Are you producing gourmet canned foods and/or prepared dishes? Then you know that pasteurization or sterilization is essential. Without this crucial final step, your products could pose a public health risk and cannot be authorized for sale.
What is the difference between pasteurization and sterilization?
Both techniques are used to preserve food in hermetically sealed containers by eliminating microorganisms and enzymes through heat. However, there are key differences between the two:
- Pasteurization involves heating food to temperatures between 60°C and 100°C for a few minutes or even seconds. Because the process is less intense, it better preserves the food’s organoleptic properties, but it does not destroy all microorganisms. As a result, pasteurized products must be kept refrigerated and have a shorter expiration date.
- Sterilization, on the other hand, exposes canned food to temperatures above 100°C for a specific period of time. While this method is more intense, it completely eliminates microorganisms and spores. This ensures a much longer preservation time without the need for refrigeration, allowing storage at room temperature.
When packaging food, remember that glass jars with screw-on lids require a small empty space at the top. Without this headspace, the container may not seal properly, or could even crack during the process.
What is pasteurization?
Pasteurization is a heat treatment that uses moderate temperatures (60–100°C) for a short period, seconds to minutes, to reduce microorganisms and enzymes.
Key points about pasteurization:
- Preserves most of the food’s organoleptic properties (flavor, color, texture).
- Does not eliminate all microorganisms or spores, so refrigeration is required.
- Shelf life is shorter, typically 2–3 weeks, depending on the product.
- Commonly applied to:
- Milk and dairy products
- Flavored juices and beers
- Prepared sauces and ready meals
Important note: for acidic foods (pH < 4.5), pasteurization can be so effective that it behaves like sterilization, destroying nearly all microorganisms and spores.
Pros of pasteurization | Cons of pasteurization |
|---|---|
Low temperatures prevent the aromas from volatilizing excessively, allowing the flavor and nutritional properties to remain unchanged.
| The shelf life of pasteurized food is usually two to three weeks, and it must be kept refrigerated between 3ºC and 6ºC. |
Unlike sterilization, pasteurization does not eliminate spores, so physical and chemical changes can still occur over time. |
What is sterilization?
Sterilization uses higher temperatures (above 100°C) for a specific time to completely eliminate microorganisms and spores.
Key points about sterilization:
- Enables storage at room temperature for months or even years.
- Often slightly affects organoleptic and nutritional properties due to higher heat.
- Suitable for low-acid foods (pH > 4.5) like vegetables, meat, fish, and neutral-pH products.
- Commonly applied to:
- Jams, syrups, and pickles
- Creams, soups, sauces, and stews
- Meat, fish, and seafood dishes
- Pet foods and baby foods
Pro tip: Proper container headspace in jars is essential to prevent cracking or improper sealing during sterilization.
Pros of sterilization | Cons of sterilization |
|---|---|
The shelf life of sterilized products can exceed four months, and unlike pasteurized foods, they do not require refrigeration. | The high temperatures used during sterilization can affect quality by reducing the nutritional value of the food and destroying certain vitamins and aromas. |
The contents remain sterile until the packaging is opened or damaged. Once opened, they should be consumed quickly.
| They can also cause organoleptic changes, such as color alterations and the development of overcooked flavors. |
Why do food pH matters in thermal processing?
The pH level of a food product determines the time and temperature needed to safely eliminate microorganisms and enzymes.
- Acidic foods (low pH): Heat-sensitive microbes are already suppressed, so lower temperatures and shorter times can suffice.
- Neutral/low-acid foods (high pH): Require higher temperatures or longer times to ensure safety.
Other important considerations:
- Food variety and ripeness affect pH (e.g., ripe apples are less acidic than unripe ones).
- Temperature during measurement matters—samples are usually tested at ~20°C.
- Fo and Po values indicate sterilization and pasteurization effectiveness, balancing time and temperature to maximize safety while minimizing quality changes.
How to choose between pasteurization and sterilization?
Consider these factors:
- Product characteristics
- Delicate textures and clear liquids often require pasteurization.
- Raw vegetables, legumes, and neutral-pH foods usually need sterilization.
- Container type
- Glass jars, metal cans, or vacuum packs may affect heat transfer and determine the method.
- Shelf life and distribution
- Sterilized foods can be sold and stored at room temperature.
- Pasteurized foods must remain refrigerated and use cold-chain logistics.
- Consumer preference
- Refrigerated pasteurized foods can be marketed as fresher.
- Sterilized foods offer convenience and longer shelf life.
What food products can be sterilized in a TERRA Food-Tech autoclave?
TERRA Food-Tech® autoclaves can sterilize or pasteurize any product containing a heat transfer medium (water, oil, or sauce).
Examples of sterilizable products:
- Meat: marinated, stewed, or sauced meat dishes, pre-cooked meals combining meat with ingredients like rice or vegetables, soups, pâtés, cooked ham or chicken breast, beef, chicken, or turkey-based pet food, baby food.
- Fish: tuna, sardines, bonito, and mackerel in oil, fish pâtés, pre-cooked dishes such as salmon or red scorpionfish pie, sea bream with potatoes, steamed fish, or peppers stuffed with tuna and cucumber.
- Seafood:
Pickled mussels, natural cockles, scallops with garlic or scallop sauce, baby squid in ink, octopus in olive oil, natural prawns, and pâtés made from king prawns, mussels, crab, scallops, or sea urchin, seafood dishes like paella or fideuá.
- Vegetables, fruit, and legumes: a wide variety of vegetables, fruits, beans, and legumes, soups, jams, and compotes.
Examples of pasteurizable products:
- Milk and dairy derivatives
- Flavored juices and beers
- Ready meals and delicate sauces
Sterilization: a step-by-step guide
Read this article to explore the key steps in the sterilization of canned foods and prepared meals.
Main differences | Sterilization | Pasteurization |
|---|---|---|
Types of food | Suitable for all types of food, including meat, fish, vegetables, fruits, legumes, jams, syrups, pâtés, sauces, marinades, broths, creams, and soups. | Applicable to most foods, although some products such as juices, plant-based milks, or dairy may experience changes in taste after autoclave pasteurization. |
Food safety | Destroys all microorganisms, including spores and enzymes, ensuring maximum food safety. | Reduces microorganisms, but does not eliminate all spores or enzymes. |
Type of thermal processing | Application of moist heat to food packaged in hermetic containers. | Application of moist heat to food packaged in hermetic containers. |
Storage and distribution temperature | Room temperature. | Requires continuous refrigeration during storage and transport. |
Best before date | Typically ranges from 12 months up to 5 years, depending on the product’s physical and chemical stability. At a microbiological level, the product will always remain safe for human consumption. | Usually ranges from a few weeks up to 3 months under optimal conditions. After this period, consumption may become unsafe. |
Organoleptic properties | They may suffer alterations in organoleptic properties. | The organoleptic and nutritional properties are better maintained. |
pH and acidity of food | In general they are processed at more than 100ºC. Some acidic foods (pH ≤ 4.5) can be processed at 85–99°C. | Uses milder heat treatment between 60°C and 100°C. Higher temperatures and longer processing times increase shelf life. |
F0-P0 thermal values | F₀ values are used for processes above 100°C, while P₀ values apply below 100°C. The autoclave automatically calculates and records both. | Uses P₀ values only. The autoclave automatically calculates and records them. |
FAQ
Why are pasteurization or sterilization necessary for canned foods?
Both processes are essential to eliminate microorganisms and enzymes that could cause spoilage or illness. Without proper heat treatment, canned foods cannot be safely sold or distributed because they pose a public health risk.
What is the main difference between pasteurization and sterilization?
Pasteurization uses moderate temperatures (60–100°C) for a short time to reduce microorganisms. It preserves flavor and texture but does not destroy all microbes, so products must be refrigerated and have a shorter shelf life.
Sterilization uses temperatures above 100°C for a defined time to eliminate all microorganisms and spores. This allows products to be stored at room temperature for months or years.
When should you choose pasteurization instead of sterilization?
Pasteurization is ideal for foods that benefit from fresh flavor and delicate textures, such as dairy products, flavored juices, beers, sauces, and ready meals. It is also highly effective for acidic foods (pH < 4.5).
When is sterilization better than pasteurization?
Sterilization is required for low-acid foods (pH > 4.5), including vegetables, meats, fish, seafood dishes, baby foods, pet foods, soups, stews, and sauces. These products require higher temperatures to ensure safety and long shelf life.
Why does food pH matter in thermal processing?
The pH determines how easily microorganisms can be destroyed. Acidic foods need shorter or lower-temperature treatments, while low-acid foods require more intense heat to ensure all microbes and spores are eliminated. pH also influences Fo and Po values, which help determine the correct processing conditions.
Does pasteurization affect food quality?
Pasteurization maintains most of the original taste, color, and texture because it uses lower temperatures. However, shelf life is shorter, and refrigeration is always required.
Does sterilization affect food quality?
Sterilization can slightly change flavor, color, or nutrient levels because of higher temperatures. However, it offers much longer shelf life and allows storage at room temperature until the package is opened.
Should I choose between pasteurization and sterilization?
The decision depends on the product’s acidity, texture, desired shelf life, packaging type, distribution conditions, and consumer expectations. Delicate foods often require pasteurization; low-acid and protein-rich foods must be sterilized.
Which foods can be pasteurized?
Milk and dairy derivatives, flavored juices and beers, ready meals and delicate sauces.
Which foods can be sterilized?
Meat (such as marinated, stewed, or sauced meat dishes, cooked ham, chicken breast, spreads, beef, …), fish (such as tuna, sardines, mackerel in oil, steamed fish, …), seafood (such as pickled mussels, baby squid in ink, octopus in olive oil, natural prawns, mussels, crab, …) and vegetables, fruit and legumes.