DEAR DR. BLONZ: I received information from the California Cheese Board indicating that milk products such as sour cream, cottage cheese and even hard cheeses can be preserved (protected from mold) with regular vinegar. In the case of plastic containers, a paper towel sprayed with vinegar and placed under the plastic cover will prolong shelf life between uses (and reapplication of the vinegar). Concerning the pink on sour cream, I have had no problems with removal and using the sour cream below. Seems to act like the green growth (mold?) on the surface of hard cheese. Hope this info is useful. — P.B., La Mesa, Calif.

DEAR P.B.: Thank you for your letter. I checked around and was not able to find a group calling itself the California Cheese Board, but let s go ahead and consider the information. First, molds are types of fungi that live on plant or animal matter. The tiny mold organism has three body parts: root threads that go down into the material being used for food, a small stalk that rises above the food and spores, which are located at the end of the stalks. The spores give the mold its color, and they travel to new sources of sustenance and begin growth anew to help propagate the species.

An acidic environment can inhibit the growth of fungi. This explains why some cheeses make use of sorbic acid (a mild acid and mold inhibitor) as a preservative. You can prevent the growth of mold on cheese by wrapping it in a vinegar-soaked paper towel or cheese cloth. Mold,

however, requires oxygen to grow, so there is also the option of storing your cheeses in airtight containers. The presence of unwanted mold on your cheese, or a pink discoloration in your sour cream, indicates that the mold has been around long enough to set up shop and reproduce. You might get away with scooping or cutting out around and under the colored area.

I checked with John Bruhn, Ph.D., Cooperative Extension Specialist Emeritus of the Department of Food Science and Technology at the University of California at Davis. He agreed that creating an acidic atmosphere using a vinegar-soaked cloth or paper towel might help in controlling mold growth but said that it is not always reliable. He advised that careful, sanitary handling of the dairy product, whether it be cheese or yogurt, should give you the best results.

Bruhn said: “Molds of any color found on yogurt are usually an air contamination at the time of filling, or more likely in the home environment after the consumer has opened the container. Small mold contaminants can be removed and the product should be safe. If there is a spot of mold in a yogurt container, remove a tablespoon of the product with the mold and that should clear out the problem. With cheeses, one needs to cut about 3/4 to 1 inch around the mold contamination. If the cheese is extensively contaminated, then it should be discarded.