A comparative study of proteolysis in cheddar cheese and yeast-inoculated cheddar cheese during ripening

[摘要] English: Proteolysis is regarded as the most important event in the ripening of Cheddar cheese tocontribute to the development of flavour. The characteristic proteolysis of each type ofcheese is brought about by the enzymes used in the manufacturing process, e.g. rennet, aswell as enzymes from the specific microbial cultures used in each cheese type. The effect ofan inoculated yeast, Oebaryomyces hansenii, and its enzymes on proteolysis in Cheddarcheese was investigated. Proteolysis and development of peptides of the yeast-inoculatedCheddar cheese was followed throughout the ripening process and compared to theproteolysis in a standard Cheddar cheese. In a sensorical comparative study, no differencewas found by a consumer panel between the two types of cheese, nor was any of the twosignificantly preferred. An expert panel however, judged the yeast-inoculated Cheddarcheese to be bitter. The proteins and peptides from the cheeses were extracted andfractionated by virtue of differences in solubility and molecular size. Yeast-inoculatedCheddar cheese contained less water-soluble nitrogen indicating a difference in proteolysisbetween the two types of cheese. Urea-polyacrylamide gel electrophoresis of the waterinsolublefraction indicated that in the yeast-inoculated cheese rennet hydrolysis of o.si-caseinwas increased with faster formation of one primary peptide, o.s1-1as well as (o.s1-CN(f102-.)),with little further hydrolysis. The ~-casein was hydrolyzed slowly but with several additionalpeptides occurring. Reversed-phase high performance liquid chromatography of the watersolublefraction indicated that a different peptide profile was formed, with at least five uniquepeptides at high amounts.

[发布机构] University of the Free State