San Diego Fat is plentiful. Fat is cheap. What's more, it's "energy dense," according to Dr. Richard Zinn, a professor of animal science at the 280-acre University of California at Davis Desert Research and Extension Center just outside the wasteland-defying patches of green that surround El Centro. This combination makes fat an attractive food supply to feedlot operators, who want to "maintain an acceptable rate of production and also, produce a carcass that has characteristics a consumer wants," while spending as little as possible. Thanks in part to the center's work in researching the effects of supplemental fat on feedlot cattle, "probably 80 percent of the cattle on feed are receiving fat" as part of their diet.
"The fat that we're talking about, mostly, it's made up of restaurant grease," explains Zinn, a square-jawed, self-contained man with rimless glasses and close-cropped hair. "It's what McDonald's and Burger King and all those other restaurants use. They cook a few french fries for a while, then that fat that's left over, you can't dump that down the drain. So, they'll put it in barrels, and then those barrels are collected by a company that will recycle the fat, filter it and centrifuge it. Then what we call the yellow grease will be sent back out to the feed lots as a feed ingredient."
The fat arrives in liquid form by train car or truck, 50,000 pounds per load. That's enough to keep the fat level in the feed for the center's 20,000 head of cattle at roughly 4 percent for three or four days. In all, Zinn estimates that 40,000 tons of fat (at $300 a ton) are delivered to the center each year, with each head of cattle munching about 140 pounds of the stuff before its journey to the slaughterhouse. "We consume all of the grease that's produced in San Diego and L.A. right down here in this feedlot," he says, noting that some of it does go to poultry.
The trucks pump their yellowish cargo into the center's four fat tanks, tanks which, thanks to the insulation that has been applied to their exteriors, have an appropriate pasty-white, lumpy cellulite look. Another tank holds molasses. The tanks stand outside a small barn; inside is a maze of pipes, pumps, and containers. Come mixing time, a person standing at the control box pushes a button and pumps the warm fat into a weigh hopper, then into a perforated bar, which sprays it down onto the feed.
Because it's energy dense, "fat happens to be one of the most important by-products that are fed back." Others include "Wonder bread and all the stale bread from the stores, chocolate chips that are turning white, and chewing gum that's gotten hard," along with more expected leftovers, such as rice straw. Zinn anticipates the consumer's hesitancy to imagine such a diet producing "carcass characteristics a consumer wants," such as lean meat, and is quick to reassure. "We go over to the packing plant and follow the cattle through the slaughter and evaluate the carcass. We look at fat distribution, take samples and measure composition of fat. There was a little bit of an increase in kidney, pelvic, and heart fat, which is what you'd expect, but it's small. It had very little effect on carcass composition."
Carcass composition is what brought me here: is science working to build the consumer a better steak? Zinn says yes, telling tales of experiments being done at Oklahoma State wherein cattle are fed "very high levels of vitamin D during the late finishing phase. It increases the absorption of calcium into the meat, and that calcium helps stabilize some of the enzymes that begin to break down the protein and make the meat more tender. They can increase the tenderness maybe 15, 20 percent by that practice." The practice is still experimental because the vitamin D may have a negative effect on "feed efficiency -- average daily weight gain." Also experimental is injecting the carcass with calcium after slaughter.
The use of enzymes to tenderize meat is not a new idea; what's new is the timing. "Those meat tenderizers you sometimes see people put on their steak are protolytic enzymes that begin to break down the tissues. Aging will do the same thing, but we don't age meat too much anymore. There's still some of that going on in fancy restaurants, but...the taste of aged meat is sometimes a little bit unacceptable, because it has that riper, fruitier flavor. Feeding high levels of vitamin D is kind of like enhanced aging without the side effects of microbial growth and the flavors that it produces -- oxidized fats and that type of thing." While your steak is still walking around, it's gearing up to decompose.
Why the emphasis on tenderness, as opposed to flavor? In his Ethics, Aristotle claims that most people, or at least the intemperate, derive enjoyment not from flavor, but from touch, "and it is in view of this that a certain gourmand prayed that his throat grow longer than that of a crane, thinking that by extended contact he would be pleased."
Zinn supports Aristotle's claim. "When you evaluate meat, you evaluate it on four criteria: tenderness, juiciness, flavor, and overall acceptability. Tenderness accounts for about 90 percent of the overall acceptability of the cut. It could have no flavor, but if it was tender, people are going to rank it real high. You want a piece of meat that's tender and juicy and flavorful, but when it gets right down to it, the average consumer, the above-average consumer, wants tender meat." He cites the results of tastings done by trained taste panels, a group of feedlot operators, and his own tongue as evidence.
This accounts for science's recent efforts to come up with a system for predicting the tenderness of meat. Right now, part of meat grading is based on marbling, the amount of intramuscular fat in the carcass. Prime, "the top one or two percentile in degree of marbling," tops the list, followed by choice, "anything between a small amount and an abundant amount," and select, "between trace amounts and slight." Zinn laments this system, saying that "marbling is not a good predictor -- it's not correlated with tenderness. Marbling enhances the juiciness of meat, [and] those fats carry the seasoning throughout the meat," which improves flavor. But when it comes to tenderness, marbling won't help.