Pasteuriser: The Custodian of Quality

Here we are. Today marks episode no.12 of the ZACMI Worldwide Tour – a fortnightly event that, as you already know, takes us on a journey to various parts of the world, right into the premises of companies where our specialised technicians provide on-site assistance, commissioning, and maintenance.

If you’ve been following this series, you know that, in addition to processing the products with our machinery, we also delve into the socio-cultural aspects associated with each specific product. This time, we have returned to England, where we carried out significant interventions on one of our pasteurisers.
How so? Were you not aware that, besides our virtually indestructible seaming and filling machines, we also manufacture a pasteuriser?
We did mention it in a post on our LinkedIn page, but this is a brilliant opportunity to explore it in greater detail.
And while we’re at it – since the company in question specialises in sauces – we’ll also take an interesting detour into this product.

Well, now that we’ve warmed up our engines, all that’s left is to get going!

Warm Up in England

Warming up the engines… no, we’re not heading to Silverstone, but to a major facility of a leading multinational that produces a wide range of sauces.
At their premises, we installed and commissioned a filling machine – a bespoke monobloc system designed specifically to operate with special containers holding up to 4 kg.
Alright, but what does all this have to do with “warming up”?
Well, this time in England, we were there to support the company during technical trials with one of our pasteurisers.
As you may know, pasteurisation is a thermal process applied to both liquid and solid foods to reduce the microbial load by controlling temperature and time.
Alright, we’ve had a bit of fun with the words – grant us a little creative licence every now and then!
Now, let’s take a closer look at how it all works.

How Does a Pasteuriser Work?

The pasteuriser, as we mentioned, is used to apply a thermal treatment to certain foods – such as raw materials, fresh semi-finished products, and sauces – in order to:

• Inactivate enzymes and destroy the majority of pathogenic microorganisms (such as bacteria, fungi, and yeasts), thereby significantly reducing health risks for consumers.
• Enhance the shelf life and food safety of products without excessively compromising their nutritional properties.
• Enable the commercialisation and distribution of food products over long distances – from wine, beer, and milk to various types of sauces.

The pasteuriser heats the food to temperatures ranging between 60–95 °C for a variable period, depending on the type of pasteurisation (low, high, or rapid HTST – High Temperature Short Time).

This thermal treatment is less intense than sterilisation, which occurs at temperatures above 120 °C.

Does Heating Alter Food Properties? And What’s the Difference with Sterilisation?

Let’s begin by establishing the difference between pasteurisation and sterilisation.

Both are food preservation techniques that use heat to eliminate microorganisms, but they differ in intensity and outcome.
Sterilisation nearly completely eliminates all microorganisms and spores, whereas pasteurisation merely reduces the bacterial load by destroying the vegetative forms of pathogenic organisms.
Furthermore, pasteurisation utilises temperatures below 100 °C, while sterilisation requires temperatures starting from 121 °C.
For acidic foods (pH < 4.5), pasteurisation can be as effective as sterilisation in eliminating all living forms.

The Advantages of Pasteurisation

In general, pasteurisation offers several benefits over sterilisation, primarily because it better preserves the nutritional and organoleptic qualities of foods.

Here are the main advantages:

• Less Impact on Nutritional Properties: Lower temperatures minimise the loss of nutrients, such as B vitamins.
• Better Preservation of Taste: The gentler heating process better retains the original aroma and flavour of the food.
• Elimination of Hazardous Bacteria: Pasteurisation effectively destroys pathogenic bacteria and other harmful microorganisms, making the product safer. In the case of acidic foods (i.e. pH < 4.5), it can be as effective as sterilisation in eliminating all living forms, microorganisms, and spores.
• Extended Shelf Life: Although it does not completely eliminate the bacterial flora, pasteurisation significantly extends the shelf life compared to fresh products.

In summary, pasteurisation is the preferred method when the goal is to retain as much of the food’s original characteristics as possible while ensuring food safety.

Pasteurisation: It’s Not Just a Matter of Temperature

During the pasteurisation process, several key parameters must be considered to ensure both the effectiveness and safety of the treatment. We’ve already mentioned one, but let’s review them all.

1. Temperature
Temperature is one of the most critical factors in pasteurisation. The temperatures used vary depending on the product type:

• Low Pasteurisation: 60–65 °C for about 30 minutes, typically used for delicate products like wine and beer.
• High Pasteurisation: 75–85 °C for 2–3 minutes or even 15–20 seconds (HTST – High Temperature Short Time) for more resilient products.

2. Time
The duration of exposure to the set temperature is equally important. Insufficient time may not achieve the required reduction in bacterial load; for example, at 63 °C, the product needs to be held for around 30 minutes, whereas at 72 °C, approximately 15 seconds are required.

3. Product pH
The pH of the food influences the choice and efficacy of the pasteurisation method. Sauces with a pH below 4.5 can be effectively treated by pasteurisation, whereas those with a higher pH may require sterilisation to ensure safety.

4. Physical Characteristics of the Product
Factors such as density, viscosity, and solid content affect heat transfer and thus the efficiency of the pasteurisation process. It is important to consider the coldest point within the container during treatment.

5. D-value and Z-value
The D-value indicates the time required at a specific temperature to reduce the microbial population by 90%, while the Z-value represents the temperature increase needed to reduce the D-value by a factor of ten. These values are essential for calculating the effectiveness of the thermal process.

6. Post-Treatment Cooling
Rapid cooling following pasteurisation is critical to inhibit the growth of any residual microorganisms and to preserve the product’s organoleptic qualities.

Taking these parameters into account is crucial for optimising the pasteurisation process, ensuring both food safety and the quality of the final product.

Given that pH is undoubtedly a critical factor, let’s delve deeper into its influence.

ow Does the pH of Sauces Influence the Choice of Pasteurisation Process?

The pH is a crucial factor in determining whether pasteurisation or sterilisation should be applied to sauces, as it affects both food safety and the organoleptic quality of the product.
Let’s see how process choices vary based on this fundamental parameter.
Do note that the process selection also depends on other factors, such as water activity (Aw) and the presence of specific ingredients (for example, meat or fish), which can influence the final product’s microbiological stability.

Acidic Sauces (pH < 4.5)

Pasteurisation is generally sufficient for sauces with a pH below 4.5, as pathogenic microorganisms struggle to thrive in acidic environments. This permits the use of lower temperatures (between 60 and 85 °C) without altering the product’s organoleptic properties. 

For tomato sauces, it is advisable to use more acidic cultivars (pH < 4.3) to reduce pasteurisation times. If the tomatoes are not sufficiently acidic, lemon juice or citric acid can be added to achieve the desired acidity. Generally, the pH of tomatoes ranges from 3.9 to 4. We even touched on this in our case history with Rodolfi (one of Italy’s best-known brands for the quality of its tomato processing)

Pasteurisation is ideal for acidic foods because it inactivates all vegetative forms of pathogenic microorganisms, and the low pH (below 4.3) prevents the germination of any residual thermoresistant forms. It is recommended to use a calibrated pH meter to accurately measure the pH of foods before subjecting them to any thermal treatment.

Non-Acidic Sauces (pH > 4.5)

For sauces with a pH above 4.5, sterilisation becomes necessary, requiring higher temperatures (above 100 °C) to ensure the elimination of all microorganisms, including spores. These products are more susceptible to the growth of dangerous bacteria such as Clostridium botulinum, hence necessitating a more rigorous thermal treatment.

To ensure safety, high temperatures (typically between 115 °C and 130 °C) must be applied for a specific duration – usually 6–7 minutes at an F₀ value between 113 °C and 118 °C – to eliminate the microorganisms and spores present. This process is essential to preserve both the quality and safety of the final product. During sterilisation, it is also important to meticulously monitor time and temperature to avoid any alterations to the product’s organoleptic properties (flavour, colour, consistency).

The ZACMI Pasteuriser? There Are Two!

Indeed! ZACMI does not settle for offering a single pasteurisation solution; it provides two, each designed to meet different production needs with the same quality and efficiency.

On one hand, there’s the tunnel pasteuriser – modular and versatile, ideal for processing large volumes of sealed containers with a linear and scalable process.

On the other, the spiral pasteuriser is a compact and innovative solution, perfect for optimising space without sacrificing performance and particularly suited for flexible containers.
Both systems ensure safety, reliability, and precise control of the thermal process, resulting in consistently impeccable products.

Modular Tunnel Pasteuriser/Cooler

The ZACMI modular tunnel pasteuriser/cooler is designed for the thermal treatment of sealed containers (metal, glass, plastic, multilayer) intended for food and beverage products.

Its main features include:

• Modular Structure: Constructed in AISI 304 stainless steel and self-supporting for easy installation and maintenance.
• Treatment Processes: Capable of pasteurisation, cooling, and heating to ensure product safety and quality.
• User-Optimised Components:
  • Showers and nozzles that can be disassembled without the use of tools.
  • Side panels with portholes and removable top covers.
  • Insulated hot zones for enhanced energy efficiency.
• Flexible Configurations:
  • Available in single or double deck versions, depending on production needs.
  • Can be equipped with a Clean-In-Place (CIP) washing system.
• Automation and Control:
  • Electrical panel with an HMI for process monitoring and control.
  • Production data recording.
• Tailored Solutions: Designed for uniquely shaped containers with features such as dual-belt loading dosers and motorised pushers.
• Testing Capabilities: Access to the ZACMI testing room for simulations using data-trace devices, enabling detailed analyses.

This technology guarantees an efficient thermal treatment, adaptable to various production requirements.

Modular Spiral Pasteuriser/Cooler

The ZACMI modular spiral pasteuriser/cooler is designed for the thermal treatment of sealed containers, ensuring the quality and safety of food and beverages.

Its main features are:

• Compact Structure: Made from AISI 304 stainless steel, reducing floor space compared to tunnel solutions.
• In-Line Loading and Unloading: Eliminates the need for additional handling systems.
• Insulated Cabin: Encloses the central drum for optimal thermal efficiency.
• Advanced Process Control: Equipped with an electrical panel and HMI for monitoring and recording production data.
• Versatile Process Options: Capable of air-based thermal treatment for sanitary applications or unpackaged products.
• Ease of Cleaning: Option to integrate a CIP washing system.

This machine is particularly suitable for flexible containers such as pouches, trays, bags, and cups, making use of vertical space to maximise production efficiency.
ZACMI, in this case as well, offers a testing room for customised thermal treatment simulations, using data-trace devices for detailed analysis and reports on heat penetration curves.

Now that you know (almost) everything about pasteurisation, why not lighten the discussion a bit and talk about sauces – especially since our client produces this delicious product?
So, here are some curiosities and anecdotes that you might not have known.

From a Means of Masking Flavours to Enhancing Taste: The Strange History of Sauces

Sauces have accompanied human cuisine since prehistory, when cooking liquids from roasted meats were repurposed to flavour other foods.
As early as the 3rd millennium BC, in Mesopotamia, similar condiments were in use, while in ancient Rome salt was mixed with herbs and spices to enrich dishes.
Highly prized at the time was garum – a fermented fish sauce with an intense flavour, comparable to modern anchovy essence or oriental fish sauce.

During the Middle Ages, sauces were often used to mask the strong flavours of preserved foods, thanks to exotic spices such as saffron, cinnamon, and cloves.

With the Renaissance, France became the centre of the art of sauces, refining their techniques and elevating them to symbols of culinary prowess – so much so that in the 17th century, chefs like François Pierre La Varenne codified their use.

The very etymology of the word “sauce” refers to its original purpose: derived from the Latin salsus (salty), it originally denoted the dippings that enriched dishes.

Among the most celebrated preparations, mayonnaise (as we discussed here) is said to have been invented in 1756 in Mahón, in the Balearic Islands, during the French occupation, when Marshal Richelieu’s chef crafted it using eggs, salt, lemon, and olive oil – dubbing it sauce mahònaise.

Over time, sauces have become more than just a condiment; they have acquired cultural and identity value, being savoured to the last drop – often collected with a piece of bread.

Thus, sauces are not merely an accompaniment to dishes, but genuine indicators of the evolution of taste and eating habits.

Their spread has often followed the routes of trade and colonisation, allowing the mingling of diverse cultures – with Eastern spices enriching European sauces and French condiments influencing the cuisines of many other nations.
Moreover, the art of sauce-making has delineated a distinction between home cooking and haute cuisine, with ever more elaborate techniques elevating certain sauces to true emblems of culinary refinement.

Today, gastronomic innovation has revived traditional sauces in a modern guise, with increased attention to ingredient quality and contemporary dietary needs, such as vegan or low-fat variants.

From the simplest tables to Michelin-starred restaurants, sauces continue to tell stories of regions, traditions, and new experiments.

ZACMI, With You Around the World

In this spirit, ZACMI continues to narrate stories of territories, traditions, and above all, new experiments.
On our Worldwide Tour, we are discovering a multitude of cultures, traditions, and curiosities, alongside the various companies that produce foods which eventually find their way onto our supermarket shelves – and, consequently, our tables.

Through our support, enthusiasm, and drive to be a leading force in the F&B sector, we at ZACMI not only champion an innovative industrialisation process – one that marries large-scale production with strict ethics and primary attention to health – but we also pride ourselves on offering all our clients continuous, dedicated, on-site support.
Our aim is to ensure that every production need is met, downtime is minimised, O.E.E. is optimised, and progress and innovation are fostered in support of our partners’ ambitions to grow in line with the historical, social, regulatory, and cultural demands of our era.

See you in two weeks.
After all, our world tour doesn’t last 80 days – it has been ongoing for over 70 years!