It is written on most milk bottles, but is also used as a process for fruit juice: Pasteurised. But what exactly does that mean? We will explain here how the process works and what influence the brief heating has on the microorganisms and thus the juice. We will mainly explain pasteurisation in relation to juice, but other foodstuffs such as wine, beer and the already mentioned milk are also preserved with this process.
Pasteurisation as a process was invented by Louis Pasteur, who also gave the process its name. He recognised in the 19th century that heating for a short time kills most microorganisms and makes food last longer - without any significant change in the product's properties. Today, it is a legal requirement in Germany that certain foods must be pasteurised. This includes almost every type of milk, except raw milk, for example. Certain foods such as fruit juice are pasteurised because they would spoil too quickly due to the natural presence of microorganisms. The shelf life of food is therefore significantly extended by pasteurisation.
Whether a juice is pasteurised or not cannot be seen by simply looking at it. The gentle heating process does not cause any change in colour and the consistency does not change either. Pasteurising the juice only physically ensures that the fruit juice is more durable. In our juice production at Rabenhorst, the pressed fruit juice, which is the basis for all our juices, is pasteurised particularly gently. We use a special pasteurisation process in which the juice is heated to temperatures of approx. 80-90°C. This process prevents the juice from fermenting. This process prevents the juice from fermenting. This is because the heating process kills the naturally contained microorganisms in the juice. These microorganisms, also called germs, would otherwise trigger the fermentation process and thus lead to the fruit juice spoiling.
Since the addition of preservatives is prohibited by law, pasteurisation is used to preserve fruit juice. This is how you can do without the use of preservatives. Due to our very gentle pasteurisation process, vitamins and other heat-sensitive ingredients are largely preserved in the juice. The colour, taste and smell of the fruit also remain unchanged. Our juices therefore taste particularly fruity, for example our pure juice from first pressing, which you can drink pure or diluted, depending on your preference.
To pasteurise food gently means to heat it only as long as necessary. Because the longer a food is heated, the greater the risk that the vitamins it contains will also be destroyed. That's why we at Rabenhorst pasteurise our juice particularly gently for a short time at 80-90° Celsius.
Pasteurising food means heating it to a temperature below 100° Celsius for a short time. This kills many germs and stops enzymes. However, heat-sensitive microorganisms remain. That is why juice, for example, does not keep indefinitely even if it has been pasteurised. Sterilisation, on the other hand, means that the food is heated to about 130° Celsius for up to one hour. After that, they are completely germ-free and can be kept for several years. However, vitamins are also destroyed in the process.
The best known is the pasteurisation of milk. The milk is heated to 72-75°C for 15-40 seconds and then immediately cooled down again. About 99.5 per cent of all germs in the milk are killed. Pasteurised milk can be kept in the refrigerator for up to 6 days. Pasteurisation is a legal requirement for all types of milk in Germany, except for raw milk and milk from speciality dairies. However, pasteurisation is also used for other foods such as wine, fruit juice or beer. Pasteurization is a mild heat treatment for relatively brief duration to kill part of the microorganisms and to eliminate human pathogens present in food. It is used specially when the aim is to kill pathogenic microorganisms and where the spoilage organisms are not very heat-resistant and the product cannot stand high-temperatures or frozen. The main purpose of pasteurization in low acid foods is destruction of pathogenic microorganisms whereas in acid foods it aims at killing spoilage microorganisms along with enzyme inactivation. For example pasteurization is used to kill pathogenic microorganisms Brucella abortis, Mycobacterium tuberculosis and Coxiella burnetti in case of milk (63°C for 30 minutes; 71.5°C for 15 seconds) and spoilage microorganisms in beers (lactic acid bacteria and yeasts at 65°C–68°C for 20 minutes in bottle), fruit juices (yeast and fungi along with pectinesterase and polygalacturonase inactivation at 65°C for 30 minutes; 77°C for 1 minute; 88°C for 15 seconds) etc. In addition to destroying some microorganisms, pasteurization also inactivates some enzymes. Pasteurization does not change the colour and flavour to any significant level. Since pasteurization does not kill all the microorganisms, this process is usually combined with another preservation method like refrigeration, freezing etc. Typical other preservation methods used in combination with pasteurization include refrigeration as in the case of milk; chemical additives- pickles, fruit juices; fermentation (additives)- sauerkraut, cheeses; and packaging (anaerobic conditions)- beers, fruit juices. The index microorganism for pasteurization is Mycobacterium tuberculosis. If this microorganism is killed by pasteurization it is assumed that all other pathogens are also destroyed. Methods of pasteurization Low temperature long time (LTLT) method: High temperature short time (HTST) method: Ultra high temperature (UHT) method: Bacterial destruction is very nearly equivalent in all temperature-time combinations; however, the 121°C for 2 seconds treatment gives the best quality products in respect of flavour and vitamin retention. Very short holding times to the tune of seconds, however, require special equipment which is more difficult to design and generally is more expensive than the LTLT/ HTST type of processing equipment. Page 2
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Pasteurization (or pasteurisation) is the process by which heat is applied to food and beverages to kill pathogens and extend shelf life. Typically, the heat is below the boiling point of water (100 °C or 212 °F). While pasteurization kills or inactivates many microorganisms, it is not a form of sterilization, because bacterial spores are not destroyed. Pasteurization extends shelf life via heat inactivation of enzymes that spoil food.
Pasteurization may be applied to both packaged and unpackaged solids and liquids. Examples of commonly pasteurized products include:
Pasteurization is named in honor of French chemist Louis Pasteur. In 1864, Pasteur developed a technique to heat wine to 50–60 °C (122–140 °F) before aging it to kill microbes and reduce acidity. However, the technique had been in use since at least 1117 AD in China to preserve wine. In 1768, Italian scientist Lazzaro Spallanzani demonstrated heating meat broth to boiling and immediately sealing the container kept the broth from spoiling. In 1795, French chef Nicolas Appert sealed foods in glass jars and immersed them in boiling water to preserve them (canning). In 1810, Peter Durand applied a similar method to preserve foods in tin cans. While Pasteur applied his process to wine and beer, it wasn't until 1886 that Franz von Soxhlet suggested pasteurization of milk. So, why is the process called "pasteurization," when it had been in use before Pasteur? The most likely explanation is that Pasteur's experiments demonstrated particles in the air, as opposed to pure air, caused food spoilage. Pasteur's research pointed toward microorganisms as the culprit for spoilage and disease, ultimately leading to the Germ Theory of Disease. The basic premise behind pasteurization is that heat kills most pathogens and inactivates some proteins, including enzymes responsible for food spoilage. The exact process depends on the nature of the product. For example, liquids are pasteurized while flowing through a pipe. Along one section, heat may be applied directly or using steam/hot water. Next, the liquid is cooled. The temperature and duration of the phases are carefully controlled. Liquid pasteurization occurs in a closed system to avoid contamination during cooling. MiguelMalo / Getty ImagesFood may be pasteurized after it has been packaged into a container. For glass containers, hot water is used to attain the desired temperature, to avoid shattering the glass. For plastic and metal containers, either steam or hot water may be applied. Early pasteurization of wine and beer was intended to improve flavor. Canning and present-day pasteurization of food primarily target food safety. Pasteurization kills yeast, mold, and most spoilage and pathogenic bacteria. The effect on food safety has been dramatic, particularly regarding milk. Milk is an excellent growth medium for numerous pathogens, including those known to cause tuberculosis, diphtheria, scarlet fever, brucellosis, Q-fever, and food poisoning from Salmonella, E. coli, and Listeria. Prior to pasteurization, raw milk caused many deaths. For example, approximately 65,000 people died between 1912 and 1937 in England and Wales from tuberculosis contracted from consuming raw milk. After pasteurization, milk-related illnesses dropped dramatically. According to the Centers for Disease Control, 79% of dairy-related disease outbreaks between 1998 and 2011 were due to the consumption of raw milk or cheese. Pasteurization greatly reduces the risk of food poisoning and extends shelf life by days or weeks. However, it does affect the texture, flavor, and nutritional value of foods. For example, pasteurization increases vitamin A concentration, decreases vitamin B2 concentration, and affects several other vitamins for which milk is not a major nutritional source. The color difference between pasteurized and unpasteurized milk isn't actually caused by pasteurization, but by the homogenization step prior to pasteurization. Pasteurization of fruit juice does not have a significant impact on color, but it does result in the loss of some aroma compounds and the reduction of vitamin C and carotene (a form of vitamin A). Vegetable pasteurization causes some tissue softening and nutrient changes. Some nutrient levels are diminished, while others are increased. In the modern era, pasteurization refers to any process used to disinfect food and inactivate spoilage enzymes without significantly diminishing nutrient levels. These include non-thermal as well as thermal processes. Examples of newer commercial pasteurization processes include high-pressure processing (HPP or pascalization), microwave volumetric heating (MVH), and pulsed electric field (PEF) pasteurization.
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What is pasteurisation used to preserve?
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