Yeasts as adjunct starter cultures in cheese making
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Date
2011-01
Authors
Mehlomakulu, Ngwekazi Nwabisa
Journal Title
Journal ISSN
Volume Title
Publisher
University of the Free State
Abstract
A literature review on the role and presence of microorganisms in cheese was reviewed. The biochemical pathways involved in the cheese manufacture from the milk to the resultant cheese curd at the end of manufacturing were also reviewed. The activity of microorganisms used in cheese manufacture and microorganisms isolated from cheeses were also discussed and their role in the cheese curd formation. Yeasts, one of the microorganisms isolated from cheeses, were reviewed in detail. The use of yeasts as adjunct starter cultures in matured Cheddar cheese was investigated. The yeast cultures (Yarrowia lipolytica, Debaryomyces hansenii, Torulaspora delbrueckii and Dekkera bruxellensis) were inoculated in milk for the manufacture of matured Cheddar cheese as adjunct starter cultures. The yeast cultures supported the role of the starter culture (LAB) – lactose fermentation, and assimilated the organic acids present and inhibited spoilage microorganisms. The growth of the yeast and LAB was mutualistic in all the cheeses and no defects were detected in the cheeses as observed by the favourable sensory scores for the yeast inoculated cheeses. Co-inoculation of yeasts in the making of matured Cheddar cheese resulted in enhanced survival of the yeasts and the LAB population in the cheeses. The yeasts exhibited increased growth, without suppressing the viability and activity of LAB. Organic acids which are associated with aroma and flavour compound production were increased in the cheeses. The cheese inoculated with Dekkera bruxellensis + Yarrowia lipolytica had superior Cheddar cheese scores which were greater than 5 as well as the cheese single inoculated with Dekkera bruxellensis. The pH measurements of the cheeses indicated the deacidification abilities of the yeasts and the spoilage inhibiting acidity in the cheeses. Free amino acid accumulation in cheeses was also investigated. It was observed that the yeast inoculated cheeses had greater free amino acid accumulation compared to the control cheese. The dominant amino acids were Leu and GABA amino acids in all the cheese samples and low concentrations were observed for the other amino acids.
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Keywords
Thesis (M.Sc. (Microbial, Biochemical and Food Biotechnology))--University of the Free State, 2011, Cheddar cheese, Cheddar cheese -- Microbiology, Bacterial starter cultures, Yeast, Lectic acid bacteria, Co-inoculated, Inoculated, Cheddar cheese, Growth, Amino acids, Organic acids, LAB