Accompanying these changes are concerns that the milk is no longer good for the baby. There are several possibilities for the cause of odor or taste changes in human milk. Solutions depend on the root cause. The first step to finding a solution is to determine whether expression, handling and storage are the source of the issues, or whether highly active lipase or chemical oxidation are the cause.
First, pumping or expressing, handling, and storage practices should be examined to ensure that all hygienic precautions are being taken. Pump parts should be cleaned thoroughly between pumping sessions to ensure no bacterial contamination is conveyed to freshly pumped milk.
Use storage containers that are specifically designed for storage of human milk. Lawrence and Lawrence recommend rigid polypropylene containers due to the fact that fewer nutrients and immunological components are lost compared to breast milk stored in other types of containers p.
If polypropylene containers are not available, Pyrex is a next-best choice. While not ideal both because of nutritional and immunological losses as well as due to the bags being weak and splitting open, plastic storage bags for human milk may be used instead.
Second, some people have excess lipase activity. Previously, it was believed that some people have excess lipase in their milk, but recent research has shown that to be a misunderstanding Lawrence and Lawrence, p.
Lipases are enzymes found in all milks. Two kinds are well known: lipoprotein lipase and bile salt-dependent lipase Lawrence and Lawrence, , pp. Each has positive roles to play in digestion and immunological effects for the baby. Lipase activity:. Even when a soapy smell is detected, the milk is still safe and nutritious for your baby. You can prevent the problem from occurring with future batches of pumped or expressed milk—no one wants to lose their precious liquid gold!
Freezing will not prevent lipase activity from altering the aroma or taste of your milk, but scalding will.
Here are the steps to de-activate lipase activity:. This third possible problem may be more challenging to resolve, and the milk is not salvageable once it has occurred. If the smell is sour or rancid, milk storage experts Jones and Tully suggest the cause is chemical oxidation rather than excess lipase activity Mohrbacher, p. Several factors may contribute to this problem, including a diet containing polyunsaturated fats or rancid fats, or drinking water with free copper or iron ions.
When chemical oxidation occurs, the milk is spoiled and must be discarded, and scalding the milk will only make the problem worse. However, the above dietary changes should help you resolve the problem completely without the extra work of heat-treating your milk! Does it smell or taste sour, or does it smell fine and taste a bit sweet? If it does smell or taste sour, then it indicates the presence of rancid fats and chemical oxidation.
Try changing your diet to eliminate the problem. There are two types of lipase in breast milk; lipoprotein lipase and bile salt-stimulated lipase 1. Lipase in breast milk breaks down fats into fatty acids a process called lipolysis and it is these fatty acids that are thought to cause the soapy taste 2. Some mothers have found that the soapy or sour smell appears to be more apparent once breast milk has been stored in the refrigerator or freezer. Theories for stored breast milk tasting or smelling sour or rancid include:.
In the past some breastfeeding authors have suggested that breast milk turns sour in mothers who have particularly high lipase levels in their breast milk. However a study by Dr Ruth Lawrence and others did not find higher lipase levels in samples of sour milk In most cases a baby will be happy to drink breast milk that has been safely stored including frozen and thawed. Sometimes a baby appears to dislike stored breast milk that tastes or smells sour or rancid and will refuse it.
The time interval before stored milk begins to have a stronger taste varies between mothers but it is not possible to reverse the taste once this has happened—which can lead to wasted breast milk. Some mothers have found that diluting the affected milk in equal parts with freshly expressed breast milk can make it acceptable to the baby. In addition, experts offer a number of options to try to avoid the unacceptable taste whether the cause is enzyme activity lipase or oxidation see below.
If diet and water supply are not affecting the taste of breast milk but a baby refuses to drink previously stored milk, lipase activity can be deactivated by heating breast milk prior to storage.
The best temperature to inactivate lipase but preserve the other living components of breast milk is not clear. Scalding breast milk will not remove the soapy or rancid smell if the milk has already become tainted. Kelly Bonyata explains that although some protection will be lost or some nutrient levels lowered this is unlikely to cause issues unless a baby is exclusively receiving heat treated milk in their diet Bonyata, Lipase is an important enzyme found in human milk.
Lipase breaks down the milk fats into small particles that babies can easily digest. Laboratory testing is the only way to confirm the level of lipase in human milk. To avoid the added expense, some mothers simply test their milk at home by placing small amounts of expressed milk on the kitchen counter at room temperature and in the refrigerator or freezer and checking it periodically for changes in taste or smell. How long the milk can be stored before it starts to smell varies from hours to days to weeks.
Fortunately, only a small number of mothers report noticeable changes in the taste of their milk as a result of storage, but if you are one of them, it can be extremely frustrating.
While the milk is still safe to consume, some babies may refuse to drink it if there is a strong change in flavor, though others don't seem to mind a mild change. If your baby refuses to drink the milk, the only option is to discard the milk or donate it to the nearest milk bank. Mothers can heat scald the milk before storing it, to reduce lipase activity and prevent odor changes.
Remove the milk from the heat as soon as the bubbles appear, then cool and store. Scalding will destroy some of the milk's anti-infective properties and may alter nutrient levels, but this is seldom a concern since babies will still accept milk during breastfeeding. Make milk storage easy and safe by storing your milk in any glass or BPA-free plastic container made for food storage—including plastic bags specifically designed for storing human milk.
Label the container with the date and time. Allow room for expansion if you plan to freeze the milk.
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