Expired whey protein: is it safe, and how long does it keep?

The date on a whey tub tells you how long the maker guarantees its quality. It does not mean the powder turns bad the next day, but powder stored badly can go off before the date. This page covers reading the date, storing an open tub and spotting whey that has gone off.

"Best before" or "expiry"

Thai food labelling rules require a date marked either "best before" or "expiry". The Thai FDA guidance defines expiry as the date the food's quality ends under the stated storage conditions. In the U.S., the USDA Food Safety and Inspection Service (FSIS) explains that a "Best if used by" date shows when flavour and quality are best and is not a safety date, except for infant formula.

Is it still OK after the date?

USDA FSIS says food handled properly may still be safe after the date until it shows signs of spoilage, such as an off smell, taste or texture, and spoiled food should not be eaten. Healthline summarises research in the Journal of Dairy Science: whey stored at room temperature, about 21°C, keeps for at least 18 months, but at 35°C only about 9 months, and in one study the amino acid lysine in whey fell from 5.5% to 4.2% within 12 months. The maker guarantees quality only up to the date on the label; past the date and unsure, throw it out.

Storing an open tub

Ultimate Nutrition advises a cool, dry place out of direct sunlight, resealing the tub tightly every time, and never leaving a wet scoop inside
Thailand is hot: don't leave the tub in a car or by a window. The 35°C above is the temperature that clearly shortened shelf life
Ultimate Nutrition advises finishing it within 30 days of opening, and the label of Ensure, a complete-nutrition formula, says to use it within 3 weeks. Brands differ, so follow the label of your tub

Which size can you finish in time?

Days to finish = scoops per tub ÷ scoops per day

Examples from our store: Biovitt Whey Protein Isolate (907 g) has 16 scoops, and Ultimate Nutrition Prostar 100% Whey (5.28 lb) has 80. At one scoop a day, the big tub lasts several times longer than the 30-days-after-opening advice. Big tubs are usually cheaper per gram, but if you use whey rarely a small tub can work out better because nothing is thrown away. Compare with the price-per-gram calculator.