Cooking blueberries decreases their polyphenol content

Polyphenols, the plant compounds that exhibit various cell-protective, antioxidant properties, can be found throughout nature, including in foods such as honey, broccoli and blueberries, to name a few.

Polyphenols comprise over 4,000 distinct species and can have a positive impact on cell-to-cell signaling, enzyme activity, receptor sensitivity and gene regulation. Scientifically, polyphenols are compounds that contain more than one phenolic hydroxyl group. This chemical structure equips them with free radical scavenging properties and the ability to upregulate certain metal-chelating reactions. Yes, some polyphenols help the body naturally detoxify from certain heavy metals.

Polyphenols, which give a boost to men and women’s cellular health, are naturally weaved into the environment. A new study from the American Chemical Society shows how essential polyphenol content is significantly reduced in natural foods like blueberries when they are cooked. This is important, because many people may think that they are eating a healthy snack, but they may not be getting the whole plethora of antioxidant benefits. Blueberry juice, baked blueberry pie or blueberry muffins can have drastically reduced antioxidant properties when compared to freshly picked, uncooked, wild blueberries.

Blueberry’s superfood powers reduced when cooked

Blueberries are high in polyphenols, including anthocyanin, which gives blueberries their blue color. Other flavonoids, like procyanidin, give blueberries their cellular regenerative properties. Quercetin gives blueberries anti-inflammatory properties, while other phenolic acids make blueberries an anti-aging powerhouse food.

These polyphenols travel into the human body and improve thinking, blood pressure and inflammation, but these benefits can be negated through certain cooking methods. For starters, certain processed blueberry drinks show reduced polyphenol content from anywhere between 22 and 81 percent.

Ana Rodriguez Mateos and fellow colleagues from the American Chemical Society sought to test the loss of polyphenol content of blueberries during the baking process, especially in cooked breads, muffins and pies. They measured the polyphenol content of the baked goods during the time when the dough rises.

What they found was that certain important polyphenol levels declined, including anthocyanin and procyanidin levels. Anthocyanin levels fell by up to 21 percent. The largest procyanidin oligomer levels dropped dramatically as well. While quercetin levels remained about the same, some phenolic acid levels increased.

Another study shows anthocyanidin degradation in cooked blueberries

Another study from Portugal examined anthocyanin and anthocyanidin composition of blueberries when cooked in stuffed fish. Three wild cultivations of blueberries were studied, including bluecrop, bluetravel and ozarkblue. 13 anthocyanins were extracted following the cooking process, and these polyphenols were separated in methanolic extracts of raw fruits. The researchers examined the polyphenols using liquid chromatography and diode array detectors.

What they found was that progressive heating of blueberries, from 12 to 99 degrees Celsius, decreases anthocyanidin and anthocyanin content. In a 60-minute heating session, polyphenol content fell between 16 and 30 percent in the blue crop variety, 30 to 42 percentfor bluetravel, and 12 to 41 percent for Ozarkblue. Despite the loss, the researchers saw no change in free radical scavenging activity, suggesting that other antioxidant levels may increase during the cooking process.

Not all is lost in the cooking process

Not all antioxidant powers are lost during the cooking process, these studies suggest. The Portuguese scientists recommend cooked blueberries right along with fresh wild blueberries for a healthy dose of dietary polyphenol antioxidants. It seems that, while cooking reduces certain polyphenol levels, other antioxidant levels may actually increase.

That’s what the American Chemical Society study found. The baked blueberries showed increased levels of a smaller variety of procyanidin oligomers. The researchers also found that yeast helped stabilize the blueberries’ polyphenol content through the baking process.