temperatura superior a los 100ºC. Y Po es cuando la temperatura es inferior a 100ºC, o sea cuando se pasteuriza. Aunque también hablaremos de Po para esterilizaciones de alimentos ácidos.

TERRA Food-Tech® autoclaves for cooking, pasteurization and sterilization of packaged foods

Importance of pH in the preparation of preserves dishes prepared with the autoclave

Our vertical or top-loading autoclaves are designed so entrepreneurs, restaurateurs, farmers and chefs can cook, pasteurize and/or sterilize all kinds of packaged foods. With a capacity of 33 to 175 liters, they are ideal for the production of gourmet preserves and artisanal ready meals.

Likewise, TERRA Food-Tech® compact autoclaves allow you to precisely adjust the Fo and Po values, the maximum temperature to be reached and the duration of time. In this way, you can avoid excesses in time or in maximum temperatures and thus ensure that the food preserves its color, texture, flavor, aroma and nutritional values to the maximum and, in addition, ensure that the food complies with all the requirements and regulations applicable in the food industry. To do so, our equipment uses a temperature probe placed inside a product sample to monitor the temperature applied throughout the pasteurization or sterilization process.

Other notable features of our autoclaves include:

  • They comply with the legislation on Safety and Hygiene for canned foods.
  • They accept any type of container suitable for withstanding treatment temperatures: cans, glass jars, semi-rigid trays, bags or pouches.
  • Easily installed. They only require a water source, a drain and an electrical connection.
  • Easy to use and program. With color touch screen and capacity to store up to 50 programs.
  • With rapid cooling technology using a water shower.
  • Programmable counterpressure and refrigeration to avoid breaking or deformation of containers.
  • Guaranteed security measures: safety valve and thermostat; door blocking system and open-door alarm; pressure and water level sensors; thermal protection around the lid; and a bodywork that protects the sterilization chamber.
  • Multiple accessories for all kind of projects: basket elevation crane; customizable, stainless steel trays and baskets; lid and semi-rigid containers hole punching kit…

In addition, by buying a TERRA Food-Tech® autoclave, you can enjoy our food consulting service and initial professional support.

In addition, at TERRA Food-Tech®, to help you estimate the feasibility and yield of your project, we have created a free online calculator to calculate the production capacity per cycle to find the number of containers you can produce depending on the type of container and model of your autoclave.

If you need more information about sterilization vs pasteurization, or to find out which autoclave best suits your business needs, contact our sales team. We will be happy to help you!

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Luca Montersino

Luca Montersino

Luca Montersino, renowned Italian chef and cooking teacher, pastry chef and creator of preserves.