THE FREEZE-DRYING PROCESS:
History, uses, and why it's great for saving breast milk
Milkify uses a process called freeze-drying to convert
frozen breast milk into powder.
Our freeze-drying process works by a simple principle called sublimation, in which the water is removed from frozen breast milk by transitioning directly from a solid (ice) to a gas (water vapor). This process is explained in more detail below, but simply put - it preserves the structure of molecules in the milk, which impacts the taste and nutritional quality of the milk. The result after freeze-drying is a fine breast milk powder, which has all of the components of the breast milk without the water. This process is very different than standard "dehydrating" techniques, which use high temperatures to remove water, thereby damaging the nutritional properties of the milk.
FREEZE-DRYING HISTORY AND USES
Freeze-drying technology as we know it has been around since the 1950s (although technically the process was also used by the Incas to preserve food centuries ago!) Freeze-drying technology is therefore widely used in the food and medical industries as it is an excellent method for preserving a wide variety of sensitive materials from probiotics to protein shakes to pharmaceuticals.
Use in the food industry: Freeze-dried foods rehydrate instantly in hot or cold water and are popular with consumers because of their quality and convenience. Freeze-drying maintains the original appearance of the food with almost no loss of flavor. Freeze-drying also maintains 97% of the nutritional value of the food compared with other methods of preservation. Other methods, such as canning and dehydrating use high temperatures that destroy much of the nutritional value of the food.
Use in the medical industry: Freeze-drying technology is also widely used in the medical industries as it is an excellent method for preserving a wide variety of heat-sensitive materials like vaccines and pharmaceuticals.
Use in human milk donor banks: Breast milk is a precious resource, especially in hospital neonatal care units. Several organizations have been researching this technology extensively, and a few are starting to use freeze-drying technology in human milk donor banks for better long-term storage of breast milk. The end product achieved by freeze-drying, a breast milk powder, easily reconstitutes with warm purified water, and is shelf-stable without refrigeration for several years.
Read more about other organizations using the freeze-dry process for breast milk storage:
HOW IT WORKS: THE BASICS
The basic steps of the process are:
FREEZE: The breast milk you provide is frozen at a very low temperature (below 40 degrees).
VACUUM: The freeze-drying chamber is then placed under a deep vacuum.
DRY: A small amount of heat is then added, and since the pressure is so low, the ice turns directly into water vapor and is removed from the frozen milk.
SEAL: The powder is then sealed in a high barrier bag to protect it from moisture, oxygen, UV, and contamination.
FREEZING vs. FREEZE-DRYING
The current standard for preserving breast milk is freezing. How does freeze-drying stack up against freezing? Freezing is not a perfect method of preservation since even at low temperatures food quality deterioration may still occur (see more here). Freeze-drying is a better long-term storage solution because the process gently removes the ice crystals without thawing, and because the enzymes and degradation components present in breast milk are inactive in the absence of water.
Healthy living cell and nutrients in fresh breast milk.
Ice crystal formation causes cells to burst or ruptures the cell membrane, releasing chemically reactive components and enzymes.
The cell is destroyed. Over time in the freezer, the released components from the cell break down the nutrients, and change the taste profile of the milk.
Healthy living cell and nutrients in fresh breast milk.
Ice crystals turn into water vapor, and exit the cell without causing damage, preventing release of degradation components.
The cell remains healthy. Cellular components and enzymes are inactivated, so do not break down nutrients.
Breast milk is a living food – this means that there are living cells in your milk!
The formation of ice can cause cells in your milk to rupture, releasing chemically reactive components. These chemically reactive components and enzymes can break down nutrients in the milk over time (even when the milk is frozen). Nutritional losses that occur during thawing can also decrease the health benefits of the milk.
Freeze-drying prevents this process from happening because it keeps the cells from rupturing (by sublimation of the ice crystals into water vapor), and also by inactivating the chemically reactive components that cause nutrient degradation (they cannot function without water present!) It's not just the nutritional value that benefits from freeze-drying – the process also prevents “freezer-taste”, which is a change in the taste of the food after freezer storage.
The reason that freeze-drying can help improve the taste of high-lipase milk is for this exact reason. Lipases are enzymes naturally found in breast milk. Lipases are helpful in that they help break down fats, which aids your baby's digestion. Lipases can stay active during freezer storage however, which means that they keep doing their job of breaking down fats, causing the milk to smell and/or taste funny after being stored in the freezer. When you remove water from the milk, the lipase enzyme can no longer work (until water is added back in). This means that when you freeze-dry breast milk, you "stop the clock" on the break down of fats due to lipase activity.