Last week in class we discussed an article in which the anthocyanin contents of various fruits were studied. Before the extracts were taken from the fruits, all were frozen (presumably for storage over the time necessary to transport the fruits). One member of the class expressed concern that this initial freezing might have reduced the levels of anthocyanins.
This reflection made me curious because of an experience I had last fall. During my semester abroad in Siena, Italy I completed a four-week internship at a winery in the Chianti. My first day at the winery I helped with the destemming process (which takes place before the grapes are crushed for the winemaking). Because we had so many grapes coming in from the fields each bin could have been sitting in the sun for 45 minutes or an hour before we dumped it into the machine. In order to stop the loss of polyphenols, which provide the wines with much of their flavor, we sprinkled dry ice into the bins and covered them to keep the grapes cool.
Of course, cooling something and freezing it are two different things. It turns out that freezing is actually the best way to store fruits over long periods of time while maintaining anthocyanin levels. In a study conducted in Australia, researchers demonstrated that blueberries that have been frozen for three months not only have the same quantity of anthocyanins as fresh blueberries but they also demonstrate the same amount of antioxidant activity! In contrast, dried berries demonstrate lower levels of anthocyanins than fresh or frozen blueberries but the same amount of antioxidant activity. You can read this article at http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1082901
I also found a site with instructions on how to freeze various fruits. One of the reasons that nurients are often lost when freezing fruit is that the skins break and lose some of their juices during the process. The following site explains how to prevent this from happening: http://ohioline.osu.edu/hyg-Fact/5000/5349.html
Subscribe to:
Post Comments (Atom)
1 comment:
it sounds like what I said was half true-- it all depends on how the freezing process occurs. I did a little more research and I discovered that cooking vegetables over a long period of time seems to make them lose many of their antioxidant properties. Perhaps I was getting the two stories confused. The link to that story can be found here:
http://www.msnbc.msn.com/id/16382205/
-Steven Sangha
Post a Comment