Storage of Milk Products

Refrigerated

All fluid milk except unopened, aseptic packs of ultrahigh-temperature pasteurized milk and certain canned milk products should be stored in the refrigerator. They need to removed only long enough to take what is to be used and then quickly returned to the refrigerator. Containers should be closed or covered to avoid rancidity, microbial contamination, and the absorption of odors from other foods in the refrigerator. Both oxidative and hydrolytic rancidity are a potential problem in milk and milk products because of the substantial amounts of short-chain fatty acids. One should never drink milk directly from the container, because bacteria in the mouth can wash back into the product. Pouring unused milk products back into the original container is also not recommended, because microbial contamination could have occurred from exposure to the air or other sources. Proper opaque containers will reduce exposure to light, which can trigger oxidation, resulting in off-flavors and the loss of riboflavin (B₂). The shelf life of certain dairy products such as cottage cheese can be doubled with the addition of carbon dioxide, which disrupts microbial functions.

The following guidelines should be followed when storing milk products in the refrigerator:

• Milk. No more than three weeks.
• Yogurt. Best consumed within the first ten days, but can last up to three to six weeks. If it separates, simply stir the liquid back into the curd before serving.
• Buttermilk. Best when used within three to four days after purchase, because it will continue to sour, but it can last up to three or four weeks.
• Sour cream. Unopened, up to one month, but best when used within a few days.

Dry Storage

Nonfat dry milk, ultrapasteurized milk, evaporated milk, and sweetened condensed milk are stored at or slightly below room temperature (72^oF/22^oC). Nonfat dry milk should not be exposed to moisture, because humidity will cause it to turn lumpy and become stale. Keeping containers tightly closed minimizes any contact with oxygen from the air. Nonfat dry milk stored in this manner will keep for about one year. Unopened cans of evaporated and sweetened condensed milks will keep up to a year in dry, ventilated areas, but double that if refrigerated. Both should be turned over every few weeks to prevent the solids from settling, thickening, and producing clots. Ultrapasteurized milk can be stored unopened at room temperature for up to three months. Once opened all these milks must be treated like fresh milks and refrigerated. The “sell by” or “expiry” date is the last day the item should be sold by the store, and this should always be checked before purchase.