Juice Pasteurization for Stability

Freshly extracted juice is highly susceptible to spoilage, emphasizing the need for thermal processes to secure the stability of the product during its intended storage period. Pasteurization, a crucial element of this thermal process, markedly improves the organoleptic characteristics of the juice. Juice that hasn't undergone heating is at risk of rapid deterioration due to microbial, enzymatic, chemical, and physical influences.

In a broader context, fruit juice constitutes a colloidal mixture of soluble and suspended solids, including low molecular-weight solutes like sugars, organic acids, pigments, and vitamins. Additionally, it encompasses high-molecular-weight solutes such as proteins, enzymes, and pectic substances.

The initial pasteurization takes place either after juice extraction or as the first step in the evaporator, typically at temperatures ranging from 95 to 98°C for a duration of 10 to 30 seconds. This step aims to extend shelf life by deactivating specific enzymes and microorganisms like yeasts, molds, and bacteria.

The subsequent pasteurization occurs before the juice is filled into its container, with a focus on eradicating microorganisms that could contaminate the fruit juice during bulk storage or in juice reconstituted from concentrate. This second pasteurization, typically carried out at a pH below 4.2, involves a temperature of 95°C and a holding time of 15 seconds.

Upon completion of the pasteurization process, there is a noted 7% increase in viscosity and a 22% decrease in cloudiness after 21 days of shelf life. The primary goal of pasteurization is to mitigate these undesirable reactions, and in certain instances, it can even enhance the inherent quality of the initial fruit.
Juice Pasteurization for Stability

Blueberry juice processing

Step of blueberry juice production:
*Washing and sorting the berries. Cleaning the blueberry fruits from contamination of dirt, mud, sand, straw, glass, etc. Blueberries are thoroughly cleaned with bubbles and water spray, and the rotten and moldy parts to be removed.

Berries can be frozen after harvesting to reduce the effects of pectin and gelling, as well as to extend utilization beyond the narrow harvest season

*Pulping in the environment at the temperature of 15° C
To improve juice recovery, berries can be treated with elevated temperatures. Heating or blanching the berries before pressing is a common step used in juicing fruits.

Before refining blueberry juice, it needs to be crushed to improve the juice yield of raw materials. A high-speed refiner is used to separate the juice. According to different process requirements, the equipment design and equipment selection of the juice extraction and separation system is carried out.

*Adding pectinase for enzymolysis
Pectinase enzymes increase juice yield by breaking down the pectin in the cell walls and in the middle lamellae between the cells. The pectin in the juice will make the juice turbid. In addition, it protects other substances and prevents clarification of blueberry juice.

Enzymes derived from bacteria, such as Aspergillus niger and Aspergillus aculeatus, can be used to improve extraction from plant tissues and liquefaction, increase juice yield, clarification, and filtration.

*Process of pasteurization
In pasteurization process juice is heated to temperatures of approx. 80-90°C. This process prevents the juice from fermenting. This is because the heating process kills the naturally contained microorganisms in the juice.

*Cooling
*Uniformly mixing; and filling

*Packaging
Commercially produced blueberry juice is packed in PET bottles which are then sealed and pasteurized to avoid spoilage and to increase shelf life.
Blueberry juice processing

Production of pineapple juice

The pineapple tree belongs to the Bromeliaceae family. The edible part of the pineapple fruit (60% of the fresh fruit) has a moisture content of 85%.

Pineapple is largely consumed around the world as canned pineapple slices, chunk and dice, pineapple juice, fruit salads, sugar syrup, alcohol, citric acid, pineapple chips and pineapple puree. Pasteurized pineapple juice is one of the most important pineapple commodities.

The pineapple juice is processed by many advanced processing techniques to reduce bacterial contamination with improved shelf life and preservation of antioxidant compounds, vitamins, and minerals.

Steps production of pineapple juice:
*Receiving of pineapple
*Sorting: removing the crown and leaves
*Washing with water
*Peeling
*Cutting
*Juice extraction
*Juice filtration
*Juice pasteurization: Fresh juice is boiled at 80°C for 30 s
*Cooling

Pineapple juice is often recovered from the ejected skins and cores from the machines which cut the pineapple in preparation for canning.

Pineapple juice can be obtained with an extraction machine only, or, in addition, enzymes can be used to increase the yield and the juice recovery from the pineapple pulp or residue.

The juice contains up to 40% pulp. The pulp content is reduced, usually by finishing with a screw-type finisher followed by centrifugation, before pasteurizations and concentration.
Production of pineapple juice

Grape juice processing

In general grape juice production can be divided into four basic principal stages.
*Front end operation
*Juice extraction
*Juice clarification and refining
*Juice pasteurization and concentration

Grapes at the plant are first conveyed to a steamer which remove residual stems, leaves and petiole from fruit. After cleaning, grapes are crushed to facilitate juice extraction during the pressing step.

The crusher consists of several ruffled rotary rollers that break the berries while they are passing through. In most commercial operations, the continuous pressing method is used. Hot pressing is appropriate for deeply pigmented grape where maximum color extraction is desired.

Whereas, the immediate or cold press procedure is necessary to maintain the initial color of light colored grapes.

Additional enzyme treatment is required before the juiced is further processed For concentration it is necessary to complete the de-pectinization process to preclude gelation of the concentrate once produced.

For bottled juice, de-pectinization speeds and simplifies polish filtration and clarification prior to bottling.

Juice may be concentrated by evaporation or freeze concentration. It is desirable to heat the juice for as short a time as possible and to rapidly cook the product in order to minimize the effect on flavor, aroma and sugar concentration.
Grape juice processing

Processing technology development of fruit juice

A freshly squeezed orange or fresh pulped and strained apple would supply a fruit juice drink for immediate consumption, but to expect it to maintain its quality for even a day or two was tempting providence.

Actually the technology to produce high quality fruit juice concentrate has been improved considerably over the years.

With the technology benefits of ultra-high temperature pasteurization, aseptic packaging techniques and system, pressed juices can be stored for extended periods with very little deterioration in quality.

There has also been a range of developments leading to the removal of acidity, color and minerals from clear juices such as apple.

Previously reliance had to be places upon the use of preservatives and classical pasteurization at lower temperature and longer holding times. The traditional process of hot filling juice in containers to produce shelf stable precuts is now being replaced by newer technologies.

Enzymes and finishing treatments are widely used in the processing of fruit juices to obtain products of particular specification. It is more oriented towards flavor orientation, nutrition protection and product stabilization though enzyme control and pasteurization.

During the second half of the twentieth century, apart from the continues move towards more efficient means of production and marketing of bottles or canned soft drink products, there was much progress of knowledge about flavor technology.

Further advanced techniques include the use of membrane technology to achieve cold sterilization, freeze concentration, combination of cold and hot processes, accompanied by aseptic filling technology and irradiation technology.

Pulsed electric field technology also has a potential to replace traditional thermal processes for the pasteurization of fruit juice.
Processing technology development of fruit juice