Muffins with resistant starch: Baking performance in relation to the rheological properties of the batter

The effect on baked muffins of progressively replacing wheat flour with resistant starch (RS) was studied. Muffin volume and height and the number and area of gas cells decreased significantly when the RS level reached about 15% (by weight of total formulation) or higher. Rheological properties of the raw batters were studied: the mechanical spectra of batters at 25 °C, the evolution of the dynamic moduli (G′ and G″) with rising temperatures (from 25 to 85 °C) and the mechanical spectra at 85 °C were obtained from oscillatory rheological tests. The decrease in the viscosity and in the elastic properties of the muffin batter as the flour was increasingly replaced by RS was related to the baking performance of the final baked products.     

Amylopectin Fine Structure and Rice Starch Paste Breakdown

Ten rice starches with a fairly narrow range of amylose content, but wide variation in RVA pasting curves, were selected to study a possible relationship between amylopectin fine structure and RVA paste viscosity parameters. Amylopectin fine structure was found to significantly correlate with paste breakdown. Proportion of long chains of amylopectin (FrI) was negatively correlated (r=0·84, p<0·01) and proportion of short chains of amylopectin (FrIII) was positive correlated (r=0·89, p<0·001) with paste breakdown. The findings imply that amylopectin fine structure relates to the extent of breakdown of swollen granules and the viscosity after gelatinised starch granule structure is disrupted. The results suggest the possibility that lines can be selected with high proportion of amylopectin long chains for reduced paste breakdown.     

The Role of Gluten Proteins in the Baking of Arabic Bread

Fractionation and reconstitution/fortification techniques were utilised to study the role of gluten in Arabic bread. Glutens from two wheat cultivars of contrasting breadmaking quality were fractionated by dilute HCl into gliadin and glutenin. Gluten, gliadin and glutenin doughs from the good quality flour had higher G ′ and lower tan δ values than those from the poor quality flour at all the frequencies examined. Interchanging the gliadin and glutenin fractions between the reconstituted flours showed that the glutenin fraction is largely responsible for differences in the breadmaking performance. Fortification of an average quality flour with the gliadin and glutenin fractions from the poor and good quality flours, at the levels of 1% and 2% (protein to flour mass), induced marked differences in the mechanical properties of bread. The resilience of the loaves was not adversely affected by the addition of gliadins and increased, with a concomitant significant (p<0·05) improvement in quality, at the 2% level of fortification with gliadins from the good quality flour. Addition of glutenin resulted in loaves with leather-like properties that became particularly apparent at the higher level of fortification; the observed deterioration in quality paralleled the increase in the elastic character of the doughs. It is suggested that highly-elastic doughs are not compatible with the rapid expansion of gases at the high-temperature short-time conditions employed in the baking of Arabic bread and that there exists a threshold in dough elasticity beyond which a rapid decline in quality takes place.     

Digitization of farinogram plots and estimation of mixing stability

Twenty-four farinograms and accompanying flour characteristics obtained from a bakery were used to get additional information for baking characteristics of flours. Farinograms were digitized and four novel parameters were included for comparison: a and b were extracted from an equation of the form y = ae^−bt; the height of the upper curve and the width of the farinograph curve at a time value equal to the dough development time. Stepwise multiple regressions were carried out relating bread volume to novel and existing parameters (water absorption, development time, arrival time, departure time, stability and degree of softening). Results indicated that four farinogram parameters, resistance, water absorption, a and b were related to bake height with an overall value of 61%. A relatively weak correlation (R = 0.44, P < 0.05) was detected between specific loaf volume and bake height.     

Fate of ACE-inhibitory peptides during the bread-making process: Quantification of peptides in sourdough,bread crumb,steamed bread and soda crackers

This study compared the concentration of angiotensin-converting enzyme (ACE) inhibitory peptides at different stages of the bread-making process, including kneading, proofing, and final products. Steamed bread, baked bread, and soda crackers were produced with 3–20% addition of rye malt sourdoughs to assess products differing in their thermal treatment. Eight tripeptides with known or predicted ACE-inhibitory activity were quantified by LC/MS in multiple reaction monitoring (MRM) mode. In wheat sourdough and rye-malt gluten sourdough, IPP was the predominant tripeptide at 58 and 473 μmol kg⁻¹, respectively, followed by LQP, IQP, and LPP. During the bread-making process, peptide concentrations were modified by enzymatic conversions at the dough stage and by thermal reactions during baking. The concentrations of IPP, LPP and VPP remained stable during dough preparation but decreased during thermal treatment; the concentrations of other peptides were changed at the dough stage but remained relatively stable during baking. The cumulative concentration of 8 ACE-inhibitory peptides in steamed bread and bread crumb exceeded 60 μmol kg⁻¹, while soda crackers contained less than 3 μmol kg⁻¹. The peptide levels in bread thus likely meet in vivo active concentrations.     

Effect of structured lipid on alveograph characteristics, baking and textural qualities of soft wheat flour

The effect of substituting canola oil/caprylic acid structured lipid (SL) for partially hydrogenated shortening (at 0, 25, 50, 75, and 100% levels) on the rheology of soft wheat flour dough (28.4% total lipid on flour weight basis, 43% moisture) was determined using the Alveograph. The effect of SL substitution on baking and textural qualities of sugar-snap cookies was also investigated. Addition of shortening to soft wheat flour dough resulted in a significant (P<0.05) decrease in dough resistance to deformation (P), dough extensibility (L), and dough baking strength (W), suggesting a less developed gluten network. SL substitution for shortening did not affect P and W. The cookies incorporating SL (50 and 75% SL substitution) were similar (P<0.05) to the shortening control cookies in both baking and textural qualities, but exhibited some baking and textural quality differences at the 25 and 100% SL substitution levels. Correlations (P<0.05) were found between some Alveograph characteristics, and baking and textural qualities.     

Improvements in the qualities of gluten-free bread after using a protease obtained from Aspergillus oryzae

From a nutritional perspective, rice flour is one of the most valuable flours and it is suitable for preparing food for people suffering from wheat allergy. However, bread made from rice flour is very difficult to bake because it lacks gluten. We found that pre-fermenting of rice flour using Aspergillus oryzae facilitated a better formulation of gluten-free rice bread. Bread swelling was remarkably improved with a longer pre-fermenting period at 55 °C. The specific loaf volume (SLV) without polymeric thickeners after a 12 h fermentation was approximately 2.2-fold (2.98 ml/g) higher than that after 0 h (1.36 ml/g). An enzymatic assay of the batter indicated that protease activity during the pre-fermentation period increased from 0.38 to 1.44 U/ml and this activity correlated with bread swelling. Furthermore, a commercial protease from A. oryzae also produced similar results with an adequate SLV of 3.03 ml/g. Rheological analysis showed that batter treated with protease had an increased batter viscosity and decreased flour settling behavior because of the aggregation of flour particle after partial cleavage of storage proteins. These results indicated that the improved SLV was mainly because of an A. oryzae protease, which affected the batter rheology thereby improving gas retention before baking.     

Evaluation of partial-vacuum baking for gluten-free bread: Effects on quality attributes and storage properties

The purpose of this study was to evaluate the impact of partial-vacuum baking on the quality and storage properties of gluten-free bread (GFB). Conventional (180°C-30 min at atmospheric pressure) and partial-vacuum (180°C-15 min at atmospheric pressure and at 180°C-15 min at 60 kPa vacuum pressure) methods were conducted to bake GFB. Quality attributes (specific volume, colour, texture, total water loss) were assessed, DSC and SEM analyses were carried out to understand the effect on the bread's microstructure when using vacuum during baking. No significant differences (p > 0.05) were observed in the hardness and specific volume of the partial-vacuum baked GFB; however, changes in the total water loss and in the total colour change were statistically significant (p < 0.05). The DSC, SEM and XRD results showed that more crystalline structure and different starch crystal types formed after partial-vacuum baking. Storage properties were also investigated over a 3-day period. Partial-vacuum baking significantly affected the total water loss and the texture parameters (p < 0.05) during storage. Partial-vacuum baked samples were softer and had a tendency to become stale more slowly than the control. The findings indicate that the partial-vacuum baking method increases the shelf life of gluten-free products by modifying the microstructure of the bread.     

Effect of legume flours on baking characteristics of gluten-free bread

The objective of this work was to study the characteristics of four gluten-free bread formulations and the possibility of substituting soya protein with other legume proteins. Four bread recipes were prepared with chickpea flour, pea isolate, carob germ flour or soya flour. Carob germ flour batter structure was thicker compared with the other batters, probably due to the different protein behaviour and the residual gums present in carob germ flour. However, carob germ flour bread obtained the lowest specific volume values (2.51 cm³/g), while chickpea bread obtained the highest (3.26 cm³/g). Chickpea bread also showed the softest crumb. Confocal scanning-laser microscopy results showed a more compact microstructure in carob germ flour bread compared with soya and chickpea formulations. Chickpea bread exhibited the best physico-chemical characteristics and, in general, good sensory behaviour, indicating that it could be a promising alternative to soya protein.     

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.     

Effect of steam explosion on enzymatic hydrolysis and baking quality of wheat bran

In this study, the effect of steam explosion (SE) treatment on microstructure, enzymatic hydrolysis and baking quality of wheat bran was investigated. Coarse and fine bran were treated at different steam temperatures (120–160 °C) and residence times (5 or 10 min) and then hydrolysed with carbohydrase enzymes. The SE treatment increased water extractable arabinoxylan (WEAX) content from 0.75 to 2.06% and reducing sugars from 0.92 to 2.41% for fine bran. The effect was more pronounced with increased SE temperature and residence time. The highest carbohydrate solubilisation was observed in fine bran at SE treatment of 160 °C, 5 min. WEAX content increased to 3.13% when this bran was incubated without enzyme, while WEAX content increased to 9.14% with enzyme addition. Microscopic analysis indicated that cell wall structure of wheat bran was disrupted by severe SE conditions. Supplementation of SE treated (150 °C, 10 min) bran at 20% replacement level decreased the baking quality of bread. However SE followed by enzymatic hydrolysis increased specific volume and decreased crumb hardness (on the day of baking and after three days of storage). Phytic acid content of bread supplemented with SE treated bran was lower than the one supplemented with untreated bran.     

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.     

Characterization of two 1D-encoded ω-gliadin subunits closely related to dough strength and pan bread-making quality in common wheat (Triticum aestivum L.)

Gliadin proteins of 113 common or bread wheat (Triticum aestivum L.) cultivars and advanced lines from China and other countries, were analyzed by high performance capillary electrophoresis (HPCE) and reversed-phase high performance liquid chromatography (RP-HPLC). A major protein peak migrating at 3 min by HPCE and eluting at about 20 min by RP-HPLC was identified in the ω-gliadin region. It was present in cultivars with good pan bread-making quality, whereas most cultivars with poor bread-making quality lacked this protein peak. Quality testing and statistical analysis showed that this ω-gliadin peak was significantly related to dough strength, loaf volume and loaf score. It was separated into two apparent protein components by one-dimensional SDS-PAGE and two-dimensional electrophoresis (2-DE). According to their relative mobilities on the gels, the proteins were designated ω-15 and ω-16, and their accurate molecular masses (42590.5 Da for ω-15 and 41684.1 Da for ω-16) were determined by MALDI-TOF-MS. The ω-15 and ω-16 gliadins possessed the N-terminal amino acid sequences of ARELNPSNKELQQQQ and KELQSPQQQF, and therefore they belonged to 1D-encoded ω-2 type and ω-1 type gliadins, respectively. Both gliadin subunits were always present together among the 86 cultivars analyzed, suggesting that they were encoded by two closely linked genes at Gli-D1 locus. The accumulative characteristics of gliadins during grain development indicated possible additive quantitative effects of ω-15+16 on dough strength. The ω-15 and ω-16 gliadins could be used as valuable genetic markers for wheat quality improvement.     

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.     

Study of the effect of hydrothermal process conditions on pasta quality

The effect of hydrothermal treatment on the pasting, hydration properties and colour quality of commercial fresh pasta were studied following an Instantaneous Controlled Pressure Drop treatment. This hydrothermal procedure involves a physical modification at high temperature (<144 °C) and restricted moisture content (<30%) during a very short time (15–40 s) followed by a rapid pressure drop to a vacuum (50 mbar). Two process variables (steam pressure level and processing time) were investigated using response surface methodology. Steam pressure level had the greatest effect on hydration and pasting parameters. Increased pressure resulted in elevation of mass ratio between cooked and uncooked pasta (W_i/W₀)_{100 °C} and reduction of for all treated pasta. The optimum cooking time of untreated pasta was 7 min (W/W₀=2.4), whereas for the same ratio it was less than 1 min for pasta treated at pressures ranging between 2.5 and 3.5 bar. The viscosity at 10 min (V₁₀) increased linearly when the pressure level increased. V₁₀ was 146 cP for untreated pasta whereas it reached 2659 cP for pasta treated at 3.9 bar (144 °C) for 25 s. The cold paste viscosity and setback viscosity decreased when the pressure varied from 1 to 3.9 bar.     

Fundamental evaluation of the impact of high Hydrostatic Pressure on oat batters

The use of grains alternative to wheat or rye is a challenging task for cereal technologists, and currently new technologies are under investigation as tools to improve the performances of these alternative grains. In this work the effects of high Hydrostatic Pressure (HP) on oat batters were investigated. Oat batters were treated for 10 min at 200, 300, 350, 400 or 500 MPa. Scanning electron microscopy and bright field microscopy showed that high HP significantly affected oat batter microstructure, and both starch and proteins were affected. Treatment at high HP significantly improved batter viscosity and elasticity. At pressures ≤300 MPa the increase in the viscous component was higher than the increase in the elastic component. On the contrary, at pressures ≥350 MPa the elastic component was predominant. Differential scanning calorimetry revealed that high HP induced starch gelatinisation, which started at 300 MPa and was almost complete after treatment at 500 MPa. High HP also affected water- and salt-soluble as well as urea-soluble oat proteins. Analysis of proteins soluble in different buffers revealed that pressures ≥300 MPa induced the formation of urea-insoluble complexes and/or disulfide bonds. Overall, the extent of starch gelatinisation and protein modification was dependent on the applied pressure, but the results collected so far clearly show that high HP can be used to improve the functionality of oat batters.     

Sensitivity of yield and grain nitrogen concentration of wheat, lupin and pea to source reduction during grain filling. A comparative survey under high yielding conditions

Several studies have been conducted to evaluate the response of crops, especially temperate cereals, to different source–sink ratios during grain filling. However, there is much less information about temperate legumes and even less work comparing the two. The objective of this study was to evaluate the response of both grain yield and grain nitrogen concentration of wheat (Triticum aestivum L.), narrow-leafed lupin (Lupinus angustifolius L.) and pea (Pisum sativum L.) to similar source reduction during grain filling. Two field experiments were conducted in a high yielding environment of Southern Chile. In experiment 1 wheat and narrow-leafed lupin were grown for two consecutive years. Experiment 2 evaluated wheat and pea on two sowing dates. In both experiments a reduction in the source–sink ratio was imposed by using black nets that intercepted 90% of the incident solar radiation from the commencement of the linear dry matter accumulation to physiological maturity. Grain yield was differentially (p < 0.01) decreased by the source reduction in lupin (98%), wheat (63%) and pea (26%). Given that these experiments were carried out in a high yielding environment, the higher response of wheat relative to previous studies supports the hypothesis that the higher the yield potential, the higher the source sensitivity of this crops during the grain filling period. On the other hand, source reduction positively affected (p < 0.05) grain nitrogen concentration in wheat (66%) and pea (18%) but negatively affected lupin (40%). The higher sensitivity of grain yield compared to that of grain nitrogen yield was the cause of the positive effect of the lower source–sink ratio recorded in wheat and pea. In contrast, source shortage in lupin decreased grain nitrogen concentration probably as result of the quick response of grain growth to source limitation. The contrasting sensitivities of lupin, wheat and pea to source reduction during grain filling prevent us to see grain yield and quality response of these crops as separate groups, i.e. temperate cereals vs. temperate legumes.     

Rheofermentometer parameters and bread specific volume of frozen sweet dough influenced by ingredients and dough mixing temperature

Response surface methodology described the effects of salt, lactic acid, shortening, and exogenous trehalose and dough mixing temperature (DMT) and their interactions on the three rheological and fermentation parameters. These included maximum dough height (Hm), maximum height of gas release (Hm′) and CO₂ production, measured by the Rheofermentometer F3, and bread specific volume (Sp. Vol.) of frozen sweet dough. The models could estimate the four parameters with R² values of 0.76, 0.69, 0.93, and 0.59, respectively. Salt significantly influenced all four parameters in a negative way. DMT affected positively the Hm and Sp. Vol. of bread. Lactic acid affected Hm only, but its interactions with other variables influenced all four parameters. Shortening level affected Hm′ and CO₂ production positively and Sp. Vol. negatively. The added exogenous trehalose improved Hm, Hm′, and CO₂ production significantly, but not the Sp. Vol. of bread. Among the three Rheofermentometer parameters, Hm showed the highest correlation with Sp. Vol. (R² = 0.75). DMT for the maximum Hm and Sp. Vol. varied with the level of other ingredients. Trehalose alone could not overcome the challenges in a sweet frozen dough system to improve the Sp. Vol., and its combined effects with other ingredients will need to be evaluated to restore the impaired gas retention of the frozen sweet dough.     

Role of enzymes in improving the functionality of proteins in non-wheat dough systems

Gluten free systems lack the viscoelastic network required to resist gas production and expansion during baking. Enzymatic treatments of the GF flours have been proposed initially for creating protein aggregates that mimic gluten functionality but then also for modifying proteins changing their functionality in GF systems. To better exploit the technological function and the potentials of enzymatic processing for improving GF bread quality, it is important to understand the key elements that define the microstructure and baking functionality of GF batters as compared to wheat dough. In this review, some keys are pointed out to explain the different mechanisms that are available for understanding the action of enzymes to effectively design GF viscoelastic matrixes. Focus will be on protein modifying enzymes, because they play a decisive role in the formation of the fine network responsible for improving the expansion of rice batters.     

Relationship between the glass transition temperature and the melt flow behavior for gluten, casein and soya

The effects of moisture content (25–45% wwb) and temperature (75–120 °C) on the viscosity of gluten, soya and rennet casein systems was studied using a capillary rheometer. An attempt was made to relate the viscosities to the glass transition temperature measured by differential scanning calorimetry, dynamic mechanical thermal analysis and the phase transition analyzer. The temperature where the material flowed was also determined by the latter technique. All three-protein systems showed shear and extension thinning. Over the shear rate range investigated (1–10³ s⁻¹), gluten had a substantially lower viscosity than the other two proteins, although the difference was less pronounced at the highest temperature studied. This low viscosity is reflected by lower values of the glass transition temperature, the melt flow temperature and the dynamic moduli E′ and E″ in the rubbery state. The results are discussed in terms of the structure and heat induced changes for the three proteins and their relevance to food processing considered.