Ropiness is milk… Psychrophilic bacteria and California milk quality
AuthorsB. E. Hubbell
E. B. Collins
Authors AffiliationsBruce E. Hubbell, Jr., is Lecturer in Food Science and Technology and Specialist in the Experiment Station; Edwin B. Collins is Associate Professor of Food Science and Technology and Associate Dairy Bacteriologist in the Experiment Station, Department of Food Science and Technology, University of California, Davis.
Hilgardia 16(10):14-15. DOI:10.3733/ca.v016n10p14. October 1962.
Although California's milk supplies, with rare exception, are easily kept well within California Agricultural Code specifications, a few dairy plants have occasionally encountered ropiness in pasteurized milk. This ropiness and some other storage defects such as fruity flavor are attributable to psychrophilic bacteria introduced following pasteurization. Psychrophiles are organisms that grow at refrigerated storage temperatures and can cause noticeable symptoms in milk after about a week. Ropiness in pasteurized milk is likely to become more of a problem for processors as total bacteria counts continue to be lowered by refrigeration and improved sanitation and as storage periods become longer. Under these conditions, a larger fraction of the organisms present in milk will undoubtedly be psychrophiles. Since many of these psychrophiles do not grow at the standard plate count temperature of 35° C used for routine laboratory testing, this study suggests modifications in procedure to allow more accurate determination of the quality of pasteurized milk.
Also in this issue:Pear decline research—Methods of propagating own-rooted old home and Bartlett pears to produce trees resistant to decline
Soil fumigation found essential for maximum strawberry yields in southern California
Root-soil boundary zones as seen by the electron microscope
Wildland value survey shows agreement on fire protection priority
Hot water treatment of hop rhizomes for nematode control
The Economics of farm relocation
Toxicity of certain herbicides in soils
Studies on the activation of herbicides
Movement of carbon disulfide vapor in soils as affected by soil type, moisture content, and compaction