High insoluble fibre content increasesin vitrostarch digestibility in partially baked breads

Effect of fibers on starch structural changes during hydrothermal treatment: multiscale analyses, and evaluation of dilution effects on starch digestibility

BACKGROUND

Dietary fibers (DFs) may influence the structural, nutritional and techno-functional properties of starch within food systems. Moreover, DFs have favorable effects on the digestive system and potentially a lower glycemic index. These potential benefits may change depending on DF type. Starch processed in the presence of soluble and insoluble fibers can undergo different structural and functional changes, and the present study investigated the effects of short-chain and long-chain inulin and cellulose on the structural and digestive properties of wheat starch.

RESULTS

The combined use of differential scanning calorimetry, Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) provided insights into the structural changes in starch and inulin at different levels. Short-chain and long-chain inulin had higher water retention capacity and a potential to limit starch gelatinization. The FTIR results revealed an interaction between starch and inulin. Scanning electron microscopy analysis showed morphological changes in starch and inulin after the hydrothermal treatment. Cellulose fiber was not affected by the hydrothermal treatment and had no influence on starch behavior. The structural differences observed through XRD, FTIR and scanning electron microscopy analyses between starch with and without inulin fibers did not significantly impact starch digestibility, except for the dilution effect caused by adding DFs.

CONCLUSION

The present study highlights the importance of utilizing different analytical tools to assess changes in food samples at different scales. Although short-chain and long-chain inulin could potentially limit starch gelatinization, the duration of the heat treatment (90 °C for 10 min) was sufficient to ensure complete starch gelatinization. The dilution effect caused by adding fibers was the primary reason for the effect on starch digestibility. © 2024 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Mitigation of acrylamide formation in wood oven baked pizza base using wholemeal and refined wheat flour with low free asparagine content: considerations on fibre intake and starch digestibility

BACKGROUND

In wheat-derived bakery products, the quantity of free asparagine (fAsn) has been identified as a key factor in acrylamide (AA) formation. Based on this assumption, four varieties of common wheat (Triticum aestivum L.), Stromboli, Montecarlo, Sothys and Cosmic, selected for their different fAsn content inside the grain, were studied to evaluate their potential in the production of pizza with reduced AA levels. To this purpose, wholemeal and refined flours were obtained from each variety.

RESULTS

The fAsn content ranged from 0.25 to 3.30 mmol kg-1, with higher values for wholemeal flours which also showed greater amount of ash, fibre and damaged starch than refined wheat flours. All types of flours were separately used to produce wood oven baked pizza base, according to the Traditional Speciality Guaranteed EU Regulation (97/2010). AA reduction in the range 47-68% was found for all the selected wheat cultivars, compared with a commercial flour, with significantly lower values registered when refined flour was used. Moreover, refined leavened dough samples showed decreased levels of fAsn and reducing sugars due to the fermentation activity of yeasts. Furthermore, it was confirmed that pizza made with wholemeal flours exhibited lower rapidly digestible starch (RDS) and rapidly available glucose (RAG) values compared to that prepared with the refined flour.

CONCLUSION

This study clearly shows that a reduced asparagine content in wheat flour is a key factor in the mitigation of AA formation in pizza base. Unfortunately, at the same time, it is highlighted how it is necessary to sacrifice the beneficial effects of fibre intake, such as lowering the glycaemic index, in order to reduce AA. © 2024 Society of Chemical Industry.

Study of Physico-Chemical Properties of Dough and Wood Oven-Baked Pizza Base: The Effect of Leavening Time

The research objective was to investigate the morpho-rheological, chemical, and structural changes of dough and Neapolitan pizza TSG as the leavening time varies and to evaluate their effects on the digestibility of starch and on the formation of acrylamide during baking. Pizza dough leavening was monitored for 48 h at 22 °C/80% RH, and the analyses were conducted at selected leavening times (0, 4, 8, 16, 24, and 48 h). It was observed that in 30 h the volume tripled and the viscoelastic dough relaxed in the first 4 h, as evidenced by the lower value of the relaxation percentage “a” and the higher rate of decay “b”, associated with a high value of the compression work, indicating the presence of a very strong gluten mesh. In the following hours, the dough lost elasticity, and in fact, the G’ modulus decreased due to the weakening of the weak interactions between the gluten proteins and the starch. This suggests that a long leavening improved the extensibility of the pizza disc, facilitating the action of the pizza maker. Thermal (TGA and DSC) and morphological (SEM) analyses evidenced the highest water removal rate from the dough, a wider starch gelatinization temperature range, a ∆H of 0.975 ± 0.013 J/g, and a more open and weak gluten structure in dough balls leavened for 16 h. As the leavening time increased, both dough and pizza base samples showed an increase in reducing sugars and free amino groups, while the rapidly digestible starch decreased in the dough following the metabolism of the yeasts and increased in the pizza base due to the starch gelatinization that occurs during baking, which makes it much more susceptible to α-amylase. Finally, the levels of acrylamide remained at the same values despite the higher availability of reducing sugars and its precursors during leavening.

Chestnut peels and wheat bran at different water level influence the physical properties of pan bread

In breadmaking, dietary fibres are used to improve the nutritional quality of the final products; on the other hand, they may affect the physical and sensory properties. This work aimed to the evaluate, on pan breads, the effect of substituting 3 g of wheat flour with an equivalent amount of fibre rich ingredients: chestnut peels (CP) or wheat bran (WB), in comparison to a traditional wheat bread formulation (C). The effect of four levels of added water (54, 60, 66, 71 g/100 of flour) was also tested. The fibre content of CP (33%) and WB (42%) affected their water binding capacity and, consequently, the quality of the final loaves, according to the different water addition levels. In bread crumb, water content and water activity increased proportionally to the water addition levels, being instead in the crust also affected by the presence of fibres: lower water retention capacity was observed for CP, in comparison to WB and C. The loaf volume resulted higher for C in comparison to WB and CP, in relation to the larger dimensions of the crumb pores, probably due to the interfering effect of fibres during the development of the gluten network. Crumb hardness resulted higher for C at low water addition levels, being instead higher for CP at high water addition levels. CP showed a darker and redder colour, than both WB and C bread, for the presence of the brown pigments carried by chestnut peels. PCA analysis confirmed that more water is required for both the fibre-enriched breads to show characteristics similar to the control loaves.

Enhancing the Nutritional Properties of Bread by Incorporating Mushroom Bioactive Compounds: The Manipulation of the Pre-Dictive Glycaemic Response and the Phenolic Properties

Wheat bread supplemented with mushroom powder from three different species of mushrooms was investigated in terms of starch characteristics (content, gelatinisation, and digestibility) and antioxidant capacities. The decrease in total starch contents, and increase in phenolic contents of the breads, were associated with increased mushroom powder contents. Mushroom inclusion reduced the rate of reducing sugar released over 120 min in an in vitro digestion compared to the control sample, implying a lower area under the curve (AUC) value with the inclusion of mushroom powder and a potentially lower predicted glycaemic response of the bread. Mushroom powder incorporation also enhanced the DPPH radical scavenging assay and oxygen radical absorbance capacity (ORAC) compared to control bread. The action of the addition of different mushroom powders on the bread crust and crumb microstructure properties was also studied. Mushroom powder altered the internal microstructure of the bread crust and crumb by affecting the interactions between starch and the other components of the bread. Overall, this shows that mushroom powder could be added to bread to deliver health benefits to consumers.

Development of healthy gluten-free crackers from white and brown tef (Eragrostis tef Zucc.) flours

This study evaluated the effect of inclusion of two types of tef flours (white and brown) at different levels (25, 50 and 100 %, total flour) on the nutritional (proximal and mineral composition), in vitro bioactive (antioxidant capacity and starch digestibility) and sensory properties of rice-tef crackers. The aim was to formulate a gluten-free product with nutritional and healthy benefits, and acceptable for consumers. Results showed than crackers enriched with white tef had a significant (p ≤ 0.05) higher concentration of all the minerals tested, except for calcium and manganese, compared to brown tef. Iron content of white tef was almost twice that of brown tef, and copper and magnesium increased from 0.12 mg/100 g and 39.2 mg/100 g in control crackers to 0.56 mg/100 g and 197 mg/100 g in white tef crackers (WT 100%), respectively. Moreover, white tef flour and crackers showed significantly higher antioxidant activity than rice or brown tef counterparts. Formulation with tef flour significantly contributed to a reduction of the rapidly available glucose and rapidly digestible starch of crackers.

Physicochemical Properties of Dough and Steamed Bread Made from Regular and Whole Wheat Flour

Mantou (steamed bread) is a Chinese fermented wheat product that is cooked in steamer. Whole wheat flour (WWF) is healthier than regular wheat flour (WF). This study investigated the physicochemical properties of dough and mantou made from WF and/or WWF. Results showed that the substitution of WF by WWF resulted in stiffer and less extensible dough. Both Peleg–Normand and Wiechert models fitted well to the stress relaxation data of mantou. Increasing the substitution level of WWF led to the decrease of k1 and k2 in Peleg–Normand model as well as λ1 and λ2 in Wiechert model. Mantou with 100 % WWF had significantly higher hardness but lower cohesiveness and specific volume than regular mantou. However, free and bound phenolics and DPPH radical scavenging capacity of mantou obviously increased with the amount of WWF. Mantou with 25 % WWF had the highest overall sensory score among all mantous tested.

Can bread processing conditions alter glycaemic response?

Bread is a staple food that is traditionally made from wheat flour. This study aimed to compare the starch digestibility of western baked bread and oriental steamed bread. Four types of bread were prepared: western baked bread (WBB) and oriental steamed bread (OSB), modified baked bread (MBB) made with the OSB recipe and WBB processing, and modified steamed bread (MSB) made with the WBB recipe and OSB processing. MBB showed the highest starch digestibility in vitro, followed by WBB, OSB and MSB. A similar trend was observed for glycaemic response in vivo. MBB, WBB, OSB and MSB had a glycaemic index of 75±4, 71±5, 68±5 and 65±4, respectively. Processing differences had a more pronounced effect on starch digestibility in bread, and steamed bread was healthier in terms of glycaemic response. The manipulation of processing conditions could be an innovative route to alter the glycaemic response of carbohydrate-rich foods.