Thursday, September 13, 2012
I rarely talk about materials science on this blog, but today is your lucky day if you get excited about the physical properties of matter. As it turns out, all glass baking items are not created equal, because all types of glass are not created equal. A report in the Bulletin of the American Ceramic Society (also covered in this Scientific American Podcast) reports on changes in the material that Pyrex glassware is made from that affects its performance.
Prior to 1994, all Pyrex cookware was made of borosilicate glass (which is also what most laboratory glassware is made from). The advantage of this type of glass over normal glass is that it has a low coefficient of thermal expansion. This means that when the glass is heated, it expands less than normal glass. This might seem insignificant, but it can be important if the glass is going to be used in a way that results in it being rapidly headed or cooled, such as going from an oven to a refrigerator. Rapid changes in temperature can cause glass to expand unevenly, causing stress within the glass that leads to cracks or even breakage. Glass with a lower coefficient of thermal expansion is less likely to crack or shatter after exposure to rapid changes in temperature, making it ideal for kitchen (or laboratory) use.
However, since 1994, Corning has been licensing the Pyrex name to companies that produce products made of soda lime silicate glass, which is the type of glass found in most common glass items in your home. This glass is less likely to break when dropped (although this is not tested in the above bulletin), but has a coefficient of thermal expansion that is about three times that of borosilicate glass, making it more likely to shatter when exposed to thermal stress. In fact, the report says that a temperature change of 100 degrees F is enough to break the new Pyrex products, while a change of 330 degrees F was required to break the old borosilicate products. To put this in perspective, the difference between a raw, room-temperature roast and a hot oven is about 275 degrees F.
The take home message is that if you want the old, shatter-resistant formulation of Pyrex, look for older pieces (or, presumably, look for items that are labeled as being made from borosilicate glass). That casserole dish from the thrift store might be an even better deal than you previously thought. And, if you're a fan of pictures of glass shattering, definitely check out the full report from the ACS bulletin above!
(Image: IMG_5201, a Creative Commons 2.0 licensed image from gruntusk's photosream)
Wednesday, September 12, 2012
Charles Wysocki, a neuroscientist at Monell Chemical Senses Center in Philadelphia has found evidence of the genetic basis of cilantro hate in his studies of twins. He says that 80% of identical twins share their preference for cilantro, while among fraternal twins the number is only 50%, indicating that there is some genetic basis for cilantro preference. Scientists at the University of Toronto in Canada have linked variants in genes for an olfactory receptor (those are the proteins on the surface of cells in your nose that let you detect scents) and a bitter taste receptor to cilantro preference. Additionally, researchers at the genetics company 23andMe found that dislike of cilantro was linked to a different olfactory receptor. All of these studies suggest that preference for cilantro may be genetic, and that the reason that some people dislike cilantro is because they perceive the taste of the herb differently. Still, differences in cilantro preference between even identical twins does indicate that there are some environmental factors that affect how much you enjoy the herb.
What does this mean for you? Well, it's more evidence that a person's genetic makeup affects the way that they perceive and interact with the world, including the things we eat. Right now, we have no way to affect a person's genes, so, at least for now, cilantro haters gonna hate.
(Image: cilantro, a Creative Commons 2.0 licensed image from looseends' photostream)
Monday, September 10, 2012
There has been a lot of kerfuffle on the internet in the past week since Stanford University scientists published a meta-analysis of many studies regarding health and organic foods. They found that there was no evidence that organic foods are "more nutritious" than conventional foods. However, they did note some differences between conventionally grown and organic foods. Organic fruits and veggies had less pesticide residue, and organic meats were less likely to be contaminated with antibiotic-resistant bacteria.
At this point, many people have thrown down on either side of the organic food divide. Proponents of eating organic say that we still don't know the long-term health benefits of an organic diet, as these studies mostly looked at short term effects of an organic diet. Opponents say that organic food is a pricey fad, a method of food production that can not feed the world's large population, and offers little benefit to the consumer.
Overall, I do still think organic food offers some benefits. Organic farming reduces our dependence on fossil fuels and prevents the damage done to soil and ecosystems that are a result of industrial monoculture. As the farmer from the CSA that I belong to pointed out, most people on the planet currently do not get their food from an industrial agricultural system like one that we have in the US, suggesting that feeding the world's populations using organic methods might be feasible. Eating organic also reduces our exposure to pesticides and antibiotic resistant bacteria, the long term effects of which I agree are not well studied. However, this study did not interrogate the long-term health effects of organic food, nor did it consider the effects of organic agriculture on anything besides consumer health, and it also grouped all organic food into one category, when there are a diversity of types of "organic" farming practices, from industrial organic to small-farm biodynamic.
Overall, this study is part of the big picture of food production in the United States. This also an excellent example of a study that can be interpreted multiple ways. We should take the conclusions of this study, that organic produce does not seem to be higher in nutrients than conventional, into consideration. We should also avoid extrapolating the data in an unfounded way to align with whatever political point we're trying to make. This study sought to help inform consumers of organic food to make better decisions about what to buy, but it did not address the larger questions of what type of food production are best for the economy, environment, or long-term sustainability of agriculture. Organic food has not been proven to be healthier, but neither has it been condemned as being completely without benefit.
(Image: The sign reads "Organic no chemicles" a Creative Commons 2.0 image from friendsoffamilyfarmers's photostream)