|Muck and Mystery
Loitering With Intent
|blog - at - crumbtrail.org|
Perhaps the most shocking discovery from this new science of taste, however, is that the act of eating is not the only source of gustatory pleasure. Instead, a big chunk part of our sensory delight — the joy that makes us crave particular foods — comes afterwards, when the food is winding its way through the gut. Look, for instance, at a recent paper in Neuron, led by a team of scientists at Duke. They came up with a clever paradigm for isolating this more indirect pleasure pathway: They studied mice without a functional TRPM5 channel, which is essential for detecting sweetness. As a result, these mutant mice showed no immediate preference for sugar water.People are not mice: we cook, we are "cookivores". Flavor depends significantly on the chemistry of cooking, especially the Maillard Reaction.
But here comes the cool part of the experiment. The scientists then allowed the mice to spend some time with the sugar water and normal water. After a few hours, it became clear that the mutant mice greatly preferred the sugar water, even though they couldn’t taste the sugar. (A control experiment with sucralose, an artificial sweetener, demonstrated that the rats were responding to the caloric intake, not the sweet taste.)
Finally, the scientists measured dopamine levels (via in vivo microdialysis) in the nucleus accumbens (a brain area that processes rewards) in the mutant mice and normal mice.* While normal mice exhibited an increase in dopamine in response to both fake sugar and real sugar — the reward was the sweet taste — the mutant mice only demonstrated a dopaminergic spike when consuming genuine sugar water. What they enjoyed were the calories. ...
a brand new paper, published in The Journal of Neuroscience by scientists at the University of Colorado, extends this line of thinking to that fifth taste sensation, umami. Once again, the researchers began by studying a strain of mutant mice that were utterly unable to enjoy glutamate. This is roughly equivalent to a human who doesn’t like the taste of aged cheese, or a well grilled steak, or a ripe tomato. (All of these foods are rich in umami.) While these mice didn’t seem to prefer umami at first, they eventually learned to prefer it to a non-umami alternative, suggesting that they had an alternate means of enjoying the tastant. (The scientists used water flavored with MSG, or monosodium glutamate, as the bait. MSG is just umami in concentrated form. This research helps explain why food manufacturers have been seasoning their canned soups and processed products with MSG for decades.) By looking at patterns of activity inside the mouse brain, the scientists were able to see that, although the mutant mice were missing that immediate rush of protein pleasure, they did show similar neural activity (albeit with a slight lag) in other parts of the brain responsible for representing “viscerosensory” cues. In other words, they were enjoying the sensation of protein via their digestive tract, which is why they kept on coming back to the umami water they couldn’t even taste.
This, of course, is perfectly logical. We love the flavor of denatured protein, because, being protein and water ourselves, we need it. Our body produces over 40 grams of glutamate a day, so we constantly crave an amino acid refill. In fact, we are trained from birth to savor umami: breast milk has ten times more glutamate than cow milk. Needless to say, this research is bad news for those admirable souls trying to go vegan, since umami remains mostly easily accessible in meats and cheeses. It turns out that, when we give up animal products, we don’t just need to trick the tongue into thinking that those tofu hot dogs are full of glutamate. We also need to pull off an even more difficult deception: We have to convince our stomach and intestines that what we’re eating is full of meaty amino acids ...
It results from a chemical reaction between an amino acid and a reducing sugar, usually requiring heat. ...And so we roast our coffee beans, toast our bread, and malt our barley for beer and whiskey flavor too.
The reactive carbonyl group of the sugar reacts with the nucleophilic amino group of the amino acid, and forms a complex mixture of poorly-characterized molecules responsible for a range of odors and flavors. This process is accelerated in an alkaline environment, as the amino groups are deprotonated and, hence, have an increased nucleophilicity. The type of the amino acid determines the resulting flavor. This reaction is the basis of the flavoring industry. At high temperatures, acrylamide can be formed.
In the process, hundreds of different flavor compounds are created. These compounds, in turn, break down to form yet more new flavor compounds, and so on. Each type of food has a very distinctive set of flavor compounds that are formed during the Maillard reaction. It is these same compounds flavor scientists have used over the years to create reaction flavors. ...
The browning reactions that occur when meat is roasted or seared are complicated, and occur mostly by Maillard browning with contributions from other chemical reactions, including the breakdown of the tetrapyrrole rings of the muscle protein myoglobin.
One of the conflicts I have with grass fed beef cooking lore is that somehow the idea became fixed that you can't brown such beef because it is too lean. This is nonsense and cooking that way robs the meat of some fine flavors that result from the Maillard reaction. What is true of cooking all lean meat, grass fed or not, is that it's easy to overcook it and create something more like jerky than steak. Any good cook can handle this issue easily, it's just a matter of browning at higher temperatures and then letting that heat penetrate the interior more slowly. This is good even for fatty meats, it's just that fat can mask cooking blunders to some extent.
I should also note that well finished grass fed beef is not especially lean and cooks just like other beef. And for ground beef that has its fat content controlled the only issue is the fat percentage. A 22% fat grass fed burger cooks just like a 22% grain fed burger.