Effects of sourdough and dietary fibers on the nutritional quality of breads produced by bake-off technology

The aim was to evaluate the effect of sourdough and dietary fiber addition, as well as partially baked frozen (PBF) technology, on biological value of proteins, lipid profile, and some minerals content in selected tissues of rats.In all breads, the limited amino acid was lysine. Proteins of PBF conventional and PBF breads with an addition of dietary fiber (PBF DF breads) had significantly higher Chemical score and Essential amino acid index in comparison to proteins of Direct bread (P < 0.05). Protein digestibility corrected amino acids score was significantly lower in Direct DF and PBF improved breads (P < 0.05).Addition of fiber to Direct and PBF bread decreased significantly total digestibility of protein compared to all groups (P < 0.05).Concentration of calcium was significantly lower in liver of rats fed with Direct sourdough and PBF improved breads in comparison to rodents fed with Direct bread. The concentration of iron was significantly higher in liver of animals fed with Direct bread. The highest level of calcium in femoral bones of rats was shown in groups fed with PBF conventional bread. The lowest level of iron was measured in femoral bone of rats fed with PBF sourdough bread in comparison to the rest of the experimental groups.     

Scouting the application of sourdough to frozen dough bread technology

The use of sourdough, even in combination with cryoprotectant (skim milk, sucrose and trehalose), conventional additives (guar gum, diacetyl tartaric acid esters of monoglycerides, ascorbic acid), honey or fructose and glucose, in frozen dough technology was investigated. After frozen storage, the leavening performance of doughs, and the hardness and texture of breads were compared to those of an unfrozen dough, and to those of a conventional frozen dough. All frozen doughs showed a longer fermentation time and a lower volume increase, with respect to unfrozen dough. When sourdough was combined with cryoprotectant, honey or both, the leavening performance improved compared to the use of sourdough alone. Compared to the conventional frozen dough, higher leavening performance was reached combining sourdough with cryoprotectant alone or together with honey. Sourdough combined with honey, fructose and glucose, honey and cryoprotectant, or conventional additives decreased bread hardness compared to the unfrozen dough bread and to the conventional frozen dough bread. Independently from the use of sourdough, conventional additives allowed to reach a specific volume not significantly different from that of unfrozen dough bread, and breads containing honey were characterized by low values of hardness and by high values of red index.     

Staling of frozen partly and fully baked breads. Study of the combined effect of amylopectin recrystallization and water content on bread firmness

Partly baked (PB) and fully baked (FB) breads were frozen at −18 °C for 7, 21, 63, 92, 126 and 188 d and were analysed after its thawing (FB) or thawing and final baking (PB). The starch retrogradation, the moisture content and the firmness were measured as properties closely related to the aging of bread. The temperature of glass transition of the maximally freeze-concentrated state, T_g′, was also measured and established in (−18 ± 0.8) °C. This value cannot ensure molecular immobility in both types of bread during its frozen storage at (−18 ± 2) °C. Consequently, the rearrangements of starch component molecules, needed for its recrystallization and for the diffusion of water during frozen storage, could take place and could justify the changes observed in the bread. PB bread showed a significant decrease in firmness with frozen storage, while the firmness of the FB bread did not change significantly, although an increase when compared with the control, not frozen bread, was detected. A regression study led to the conclusion that the combined effect of starch component crystallization and water loss could explain the firming evolution and that both variables exerted an effect of similar intensity on crumb firmness.     

Glycaemic response to frozen stored wheat rolls enriched with inulin and oat fibre

The aim of this study was to examine the effect of dietary fibre addition to partially baked and frozen wheat rolls on the glycaemic index (GI).Healthy humans volunteers (n = 15) took part in the study. They were asked to attend six times in the early morning, over three weeks. Each tested four types of wheat rolls – two without dietary fibre addition: (1) fully baked, non-frozen (FBNF), (2) partially baked and frozen (PBF); and two with the addition of 10% dietary fibre: (3) fully baked, non-frozen (FBNF + F), (4) partially baked and frozen (PBF + F). Glucose solution was used as a reference food and tested twice. Blood glucose concentrations were measured before consumption, as well as at 15, 30, 45, 60, 90 and 120 min after the start of the meal. Dietary fibre consisted of oat fibre (75%) and of inulin (25%).It was concluded that both factors (freezing and fibre), applied to the wheat rolls at the same time, reduced statistically significantly (P ≤ 0.05) the glycaemic index by 34% – PBF + F (GI = 53 ± 7) compared to control – FBNF roll (GI = 87 ± 11). This effect was not observed when fibre supplementation or frozen storage were applied separately.     

Influence of formulation and process on the aromatic profile and physical characteristics of bread

This work consisted of two complementary sets of experiments in which breads differing in their recipe and/or process were characterised according to their odorant perception, volatile compound composition and physical properties. The results revealed that commercial partially baked and/or partially baked frozen breads were characterised by a different odour compared to commercial conventional, fully baked frozen and frozen dough breads, which were perceived similarly. These differences were explained by their variable aromatic composition. By analysing breads based on the same recipe but from different processes, it was demonstrated that adding a freezing stage before dough proofing or at the end of the conventional process, as well as after partial baking, did not influence bread aroma. Likewise, partial baking had no effect on bread odour and aromatic profile. Thus, the aromatic differences between commercial conventional, fully baked frozen and frozen dough breads on the one hand, and commercial partially baked breads on the other hand, were due to their different formulations. Concerning bread physical properties, the recipe also influenced bread crust/crumb ratio and density. Moreover, adding a partial baking stage to the process led to breads with a more compact crumb.     

Effects of Amylose/Amylopectin Ratio and Baking Conditions on Resistant Starch Formation and Glycaemic Indices

The possible improvement of the nutritional properties of starch in barley flour-based bread by using barley genotypes varying in amylose content (3–44%) was evaluated. Breads were made from 70% whole-meal barley flour and 30% white wheat flour. Test breads were baked from waxy barley (WB), ordinary barley (OB), ordinary Glacier barley (OGB) and high-amylose barley (HAB). Each bread was baked either at conventional baking conditions (45 min, 200 °C) or at pumpernickel conditions (20 h, 120 °C). A white wheat bread (WWB) was used as reference. The resistant starch (RS) content and rate of starch hydrolysis were measuredin vitro. The glycaemic index (GI) and the insulinaemic index (II) of the high-amylose breads were determined in healthy subjects. The amount of RS (total starch basis) varied from <1% (WB) to approximately 4% (HAB) in conventionally baked bread, and from about 2% to 10% in the corresponding long-time/low-temperature baked products. The long-time/low-temperature baked HAB displayed a significantly lower rate of starch hydrolysisin vitrocompared with WWB and reduced the incremental blood-glucose response in healthy subjects (GI=71). In contrast, the GI of the conventionally baked HAB was similar to that for WWB. It is concluded that a barley flour-based bread of low GI and high RS content can be obtained by choosing high-amylose barley and appropriate baking conditions.     

Wholemeal wheat bread: A comparison of different breadmaking processes and fungal phytase addition

The effect of different breadmaking processes (conventional, frozen dough, frozen partially baked bread) and the effect of the storage period on the technological quality of fresh wholemeal wheat breads are investigated. In addition, the impact of the exogenous fungal phytase on the phytate content was also determined. Results showed that breadmaking technology significantly affected the quality parameters of wholemeal breads (specific volume, moisture content, crumb and crust colour, crumb texture profile analysis and crust flaking) and frozen storage affected to a different extent the quality of the loaves obtained from partially baked breads and those obtained from frozen dough, particularly crust flaking. Freezing and frozen storage of wholemeal bread in the presence of fungal phytase decreased significantly the phytate content in whole wheat breads. The combination of fungal phytase addition, breadmaking process and frozen storage could be advisable for overcoming the detrimental effect of bran on the mineral bioavailability.     

Improving the quality of nutrient-rich Teff (Eragrostis tef) breads by combination of enzymes in straight dough and sourdough breadmaking

The growing interest in the benefits of wholegrain products has resulted in the development of baked products incorporating less utilised and ancient grains such as, millet, quinoa, sorghum and teff. However, addition of wholegrains can have detrimental effects on textural and sensory bread product qualities.Enzymes can be utilised to improve breadmaking performance of wholegrain flours, which do not possess the same visco-elastic properties as refined wheat flour, in order to produce a healthy and consumer acceptable cereal product.The effects of Teff grain on dough and bread quality, selected nutritional properties and the impact of enzymes on physical, textural and sensory properties of straight dough and sourdough Teff breads were investigated.Teff breads were prepared with the replacement of white wheat flour with Teff flour at various levels (0%, 10%, 20%, and 30%) using straight dough and sourdough breadmaking. Different combinations of enzymes, including xylanase and amylase (X + A), amylase and glucose oxidase (A + GO), glucose oxidase and xylanase (GO + X), lipase and amylase (L + A) were used to improve the quality of the highest level Teff breads. A number of physical, textural and sensory properties of the finished products were studied. The nutritional value of breads was determined by measuring chemical composition for iron, total antioxidant capacity, protein, fibre and fat. The obtained results were used to estimates intakes of nutrients and to compare them with DRIs.The incorporation of Teff significantly (P < 0.05) improved dietary iron levels as 30% Teff breads contained more than double the amount of iron when compared to corresponding wheat bread (6 mg/100 g v 2 mg/100 g). Addition of Teff also significantly (P < 0.05) improved total antioxidant capacity from 1.4 mM TEAC/100 g to 2.4 mM TEAC/100 g. It was estimated that an average daily allowance of 200 g of Teff enriched bread would contribute to DRIs in the range of 42-81% for iron in females, 72-138% for iron in males; 38-39% for protein in males, 46-48% for protein in females; and 47-50% of fibre in adults.The major challenge was encountered in producing the highest level of Teff bread with good textural and sensory attributes. Increasing the level of Teff significantly (P < 0.05) increased dough development time, degree of softening, crumb firmness and bitter flavour whilst decreasing the dough stability, specific loaf volume and overall acceptability of the bread. Teff breads produced with the addition of enzyme combinations showed significant improvements (P < 0.05) in terms of loaf volume, crumb firmness, crumb structure, flavour and overall acceptability in both straight dough and sourdough breadmaking.     

Improvement of the quality and shelf life of wheat bread by fermentation with the antifungal strain Lactobacillus plantarum FST 1.7

Lactobacillus plantarum FST 1.7 was screened for in vitro antimicrobial activity and was shown to be active against spoilage moulds and bacteria. Isolation of antimicrobial compounds from cell-free supernatant identified lactic acid, phenyllactic acid and the two cyclic dipeptides cyclo (l-Leu-l-Pro) and cyclo (l-Phe-l-Pro) as the major components responsible for this activity. L. plantarum FST 1.7 was tested for the ability to produce the antifungal compounds during sourdough fermentation and to produce bread of good quality and increased shelf-life. A rheofermentometer was used to examine the gaseous release and development characteristics of the dough. A range of parameters was determined including pH, TTA and specific loaf volume. The results were compared with those obtained using Lactobacillus sanfranciscensis, a chemically acidified and a non-acidified dough. The quality of sourdough and bread produced using L. plantarum FST 1.7 was comparable to that obtained using common sourdough starters, e.g. L. sanfranciscensis. Sourdoughs and breads were evaluated for the ability to retard growth of Fusarium culmorum and Fusarium graminearum two fungi found on breads. Sourdough and bread produced with strain FST 1.7 showed consistent ability to retard the growth of both Fusarium species, thus indicating that L. plantarum FST 1.7 has also the potential to improve the shelf-life of wheat bread.     

Staling of fresh and frozen gluten-free bread

The difficulty in finding gluten-free bread and its high price make it necessary to prolong its shelf life to facilitate its availability. Freezing is an interesting alternative. The storage of bread at over zero temperatures, 20 °C and 4 °C, showed faster staling at refrigerator temperatures. A good relationship between crumb firmness and the extent of starch recrystallization was obtained, although the effect of water loss was also detected. The study of freezing and frozen storage at −14 °C and −28 °C for 7 days showed a substantial effect of the storage temperature on gluten-free bread quality and shelf life. Breads stored at −28 °C retained a quality similar to that of fresh breads while a marked deterioration of the breads stored at −14 °C was observed. This effect, the strongest on bread texture, was a result of starch recrystallization. The glass transition, T_g’ and onset of ice melting, T_m’ of the maximally freeze-concentrated bread crumb were −37.1 ± 0.6 °C and −19.3 ± 0.2 °C respectively. The higher amount of unfrozen water at −14 °C could explain the acceleration of reactions responsible for bread staling during frozen storage. The use of storage temperatures below T_m’ is recommended to retain high quality of the gluten-free bread during frozen storage.     

The potential of naked barley sourdough to improve the quality and dietary fibre content of barley enriched wheat bread

The possibility of using naked barley for food products is gaining popularity due to its dietary fibre content, especially β-glucans. The technological process (dough preparation, fermentation and baking) influences bread quality but also may contribute to degradation or preservation of valuable grain components. The aim of the study was to investigate the effects of different wholemeal barley flour share and bread production method on the quality of bread and non-starch polysaccharides content and solubility.Barley enriched bread contained more both soluble and insoluble dietary fibre and β-glucans, products of 40% barley share contained 67% more total dietary fibre and 160% more β-glucans than control. However, barley incorporation decreased the amount of soluble arabinoxylans. High barley contents contributed to the breads’ volume reduction by 14% and change in their crumb and crust colour. However, barley enriched breads gained higher ratings of taste than wheat bread. Barley sourdough fermentation improved breads’ volume, colour and sensory properties. Sourdough fermentation also resulted in higher concentration of dietary fibre, arabinoxylans and β-glucans. The beneficial effect of barley addition to wheat bread may be successfully enhanced by using barley wholemeal sourdough fermentation.     

In vitro starch digestibility and predicted glycaemic indexes of buckwheat,oat, quinoa,sorghum, teff and commercial gluten-free bread

The in vitro starch digestibility of five gluten-free breads (from buckwheat, oat, quinoa, sorghum or teff flour) was analysed using a multi-enzyme dialysis system. Hydrolysis indexes (HI) and predicted glycaemic indexes (pGI) were calculated from the area under the curve (AUC; g RSR/100g TAC*min) of reducing sugars released (RSR), and related to that of white wheat bread. Total available carbohydrates (TAC; mg/4 g bread “as eaten”) were highest in sorghum (1634 mg) and oat bread (1384 mg). The AUC was highest for quinoa (3260 g RSR), followed by buckwheat (2377 g RSR) and teff bread (2026 g RSR). Quinoa bread showed highest predicted GI (95). GIs of buckwheat (GI 80), teff (74), sorghum (72) and oat (71) breads were significantly lower. Significantly higher gelatinization temperatures in teff (71 °C) and sorghum flour (69 °C) as determined by differential scanning calorimetry (DSC) correlated with lower pGIs (74 and 72). Larger granule diameters in oat (3–10 μm) and sorghum (6–18 μm) in comparison to quinoa (1.3 μm) and buckwheat flour (3–7 μm) as assessed with scanning electron microscopy resulted in lower specific surface area of starch granules. The data is in agreement with predictions that smaller starch granules result in a higher GI.     

In vitro starch digestibility and predicted glycaemic indexes of buckwheat,oat, quinoa,sorghum, teff and commercial gluten-free bread

The in vitro starch digestibility of five gluten-free breads (from buckwheat, oat, quinoa, sorghum or teff flour) was analysed using a multi-enzyme dialysis system. Hydrolysis indexes (HI) and predicted glycaemic indexes (pGI) were calculated from the area under the curve (AUC; g RSR/100g TAC*min) of reducing sugars released (RSR), and related to that of white wheat bread. Total available carbohydrates (TAC; mg/4 g bread “as eaten”) were highest in sorghum (1634 mg) and oat bread (1384 mg). The AUC was highest for quinoa (3260 g RSR), followed by buckwheat (2377 g RSR) and teff bread (2026 g RSR). Quinoa bread showed highest predicted GI (95). GIs of buckwheat (GI 80), teff (74), sorghum (72) and oat (71) breads were significantly lower. Significantly higher gelatinization temperatures in teff (71 °C) and sorghum flour (69 °C) as determined by differential scanning calorimetry (DSC) correlated with lower pGIs (74 and 72). Larger granule diameters in oat (3–10 μm) and sorghum (6–18 μm) in comparison to quinoa (1.3 μm) and buckwheat flour (3–7 μm) as assessed with scanning electron microscopy resulted in lower specific surface area of starch granules. The data is in agreement with predictions that smaller starch granules result in a higher GI.     

Folates Stability in Two Types of Rye Breads During Processing and Frozen Storage

High-performance liquid chromatography was used to study the stability of folate vitamers in two types of rye breads after baking and 16 weeks of frozen storage. Bread made using sourdough seeds contained less total folate (74.6 μg/100 g dry basis, expressed as folic acid) than the whole rye flour (79.8 μg/100 g dry basis) and bread leavened only with baker’s yeast (82.8 μg/100 g dry basis). Most importantly, it was generated by a significant decrease in 5-CH₃-H₄folate form. The baking process caused some changes in folate distribution. Storage of breads at -18°C for 2 weeks did not have a significant effect (p < 0.05) on total folates compared to the content directly after baking. After a 5-weeks storage period, a significant decrease (p < 0.05) in the content of total folates was recorded and it dropped on average by 14% for both type of breads. After a longer period of storage (16 weeks), a 25% loss of folates in the bread made with baker’s yeast and a 38% loss in the bread fermented with sourdough seeds was found. Retention of 5-CH₃-H₄folate and 10-HCO-H₂folate forms were much lower in the bread made with a sourdough addition than with baker’s yeast only.     

Sourdough fermentation of wholemeal wheat bread increases solubility of arabinoxylan and protein and decreases postprandial glucose and insulin responses

Glycemic responses to most of the conventional breads are high, including breads made of wholemeal flour. Baking technology is known to affect these responses. The aim of the present study was to investigate effects of xylanase enzyme treatment and sourdough fermentation in wholemeal wheat bread baking on postprandial glucose and insulin responses and on in vitro protein digestibility. The wheat breads were made of 100% flour from peeled kernels by a straight dough or sourdough fermentation method, and with or without using xylanase during mixing of dough. Standard white wheat bread was used as a reference. All test bread portions contained 50 g available carbohydrate and were served in random order to eleven insulin resistant subjects. Blood samples for measuring glucose and insulin concentrations were drawn over 4 h. The sourdough wholemeal wheat bread resulted in the lowest postprandial glucose and insulin responses among the four tested breads (treatment × time; p = 0.000 and p = 0.022, respectively). There were differences in solubility and depolymerisation of protein and arabinoxylan among the breads but these did not fully explain the in vivo findings. In conclusion, the health effects of wholemeal wheat bread can be further improved by using sourdough process in breadmaking.     

Sourdough bread: Starch digestibility and postprandial glycemic response

To evaluate the influence of sourdough fermentation on starch digestibility in bread, 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 fiber 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. We may conclude that sourdough fermentation is a technique able to reduce the glycaemic response to bread and that the mechanism does not seem related to the rate of starch hydrolysis.     

Effect of arabinoxylans and laccase on batter rheology and quality of yeast-leavened gluten-free breads

The supplementation effects of maize fiber arabinoxylans (MFAX, 0%–6%), laccase (0–2 U/g flour) and water absorption level (90%–100%) on gluten-free (GF) batter rheology and bread quality were analyzed. From viscoamylograph analysis, lower starch amount in GF flour due to MFAX addition decreased peak viscosity and retrogradation. Surface response plots showed that laccase did not have significant effect on GF batter rheology and bread quality, whilst water was the most important variable. Higher levels of water absorption benefited bread texture. Higher water level (>100 mL/100 g flour) was needed in the experimental design to evaluate correctly the effect of 6% MFAX replacement on GF bread quality. Further analyses were carried in order to adjust water absorption of batters according to their consistency index (K ≈ 100 Pa sⁿ), resulting an optimal water absorptions of 95%, 100% and 105% for control flour and flours supplemented with 3% or 6% MFAX, respectively. Thus, MFAX addition enhanced water-binding capacity of flour and yielded GF breads with higher specific volume and softer crumb texture. These quality parameters were best rated with 6% MFAX addition to flours. This research demonstrated the potential of MFAX to develop GF breads with improved quality, when optimal water level is used.     

Comparison of the impact of dextran and reuteran on the quality of wheat sourdough bread

This study investigates the influence of in situ exopolysaccharides (EPS) and organic acids on dough rheology and wheat bread quality. Dextran forming Weissella cibaria MG1 was compared to reuteran forming Lactobacillus reuteri VIP. For in situ production of EPS, sourdoughs were supplemented with 15% sucrose. Control sourdoughs were prepared with the same strain but without sucrose. W. cibaria MG1 and L. reuteri VIP formed 5.1 and 5.8 g kg⁻¹ dextran and reuteran, respectively. Formation of EPS from sucrose led to production of high amounts of acetate by L. reuteri VIP, but only small amounts were detected in W. cibaria MG1 sourdough. EPS containing sourdough or control sourdough was incorporated at 10% and 20% in wheat dough. EPS significantly influenced the rheological properties of the dough, with dextran exhibiting the strongest impact. The addition of dextran enriched W. cibaria MG1 sourdough significantly increased CO₂ production, whereas increased acidity in reuteran containing dough reduced gas production. The quality of wheat bread was enhanced when 10% of L. reuteri-sucrose sourdough was added. The positive effect of reuteran was masked by increased acidification after 20% sourdough addition. Incorporation of dextran enriched sourdough (10% and 20%) provided mildly acidic wheat bread with improved bread quality.     

Factors influencing acrylamide formation in rye,wheat and spelt breads

In this study, a simple strategy for acrylamide (AA) reduction in white and dark wheat and spelt and rye breads, including the impact of flour basic composition, flour extraction rate, type of technology and baking time and temperature was addressed. Moreover, the correlation between AA formation in breads and total phenolic compounds (TPC) and antioxidant capacity (AC) of flours and breads was calculated. The studies showed an impact of flours origin on AA formation in breads with the following rank: wheat bread ≤ spelt bread < rye bread. There was no statistically significant effect of flour extraction rates and their chemical components on AA formation in breads baked at 200 °C/35 min. However, a weak effect was noted for wheat and spelt breads baked at higher temperature. In contrast, a positive correlation between AA in wheat, spelt and rye breads baked at both applied conditions (200 °C for 35 min or 240 °C for 30 min) and AC of white and dark flours was noted. The same finding was noted between AA formation and TPC and AC of bread and its crust. The provided data indicated that AA mitigation strategy should be based on the selection of lower baking temperature with longer baking time as the main important factor amongst others.     

In vitro digestion kinetics and bioaccessibility of starch in cereal food products

The study of starch digestion in cereal-based products is essential since the extent and rate of hydrolysis affects the glycemic index associated with several food-related diseases. Besides, a unique matrix is usually studied and many variations of in vitro techniques (e.g. enzymes, pH, food:enzymes ratio) are selected, then comparison of results became difficult. The recently published INFOGEST in vitro static method with international consensus (Minekus et al., 2014) was applied to several cereal-based products to address whether it is suitable for analysis of starch hydrolysis kinetics. Bread, pasta and cookies were selected taking into account the analysis of different cereal matrixes, including gluten-free products. White bread presented the highest in vitro starch hydrolysis (87%) showing significant differences compared to gluten-free bread (76.5%). Refined flour sheeted pasta (72.6%), whole-wheat extruded pasta (92.0%) and gluten-free pasta (54.3%) showed differences in the extent and rate of hydrolysis. Cookie samples presented the lowest starch hydrolysis (∼45%). The starch availability was estimated by the dializability method, which measures the maltose equivalents dialyzed after simulating digestion. Starch dializability was 35%, 25% and 15% on average for bread, pasta and cookie samples respectively, with positive correlation with rapidly digested starch. The tested in vitro method allowed discriminating the effect of different processing techniques, product types and formulation of the three most common cereal-food matrixes in starch digestion.