What makes a meal satisfying? The body recognizes nutrients and calories, but the satisfaction of a meal comes from the entire eating experience, including the taste, aroma, and texture of the food. A study conducted by Nestlé scientists shows that oral sensory stimulation may be more important than the volume of food in the stomach for the regulation of food intake.
In the first part of the study, scientists wanted to understand how sensory properties of hot savory foods and meals influence eating behavior and food intake. The study, performed in collaboration with Wageningen University, The Netherlands, and published in Appetite, tested the oral processing characteristics (e.g., chew rate, bite size) of 35 solid, savory foods that often comprise hot meals. Examples included a variety of vegetables (e.g., boiled potatoes, broccoli, carrots), meat and prepared foods (e.g., chicken, tofu, lasagna, pizza), and snack foods (e.g., tortilla chips, fish fingers).
Study volunteers were asked to eat a standard 50 g amount of each food item, seven of which were tested over five consecutive days. Video recordings of the volunteers eating the food were then used to calculate the eating rate (g/min), chew rate (chews/min), average bite size (g/bite), average chews/bite, and overall oral duration time (secs) for each of the 35 test foods.
The data revealed surprising differences in the way foods were consumed. For example, the average number of bites for each food varied from five bites (raw tomatoes) to 33 bites (tortilla chips)—a 6-fold difference. There were also large variations between the number of chews, ranging from 27 chews for mashed potatoes, to 488 chews for tortilla chips. Softer foods such as mashed carrots, lasagna, and canned tomatoes were eaten in larger bite sizes with fewer chews per bite, resulting in a much faster eating rate (g/min).
The researchers concluded that foods consumed in smaller bite sizes that were chewed longer resulted in slower eating rates and higher expected fullness among study volunteers.
In the follow-up study, also published in Appetite, a test meal of steak and gravy, carrots, and potatoes was adapted into whole and pureed textures with gravy of high and low flavor intensity. The meal was served to four groups of volunteers to consume until they were comfortably full. Food intake was measured and compared across each group and meal condition, and the duration of each individual’s mealtime was recorded to enable comparison of eating rates. Volunteers rated their perception of fullness before and after the meal.
The researchers found that participants that ate whole vegetables and steak consumed about 10% less than those who ate the mashed vegetables and steak pieces. The difference in gravy taste intensity resulted in a higher intake only with the mashed meal. Overall, the mashed meal was consumed about 20% faster than the whole meal—the equivalent of an extra 10 g/min more of food eaten.
“The evidence from these studies provides new insights into how different foods may impact eating behaviors, such as bite size and chewing time. These, in turn, can also impact feelings of fullness and food intake,” said Ciarán Forde, Nestlé Scientist leading the studies.
Study 1 abstract
Study 2 abstract