Manufacture of Spanish hard cheeses from CO2-treated milk

The suitability of milk preserved by refrigeration and CO2 addition for the manufacture of rennet-coagulated Spanish hard cheeses was evaluated. Two types of cheeses were produced from milk preserved by refrigeration and CO2 addition (pH 6.2) and were compared with controls made from fresh milk. Degasified (50-52 degreesC and 300 mm Hg) and pasteurised milk was employed for the manufacture of 30-day-old cheeses using a commercial starter. A degasified (30-32 degreesC and 350-375 nun Hg) mixture of 90% cow's and 10% ewe's raw milk was used for the manufacture of starter-free 75 day-old cheeses. Milk preservation did not affect multiplication and acidification capacity of lactic acid bacteria in cheeses from pasteurised milk but promoted lower levels of lactococci at first days of ripening in cheeses from raw milk and rendered lower amounts of lactic, pyruvic and succinic acids. Preservation did not affect the evolution of volatile compounds. Cheeses from preserved milk showed reduced clotting time, slightly higher cheese yields and increased curd hardness and whey losses during cheesemaking. The taste panel accepted cheeses from preserved milk. These results support the interest Of CO2-addition in preservation of milk for the manufacture of Spanish hard cheeses. (C) 2002 Elsevier Science Ltd. All rights reserved.