With a two-year, $300,000 grant from the U.S. Department of Agriculture, Singh and his postdoctoral student Fanbin Kong, have built a 3-D stomach on their computer. Their virtual stomach is split into a mesh of 281,602 squares; they use fluid dynamics to calculate how the rolling waves of contraction agitate the gastric acid inside it. The researchers can then place virtual particles of food inside—each with its own physical properties—and simulate how long it takes for molecule-size nutrients to seep out.
"Each food has its own microstructure," Singh says, "Whether it is porous or compacted or its cells are held together through some binding agent. Nutrients are embedded in that matrix, and unless the matrix breaks down to the point where those nutrients get released, they are going to stay embedded."
Singh, 60, who grew up in Punjab, India, is literally the rocket-scientist scientist of the food world. In his basement laboratory he proudly shows off the next multipurpose food processor he completed in 2007 for NASA's proposed manned Mars mission. Half a dozen books on his shelf are about the physics of heat transfer and another half dozen cover fluid dynamics. He is the author of the college textbook Introduction to Food Engineering, now in its third edition. After the 1993 scare set off by the deaths of four children who had eaten undercooked hamburger patties from a Jack-in-the-Box restaurant, he helped the fast-food industry with a computational model of hamburgers cooking on fast-food grills. Most recently, he has applied for a patent for a plastic clamshell package that will help strawberry growers cool down their fruits after harvest, a critical step in keeping strawberries fresh.
Not one to get lost in his mathematical universe, Singh complements his computation with laboratory studies that uses a mechanical stomach that he designed, which looks like a heavily instrumented ice cream churner. In an experiment published last year in the Journal of Food Science, Singh took raw and boiled cubes of carrots, 0.2 inch (six millimeters) wide, and placed them inside this contraption, which was inspired by similar equipment used by the pharmaceutical industry to study how drugs dissolve.
After soaking a carrot cube in simulated saliva and shaking it for 30 seconds, it was suspended inside a spinning chamber filled with gastric acid (maintained at body temperature) and plastic beads, which simulate the shearing action of other food particles. The scientists then recorded the forces on the carrot and periodically weighed it to measure how much had dissolved. The cooked carrot cube took just 20 minutes to be reduced to 50 percent of its original mass, but the raw one took a full hour. "Mom was right when she said you've got to chew your food well," Singh says, suggesting that if you're sticking to raw food you better be prepared to chew.
Meanwhile, researchers at the Institute of Food Research in Norwich, England, have built The Model Gut, a software-controlled in vitro system digestive system to study how carrots, meat, almonds and a host of other foods break down in the digestive system. Although almonds contain about 55 percent fat, lead researcher Giusy Mandalari, a biologist, says that humans absorb less than half of that largely because the oils in almonds are stored behind a tough cell wall that must be broken for our bodies to absorb them. Much of the nutritional content of almonds serves as a "prebiotic," meaning that it supports beneficial microbial communities in our large intestines. When the group compared natural almonds to blanched almonds, which have undergone a heat treatment to remove their skins, they found that blanched almonds release slightly greater amounts of nutrients.