Pasteurization, fruit juice

To maintain cloud stability in fruit juices, high-temperature-short-time (HTST) pasteurization is used to deactivate pectolytic enzymes. Pectin is a protective colloid that helps to keep insoluble particles in suspension. Cloudiness is required in commercial products to provide a desirable appearance. The destruction of the high levels of pectin-esterase during the production of tomato juice and puree is of vital importance. The pectinesterase will act quite rapidly once the tomato is broken. In the so-called hot-break method, the tomatoes are broken up at high temperature so that the pectic enzymes are destroyed instantaneously. 

In practice pasteurization is virtually the only procedure used to give fruit juices a longer shelf life. 

Faults in pasteurization are the main reason for deficient keeping quality of fruit juices. Simple thermometers can show divergences of up to 4°C. If the temperature out of the pasteurizer falls, these thermometers still indicate the higher temperature. 

USE OF PROTECTIVE CASES. Apart from pasteurization, there are a few other methods of giving fruit juices a long shelf life. Covering with carhon dioxide is one of them. 

Since around 1800, the mechanism of fermentation has been studied in a scientific way. It started when German scientist Erxleben discovered that yeast induces fermentation. Louis Pasteur, a French scientist, made many contributions to microbiology. He explained that bacteria produce lactic acid, which then conserves the food. Pasteur also noticed that unwanted fermentation can be stopped by heat treatment of the substrate (pasteurization). This technique is still widely applied today to treat milk or fruit juices. Actually, the production of neat lactic acid was also the first nonfood industrial application of fermentation. 

Some foods have special treatment in processing that may affect the composition of volatile components. As an example, in hybrid passion fruit, the presence of about 1-2% starch makes heat processing, i.e., pasteurization and concentration, impossible or impractical, unless the starch is removed before processing. However, the step of removing starch and concentration causes loss of volatile compounds of fruit juice (Kuo et al., 1985). 

Applications of HHP in food processing were introduced for the first time about 15 years ago (i). The basic idea of this technique is to inactivate microorganisms at low temperatures. However, for some foods, such as fruit juices, this pasteurization at low temperature offers the opportunity to avoid, e.g., flavor changes by thermal... 

Pasteurization is a process applied to certain foods to check the growth of germ life. It consists in heating the liquid to a temperature below the boiling point followed by rapid cooling. It has been best applied to milk, cream, wine, beer, vinegar, and fruit juices. 

Very delicious fruit juices are prepared from blueberries, cherries, and gooseberries by expelling the juice from the fruit and pasteurizing it on two or three consecutive days at 155° F. for 30 minutes. In the preparation of these fruit juices it is important that the fruit be washed well before pressing and that the utenBils used in bottling and the bottle be sterile. 

Mendoza, S., Montemayor, L., Boscan, L.A., and Barrdro, J.A. 1982. Microflora in pasteurized fruit juices in Venezuela. Arch. Latinoam. Nutr. 32, 617-629. 

Tchango, J., TailUez, R., Njine, P.E., and Homez, J.P. 1997. Heat resistance of the spoilage yeasts Candida pelliculosa and Kloeckera apis and pasteurization values for some tropical fruit juices and nectars. Food Microbiol 14, 93-99. 

Meat cooking, packaged ham pasteurization disinfestation of fruits liquid food heating (starch solutions, guar solutions)and pasteurization (milk, fruit juices)... 

For the pasteurization of such foods as milk, fruit juices, and beer, the same mathematical and graphical procedures covered for sterilization processes in this section are used to accomplish the degree of sterilization desired in pasteurization (Bl, S2). The times involved are much shorter and the temperatures used in pasteurization are much lower. Generally, the Fq value is given at 150°F (65.6°C) or a similar temperature rather than at 250°F as in sterilization. Also, the concept of the z value is employed, in which a rise in temperature of z°F will increase the death rate by a factor of 10. An Fq value written as means the F value at 150°F with a z value of 9°F (S2). 

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