title: The effect of fat content on the microbiology and proteolysis in cheddar cheese during ripening dairy foods.
abstract: We investigated the effect of incremental reduction in fat content, in the range 33 to 6% (wt/wt), on changes in the microbiology and proteolysis of Cheddar cheese, over a 225-d ripening period at 7 degrees C. A reduction of fat content resulted in significant increases in contents of moisture and protein and a decrease in the concentration of moisture in nonfat substance. Reduced fat had little effect on the age-related changes in the population of starter cells. The populations of nonstarter lactic acid bacteria decreased with fat content, and counts in the low fat cheese (6% wt/wt) were significantly lower than those in the full fat cheese (33% wt/wt) at ripening times >1 and <180 d. Proteolysis as measured by the percentage of total N soluble at pH 4.6 or in 70% ethanol decreased significantly as the fat content decreased. However, the content of pH 4.6 soluble N per 100 g of cheese was not significantly influenced by fat content. At ripening times >60 d, the content of 70% ethanol soluble N per 100 g of full fat (33% wt/wt) cheese was significantly lower than that in either the half fat (17% wt/wt) or low fat (6% wt/wt) cheeses. The concentration of AA N, as a percentage of total N, was not significantly affected by fat content. However, when expressed as a percentage of total cheese, amino acid N increased significantly with decreasing fat content. Analysis of pH 4.6 soluble N extracts by reverse phase- and gel permeation HPLC revealed that fat content affected the pattern of proteolysis, as reflected by the differences in peptide profiles.
authors.affiliation: Dairy Products Research Centre, Teagasc Moorepark, Fermoy, Co. Cork, Ireland.
authors.forename: M A
authors.initials: MA
authors.lastname: Fenelon
authors.forename: P
authors.initials: P
authors.lastname: O'Connor
authors.forename: T P
authors.initials: TP
authors.lastname: Guinee
mesh_terms: D000818:Animals; D001419:Bacteria / Q000254:growth & development*; D002417:Cattle; D002611:Cheese / Q000032:analysis* / Q000382:microbiology*; D002851:Chromatography, High Pressure Liquid; D015169:Colony Count, Microbial; D004041:Dietary Fats / Q000032:analysis*; D000431:Ethanol; D005511:Food Handling; D005524:Food Technology; D006863:Hydrogen-Ion Concentration; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008892:Milk / Q000737:chemistry; D008894:Milk Proteins / Q000378:metabolism*; D009584:Nitrogen / Q000032:analysis; D010455:Peptides / Q000032:analysis; D013997:Time Factors
chemical_list: D004041:Dietary Fats; D008894:Milk Proteins; D010455:Peptides; D000431:Ethanol; D007770:L-Lactate Dehydrogenase; D009584:Nitrogen