How To Mummify An Apple | Science That Keeps Fruit

Mummification sounds like something from ancient Egypt, not a weekend project in your kitchen. But the same principle—dehydration—can be done with common pantry ingredients. Salt and baking soda are all you need to turn a fresh apple into a hard, preserved keepsake that lasts for months.

This experiment is straightforward: you peel the apple, carve a face if you want, bury it in a dry mixture, and wait. The salt pulls out moisture while the baking soda helps absorb it. In about a week, the apple becomes leathery and shrunken. Here’s how to do it step by step.

What You Need for Apple Mummification

The key ingredient is salt. Salt acts as a desiccant, meaning it absorbs moisture from its surroundings. When you bury an apple in salt, the water inside the apple moves toward the dry salt, effectively pulling the moisture out of the fruit.

Baking soda plays a supporting role. It absorbs extra moisture and helps control any odors that develop during the drying process. Together, they create an environment so dry that bacteria and mold cannot grow.

Ingredients and Setup

You’ll need a sharp knife or apple slicer, a plastic bag or container with a lid, and the two powders. The ratio is simple: one part salt to one part baking soda by volume. That’s all. A medium apple works best for the experiment.

Why the Simple Mixture Works

If you’re wondering why two basic ingredients work so well, it comes down to how they interact with water. Here’s what each one does.

• Salt is a desiccant: It sucks water out of the apple through osmosis. The salt crystals attract water molecules and hold them, leaving the apple drier.
• Baking soda absorbs moisture: Baking soda is hygroscopic, meaning it pulls water from the air and from surfaces it touches. It helps maintain a dry environment inside the bag.
• No moisture means no decay: Bacteria and fungi need water to survive. With the apple completely dry, they cannot grow, so the fruit stays preserved.
• The process takes time: A single day isn’t enough. The apple needs several days to a week to lose enough water to become shelf-stable.
• You can add a control group: Leave a second apple slice uncovered to see how it rots. This comparison shows the effectiveness of the desiccant.

The same principle is used in food preservation techniques like jerky drying and salt curing. For this experiment, the 1:1 ratio is the most reliable starting point.

Step-by-Step: How to Mummify an Apple

Start by washing and drying the apple. Use a vegetable peeler to remove the skin completely. Skin holds moisture and slows the drying process. You can also carve a simple face into the apple to make it look like a mummy head—something kids enjoy.

Mix equal parts salt and baking soda in a bowl. Pour a layer of the mixture into the bottom of a plastic bag or container. Place the apple on top, then pour the rest of the mixture over it until the apple is completely buried. Seal the bag or container tightly.

Checking Progress

Store the bag in a cool, dry place away from direct sunlight. Check after three days. If the apple still feels soft or moist, the Milwaukee Public Museum education team recommends you make a new mixture and repeat the process. The apple is fully mummified when it feels hard and leathery all over.

The control slice shows what happens without the desiccant: it rots within a week. The mummified apple, by contrast, can last for months if kept dry.

Tips for Best Results

A few small adjustments make the difference between a partly dry apple and a fully preserved mummy. Follow these factors.

1. Slice apples thinly: Thinner slices dry faster and more evenly. Whole apples work too, but they take longer—sometimes up to two weeks.
2. Cover every surface: The apple must be completely buried. Any exposed spot will remain damp and may mold.
3. Seal the container tightly: A sealed bag prevents outside humidity from rehydrating the mixture. Use a ziplock bag or a container with a tight lid.
4. Check after day four: Open the bag, feel the apple. If it still feels moist, make a fresh mixture and try again.
5. Wrap in cloth: Once dry, wrap the apple in strips of gauze or cloth to complete the mummy look. This is purely decorative but adds to the fun.

Adult supervision is important when using knives for peeling and carving. The experiment is safe, but sharp tools require care.

The Science Behind the Apple Mummy

At its core, mummification is about removing water. Without water, the enzymes and microorganisms that cause decay cannot function. The salt-baking soda mixture creates a hypertonic environment that pulls water out of the apple cells.

Why the Ratio Matters

The specific balance is crucial. The Xploration Station science center’s guide uses a 1 to 1 ratio of salt and baking soda for the desiccant mixture. Too much salt can make the mixture too caustic for handling, while too little won’t dry the apple effectively.

Baking soda adds an extra layer of moisture absorption. It also helps neutralize any odors that might develop as the apple dehydrates. The combination is gentle enough for a classroom or kitchen counter.

The Bottom Line

Mummifying an apple is a simple, low-cost science experiment that demonstrates dehydration and preservation. With just salt and baking soda, you can turn a fresh apple into a long-lasting keepsake. The key steps are peeling, covering completely with the mixture, and waiting about a week until the apple feels hard and leathery.

If you’re doing this with kids, supervise the knife work for peeling and carving. The experiment itself is safe, but sharp tools require caution. For a school project or science fair, consider setting up a control slice so you can show the difference between preservation and decay.