How long does a smoothie last in the fridge?

Drink it the day you make it, and keep it in the fridge until you do. The browning you see after a few hours is the fruit’s own enzyme meeting air, the same thing that browns a cut banana. If you want smoothies ready for the week, freeze the fruit and greens in bags and blend each morning instead.

The make-ahead smoothie sounds like the perfect plan for busy mornings. Then you open the fridge to a jar that’s turned brown on top and separated into layers, and you’re not sure whether to drink it. Most of what you’re seeing is harmless chemistry, but a glass made with milk or yogurt is still a dairy drink sitting in the fridge, and we’d treat it like one.

A blended smoothie behaves like a sliced apple. Whole, it keeps for days, and once it’s cut and the air gets in, it starts to change within hours.

Why does a smoothie turn brown?

Fruits like banana carry an enzyme called polyphenol oxidase. Blending breaks the fruit open and mixes in air, and the enzyme turns parts of the fruit brown, the same reaction you see on a cut banana. In a 2023 study, a banana smoothie cut how much of its added flavanols reached the blood by 84%, and the researchers put that down to this enzyme.

Browning changes the color and the taste. It isn’t how you tell whether a glass is safe, though, and neither is separation, which is just the heavier parts settling. Give it a shake and it comes back together.

How do I keep a smoothie from browning?

• Leave out the banana if it has to sit, since it’s the strongest browner in most glasses.
• Fill the jar to the top so there’s little air inside, and seal it.
• Keep it cold the whole time, and drink it within the day.

How do I make smoothies ahead for the week?

Make freezer bags. Each one holds everything except the liquid and the yogurt, so it’s a meal you can dump straight into the blender.

In the freezer bag

A cup of frozen strawberries, a sliced banana, a cup of spinach and a tablespoon of ground flax.

From the fridge each morning

A cup of milk and 7 oz of plain Greek yogurt. Pour, add the bag, blend.

Frozen fruit and spinach blend thick and cold with no ice, and a cup of spinach adds 7 calories you won’t taste. Five bags on a Sunday is five breakfasts. The recipes marked as keeping a week work the same way, and how to make a smoothie has the order to blend them in.