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Comparison of curd washing and lactose standardization for manufacture of Colby cheese.

H. Jiang




Comparison of curd washing and lactose standardization for manufacture of Colby cheese.
H. Jiang*, S. Govindasamy-Lucey, J. Jaeggi, M. Johnson, J. A. Lucey. Center for Dairy Research Madison, WI.

Curd washing (CW), a technique which adds water to curds to aid in lactose removal, is mostly used in the manufacture of Colby cheese. However, CW uses a lot of water and if improperly done, curds may still contain excessive lactose which eventually results in acidic Colby. Lactose-standardization (LS) is a technique that was developed by our center to remove some lactose from milk through ultrafiltration and diafiltration and thus eliminate the need for CW. In our study, the efficiency/feasibility of lactose removal through CW or LS technique were compared on Colby cheese manufacture (n = 5). CW-milk was regular cheese milk with ~4.3% lactose, while LS-milk was standardized to 2.2% lactose, but had similar casein (~2.5%) and casein-to-fat ratio (~0.7) as CW-milk. CW-milk and LS-milk were pre-acidified to reduce the insoluble colloidal calcium phosphate. After the whey was completely drained, CW curds were washed with 32�C water at a ratio of 1:14 to milk (a typical CW level used in industry) for 10 min. There was no curd washing step used for LS curds. CW and LS cheeses had similar moisture, fat, protein, salt, total calcium content and proteolysis (soluble nitrogen as a percentage of total nitrogen in both pH 4.6 and 12% TCA tests at 14 d). LS cheeses had higher pH (P < 0.05) and less lactic acid content than CW cheeses during the 6 mo-ripening period. LS cheeses had ~40% lower hardness values (measured by texture analyzer, P < 0.05) than CW cheeses at 60 d of ripening but both had similar melting points (50�C, measured by dynamic small amplitude oscillatory). Changes in sensory flavor and texture properties were evaluated by trained sensory panelists (8—10) using quantitative descriptive analysis. Most of the sensory characteristics were similar (P > 0.05) between CW and LS cheeses, except that LS cheeses had lower particle size, acid and astringency values (P < 0.05). Thus, LS technique has great potential in replacing CW technique used in traditional Colby cheese manufacture to control the amount of lactose and thus acidity in cheese.

Keywords: Colby, curd washing, lactose standardization.