title: Influence of calcium and phosphorus, lactose, and salt-to-moisture ratio on cheddar cheese quality: pH changes during ripening.
abstract: The pH of cheese is an important attribute that influences its quality. Substantial changes in cheese pH are often observed during ripening. A combined effect of calcium, phosphorus, residual lactose, and salt-to-moisture ratio (S/M) of the cheese on the changes in cheese pH during ripening was investigated. Eight cheeses with 2 levels of Ca and P (0.67 and 0.47% vs. 0.53 and 0.39%, respectively), lactose at pressing (2.4 vs. 0.78%), and S/M (6.4 vs. 4.8%) were manufactured. All the cheeses were salted at a pH of 5.4, pressed for 5 h, and then ripened at 6 to 8 degrees C. The pH of the salted curds before pressing and the cheeses during 48 wk of ripening was measured. Also, cheeses were analyzed for water-soluble Ca and P, organic P, and bound inorganic P during ripening. Changes in organic acids' concentration and shifts in the distribution of Ca and P between different forms were studied in relation to changes in pH. Cheeses with low S/M exhibited a larger increase in acid production during ripening compared with high S/M cheeses. Cheeses with the highest concentration of bound inorganic P exhibited the highest pH, whereas cheeses with the lowest concentration of bound inorganic P exhibited the lowest pH among the 8 treatments. Although conversion of lactose to short-chain, water-soluble organic acids decreased cheese pH, bound inorganic phosphate buffered the changes in cheese pH. Production of acid in excess of the buffering capacity (which was the case in low Ca and P and low S/M treatments) led to a low pH, whereas solubilization of bound inorganic P in excess to acid production (which was the case in high Ca and P and high S/M treatments) led to an increase in pH. However, for cheeses with high Ca and P and low S/M, changes in cheese pH were influenced by the level of residual lactose. Hence, pH changes in Cheddar cheese can be modulated by a concomitant control on the amount and state of Ca and P, level of residual lactose, and S/M of the cheese.
authors.affiliation: MN-SD Dairy Foods Research Center, Department of Food Science and Nutrition, University of Minnesota, St. Paul 55108, USA.
authors.forename: P
authors.initials: P
authors.lastname: Upreti
authors.forename: L E
authors.initials: LE
authors.lastname: Metzger
mesh_terms: D000143:Acids / Q000737:chemistry; D002118:Calcium / Q000032:analysis*; D002611:Cheese / Q000032:analysis* / Q000592:standards*; D005511:Food Handling; D006863:Hydrogen-Ion Concentration; D007785:Lactose / Q000032:analysis*; D010758:Phosphorus / Q000032:analysis*; D012492:Salts / Q000032:analysis*; D012995:Solubility; D013997:Time Factors; D014867:Water / Q000032:analysis
chemical_list: D000143:Acids; D012492:Salts; D014867:Water; D010758:Phosphorus; D007785:Lactose; D002118:Calcium