Is Expired Protein Powder Safe to Use?
Use By and Best Before Dates
Food Standards Australia New Zealand (FSANZ) requires that most foods have a date mark that shows how long a food can be kept before it deteriorates or becomes unsafe to eat. We all know that some foods can ‘go off’. By that we mean that after a period of time a particular food may start to smell bad and not be safe to eat. Regular milk, for example, has a use by date and foods like this should not be consumed after the use by date as they may pose a health or safety risk. Foods with a use by date cannot be legally sold after that date.
However, most foods, have a best before date that indicates the period of time the manufacturer believes that the food will retain all its original quality, including taste and flavour. Foods like this are still safe to eat after the best before dates and can be legally sold after this date as long as the retailer believes they are still fit for human consumption. There are even some foods that have a shelf life of two years or longer do not need to labelled with any dates as they retain their quality over a long time. Canned foods are an example.
Protein Powders
Dairy protein powders have a shelf life of at least two years from the date of manufacture which suggests that they are pretty stable when stored properly. They don’t expire and because protein powders are dry powders that are low in fat there’s very little risk of bacterial growth or spoilage. 
Proper storage is important. A cool dry place,like a pantry or a cupboard, is ideal. In the fridge is too damp and on top of the fridge is not a good place either (hot and humid). It is also best to avoid leaning bags against brick or concrete walls or sitting on a tile or concrete floor.