Numerous sour milk products can be made by combining milk containing different levels of fat and dry matter with various starter cultures. The table below gives brief details of a few sour milk products.
Product |
Mainly found in |
Remarks |
|---|---|---|
Kefir |
Eastern Europe |
«Kefir fungi» |
Kumyss |
Eastern Europe, Mongolia |
Mare's milk |
Viili |
Finland |
Geotrichum candidum |
Ymer |
Denmark |
>6 % protein |
1. Kefir
Kefir is a refreshing fermented milk product with a mildly acid taste. Kefir is made by incubating milk with kefir grains or a mother culture made from them. The microflora of the kefir grain and kefir comprise lactic acid bacteria (streptococci, leuconostoc and lactobacillae), yeasts, and possibly acetic acid bacteria. Kefir grains are a complex and specific mix of these micro-organisms and are held together by a polysaccharide matrix.
Pasteurised milk is inoculated with the kefir grains for between 18 and 24 hours at 20 to 25°C. The kefir grains are then filtered off. As well as lactic acid, the combined fermentation produces CO2, a small amount of alcohol, and aromatic substances. All together they give the kefir its organoleptically unique taste.
2. Kumyss
Kumyss, a refreshing, slightly brisk drink made from mare’s milk by lactic and alcoholic fermentation, has been used by the nomadic tribes of Asia for thousands of years. Compared with cow’s milk the lower casein content (casein/whey protein 1:1 instead of 4:1 in cow’s milk) makes the product runny and the gel softer than our sour milk products. Nowadays most kumyss production is concentrated in Russia and Mongolia. Both kumyss and kefir are said to be highly beneficial to health.
3. Viili
Viili is one of the most popular sour milk products in Finland. During production the milk is pasteurised at high temperature and kept hot. After cooling it is inoculated with a culture at approx. 18°C (Streptococcus lactis, Streptococcus cremoris, Streptococcus diacethylactis, Leuconostoc citrovorum) and Geotrichum candidum (4–5%). It is thoroughly blended, filled into tubs and incubated for 24h at approx. 18°C.
Mould formation is important to the quality of viili. Its fermentation and oxidation properties help the taste develop. As the mould grows aerobically, it prevents autooxidation of the fat.
4. Ymer
Ymer, produced especially in Denmark, is a sour milk product of increased protein content. The product contains a minimum of 6% protein, 11% non-fat dry matter and 3.5% fat. Using a traditional method, pasteurised skim milk is incubated with mesophilic mother cultures (starters) at temperatures of between 20 and 25°C until coagulation occurs. It is then gently stirred and heated and the emerging whey removed (up to approx. 50% of the milk volume). Cream is added to adjust the fat content, it is homogenised, cooled and packed. In modern production the dry matter is increased by ultrafiltration.
