Structure-function relationship of exopolysaccharides in relation to starch digestibility in fermented cereal matrix (Cereps)

Project Details


Funding: Academy of Finland
Collaboration: Dr. Kati Katina, Dr. Riikka Juvonen, Prof. Kaina Poutanen, VTT, Finland; Prof. Hannu Mykkänen, University of Eastern Finland
Project description:
Cereal foods are an essential component of the daily diet throughout Europe, and are a major source of dietary carbohydrates. The main carbohydrate sources in a Western diet, mainly base on white wheat flour, contain rapidly digestible starch and produce high glycemic responses. There are strong indications that the large amounts of rapidly available glucose derived from starch lead to periodic elevated plasma glucose and insulin concentrations that are detrimental to health in many contexts, including diabetes, and coronary heart disease.Means to slower starch digestibility in wheat flour based products are rare. The uses of pre-fermentation technology (sourdough process), or the addition of soluble hydrocolloids, are the two recently suggested means to reduce the glycemic index (GI). Effect of sourdough process is assumed to be due to formation of organic acids, especially lactic acid. The efficacy of hydrocolloids on starch digestibility is proposed to be in their ability to increase viscosity of the system leading to reduced rate of absorption on small intestine, or in their water-binding properties limiting water available for starch swelling and gelatinisation. Functionality of hydrocolloids is ependent on their structure and molecular weight. However, structure-function relationships of non-starch hydrocolloids in cereal matrix are not well known.A potential option to introduce non-starch hydrocolloids into the cereal matrix is to use lactic acid bacteria (LAB), which have ability to produce a variety of hydrocolloids, called exopolysaccharides (EPS). Cereal-associated LAB elaborate a large structural variety of homopolysaccharides, mostly various glucans such as dextrans and beta-glucans. Because LAB have a widespread use as starter cultures in cereal fermentations, EPS could be made available for cereal foods through the production in situ. The production of functional EPS is, however, a challenge due to complexity of the system.The main objective of the project is to understand the role of the structure and size of EPS in the physical properties and digestibility of starch in fermented cereal matrix. In particular, our aim is to understand the influence of the properties of EPS on the gelatinization of starch, and redistribution of water between components of cereal matrix, and link this information starch digestibility both in vitro and in vivo. The objective is also to establish possible synergistic effects of microbial EPS and fermentation-induced changes on the state and digestibility of starch, and the production of EPS with functional structures in cereal matrix. The main methodological objective is to quantify and characterize microbial EPS produced in cereal matrix. The detailed knowledge on the structure-function relationship and the physiological effects of EPS is needed to tailor starch digestibility and is basis for highly advanced fermentation technology.
Effective start/end date01/01/200931/12/2011

Fields of Science

  • 416 Food Science
  • 116 Chemical sciences