Do not use a product after the use by date. Foods can develop off odors, flavor or appearance due to spoilage bacteria. If a food has developed any of these characteristics, do not use it, regardless of the date on the package. Mishandling of fresh foods can also change the safe storage time of foods regardless of package dates. Defrosting at room temperature more than 2 hours, leaving foods out of coolers or refrigerators at picnics or parties, taking too long to get refrigerated or frozen foods home and refrigerated after purchase, or using contaminated cutting boards or utensils are other ways of mishandling foods in ways that shorten their safe storage times.
Nutrient retention is a key factor in dating of infant formula.
If consumed by the use-by date, the formula must contain at least the quantity of each nutrient as described on the label. Formula must retain a quality that allows it to pass through an ordinary bottle nipple. Dating of baby food is for quality as well as nutrient retention. The same rule about retention of nutrients in infant formula applies to baby food. Development of off-flavors or poor texture is also considered.