Impact of texture modification and dietary fibre content ...

4th International Dietary Fibre Conference ICC 2009, July 1st-3rd, Vienna, Austria

Impact of texture modification and dietary fibre content on both the glycemic index and the acceptability of French bread L. Saulnier1, M. Ducasse1, H. Chiron1, G. Della Valle1, C. Martin2, S. Issanchou2, X. Rouau3, S. W. Rizkalla4- [email protected]. 1

INRA UR-1268 BIA, Nantes, France ; 2INRA UMR 1129 FLAVIC, INRA-ENESADUniversité de Bourgogne, Dijon, France; 3INRA UMR 1208 IATE, INRA-CIRAD-SUPAGROUniversité de Montpellier 2, Montpellier, France ; 4INSERM U872, CRNH-Ile de France, Department of Nutrition, Pitié Salpêtrière, Paris, France.

Abstract The texture, is an essential element of the acceptability of the bread by the consumers, and has strong impact on the glycemic index. The elaboration of denser breads led to a reduction of the glycemic index. Among these breads, those who have increased content in dietary fibre, are generally not well accepted by the consumers. However, traditional bread making process allowed obtaining a « baguette » corresponding to nutritional expectations, with increased dietary fibres content and reduced glycemic index, which was also well appreciated when tasted by the consumers. Keywords : Dietary fibre, Glycemic Index, Bread texture, Consumer expectations. Introduction A more well-balanced diet with emphasis on increased consumption of complex carbohydrates with low glycemic index is a major nutritional goal for public health. Cereal products, and among them bread with its basic commodity, can significantly contribute to this balance. In France, French baguette represents a dominant share of the bread market. The French baguette, however, exhibits a high glycemic index and is generally made from white flour with low dietary fibre content. It is expected to improve nutritional quality of this bread by increasing its dietary fibres content and decreasing the postprandial blood glucose peaks after their consumption in humans. However the public health benefit of a French “baguette” with improved nutritional properties cannot be met if the sensory preferences and the behaviours of the consumers are ignored. A three-year interdisciplinary project was launched by INRA in association with industrial partners with the aim to develop new “baguette” with a lower glycemic index and higher dietary fibre content. In this paper, we report the main results of the project on : - the effects of texture modification and dietary fibre enrichment on bread glycemic index in healthy individuals - the acceptability of this new “baguette” by a consumer panel. Materials and methods Breads were prepared using French bread-making processes: “baguette” courante (current French, CF) or “baguette” tradition (Tradition French, TF). These two types of bread were enriched in fibres (7.5% incorporation on flour weight basis), giving CF baguette enriched with fibres (CF+F) and TF enriched with fibres (TF+F). In addition two other breads were made with a reduced yeast level (1/3 reduction) giving dense CF “baguette” (CFD), and traditional French Dense enriched in fibre (TFD+F). Finally, sour dough fermentation was used with enriched fibre flour (SD+F). The source of fibre was “shorts” an industrial milling fraction that was provided by Girardeau Mills (France). The composition in the different tissues of the grain in this industrial milling


fraction was assessed at INRA- IATE Montpellier as previously described (Hemery et al., 2009). Shorts were composed of starchy endosperm (20%), aleurone layer (29%), intermediate layer (38%) and pericarp (13%). The dietary fibre content of shorts was 48 % (g/100g), mainly as insoluble fibre. Density of bread was measured by displacement of rapeseed seeds. Dietary fibre content was determined according to AOAC 985-29 method. Arabinoxylan (AX) content in the bread were determined after acid hydrolysis as the sum of arabinose and xylose as previously described (Ordaz and Saulnier, 2005). Glycemic Index were measured on 12 healthy individuals as previously described (Rizkalla et al., 2006) Consumers expectations were tested on a panel of 128 individuals at INRA Dijon as previously described (Martin et al., 2008). The seven experimental breads were tested together with seven commercial “baguette” representative of the French market. Results and discussion Effect of texture modification and dietary fibre enrichment on bread glycemic index The addition of fibres is known to influence dough behaviour and bread quality (Cavella et al., 2008). We have shown that the effect of wheat insoluble fibre on dough development is accounted for by their capacity to retain water, whatever their origin and percentage of addition (Bonnand-Ducasse et al., 2009). We have therefore chosen to use shorts as a source of fibre easily available for future product development. The seven types of bread prepared are shown on Fig.1. The addition of flour led to enrichment of about 50% of the dietary fibre content in the bread (Table 1). Arabinoxylans that are the main component of wheat grain cell walls, were well correlated with the fibre content of breads. As expected addition of fibre had strong effect on bread texture, leading to a reduced volume, e.g. a higher density (Fig. 1, Table 1). The bread-making process had also a strong impact on crumb texture. Reducing level of yeast, sour dough fermentation or using “tradition” process lead to denser breads with an irregular texture of the crumb. Texture had a strong impact on the nutritional quality of the bread and in particular on its glycemic index (Table 1, Fig. 2). Increasing bread density from 0.16 to 0.32, either by modifying bread making process or by incorporating dietary fibres, led to a decrease in the glycemic index from 75 to 55%. Interestingly, there is a strong correlation between GI index and the density of the bread, whatever the level of addition in dietary fibre (Fig. 2). Acceptability of new “baguette” by consumer panel A panel of 128 consumers evaluated the seven experimental breads. The experimental breads were tested with 7 commercial products that were representative of the commercial market for “baguette” in France. Two set of questions were asked: first after visual examination of the bread: “do you think you would like this bread” (Fig. 3A); second after tasting the bread: “did you like the bread you have tasted” (Fig. 3B). Breads enriched with dietary fibres were generally less appreciated by the consumers, in particular in their expectations based on the appearance of the entire baguette. However, traditional bread making process allowed obtaining « baguette » corresponding to nutritional expectations, with increased dietary fibres content and reduced glycemic index, which was also well appreciated when tasted by the consumers. Conclusions We showed that the elaboration of denser breads, either enriched in dietary fibre or not led to a reduction of the glycemic index. Complementary results, not presented here, indicated that the extent of starch gelatinization (in crumb or crust) was not different between the different


breads. The explanation for a reduced GI for denser bread could lie to a lower speed of transit in the intestinal tract. As the matter of fact, denser bread exhibits higher mechanical properties that affect chewing time and may delay the ingestion of this type of product. The increase of bread density is therefore an efficient way to decrease glycemic index. However, the dense bread realized in this study did not exhibit the same texture, and only dense breads elaborated according to the “tradition” process were well accepted by consumers. Sensory evaluation indicated that the irregular texture of the crumb was highly correlated with consumer’s preference. Acknowledgements This interdisciplinary project was launched in 2005 and was financed within the framework of INRA's food research programme. It was led in narrow collaboration with the National Association of the French Milling, ARVALIS, the Biofournil company, the Girardeau mills and the pole of food-processing competitiveness VITAGORA. References Bonnand-Ducasse M., Della Valle G., Lefebvre J., L. Saulnier L. (2009) Effect of wheat dietary fibres on bread dough development and rheological properties. Submitted for publication in J. Cereal Sci. Cavella, S., Romano, A., Giancone, T., Masi, P., 2008. The influence of dietary fibres on bubble development during bread making. In: Campbell, G.M., Scanlon, M.G., Pyle, D.L. (Eds.), Bubbles in Food 2- Novelty, Health and Luxury. Eagan Press, St Paul, USA, pp. 311-322. Hemery, Y., Lullien-Pellerin, V., Rouau, X., Abecassis, J., Samson, M.-F., Aman, P., Von Reding, W., Spoerndli, C.c., and Barron, C. (2009). Biochemical markers: Efficient tools for the assessment of wheat grain tissue proportions in milling fractions. J. Cereal Sci. 49, 55-64. Martin C., Courcoux P., Chiron H., Issanchou S. (2008) Caractéristiques sensorielles clés de l’acceptabilité d’un pain de type baguette française. Industrie des Céréales, 159 , 6-19. Ordaz-Ortiz, J.J., and Saulnier, L. (2005). Structural variability of arabinoxylans from wheat flour. Comparison of water-extractable and xylanase-extractable arabinoxylans. J. Cereal Sci. 42, 119-125. Rizkalla S.W., Laromiguiere M., Champ M., Bruzzo F., Boillot J. and Slama G. (2006) Effect of baking process on postprandial metabolic consequences: randomized trials in normal and type 2 diabetic subjects. European Journal of Clinical Nutrition, 1–9.


Legends To Figure Fig. 1: View of the seven type of French “baguette”. Fig. 2: Glycemic Index as as function of bread density Fig. 3: Consumer’s expectation: visual aspect (A) and tasting (B) Experimental “Baguette”: CF: current French baguette; CF+F: CF enriched with fibres; CFD: CF dense (1/3 yeast); TF: traditional French baguette; TF+F: TF enriched with fibres; 6)TFD+F: TF enriched in fibre and dense (1/3 yeast); SDF: sour dough baguette enriched with fibre. Commercial “baguette”: C1-C7 light gray bars: better than mean, white bars: mean; dark gray bars: less than mean; (p