Fruit sterilization
Everything you need to know about canned fruit sterilization
In this article, you will learn everything you need to know about pasteurization and sterilization of gourmet canned fruit and ready-made meals based on fruits. But first, we tell you about the types of fruits that exist, their nutritional properties and the benefits of their consumption. Delicious, isn’t it?
Fruits are rich, antioxidant, satiating and purifying
You probably already know that eating fruit is good for our bodies, but do you know why? We are going to tell you:
Fruits are rich in carbohydrates, such as monosaccharide and disaccharide sugars (glucose, fructose and sucrose) that give them their sweet taste.
They provide many vitamins (A, C, B1, B2, B6 and folic acid) and minerals (potassium, iron, calcium, magnesium, silica, zinc, sulfates, phosphates and chlorides).
They are rich in fiber, especially cellulose and pectins.
They contain a high percentage of water (80-95%).
They contain antioxidants, flavonoids, terpenes, selenium, phenolic compounds and phytochemicals.
Thanks to the above, fruits are satiating and depurative, they help regulate cholesterol and intestinal transit.
Fruit consumption
Did you know that the World Health Organization (WHO) recommends eating about 400 grams of fruits and vegetables per day? That’s about the weight of 4 or 5 pieces of fruit. We advise you to consume seasonal fruits, because this is the time when they are more delicious and have more properties and nutrients. Keep in mind that the riper the fruit, the sweeter it is.
In 2020, approximately 890 million tons of fresh fruit were produced worldwide – a record! But here comes an important fact: according to the UN Environment Program, 17% of all food produced is wasted. This often happens because fruits do not look perfect for sale or are lost in the distribution and marketing process.
For this reason, an increasingly popular alternative in the agricultural sector to avoid wasting seasonal food is to make preserves with these wastes or unmarketed fruits. And, if you also want to reduce the environmental impact of transporting these products and promote the local economy, we suggest buying local fruit. Many of our customers make their canned goods with Km0 fruits and leftovers. If you wish, you can check it out in our success stories.
Types of fruits
Fruits can be categorized according to their season of harvest, fruit, color, etc. They are generally classified according to their level of acidity:
Kiwi, lemon, grapefruit, orange, apple (depending on its variety), grape, blueberry, pineapple, etc. These fruits are characterized by having a large amount of beneficial acids that contribute to reduce cholesterol, triglycerides or uric acid.
Strawberry, quince, loquat (depending on the variety), plum, peach, mango, tangerine and raspberry, among others. These fruits have a mild flavor.
Coconut, avocado, olive, almond, hazelnut, peanut, walnut, etc. They are very rich in vitamins and minerals, which are essential substances for the proper functioning of the immune system.
Banana, cherry, fig, melon, watermelon, pear, pomegranate and custard apple, among others. Most of the fruits belong to this group and are distinguished by their high content of vitamins, such as A, C and E.
Canned foods and ready-made meals prepared with fruits
The most common products are fruit preserves in syrup or marmalade. But you can also find a wide variety of compotes, juices and shakes made with fresh seasonal fruits and they are preserved to be consumed and enjoyed throughout the year.
Fruit-based canned food and ready-made meals must undergo a preservation process prior to marketing, such as pasteurization and sterilization, in order to meet current health and hygiene regulations and also to be preserved with all the quality guarantees.
How to produce canned foods with fruits
The acidic conditions of the fruits prevent the development of botulinum toxin. Thanks to their high free acid content, gourmet fruit preserves can be sterilized at temperatures below 100°.
The preserves containing pieces of fruit are covered with a liquid, called covering liquid, which can be water, juice or syrup. If the acidity level of a fruit is low, citric acid should be added to the covering liquid.
Keep in mind that the covering liquid, besides helping to preserve the product correctly, can improve or add more flavor to your canned product and/or enhance its color.
This covering liquid must be added at a temperature of 90°C minimum. If the product itself already has a temperature above 82°C, pre-sterilization is not necessary.
Regarding sugar, it can come from the fruit itself or it can be added to the covering liquid. Sugar is a natural preservative that helps control bacteria due to its antiseptic properties and is calculated in Brix degrees (ºBx).
Brix (°Bx) is a unit used in the food industry to measure dissolved sugars in fruit and vegetable products, juices, jams, jellies and other beverages. 1 Brix degree corresponds to 1 gram of sucrose in 100 g of solution. Thus, for example, for canned fruit in syrup, we have the following table:
Dilution level | Measured Brix degrees |
|---|---|
Highly diluted | 10 °Bx |
Diluted | 14 °Bx |
Concentrated | 18 °Bx |
Highly concentrated | 22 °Bx |
Depending on the canned product, a syrup with a certain concentration of sugar must be added so that the product reaches the marked graduation. In addition, the concentration of the syrup will also depend on the variety and ripeness of the fruit.
Sterilization of canned fruits
Although many people do not believe it, canned foods provide almost the same nutrients and minerals as fresh foods, because they are processed after harvesting and at their peak, reducing initial nutrient losses.
Likewise, many people also think that canned foods must have additives for their preservation and this is one of the many false myths that exist about preserves. Thanks to the heat treatment they receive to eliminate microorganisms and the fact that they are hermetically sealed, food spoilage is avoided and contamination is prevented. Therefore, it is unnecessary to use any type of preservative to prolong its shelf life.
As we have already mentioned, in order to sell your gourmet canned fruits and extend their shelf life, you must pasteurize or sterilize them using professional equipment to meet food safety quality standards.
Remember that pasteurized products that are not sufficiently acidic should always be kept refrigerated after heat treatment and will have a shorter shelf life than sterilized foods.
Due to the high acidity of fruits we will always perform sterilizations at low temperature, through P₀, which means that we will apply a temperature lower than 100ºC, typical of pasteurization, but we will manage to eliminate all existing microorganisms, which is a characteristic that only occurs in sterilization.
Thanks to the low temperatures and short sterilization times, you can also avoid certain changes in the organoleptic characteristics of your canned food.
In order to reduce as much as possible these possible variations in the organoleptic aspects of your products, before applying any heat treatment, you can carry out a semi-cooking or blanching. In addition, you will also achieve inactivation of enzymes in order to stabilize color and smell, soften the fruit and eliminate oxygen trapped in the tissues. To do this, it is only necessary to immerse the cleaned fruit in hot water, steam or antioxidant solutions (ascorbic acid, mixture of ascorbic acid with citric acid, etc.) for a few seconds.
pH of canned fruit
Knowing the pH of your canned products is essential to decide what type of heat treatment to apply, as this will determine the microorganisms that can grow in it. If the pH value is higher, there will be less acidity and more microorganisms, and vice versa.
The difference between pasteurization and sterilization lies mostly in time and temperature. Depending on the pH of your food, some microorganisms or others will grow in it, and from them we will establish the minutes and the temperature to which we must expose our preserves to sterilize or pasteurize them correctly.
The pH of your canned product should be between 3.4 and 4.4. This level of acidity is usually achieved with the acid of the fruit itself, but if this is not the case, citric acid can be added to the syrup. The addition of acid must be carefully controlled to avoid the presence of invert sugar in the syrup, a phenomenon that occurs due to the presence of acid and application of heat.
Invert sugar is formed by a chemical reaction of acid hydrolysis or enzymatic inversion, causing sucrose to break down into its basic monosaccharides , glucose and fructose, resulting in a syrup or solution that is much sweeter than ordinary sugar.
pH < 4.5 | pH 4.5 – 5.5 |
|---|---|
Apricots | Quince jelly |
Cherries | Jams |
Plums | |
Fruit cocktail | |
Raspberries | |
Strawberries | |
Figs | |
Apples | |
Peaches | |
Pears |
F₀-P₀ values for fruit sterilization
The thermal values F₀ and P₀ refer to the thermal death time or duration in minutes and the temperature required to reduce and eliminate the most heat-resistant pathogenic microorganisms present in food.
The F₀ value is specific to sterilization because a temperature above 100°C is used. And P₀, on the other hand, corresponds to pasteurization because the temperature used is below 100°C.
However, in some cases we may be able to perform sterilization through P₀ to those gourmet canned fruit with an acidic pH, as in most cases. In other words, we can carry out sterilization, thus eliminating most of the microorganisms, at a temperature below 100ºC and the product will not require refrigeration, like pasteurized products.
The P₀ values vary depending on the pH of the product, i.e. the lower the pH, the lower the corresponding P₀. Those canned foods that are more alkaline should be processed with F₀, although, as mentioned above, most of them have an acidic nature.
Keep in mind that the values of F₀ and P₀ will depend on different variables such as, the type of product, the combination of ingredients, how it has been previously elaborated, etc.
For this reason, TERRA Food-Tech® advises you to study each one of your products, measure its pH correctly and carry out subsequent controls to evaluate the entire process and thus be able to select the most appropriate F₀ – P₀ values.
Common problems in fruit sterilization
When processing any fruit, whether for fresh consumption, drying or dehydrating, freezing or for the production of by-products and preserves:
- They must be freshly harvested or in perfect preservation conditions, free of abnormal external humidity and without strange smell or taste.
- They must be free of any kind of bugs (arthropods, worms, mollusks...) and parts or excrement of any of them.
- They must not have cryptogamic diseases.
- They must be free of wilted parts and strange matter adhered to their surface.
- They must be free of pathogenic microbial agents.
- They must not contain pesticide impurities in a proportion higher than the tolerance limits established by the regulations.
Most fruits are susceptible to various species of fungi, giving rise to alterations or rots that are easily perceptible. The fungi responsible for these variations belong to the genera and species of Trichomycetes, Ascomycetes and Deuteromycetes as external colonizers and Basidiomycetes (fungi) as internal colonizers. The most important genera, from a public health point of view, are Penicillium and Aspergillus, since under certain environmental conditions they can cause dangerous mycotoxin intoxications.
As for bacteria, fruits are less sensitive. Therefore, the bacterial flora is less numerous. Saprophytic bacteria are responsible for approximately one third of all alterations and deteriorations. On the other hand, pathogenic bacteria responsible for typhoid fever, salmonellosis and listeriosis can be found.
Recommended containers for canned fruit sterilization
The containers of gourmet canned fruit are varied and usually depend on their texture, i.e., whether they are more liquid or thicker. For example, fruits in syrup tend to be presented in glass jars or cans. Jams, on the other hand, are always marketed in glass containers.
Fruit compotes, in addition to being presented in glass, can also be packaged in aluminum cups or pouches. And juices are usually sold in tetrabriks, pouches or glass bottles.
Fruit sterilization with the TERRA Food-Tech® autoclaves
The different features of TERRA Food-Tech® autoclaves for canned fruit sterilization turn a small piece of equipment into a great production partner that is cost-efficient, fast and versatile.
Adjustable F₀ - P₀
Accurately pasteurizes or sterilizes using F₀ and P₀ values
Rapid cooling
Rapid cooling through water shower to avoid product overcooking
Adjustable back pressure
Programmable back pressure value according to container type
Traceability for auditing
Manage and record the process from start to finish with our software
Accurate control
Continuous monitoring of processes thanks to the heart probe
Protection
Excellent security measures for users and their products
Success stories of canned foods and ready-made meals with fruits
If you are thinking of getting into gourmet canned fruit production and starting your own business, our success stories will inspire you with the stories of others who have already done it.
More information about food sterilization
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