Impact of thermostable amylases during bread making on wheat bread crumb structure and texture

Mechanism of action of three different glycogen branching enzymes and their effect on bread quality

Bread staling adversely affects the quality of bread, but starch modification by enzymes can counteract this phenomenon. Glycogen branching enzymes (GBEs) used in this study were isolated from Deinococcus geothermalis (DgGBE), Escherichia coli (EcGBE), and Vibrio vulnificus (VvGBE). These enzymes were characterized and applied for starch dough modification to determine their role in improving bread quality. First, the branching patterns, activity on amylose and amylopectin, and thermostability of the GBEs were determined and compared. EcGBE and DgGBE exhibited better thermostable characteristics than VvGBE, and all GBEs exhibited preferential catalysis of amylopectin over amylose but different degrees. VvGBE and DgGBE produced a large number of short branches. Three GBEs degraded the starch granules and generated soluble polysaccharides. Moreover, the maltose was increased in the starch slurry but most significantly in the DgGBE treatment. Degradation of the starch granules by GBEs enhanced the maltose generation of internal amylases. When used in the bread-making process, DgGBE and VvGBE increased the dough and bread volume by 9 % and 17 %, respectively. The crumb firmness and retrogradation of the bread were decreased and delayed significantly more in the DgGBE bread. Consequently, this study can contribute to understanding the detailed roles of GBEs in the baking process.

Maltogenic amylase: Its structure, molecular modification, and effects on starch and starch-based products

Maltogenic amylase (MAA) (EC3.2.1.133), a member of the glycoside hydrolase family 13 that mainly produces α-maltose, is widely used to extend the shelf life of bread as it softens bread, improves its elasticity, and preserves its flavor without affecting dough processing. Moreover, MAA is used as an improver in flour products. Despite its antiaging properties, the hydrolytic capacity and thermal stability of MAA can't meet the requirements of industrial application. However, genetic engineering techniques used for the molecular modification of MAA can alter its functional properties to meet application-specific requirements. This review briefly introduces the structure and functions of MAA, its application in starch modification, its effects on starch-based products, and its molecular modification to provide better insights for the application of genetically modified MAA in starch modification.

The Impact of Germinated Chickpea Flour Addition on Dough Rheology and Bread Quality

The research focused on the effect of germinated chickpea flour (GCF) in a lyophilized form on dough rheology, microstructure and bread quality. The GCF addition levels in refined wheat flour with a low α-amylase activity were 5%, 10%, 15% and 20%, up to an optimum falling number value of the mixed flour. Generally, the dough rheological properties of water absorption, tolerance to mixing, dough consistency, dough extensibility, index of swelling, baking strength and loss tangent (tan δ) for the temperature sweep test decreased with the increased level of GCF addition, whereas the total volume of gas production and G′ and G″ modules for the temperature sweep test increased. Dough microstructure analyzed by epifluorescence light microscopy (EFLM) clearly showed a change in the starch and gluten distribution from the dough system by an increase in protein and a decrease in starch granules phase with the increased level of GCF addition in wheat flour. The bread physical characteristics (loaf volume, porosity, elasticity) and sensory ones were improved with up to 15% GCF addition in wheat flour. The bread firmness increased, whereas the bread gumminess, cohesiveness and resilience decreased with increased GCF addition in wheat flour. The bread crust and crumb color of the bread samples become darker with an increased GCF addition in the bread recipe.

Effects of water and gelatinized starch on the viscoelasticity of pizza dough and the texture of pizza crust

The soft texture of the pizza crust rim is generated by baking at a high temperature for a short period in a stone oven. In the case of baking in an electric oven, the pizza dough is baked at a much lower temperature and for a longer period, resulting in a harder texture. To improve the texture of electric oven-baked pizza crust, the effects of water and gelatinized starch on the viscoelasticity of pizza dough and the texture of pizza crust were investigated. Rheological properties (storage modulus, loss modulus, and yield stress) of pizza dough decreased with an increase in water content. When wheat flour in the dough was partially replaced with pre-gelatinized wheat starch, the rheological properties of the dough were maintained even at a high-water content. These results indicate that water-enriched dough can be prepared with gelatinized starch and baked using an electric oven. There was no significant difference in apparent density between the conventional and modified pizza crusts. Water content of the crumb part of the modified crust was significantly higher than that of the conventional crust. Texture analysis revealed that the modified pizza crust showed significantly lower stress at high strain than the conventional crust. In addition, sensory evaluation showed that the modified pizza crust exhibited greater firmness and stickiness than the conventional crust, which was attributed to the increased water content with gelatinized starch of the dough.

Quantification of Soy-Derived Ingredients in Model Bread and Frankfurter Matrices with an Optimized Liquid Chromatography-Tandem Mass Spectrometry External Standard Calibration Workflow

ABSTRACT

The detection and quantification of soy protein is important for food allergen management and identifying the presence of undeclared soy proteins. Heat processing and matrix interactions can affect the accuracy of allergen detection methods. The sensitivity of enzyme-linked immunosorbent assay methods can be compromised if protein epitopes are modified during processing. Therefore, a mass spectrometry (MS)-based method was evaluated for the recovery of total soy protein in incurred matrices. MS-based quantification of total soy protein was assessed by using a combination of external and internal standards. The reproducibility of the standard curves was investigated by comparing within-day and among-day variation. Incurred samples were prepared using bread and frankfurters as model food matrices. Several soy-derived ingredients were used to prepare the matrices with varying levels of soy protein (1, 10, 50, or 100 ppm of total soy protein). A pooled standard curve was used to estimate the total soy protein concentration of the incurred food matrices and the percent total protein recovery. The variation of replicate standard curves between days and among all days was not significant. The differences in slopes obtained from replicate standards run on different days were minimal. The most influential factor on the quantitative protein recovery in incurred samples was the effect of the physical matrix structure on protein extraction. The lowest percent protein recoveries, less than 50%, were calculated for uncooked matrices. The cooked matrices had percentage recoveries between 50 and 150% for all total soy protein levels. Other factors, such as type of ingredient, were determined to be not as impactful on recovery. The MS method described in this study was able to provide sensitive detection and accurate quantification of total soy protein from various soy-derived ingredients present in processed food matrices.

HIGHLIGHTS

Impact of exogenous maltogenic α-amylase and maltotetraogenic amylase on sugar release in wheat bread

The use of exogenous maltogenic α-amylases or maltotetraogenic amylases of bacterial origin is common in wheat bread production, mainly as antistaling agents to retard crumb firming. To study the impact of maltogenic α-amylase and maltotetraogenic amylase on straight dough wheat bread, we performed a discovery-driven proteomics approach with commercial enzyme preparations and identified the maltotetraogenic amylase P22963 from Pelomonas saccharophila and the maltogenic α-amylase P19531 from Geobacillus stearothermophilus, respectively, as being responsible for the amylolytic activity. Quantitation of mono-, di- and oligosaccharides and residual amylase activity in bread crumb during storage for up to 96 h clarified the different effects of residual amylase activity on the sugar composition. Compared to the control, the application of maltogenic α-amylase led to an increased content of maltose and especially higher maltooligosaccharides during storage. Residual amylase activity was detectable in the breads containing maltogenic α-amylase, whereas maltotetraogenic amylase only had a very low residual activity. Despite the residual amylase activities and changes in sugar composition detected in bread crumb, our results do not allow a definite evaluation of a potential technological function in the final product. Rather, our study contributes to a fundamental understanding of the relation between the specific amylases applied, their residual activity and the resulting changes in the saccharide composition of wheat bread during storage.

Investigation of starch functionality and digestibility in white wheat bread produced from a recipe containing added maltogenic amylase or amylomaltase

In the crumb of fresh white wheat bread, starch is fully gelatinized. Its molecular and three-dimensional structure are major factors limiting the rate of its digestion. The aim of this study was to in situ modify starch during bread making with starch-modifying enzymes (maltogenic amylase and amylomaltase) and to investigate the impact thereof on bread characteristics, starch retrogradation and digestibility. Maltogenic amylase treatment increased the relative content of short amylopectin chains (degree of polymerization ≤ 8). This resulted in lower starch retrogradation and crumb firmness upon storage, and reduced extent (up to 18%) of in vitro starch digestion for fresh and stored breads. Amylomaltase only modestly shortened amylose chains and had no measurable impact on amylopectin structure. Modification with this enzyme led to slower bread crumb firming but did not influence starch digestibility.

Impact of exogenous α-amylases on sugar formation in straight dough wheat bread

The use of bacterial or fungal α-amylases is common in wheat bread production to improve several quality-related parameters such as loaf volume, crust color or staling behavior. To study the impact of exogenous α-amylases on straight dough wheat bread, we quantitated mono-, di- and oligosaccharides and residual α-amylase activity in bread crumb during storage for up to 96 h. Discovery-driven proteomics of the five α-amylase preparations studied showed that only a few different amylases per preparation were responsible for the hydrolytic effect. Compared to the control, the supplementation with α-amylase from Bacillus amyloliquefaciens in wheat dough preparation led to major changes in the sugar composition of bread crumb during storage with the formation of oligosaccharides like maltopentaose, maltohexaose, maltoheptaose, and maltooctaose. A residual activity corresponding to 4.0% of the applied activity was determined in the breads prepared with α-amylase from B. amyloliquefaciens, but no residual activity was detected for any of the other fungal or bacterial α-amylases from Aspergillus oryzae or Thermoactinomyces vulgaris. Whether the detected residual activity is related to the characteristics of bread staling or bread crumb properties must be clarified in further studies.

Amylose and amylopectin functionality during storage of bread prepared from flour of wheat containing unique starches

Bread crumb firming is largely determined by the properties of gluten and starch, and the transformations they undergo during bread making and storage. Amylose (AM) and amylopectin (AP) functionality in fresh and stored bread was investigated with NMR relaxometry. Bread was prepared from flours containing normal and atypical starches, e.g., flour from wheat line 5-5, with or without the inclusion of Bacillus stearothermophilus α-amylase. Initial crumb firmness increased with higher levels of AM or shorter AM chains. Both less extended AM and gluten networks and too rigid AM networks led to low crumb resilience. AP retrogradation during storage increased when crumb contained more AP or longer AP branch chains. Shorter AP branch chains, which were present at higher levels in 5-5 than in regular bread, were less prone to retrogradation, thereby limiting gluten network dehydration due to gluten to starch moisture migration. Correspondingly, crumb firming in 5-5 bread was restricted.

Determination of the Direct Activity of the Maltogenic Amylase from Geobacillus stearothermophilus in White Bread

An assay-based method was developed to determine the residual activity of the maltogenic amylase from Geobacillus stearothermophilus in white bread. It was found that the important step for amylase extraction from the bread matrix was the addition of 10% (w/v) maltodextrin in the extraction buffer. The endogenous amylase activity in dough was investigated, and its inactivation during bread baking was proven. Thus, all amylase activities measured after baking have an exogenous origin. The amylase activities in the loaf of self-baked white bread containing defined dosages of exogenous amylase (10–100 μg per g flour) were reproducibly determined with 17.8 ± 1.24% residual activity. Moreover, an amylase activity of 369 ± 34.3 pkat gbread−1 was determined in three batches of a commercial white bread. The real temperature impact on the amylase during bread baking was investigated. The highest temperature in the crumb was 97 °C and, therefore, is significantly lower than the oven temperature (230 °C).

The optimized production, purification, characterization, and application in the bread making industry of three acid-stable alpha-amylases isoforms from a new isolated Bacillus subtilis strain US586

A new alpha-amylase-producing strain was assigned as Bacillus subtilis US586. The used statistical methodology indicated that amylase production was enhanced by 5.3 folds. The crude enzyme analysis proved the presence of three amylases isoforms Amy1, Amy2, and Amy3 called Amy586. The purified amylases had molecular masses of 48, 52, and 68 kDa with a total specific activity of 2,133 U/mg. Amy586 generated maltose, maltotriose, and maltopentaose as main final products after starch hydrolysis. It exhibited a large 4-6 optimal pH, a 60°C temperature activity, and a moderate thermostability. Amy586 displayed a high pH stability ranging from 3.5 to 6. The addition of Amy586 to weak wheat flour decreased its P/L ratio from 1.9 to 1.2 and increased its dough baking strength (W) from 138 × 10^-4 to 172 × 10^-4  J. Amy586 also improved the bread texture parameters by reducing its firmness and boosting the cohesion and elasticity values. PRACTICAL APPLICATIONS: Bacterial alpha-amylases with novel properties have been the major extent of recent research. In this paper, we managed to demonstrate that the addition of a purified amylolytic extract from the new isolated Bacillus subtilis strain US586 to weak local flour improves dough rheological proprieties and bread quality. Therefore, Amy586 can be considered as a bread making improver.

Thermo-reversible inhibition makes aqualysin 1 from Thermus aquaticus a potent tool for studying the contribution of the wheat gluten network to the crumb texture of fresh bread

The thermo-active serine peptidase aqualysin 1 (Aq1) of Thermus aquaticus was applied in bread making to study the relative contribution of thermoset gluten to bread crumb texture. Aq1 is active between 30 °C and 90 °C with an optimum activity temperature of around 65 °C. It is inhibited by wheat endogenous serine peptidase inhibitors during dough mixing and fermentation and starts hydrolyzing gluten proteins during baking above 80 °C when the enzyme is no longer inhibited and most of the starch is gelatinized and contributes to structure formation. Aq1 activity reduced the molecular weight of gluten proteins and significantly increased their extractability in sodium dodecyl sulfate containing medium. While it had no impact on the specific bread volume and only limited impact on hardness, cohesiveness, springiness, resilience and chewiness, it impacted bread crumb coherence. We conclude that starch has a greater impact on crumb texture than thermoset gluten.

Use of fermented glutinous rice as a natural enzyme cocktail for improving dough quality and bread staling

Jiu-niang (rice wine) could be used as a natural enzyme cocktail for the improvement of bread quality.

Impact of amylases on biopolymer dynamics during storage of straight-dough wheat bread

When Bacillus stearothermophilus α-amylase (BStA), Pseudomonas saccharophila α-amylase (PSA), or Bacillus subtilis α-amylase (BSuA) was added to a bread recipe to impact bread firming, amylose crystal formation was facilitated, leading to lower initial crumb resilience. Bread loaves that best retained their quality were those obtained when BStA was used. The enzyme hindered formation of an extended starch network, resulting in less water immobilization and smaller changes in crumb firmness and resilience. BSuA led to extensive degradation of the starch network during bread storage with release of immobilized water, eventually resulting in partial structure collapse and poor crumb resilience. The most important effect of PSA was an increased bread volume, resulting in smaller changes in crumb firmness and resilience. A negative linear relation was found between NMR proton mobilities of water and biopolymers in the crumb and crumb firmness. The slope of that relation gave an indication of the strength of the starch network.

Role of non-prolamin proteins and low molecular weight redox agents in protein folding and polymerization in wheat grains and influence on baking quality parameters

The various enzyme systems and low molecular weight (LMW) redox agents are related to the folding and polymerization of prolamins in the ripening wheat grains and the formation of baking quality. Protein disulfide isomerases (PDIs) and cyclophylins accelerate "correct" folding of prolamins, which is most likely necessary for the subsequent formation of the macromolecular structure of the gluten protein matrix. PDIs are also involved in the polymerization of prolamins, catalyzing the oxidation of protein sulfhydryl groups. Molecular chaperone binding BiP protein facilitates folding of prolamins, with its role increasing in the stressful conditions. Reducing systems of thioredoxin and glutaredoxin, LMW redox pairs GSH/GSSG and Asc/DHAsc, thiol oxidases, and lipoxygenases (LOXs) regulate redox balance and the rate of polymerization of prolamins at the different stages of grain ripening. Additionally, LOX is probably involved in the protein-starch-lipid interactions between the starch granule and the protein matrix, mediated by puroindolines, determining the formation of grain texture. It is assumed that the high variability of baking quality in different environmental conditions is due to the interaction of labile enzyme systems with the storage proteins in the developing wheat caryopsis.

Antifirming effects of starch degrading enzymes in bread crumb

Antifirming properties of amylases in bread crumb were evaluated in straight dough breadmaking and related to the amylolytically modified starch structure. Amylase properties and action mechanisms determine starch structure in the breads and, hence, how amylopectin recrystallization, starch network formation, water redistribution, and water mobility occur during breadmaking and storage. A bacterial endo-alpha-amylase mainly hydrolyzed the longer starch polymer chains internally. It thus reduced the number of connections between the crystallites in the starch networks, resulting in a softer bread crumb. However, because the enzyme had only little impact on the outer amylopectin chains, amylopectin recrystallization and the concomitant water immobilization presumably were not hindered. The loss of plasticizing water as a result of recrystallization presumably reduces the flexibility of the gluten network and results in poor crumb resilience. In contrast, in breadmaking, the Bacillus stearothermophilus maltogenic alpha-amylase acted as an exoacting amylase with more pronounced endoaction at higher temperatures. This enzyme caused extensive degradation of the crystallizable amylopectin side chains and thus limited amylopectin recrystallization and network formation during storage. As a result, it prevented the incorporation of water in the amylopectin crystallites. In this way, the different starch and gluten networks kept their flexibility, resulting in a softer crumb with good resilience.