Production of Fruit Juice

Fruit juices are available on the market as ready to drink, concentrated, nectar, syrup, or powders. Although they are differently prepared, all of them are subjected to thermal treatment.

 


It is generally recognized that fresh fruits are important components for a well-balanced diet due to their nutritional value and also for presenting differences in color, shape, taste, aroma, and texture. Fruit juices with the same health benefits are developed and manufactured, providing a more convenient way of consumption. However, the perishable nature of these products, which stated their fast consumption, and also the number of outbreaks associated with nonpasteurized juices identified the importance of an accurate thermal treatment.

A thermal process is a time-temperature schedule that can be classified according to the intensity of the heat treatment. When the temperature is below 100 ºC, the process is called pasteurization; when it is equal to 100 ºC, it is designated as canning; and when it is higher than 100 ºC, it is named sterilization. In all its forms of application, thermal processing persists as the most widely used method of food preservation. Pasteurization is designed mainly for the inactivation of: (1) pathogenic vegetative bacteria, such as, Escherichia coli , Listeria, and Salmonella; (2) spoilage microorganisms, such as yeasts and moulds; and (3) natural toxins and enzymes. Typical pasteurization conditions for fruit juices are 65 ºC for 30 min, 77 ºC for 1 min, or 88 ºC for 15 s. After this mild treatment, the juice is not sterile and, therefore, other preservation techniques are required for product preservation. Exceptions are fruit juices with a pH lower than 4.5 that, after treatment, are stable at ambient conditions. In these high-acid foods, the product acidity eliminates the possible development of Clostridium botulinum spores, and consequently there is no toxin production.

 

 

 

Figure: Pasteurization unit in a pilot scale (Property of Escola Superior de Biotecnologia, Universidade Católica Portuguesa, Porto, Portugal)

 

 

 

 

 

 

 


This text was prepared by Cristina L.M. Silva, Universidade Católica Portuguesa, Escola Superior de Biotecnologia, Porto, Portugal.

For further questions please refer to: clsilva@esb.ucp.pt