Prepared by: Dr. Nurul Izzah Khalid

Senior Lecturer

Department of Food Technology, Faculty of Food Science and Technology, UPM

Figure 1: A comparison of pasteurization and UHT sterilization, illustrating how food engineers and technologists collaborate to balance processing safety with product quality, ultimately determining the shelf life and storage requirements of milk.

Fresh milk in the chiller. UHT milk on the shelf. Same product family, different storage rule. Why?

The answer lies in the combined work of food engineering and food technology.

At first glance, milk is just milk. But from a food science perspective, the way milk is heated, packed, stored, and distributed determines its safety, shelf life, and convenience. This is where two important thermal processes come in: pasteurization and sterilization.

Both use heat. Both help make food safer. But both are designed for different purposes.

The difference between fridge milk and shelf milk is not just packaging — it is the result of food engineers and food technologists working together.

A tale of two heat treatments

Let us start with pasteurization.

Pasteurization is a mild heat treatment used to reduce harmful microorganisms and slow spoilage while keeping the food as close as possible to its fresh quality. Because the treatment is milder, pasteurized foods usually still need to be kept cold.

That is why pasteurized milk is normally found in the refrigerator section. It is safe and suitable for daily use, but it has a shorter shelf life and must be stored properly.

Now compare that with sterilization.

Sterilization is a stronger heat treatment. It is designed to destroy far more microorganisms, including more heat-resistant ones. As a result, sterilized foods can last much longer and are often stored at room temperature before opening.

This is why products such as UHT milk, canned soup, canned fish, and bottled sauces can sit safely in the pantry.

So where do food engineers and food technologists come in?

This is where the story becomes more interesting.

Food engineers are involved in designing and controlling the processing system. They focus on questions such as:

• How much heat is needed?
• How long should the food be heated?
• How can heat be transferred efficiently?
• Should the product be refrigerated or shelf-stable?

These are engineering decisions involving thermal processing, equipment design, process control, and shelf-life planning.

At the same time, food technologists focus more on the food product itself. They help ensure that the processed food remains acceptable in terms of:

• taste,
• texture,
• colour,
• quality, and
• consumer acceptance.

In simple words, the food engineer helps design how the process works, while the food technologist helps ensure the final food is still appealing and suitable for consumption.

Look around your kitchen

Your kitchen already tells this story.

The milk in the fridge? Most likely pasteurized.

The milk stored in a carton on the shelf? Most likely sterilized or UHT-treated.
The canned sardines in the cupboard? Another example of stronger thermal processing.

Behind these products are decisions made by food engineers and food technologists. One side ensures the process is safe and efficient. The other ensures the food still has acceptable quality for consumers.

Food engineering makes the process possible. Food technology makes the product practical and acceptable.

Why does this matter?

Because understanding pasteurization and sterilization helps us understand everyday food choices.

• Why does one product spoil faster?
• Why must one be chilled while another can stay unopened on the shelf?
• Why does one product taste fresher than another?
• These differences are not random. They are the result of carefully planned processing decisions that balance safety, quality, and convenience.

Final thought

The next time you buy milk, notice where it is stored.

If it is in the fridge, it is likely pasteurized.

If it is on the shelf, it is likely sterilized or UHT-treated.

That simple observation opens the door to a bigger idea: food at home is shaped not only by ingredients, but also by the expertise of food engineers and food technologists.

Pasteurization and sterilization are more than preservation methods. They are examples of how food engineering and food technology work together to make food safer, longer-lasting, and more practical for daily life.

So yes, the story of milk in your kitchen is also the story of food engineers and food technologists at work.

References:

Zeki, B. (2018). Food Process Engineering and Technology (3rd ed.). Academic Press.

Date of Input: 15/06/2026 | Updated: 18/06/2026 | nur_jasni