Pasteurization of fruit juices: how does it work?

Extending the shelf life of our food products is the leitmotif of the entire food industry. The latter has found a tailor-made solution to offer fruit juices with good nutritional qualities. After the pasteurization of milk, the pasteurization of fruit juices is growing. Find out more about the fruit juice pasteurization process. It requires manufacturing quality, control and respect for the taste of the fruit in its natural version.

Which fruit juices are eligible for pasteurization?

In the food industry, all types of fruit and vegetables can be eligible for pasteurization. Apple juice, carrot juice or other products can be divided into two categories.

• Liquid juices: these contain only natural fruit or vegetable products produced by mechanical pressing.
• Nectars: the proportion of juice in a nectar is between 25 and 99%. Sugar and water are added to the fruit mash with a small amount of juice. Note that nectar provides more fibre than juice.

The two pasteurization processes

There are two types of pasteurization processes for fruit juices:

• Continuous process of pasteurization, followed by aseptic packaging;
• Pasteurization after packaging by passage through an autoclave or pasteurization tunnel.

However, whatever the process used, the choice of products, the preparation of the foodstuffs and their cold pressing are identical phases.

Choice of quality products for pasteurization

Most fruits and vegetables are eligible for the pasteurisation process. Whether it is apples or other fruit, the product should be mature and healthy. The quality of the product is essential for good juice. Fruit juices should be stored in an appropriate container, such as a glass bottle, regardless of its diameter

. Food preparation by cleaning with water or hygienic solutions

The fruit should be cleaned and brushed under water. The washing of the fruit should be done carefully to limit contamination. In the continuous pasteurisation process, hygienic solutions should be used for washing the pasteuriser, followed by a water rinse.

Cold pressing of fruit for juice extraction

The fruits and vegetables will be cold pressed to preserve the nutritional quality of the products. It is possible to use a stainless steel press with a steel tube that recovers the liquid juice from the pressed fruit.

Details of the continuous pasteurization process

Here are the details of the different steps that make up pasteurization by continuous process. It concerns products with a pH below 4.5. From the heating of products to the packaging of fruit juices, we tell you everything about this principle.

Temperature rise of the fruit juice in the pasteuriser

The heat treatment of pasteurization aims to eliminate the moulds and yeasts naturally present in fruit juices. It also inactivates pathogenic micro-organisms. The temperature of 75 °C must be reached. The temperature increase can be done in two different ways.

• With a heat exchanger: the energy source can be gas or electricity.
• With an integrated immersion heater probe. The probe is immersed in the fruit juice and gradually increases in temperature.

Filling and packaging of fruit juice

Once the temperature treatment is complete, the filling of the bottles can begin. The bottles must be heated to a minimum temperature of 50 °C before filling can begin. Filling should be done with the juice temperature not lower than 70 °C. A filling tube can be used. The bottles must be sealed under vacuum.

Control and preservation of food after pasteurization

After pasteurization, the bottles of juice must be cooled. The juice bottles should be stored in a cold and dry place. The storage method depends on the product. If it is sufficiently acidic and pasteurized, it can be stored at ambient temperature.

The autoclave pasteurization process

As contrasted with the continuous pasteurization process, pasteurization can take place in an autoclave. It concerns products with a pH below 4.5.

Temperature rise of the fruit juice in the autoclave

It is done according to the temperature control programme of the autoclave. Pasteurization tunnels and autoclaves are used to pasteurize juices in their containers. It is necessary to respect the different operating phases of the autoclave.

1. Purge (for the steam process autoclave): this allows air to be removed, which leads to poor heat distribution in the autoclave.
2. Heating: this allows the autoclave to be heated up.
3. Phase of maintaining the pasteurization temperature or cooking phase. This is the most important and critical phase of the heat treatment. The respect of the time/temperature pair is essential.
4. Cooling: This allows the temperature of the autoclave and the products to be reduced. The beginning of the cooling phase is critical. Thermal shock can damage the packaging.

Filling and packaging of fruit juice

This step does not exist with an retort, because the containers are pasteurized at the same time as the contents, i.e. directly in the packaging.

Control and preservation of food after pasteurization

As the product has a pH below 4.5, it can be stored at ambient temperature.

Why pasteurization of fruit juices?

Pasteurization mainly extends the shelf life of products and ensures their microbiological quality, although it does not ensure a vitamin concentrate. Indeed, the possibility of ensuring a vitamin concentrate depends on the time between the harvesting of the fruit and vegetables and the moment of treatment. The shorter the time period is, the higher the vitamin content. Let’s take a look at the reasons for this production process.

Extending the shelf life of fruit

Pasteurization allows fruit and vegetables to be prepared for consumption while preserving their nutritional qualities. The vitamins are preserved, and this for a shelf life indicated on the packaging. The shelf life of fruit and vegetables is thus extended and their organoleptic properties are also preserved.

Pasteurization of fruit to avoid sterilization

Since most fruit is acidic (pH below 4.5), there is no need to use sterilization. Pasteurization is therefore the most appropriate process for a longer shelf life.

Pasteurization for the preservation of nutritional and taste qualities

The pasteurization process maintains the properties of the fruit, making it attractive and enjoyable to consumers. As a result, taste and appearance are maintained after the process, as well as the majority of the vitamins.

You wish to invest in a pasteurization unit or in another equipment to pasteurize your fruit juices?  Call on Steritech’s experience in pasteurization. Contact us for details of the different solutions available for the preservation of your food products.