A preliminary study on the effect of adding yeast extract to cheese curd on proteolysis and flavour development of reduced-fat Cheddar

• Published in: Journal of dairy research 2003-02, Vol.70 (1), p.99-103
• Main Authors: Shakeel-Ur-Rehman, Farkye, Nana Y, Vedamuthu, Ebenezer R, Drake, Mary A
• Format: Article
• Language: English
• Subjects: Amino acids; Bacteria; Biological and medical sciences; Cheese - analysis; Cheese - microbiology; Colony Count, Microbial; Dairy products; Electrophoresis, Polyacrylamide Gel; Endopeptidases - metabolism; Fermentation; Food industries; Food Technology; Fundamental and applied biological sciences. Psychology; Humans; Hydrogen-Ion Concentration; Lactobacillus - growth & development; Lipids - analysis; Milk and cheese industries. Ice creams; NSLAB; Pasteurization; Proteins - analysis; reduced-fat Cheddar; Saccharomyces cerevisiae - metabolism; Salts; Taste; Yeast extract; Yeasts
• ISSN: 0022-0299; 1469-7629
• DOI: 10.1017/S0022029902005861

Yeast extract was used as a nutrient for growing lactobacilli in reduced-fat Cheddar cheese as early growth of non-starter lactic acid bacteria (NSLAB) in Cheddar cheese is suppressed by pasteurization of milk and the hostile environment of the cheese. Reduced-fat Cheddar cheese was manufactured from 100 kg standardized milk on two occasions. After milling, the curd was divided into two portions, C and E. To control portion, C, salt was added at normal levels. A mixture of salt and yeast extract was added to the experimental, E. The cheeses were ripened for 7 months at 8 °C and assessed for proteolysis and NSLAB growth during ripening. Mean % moisture, fat, protein, salt and pH were 40·6, 20·5, 31·1, 1·72 and 5·22 respectively, in E cheeses, and 39·5, 20·5, 30·9, 1·68 and 5·22, respectively, in C cheese. NSLAB counts in E cheeses were 101, 103, 105 cfu/g compared with 0, 101, 104 cfu/g in C respectively, after 1, 7 and 30 d of ripening. After 60 d, cell densities of NSLAB were similar (∼106 cfu/g) in C and E cheese. Addition of yeast extract to curd affected neither the electrophoretic patterns of cheese nor its water-soluble N content during ripening. However, the total free amino acids were significantly higher in E cheese than C cheese throughout ripening, suggesting faster secondary proteolysis in the former cheeses. A 6-member trained descriptive panel evaluated the cheese at 7 months and found that the E cheeses had higher intensities of whey, fruity, sulphur, nutty, sweet and sour flavours, but had lower intensities of brothy flavours as compared to C cheeses. Also, the E cheeses were perceived to be more mature than corresponding C cheese. Results show that addition of yeast extract to cheese curd is a promising method of enhancing flavour development in ripened cheeses.