Automated Quality Control of Fermented Milk Drinks

Fermented dairy products are economically the most important food factor. Thus these products are subject of strong quality control regulations. Anton Paar´s density meters in combination with the sample changer Xsample 530 offer a fully automated solution to fulfill the high quality demands.


In the following section we will present you a fully automated system using the Xsample 530 sample changer for filling and cleaning with a connected sample recovery unit (SRU), combined with a
DMA density meter for measuring the specific gravity of fermented milk products.

Composition of milk

Milk and dairy products are very complex substances that are composed of an expansive diversity of different molecular species. Many factors affect the composition of raw milk, like kind and age of mammal or feeding [1]. Only an approximate milk composition of 87 % -88 % water and 12 % - 13 % total solids can be given. The major chemical components of milk include water, fats, proteins, carbohydrates, minerals, organic acids, enzymes and vitamins.

Fermented diary products

Among the over 3500 traditional fermented foods existing worldwide, fermented milks have long been an important component of nutrition and diet [2].

Fermented milk products or fermented dairy products are dairy foods that have been fermented with lactic acid bacteria such as Lactobacillus, Lactococcus or Leuconostoc. The fermentation process increases the shelf life of the product while enhancing its taste and improving the digestibility of the milk [3].

Fermentation means the milk is partially digested by the bacteria. This makes the milk product easier to digest, especially for people who have milk allergies or are lactose-intolerant [4].

Specific gravity as quality parameter

The determination of physical parameters, such as the specific gravity of milk, plays an important role in the dairy industry. The measurement of specific gravity using Anton Paar´s density meters proves to be a fast and precise method for the detection of deviations of the milk composition.

The specific gravity, also called relative density, is the ratio of the density of a substance to that of a standard substance [5].

In our case it is the ratio of the density of milk to the density of water.


If the measured specific gravity changes, this could be for instance an indication that the water content is higher than normal.


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