����E-Module on�Microbiology of Starter Culture

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Dr.Jitender Kumar

Dept. Biotechnology

HMV ,Jalandhar

Streptococcus as starter culture

• Gram positive organism that usually form pairs or chains.
• In 1937, Sherman separated the genus according to physiogical and growth characteristics, especially with regards to temperature limitations on growth.
• Four general groups designated by Sherman are (1) pyogenic. (2) viridians (3) enterococcus and (4) lactic.
• The only species used as starter culture is Stretococcus salivarius subsp themophilus.
• This is a yoghurt culture, which is thermophilic in nature with optimum growth temperature of 38.42⁰C.
• All are homo fermentative organisms.

Leuconostoc sp. as starter culture

• All are hetero fermentative organisms.
• capable of producing lactic acid, CO2 and aromatic compounds (ethanol and acetic acid) from glucose.
• These organisms are normally used along with lactic acid bacteria (LAB) in multiple or mixed strain cheese starter cultures, which produces flavor compounds.
• Leuconostoc creamoris
• Leuconostoc citrovorum
• Leuconostoc dextranicum

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Leuconostoc sp. as starter culture

• These are responsible for providing aroma and texture to food.
• These organisms are normally used along with lactic acid bacteria (LAB) in multiple or mixed strain cheese starter cultures, which produces flavor compounds.
• Leuconostoc creamoris
• Leuconostoc citrovorum
• Leuconostoc dextranicum

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Genus Lactobacillus as starter culture

• Lactobacillus delbruekii subsp bulgaricus is used for the preparation of yoghurt along with Streptococcus salivarius subsp thermophilus.
• These two organism exhibit a symbiotic relationship.
• They are heterofermentative.

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Genus Lactobacillus as starter culture

• Lactic acid bacteria are found on plants in nature, but some species occur in particularly large numbers in places where there is milk. Others are found in the intestines of animals. The group includes both bacilli and cocci, which can form chains of varying length, but which never form spores.
• Lactic acid bacteria are facultatively anaerobic. Most of them are killed by heating to 70 ºC, though the lethal temperature for some is as high as 80 ºC. Lactic acid bacteria prefer lactose as a source of carbon. They ferment lactose to lactic acid. The fermentation may be pure or impure, i.e. the end product may be almost exclusively lactic acid (homofermentative fermentation), or other substances may also be produced, such as acetic acid, carbon dioxide and ethanol (heterofermentative fermentation.

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Genus Lactobacillus as starter culture

• Lactobacillus acidophilus is a probiotic cultre, used for preparation of acidophilus milk and other probiotic milk products like Bifighurt, Bioyoghurt, etc.
• The members of lactobacillus are classified based on fermentation of glucose into three groups.
• They are rod shaped.

�Fermentation of Glucose

Bifidobacterium as starter culture

• Found in the gut of infants, intestines of man, various animals and honeybees.
• These organisms are generally used in preparation of therapeutic fermented milk products in combination with yoghurt, acidophilus milk or yakult starter cultures.
• Eg: Bioghurt, Biograde, Bifighurt, Cultura 'AB, Yakult, Miru-Miru.

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Bifidobacterium as starter culture

• The optimum growth temperature is 37⁰C-50⁰C.
• Anaerobic conditions are essential for optimum growth.
• Milk fermented with bifidobacteria has a distinctive vinegar taste due to the production of acetate plus lactate from the metabolism of carbohydrates.
• These are acidophilic in nature.

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Bifidobacterium as starter culture

• Used as starter culture in dairy industries.
• Lactic acid production.
• Bifidobacterium bifidum, Bifidobacterium longum, Bifidobacterium infantis, Bifidobacterium breve, etc.
• Used as Mixture culture
• Used as probiotics.

Propionibacter and Brebibacterium

• Propionifacterium : Propionibacterium, freuderveichii and Propionibactrium shermanii are used in swiss cheese.
• It has the ability to produce large gas holes in the cheese during ripening/maturation period.
• Provide fixed texture to cheese.
• It provide nutritional value also.

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Propionibacter and Brebibacterium

• Genes Brevebactirum : Brevebacterium lines is used a as starter culture in preparation of bacterial surface ripened cheese.
• It imparts distinctive, reddish orange colour to the rind of (or formation of smear on) Brick and Limburger cheese or Camembet cheese.
• It is homofermentative in nature.

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Mould and Yeast

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Moulds

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• Moulds are used for the manufacture of some semi soft cheese varieties and in some fermented milk products.
• Moulds enhance the flavor and modify slightly the body and texture of curd.
• White mold is used in manufacture of surface mould ripened chees like camembert and Brie cheese. Eg; Penicillium camemberti, Penicillium caseicolum, Penicillium condis.
• Blue mold is used in manufacture of internal mould ripened cheeses like Roquerfort, Blue Stilton, Danish blue, Gorgonzol and mycella cheeses.Eg; Penicillium, roquefortii

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Mould and Yeast

• Mucor rasmusen – used in Norway for the manufacture of ripened skim milk cheese.
• Aspeigillus oryzae _ used in Japan for the manufacture of Soya milk cheese.
• Geotricum candidum – used in the manufacture of villi a cultured product of Finland.
• The mould grows on the surface of the milk to form the white velvety layer.
• Yeasts : Yeasts are used in the manufacture of Kefir and Kumiss.
• Kefir grains : kefir grains consist of a mixture of different microorganisms such as Candida kefir, Kluyeromyces marxianus, Saccharomces kefir, Torulopsis kefir.
• Kumiss : the important starter microflora of kumiss include Torulopsis spp.
• Khuyeromyces marxianus var lactis, Saccharomyces cervisiae.

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Purpose of Propagation, Traditional Methods-Advantage �

• Advantage
• Aim of propagation is to maintain pure cultures and activate cultures without any loss of viability.
• The culture organisms are preserved in small qualities known as stock cultures.
• Fermentation process of any cultured dairy product relies on the 'purity' and activity of the starter culture.

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References

• GENERAL MICROBIOLOGY BY STANIER.
• EXPANDING HORIZON BIOTECHNOLOGY BY B.D.SINGH.
• GENERAL MICROBIOLOGY BY P.TAURO.
• MODERN FOOD MICROBIOLOGY BY JAMES JAY.

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THANKS