Cereal foods: Structure influences nutritional properties and satiety, VTT research suggests

15 Jun 2018 --- The structure of cereal foods has an impact on their digestion process and satiating capacity, a doctoral research conducted by Saara Pentikäinen, a research scientist at VTT in Finland, has found. Foods that consumers envision to be more filling produce higher feeling levels of satiety and foods that hydrate easily may also produce higher feelings of satiety. Furthermore, nutrients dissolved from the cereal foods into saliva and the body are higher in rye than wheat bread. Cereal foods are a significant source of carbohydrates, protein, vitamins and minerals and they can provide over half of all the dietary fiber (DF) depending on the population.

The research sought to study how breads with different structures disintegrate while being chewed (the first step of digestion), what kind of compounds dissolve from the bread matrices to saliva and how this cereal food structure influences post-eating satiety.

It was observed that rye bread disintegrated into smaller particles than wheat breads while being chewed. However, due to the influence of salivary amylase (the enzyme that processing starch to sugars), the starch in rye bread tended to hydrolyze at a slower rate than the starch from wheat bread. 

The study gave new information on the compounds that were dissolved to saliva already while being chewed. Specifically, peptides and amino acids were dissolved from rye breads and sugars from wheat bread. Essentially, rye bread, due to their structural properties, offer more nutrition that wheat bread.

Not only composition but also the structure of food affects its nutritional properties. For example, the carbohydrates of porous wheat hydrolyze much faster in digestion than the carbohydrates of dense pasta, causing a rapid jump in the blood glucose level. Porridge with whole rye kernels is more effective than rye porridge with milled kernels to maintain satiety, for example.

Surprisingly, the food structures that required the most intense chewing did not result in higher feelings of satiety. However, other factors such as expectation and liking did contribute to satiety.

“Expectations about the satiating capacity of food seemed to be self-fulfilling prophecies and less pleasant food portions resulted in enhanced satiety,” says Pentikäinen in her research.

Furthermore, hydration played a role in satiety. Foods with potentially good hydration capacities (porous products, bread and extruded puffs) or those, which were ingested as partly hydrated (rye smoothie, juice with oat bran) enhanced some aspects of satiety compared to those products likely hydrating at a slower rate (dense flakes, oat bran biscuit).

“Breads baked with different raw materials and methods had distinct structures and were digested differently already in mouth and meals with similar ingredients but different structures resulted in distinct responses of some aspects of satiety. Therefore, understanding is needed about not only the chemical composition of foods but also the formation of 67 structures in food processing and the disintegration of structure in digestion,” she says. 

Concerning the food industry, speaking to NutritionInsight Pentikäinen suggests that products should manufacture foods “that have satiety supporting structures, for example, including dietary fibers and whole grain liquid matrices to be beneficial.”

Furthermore, as the expectation of fullness plays a significant role, manufacturers should package and market foods in such a way that consumers expectation toward the satiety of the food is raised.

By Laxmi Haigh