How to avoid unexpected changes in preserves or ready meals after pasteurizing or sterilizing them

How to avoid unexpected changes in preserves or ready meals after pasteurizing or sterilizing them

Key tips to ensure that your preserves and ready meals do not suffer unexpected changes in their smell, taste, color and texture after pasteurization or sterilization.

It is necessary to say things as they are. And the truth is that when you pasteurize or sterilize a food product to extend its useful life by subjecting it to a high temperature it can experiment changes. It is not exactly what it used to be anymore. This means that it undergoes organoleptic changes (of what can be perceived by the sensory organs) and nutritional changes. Changes that can be significant or unnoticeable depending on the chosen combination of time-temperature when subjecting it to a heat treatment.

In other articles we have already explained the differences between pasteurization and sterilization. As well as we have delved, separately, into the peculiarities of each of these processes: the pasteurization and the sterilization.

We are sure that you already know that, although pasteurization respects the characteristics of the different ingredients to a greater extent, it offers a shorter shelf life and requires refrigeration at all times. On the contrary, sterilization is a bit more aggressive, since it requires higher temperatures, but it results in food products with a much longer shelf life and no cold chain required at all.

Depending on the food product to preserve, its specific conservation needs and your target shelf life objectives, you will have to choose one method or another. Whichever you choose, both time and temperature are crucial in the possible changes that the food product may undergo in its color, smell and texture.

The combination of time and temperature in sterilization

Pasteurization process

We will focus this post on the sterilization process because, as we have already explained, it has a little more impact on the organoleptic and nutritional qualities of food products.

When we point out the time-temperature binomial, we are referring to the relationship that occurs when sterilizing a food, since a longer sterilization time requires a lower sterilization temperature and vice versa, a shorter sterilization time requires a higher temperature. Easy, right? Well, not so much, because to find the optimal sterilization balance point for your gourmet preserves or your ready meals, you will have to carry out at least two or three tests. With the aim of experimenting with these parameters until you find the exact combination of time and temperature that offers you the ideal smell, flavor, color and texture for your food product.

Achieving that exact formula, the Fo and Po values, is known as F0 for sterilization processes, and P0 for pasteurization processes.

Did you know…

When we talk about sterilization, remember that it means that any form of life present in the food has been eliminated and that we have exceeded at least 100ºC.

Except in dairy products or those containing sugar, since an excess of heat ends up caramelizing the food. So it is preferable to work at a lower temperature and longer times.

The 5 senses in preserved food

It has always been said that food is firstly tasted by sight. And it is true, because if a food does not look good we no longer feel like trying it. Aesthetics play a crucial role when choosing food.

When we talk about aesthetics we are not only referring to color and texture, we are also talking about smell and taste. Factors that can be perceived by our senses.

In the case of your preserves and ready meals, the same thing happens. They should look, and be, palatable to the naked eye. Also, you must remember that what you are offering are preserves and ready meals. And that’s not just anything, since it means that you use high-quality products that taste great, often organic and local, furthermore, you try to avoid all kinds of unnatural additives. That can complicate things, because it means that you leave the organoleptic and nutritional qualities of your food products in the hands of the type and duration of heat treatment used. And this has its pros and cons.

Its main pro is the high quality of your product. Quality in which you vehemently believe and to which you dedicate all your efforts.

And its cons can range from a slight loss of what we have previously included as the organoleptic qualities, that is, the possible changes in smell, flavor, color and texture.

Quality vs aesthetics

We will delve a little deeper into the subject and explain sense by sense.

Taste: changes in the taste of sterilized food

How to avoid possible changes in the flavor of preserves when sterilizing them

Acidity plays a key role in the flavor of an ingredient. Above all, if we take into account that the pH is directly correlated with the required combination of time and temperature to sterilize a preserve. And this process, as we have already commented at the beginning, has an impact on the top layer of any food product.

Also, you should consider that if the sterilization process is too long, the overcooked taste increases. This does not usually happen in stews or products that, in themselves, already require a long cooking time to increase their flavor.


  • Do not fully cook your preserve or ready meal. Let a part of the cooking process take place in the autoclave. In this way, you will avoid the overcooked taste and also nutrients loss due to overcooking.

Color: changes in the color of sterilized food

When cooking, pasteurizing or sterilizing food, it tends to lose its color intensity. The orange of a carrot or pumpkin or the red of a strawberry also declines somewhat. That’s normal.

Whether our food loses more or less color depends, in part, on its acidity level, that is, on its pH. The pH of an ingredient indicates its degree of hydrogen ion concentration. The more acidic a food is, the lower its pH value. The vast majority of foods are on a pH scale between 3 and 7.

Did you know…

The green color of vegetables is best preserved in neutral or slightly alkaline media or, what is the same, less acidic media.


  • If you think that the color of your canned vegetables is a little off you can add a little bit of baking soda.
  • You can also add some type of natural coloring that does not add any flavor. Or if you are looking to give a reddish touch with a smoky touch, you can add red paprika.

Another adversity that gourmet preserves and ready meals can suffer is the darkening or browning of the surface. This may be due to oxidation. That is, vacuum is hardly ever absolute, this means that some air has remained between the food and the closure. Air containing oxygen, which can darken the top of the product. This usually happens especially in canned vegetables whose upper part is dark or gray.


  • Add a drizzle of olive oil on the product before sterilizing it.
  • Hide the top layer of the canned or ready meal with a label so that the potential customer cannot see the difference in color. Let us remember that we are only talking about a certain darkening or browning that does not affect the quality of the product.

Excessive drying is another factor that can affect the aesthetics of our preserves. Some products dry out on top, especially if they are not covered by some type of solution (sauces or other liquids). This sometimes appears in preserves or ready meals, such as meatballs or meats cooked in sauce.

Odor: changes in the smell of sterilized food

How to avoid possible changes in the smell of preserves when sterilizing them

Here we refer to the aroma, that your canned or ready meal maintains its aroma of tasty food. It may happen that, when packaging and sterilizing your product, it loses part of its essence or, on the contrary, it acquires a stronger smell due to its acidity. This can be reduced naturally with vinegar, lemon or more tomato if it is some type of sauce that already incorporates this ingredient.

Texture: changes in the texture of sterilized food

How to avoid possible changes in the texture of preserves when sterilizing them

The texture would refer to the sense of touch, since we refer to the structure of the product that contains your gourmet preserve or ready meal.

The texture of our preserves may undergo a certain change when its pH decreases. In other words, reducing the pH of your preserve, increasing its acidity, can cause variations in protein structure.

By lowering the pH, the electrical charge of the proteins changes and they are no longer hydrated, tending to precipitate and coagulate. This will cause the texture of protein foods such as meat, fish or dairy to change.

We give you an example, do you know what happens to milk if you add lemon? Exactly, it cuts, it sort of separates, a transparent liquid remains at the top and the rest remains at the bottom.

Likewise, an acidic pH in a sauce thickened with flours or starches can cause the sauce to liquefy over time since the acidity, combined with the sterilization temperature, will break the starch chains and the starch will no longer have its thickening effect.

On the other hand, in preserves with sugar (sucrose), a low pH may produce inverted sugar. We clarify it, sucrose is made up of two types of sugars linked together (glucose and fructose). When heated in an acidic medium, glucose and fructose separate and form the so-called inverted sugar. This happens, for example, in the production of jams. Inverted sugar, compared to “normal” sugar, is sweeter and crystallizes less, so syrups or jams can be made sweeter and sugar crystals do not form when it dries a little bit.

It can also happen that your preserve or prepared dish is some type of vegetable cream or sauce that, after being sterilized, experiences a separation of its ingredients, leaving the oil, on the one hand, the water on the other and the vegetables at the bottom. Resulting in a triphasic frame, an appearance not very attractive, although very normal and easy to solve. You just need to shake and go.


  • The preserves must be left to rest for a few days before tasting them. Testing a freshly sterilized product is a mistake. The flavors and smells will change a bit with standing, especially the burnt notes will diminish. For this reason, we recommend that you try the preserves after several days of rest to better evaluate the result.

Technical and food consultancy

Throughout the article we have explained how to get your gourmet preserves and/or ready meals to maintain their smell, flavor, color and texture after sterilization. At TERRA Food-Tech® we know that this is an issue that concerns our customers. And we also know that, in the end, with our help and our autoclaves, everyone has managed to ensure that their gourmet preserves and/or ready meals safeguard their organoleptic and nutritional characteristics.

This is because for TERRA Food-Tech® the fact that you, your business and your brand continue to grow and consolidate is a source of pride, because your success is also ours. A clear example of this is our success stories.

Our autoclaves have several features whose sole purpose is to respect the organoleptic and nutritional characteristics of your gourmet preserve or ready meal. And they do it by incorporating:

Importance of pH in the preparation of preserves and ready meals with an autoclave
  • A direct control over the F0-P0 value and thus optimizing the cycle time, which allows to have an exact control that we will do things well and without unnecessarily overcooking the food.
  • Possibility of programming a gentle cooking phase before pasteurization or sterilization. There is the possibility of introducing prepackaged raw or undercooked foods into the autoclave, doing a preliminary cooking phase at a low temperature, for example at 60°C for 30 minutes and then briefly sterilizing them at 110°C, all at once, so that you will save time and energy costs.
  • Fast cooling by means of a water shower at the end of the cycle. Once you get the F0-P0 values you have programmed, the equipment cools down quickly with water immersion, to minimize overcooking your product.
  • Control and regulation of the entire cycle by a heart temperature probe, and we always provide you with a perforator kit for both caps or semi-rigid containers to be able to insert the probe and perfectly control the temperature throughout the process.
  • Continuous monitoring of all sterilization parameters. In case of failure or not reaching the expected results, the program is interrupted and generates a warning message.

Likewise, we put at your disposal our consultancy service, where our experts will guide you, from start to finish, in the preparation of your preserved food product. From solving problems in your production process to doubts regarding legislation, batch labeling and other technical issues. For more information, do not hesitate to contact us, we will be happy to help you.

Este es el elemento que se ocultará en pantallas de escritorio.
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