Food Texture Influenced by Oral Enzyme

PHILADELPHIAFood texture is perceived differently, depending on individuals and the amount of an oral enzyme, salivary amylase, they produce, according to new research from the Monell Chemical Senses Center.

Starch is a major U.S. dietary component and comprises 40 percent to 60 percent of caloric intake, mostly from wheat, potatoes, corn and rice. Amylase enzymes secreted in saliva help break down starches into simpler sugar molecules that ultimately are absorbed into the bloodstream and influence blood glucose levels.

"Differences in starch perception likely affect peoples nutritional status by influencing their liking for and intake of starchy and starch-thickened foods," said study lead author Abigail Mandel, a nutritional scientist at Modell.

Researches analyzed enzyme levels and activity using saliva collected from 73 subjects. First, each persons saliva was mixed with a standardized starch sample and a sensor measured the enzymatic break-down of the starchs consistency. Next, enzyme and protein assays directly measured the amount and activity of salivary amylase in the saliva samples. Subjects completed continuous evaluations over a 60-second interval to rate the perceived breakdown of a starch sample while in the mouth.

Taken together, this means that foods with different starch levels will be perceived very differently by people as a function of how much salivary amylase they produce. What may seem like a thick and resistant pudding or starchy food to some may seem noticeably thin in the mouths of others," said senior author Paul A. S. Breslin, a Monell sensory geneticist.

The researchers suggest the findings may impact starch digestion and metabolism and lend insight into why some people develop metabolic diseases while others dont. Individuals who have more salivary amylase may break starchy foods down more quickly, leading to a more rapid increase of post-meal blood glucose levels.

The study also found a genetic influence on salivary amylase activity. Previous research had revealed that an individual can have anywhere from 2 to 15 copies of AMY1, the gene that codes for salivary amylase. Researchers analyzed DNA samples from 62 subjects and found that the number of AMY1 copies a person has is directly related to the amount and activity of their salivary amylase.

Combining the findings, the study demonstrated a series of relationships extending from variation in genes to individual differences in nutrient perception in the mouth.

A link from genetic variation to enzymatic proteins to altered physiology to oral perception of textures is quite novel and provides a complete story," Breslin said.