Reference Number: 6
The estimated annual intake of bread in European countries has been reported to range from 46 kg (Sweden, Great Britain, Finland and Austria) to 100 kg (Greece, Portugal, Spain and Italy) per person. Hyperglycemia (high blood sugar) is a key factor involved in the etiology of diseases related to the metabolic syndrome, its control being an important nutritional goal. Sourdough fermentation has been reported to improve nutritional properties of starch and the effect could be attributed to organic acids produced during sourdough fermentation which could ameliorate glucose disposal delaying gastric emptying or suppressing enzymatic activity.
The aim of the present study was to evaluate the possible influence of sourdough fermentation in wholemeal or white breads on starch digestibility and postprandial glycemia in healthy subjects.
Four experimental breads were obtained, prepared from two different wheat flours (whole or white) by two different leavening techniques (sourdough and with Saccharomyces cerevisiae). Products were analyzed for their starch, fiber and resistant starch (RS) content and then submitted to in vitro hydrolysis with porcine alpha-amylase. On the same breads, postprandial blood glucose was evaluated in healthy human subjects.
Both sourdough fermented breads gave glycaemic responses significantly lower (p < 0.001) than the corresponding products leavened with S. cerevisiae. On the contrary, the presence of fibre did not influence the glycaemic potential of breads. RS levels were higher in the sourdough products, whereas no differences were observed either in the rate of starch hydrolysis or in the degree of polymerization of the starch residues after the in vitro hydrolysis.
The results indicate that sourdough fermentation is a technique that is able to reduce the glycaemic response to bread and that the mechanism does not seem related to the rate of starch hydrolysis.
SIGNIFICANCE OF THIS STUDY
This study clearly demonstrates that the sourdough process is able to improve glucose response in healthy subjects. The study states that the organic acids produced by sourdough microflora during the slow fermentation process could delay gastric emptying or in other words delay the rate of digestion thereby improving glucose response. They found that dietary fibre such as resistant starch which was shown to increase in sourdough bread was less likely to influence glycemic response by slowing down the rate of digestion which is an interesting finding.