Types of Starters

In general, three different types of starter cultures are used in dairy industry for the manufacture of a variety of fermented products.

i. Single Strain Starters

A single strain starter is a pure culture of lactic acid bacteria such as Lactococcus lactis subsp. lactis or L. lactis subsp. cremoris, etc. This type of culture, if found satisfactory in vigor and flavour, it can give a steady acid production and thereby, a predictable quality of fermented milk product. However, there is a serious disadvantage with this type of starter as during its application, if it gets attacked by a phage of fails due to any other reason, the quality of the resultant product can be adversely affected.

ii. Mixed Strain Starters

These consists of two or more strains or species and thus, may be more variable in behaviour. The mixed strain starters are generally combinations of L. lactis subsp. lactis and L. lactis subsp. cremoris and the gas and aroma producing mesophillic lactic acid bacteria (L. lactis subsp. diacetilactis and Leuconostoc spp.). Mixed starters are considered safe because if one strain is attacked by a phage, the others usually continue to work because of high phage specificity. A wider tolerance to other factors like temperature and pH, changes, etc. may be an additional advantage.

iii. Multiple Strain Starters

Multiple strain starters are mixture of known compatible, non-phage related, carefully selected strains which give generally consistent products when used commercially for production of fermented milk products. Although, their overall phage relationships may be known, the number of individual phage relationships among the strains in these cultures to relatively unknown. A multiple strain starter culture consists of known number of single strains so that the starter can be used for an extended period of time.

Thermophilic lactic acid bacteria (LAB)

Thermophilic LAB (37-45oC) are also used in dairy industry for the manufacture of some fermented products like yoghurt, acidophilus milk and high temperature scalded cheese such as Swiss cheese. The examples of thermophillic LAB are S. thermophilus and the Lactobacillus species. These starters produce lactic acid at faster rate at high temperature and the rate of acid production is further enhanced if symbiotic relationships exist between different species. The such typical example is of yoghurt culture namely, S. thermophilus and L. delbrueckii bulgaricus. Similarly,the combined activity of mesophillic and thermophillic LAB and yeasts leads to lactic acid/ alcohol fermentation in milk during the manufacture of Kefir and Kumiss.