UHT milk
UHT milk [ haːmɪlç ], and long-life milk , is by UHT preserved, homogenized milk . It is also known as UHT milk or Up milk (ultra high temperature or superised).
Long-life milk was introduced to the market in the second half of the 1960s.
Manufacturing
To produce it, cow's milk is first subjected to ultra-high temperature heating. To do this, it is heated to 135–150 ° C for a few seconds and then immediately cooled down to 4 to 5 ° C. The milk is sterilized by the action of heat . In addition, a small percentage of milk proteins are denatured . When heated, hydrogen sulfide and other sulfur compounds from sulfur-containing amino acids ( cysteine & methionine ) are released in the proteins of milk and methyl ketones and lactones are formed from fatty acids , which results in a slight change in the taste of the milk ("cooking taste") and improved digestibility can lead. In addition, the viscosity of the milk increases slightly, which makes it appear less watery in the mouth. The milk is then homogenized in order to improve the cream stability. The aim of homogenization is to reduce the mean diameter of the fat droplets and thereby slow down creaming.
Long-life milk is usually filled into aluminum-coated beverage cartons (eg " Tetra Paks ") and sealed airtight. This prevents the milk from being contaminated by new microorganisms. Filling into brown glass bottles is also practiced.
advantages
- Long-life milk can be stored unopened at room temperature for several months.
- Long-life milk is easier to digest.
- Long-life milk is cheaper.
- Pathogenic microorganisms are killed.
disadvantage
- The result of the treatment process is a greater loss of ingredients that are important for humans, such as vitamins , than with normal pasteurization . This loss cannot be compensated for even with light-tight packaging. In addition, the milk no longer tastes the same as fresh milk.
- The vitamin content decreases with longer storage (within the minimum shelf life), possibly by up to a further 30%. The decisive factor is the storage temperature as well as the quality and care of the heating process (difficulty: degassing after the steam injection ).
- Like fresh milk, long-life milk can only be kept for a few days when opened. Since the lactic acid bacteria are killed when heated, an incipient spoilage z. B. not necessarily recognizable by curdling of the milk.
| Type of heating | Vitamin B1 | Vitamin B2 | Vitamin B12 | Folic acid | vitamin C |
|---|---|---|---|---|---|
| pasteurization | <10% | ≤ 8% | <10% | <10% | 5-15% |
| Ultra high temperature | 5-15% | <10% | 10-20% | 5-20% | 10-20% |
| Cook | 10-20% | ≈ 10% | ≈ 20% | ≈ 15% | 5-15% |
| Sterilize | 20-50% | 20-50% | 20-100% | 30-50% | 30-100% |
In a new process, the long-life milk is not to be preserved by heating, but by pressure (between 4,800 and 6,200 bar ). This type of preservation should have less of an impact on the milk taste.
Nutrients, taste and physical properties
The taste of pasteurized milk is more similar to that of fresh cow's milk than that of ultra-high temperature milk. This is due to a partial caramelization of the milk sugar ( lactose ) during ultra high temperature heating. The nutritional value of milk depends mainly on its fat content. Whole-fat milk contains significant amounts of vitamins A, B and D as well as calcium. Low-fat or fat-free milk contains the same amounts of protein, calcium, magnesium, phosphorus, potassium, zinc and vitamin B as full-fat milk, but the amount of vitamins A and D is halved or even non-existent.
See also
Web links
Individual evidence
- ^ Hans-Dieter Belitz , [[Werner Grosch (chemist) |]]: Textbook of food chemistry. Springer-Verlag, 2013, ISBN 3662083086 . P. 433.
- ↑ P. Eberhard, U. Bütikofer, R. Sieber: Vitamins in stored highly heated milk . ( Memento of the original from March 6, 2008 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. Agroscope Liebefeld-Posieux ALP research station (Swiss federal authorities)
- ↑ Shelf life of opened milk (ESL, H-, Frisch). In: Expert forum: You ask - aid answers. Federal Center for Nutrition, November 4, 2013, accessed on February 22, 2019 : “UHT milk goes bad without acidification, so you can't taste the spoilage. An opened carton of milk - regardless of the type - should always be tightly closed, stored in a cool place and used within 3–4 days. "
- ↑ Product knowledge milk . LEL Schwäbisch Gmünd (Ministry for Food and Rural Areas Baden-Württemberg)
- ↑ Milk under pressure . Wissenschaft.de, November 14, 2006
- ^ Nutrient preservation in the process on the website of the European Food Information Council
