Different approaches for increasing the shelf life of partially baked bread: Low temperatures and hydrocolloid addition

Partially baked bread is a product with short shelf life that requires sub-zero temperatures for extending it. The storage of par-baked bread at low temperatures and the addition of bread improvers with antistaling effects, such as hydroxypropylmethylcellulose (HPMC), are very attractive alternatives for extending the shelf life of these products. In this study, staling during storage of partially baked bread (in the presence and absence of HPMC) at low temperatures (2 °C) is studied in terms of hardness increase and amylopectin retrogradation. Simultaneously, the staling of the derived full baked breads when stored at 25 °C is assessed. During the storage of par-baked bread at low temperatures, progressive crumb hardening and rapid crystallization of the amylopectin chains were produced. However, heat applied during full baking reversed those processes, and the extent of that improvement was dependent on the time of par-baked bread storage. Concerning the staling of the derived full baked bread, the time of par-baked bread storage did not significantly (P < 0.05) affect the staling process of the resulting full baked breads. The addition of HPMC decreased the crumb hardness in both par-baked and full baked breads, and also promoted a reduction of the amylopectin retrogradation. Overall results indicate that HPMC addition significantly retards the staling of par-baked bread during its storage at low temperatures and, moreover, the same effect is observed in the full baked bread.     

Effect of frozen storage time on the bread crumb and aging of par-baked bread

The effect of frozen storage time of par-baked bread on the bread crumb and staling of bread obtained after thawing and full baking is described. The moisture content, hardness and retrogradation enthalpy of the amylopectin were determined in the par-baked bread and in the full baked bread after 7, 14, 28 and 42 days of frozen storage at −25 °C. In addition, the effect of frozen storage on the crumb microstructure was analyzed by cryo scanning electron microscopy (Cryo-SEM). The moisture content of both partially and full baked bread decreased with the time of frozen storage. The crumb hardness of the par-baked bread after different periods of frozen storage was kept constant, while that of their full baked counterpart increased with the time of frozen storage. In both types of breads, the enthalpy of amylopectin retrogradation did not vary with the period of frozen storage. The staling, measured as hardness increase and amylopectin retrogradation, increased along the frozen storage. The changes observed on the frozen par-baked bread after thawing were attributed to the damage of bread structures produced by the ice crystallization, and the microstructure study support that conclusion.     

Investigation of physicochemical properties of breads baked in microwave and infrared-microwave combination ovens during storage

Staling of breads baked in different ovens (microwave, infrared-microwave combination and conventional) was investigated with the help of mechanical (compression measurements), physicochemical (DSC, X-ray, FTIR) and rheological (RVA) methods. The effect of xanthan-guar gum blend addition on bread staling was also studied. Xanthan-guar gum blend at 0.5% concentration was used in bread formulation. The gums were mixed at equal concentrations to obtain the blend. After baking, the staling parameters of breads were monitored over 5 days storage. During storage, it was seen that hardness, retrogradation enthalpies, setback viscosity, crystallinity values, and FTIR outputs related to starch retrogradation of bread samples increased, whereas FTIR outputs related to moisture content of samples decreased significantly with time. The hardness, retrogradation enthalpy, setback viscosity, and crystallinity values of microwave-baked samples were found to be highest among other heating modes. Using IR-microwave combination heating made it possible to produce breads with similar staling degrees as conventionally baked ones in terms of retrogradation enthalpy and FTIR outputs related to starch retrogradation. Addition of xanthan-guar gum blend decreased hardness, retrogradation enthalpy and total mass crystallinity values of bread samples showing that staling was delayed.     

Combined effects of inulin,pectin and guar gum on the quality and stability of partially baked frozen bread

Many attempts have been made to increase the nutritional value of bread by adding dietary fibre. However, fibre enrichment is usually associated with various technological problems. The aim of this study was to optimise the composition of a blend of inulin, pectin and guar gum to enrich the fibre content of partially baked frozen bread without impairing its technological quality. We prepared 20 formulations following a central composite design, together with 4 control breads. Bread enriched with inulin had higher crumb hardness, lower specific volume, shape, moisture content, and crumb cohesiveness than control bread, but improved flavour. Pectin and guar improved moisture content and crumb cohesiveness. There was no interaction between inulin and pectin for any of the bread attributes investigated, while interactions between inulin and guar were small. In contrast, guar and pectin significantly interacted to decrease volume and increase crumb hardness and chewiness. A desirability function method identified the optimised blend as containing 3% inulin, 0.9–1% pectin and 0.3–0.4% guar. Bread enriched with such blend had the following characteristics: specific volume, 4.06 cm³/g; shape, 0.63; crumb hardness, 189 g; resilience, 0.36; cohesiveness, 0.84; chewiness, 169 g; and flavour score, 4.6. Experimental values were close to the predicted ones, with prediction errors below 10% for all attributes tested. The specific volume, crumb hardness and chewiness of the enriched bread were superior to those of unenriched bread. However, undesirable textural changes occurred in the enriched bread during 12 weeks of frozen storage, and these changes strongly depended on the fibre blend composition.     

The role of buckwheat and HPMC on the breadmaking properties of some commercial gluten-free bread mixtures

Although the food industry has risen to the formulation challenges associated with removing gluten from dough, and a number of gluten-free (GF) products are now commercially available, many GF bread formulations are still based on pure starches, resulting in low technological and nutritional quality. The aim of this research was to evaluate the role of buckwheat and HPMC on the breadmaking properties of two commercial GF bread mixtures. A dehulled (DBF) and a puffed (PBF) buckwheat flour were used, and high substitution levels (40%) were tested, with the aim of improving the nutritional value of the final GF breads without decreasing their technological quality. Ten mixtures (2 commercial, 8 experimental) were evaluated. The inclusion of 40% DBF was demonstrated not to reduce but actually improve the baking performances of the commercial GF mixtures. Moreover, the presence of a small amount of PBF, as well as of HPMC, turned out to be useful in limiting both the diffusion and the loss of water from the bread crumb and the interactions between starch and protein macromolecules, resulting in a softer GF bread crumb and reduced staling kinetics during storage.     

Improvement of the breadmaking quality of wheat flour by the hyperthermophilic xylanase B from Thermotoga maritima

The study was carried out to investigate the effect of hyperthermophilic xylanase B (XynB) from Thermotoga maritima on the properties of wheat bread and its staling during storage. The presence of XynB in the dough led to improvements in the breadmaking quality (i.e. specific volume and crumb structure) and provided an anti-staling effect on breads compared to the control. Addition of XynB could cause ≈60% increase in specific volume in comparison with the control. By fitting the crumb firming kinetics during storage to the Avrami equation, it showed that XynB retarded the bread staling by reducing the initial crumb firmness and the firming process during storage. XynB hydrolyzed the isolated WU-AX faster than WE-AX under the ratio of wheat AX in wheat flour. Improvement of bread quality by XynB can partly be ascribed to the enzyme specificity.     

Techno‐functional properties of wheat flour‐resistant starch mixtures applied to breadmaking

Resistant starch can be used to reduce the availability of carbohydrates in baked products. In this study, the effect of type 4 resistant wheat starch (RS₄) on wheat flour dough and breads was evaluated. Wheat flour was substituted by RS₄ at 10%, 20% and 30% w/w (RS10, RS20 and RS30, respectively). Rheological and thermal behaviours of dough were evaluated. Besides, bread quality, starch digestibility and bread staling were analysed. All substituted dough exhibited viscoelastic behaviour but lower elastic and viscous moduli. Regarding to bread quality, specific volume and crumb texture were negatively affected in samples with RS₄. However, all samples were technologically acceptable. During storage, crumb hardening was observed in breads without and with RS₄ but amylopectin retrogradation was not particularly affected. The in vitro digestibility of bread with RS showed a lower release of reducing sugars and a lower estimated glycaemic index, suggesting a healthier profile for these breads.     

The impact of resistant starch on characteristics of gluten-free dough and bread

The study focused on partial replacement in gluten-free breads of corn starch with tapioca and corn resistant starch preparations. The use of resistant starch resulted in the increase of storage and loss moduli of the dough, and the lowering of loss tangent, which indicates its more elastic character. The incorporation of resistant starch reduced creep and recovery compliance and elevated zero shear viscosity. Modified doughs displayed higher starch gelatinization temperatures and lower viscosities that were proportional to the share of RS. It was found that the loaves baked with the share of resistant starch had less hard crumb than bread without RS addition. The crumb hardness diminished with the increasing amount of applied RS preparation. The addition of resistant starch raised total dietary fibre, by up to 89%, as compared to control (bread without RS addition). The most pronounced change was observed for insoluble dietary fibre (increase 137%), while only slight increase was found for its soluble fraction (18%).     

A Study on Staling Characteristics of Gluten-Free Breads Prepared with Chestnut and Rice Flours

The effects of chestnut flour and a xanthan–guar gum blend–DATEM mixture on staling of gluten-free rice breads baked in conventional and infrared–microwave combination ovens were studied. Staling properties of the bread were assessed using mechanical compression (TA), differential scanning calorimetry, X-ray diffraction, and fourier transform infrared spectroscopy (FT-IR). Hardness, moisture loss, and retrogradation enthalpy values for all bread samples increased significantly during storage. FT-IR spectra showed that the integrated area of peaks around 1,041 and 1,150 cm^?1 wave lengths, which are related to the structure of starch retrogradation, increased with storage time. The X-ray diffractograms of aged breads indicated a B-type structure with the appearance of peaks at around 17°, 19.5°, and 22°. An additional peak at 24° was observed in breads stored for longer periods. Higher values of hardness and lower moisture contents were obtained for breads baked in an infrared–microwave combination oven, but the use of infrared–microwave combination oven did not result in excessive hardness after storage. Retrogradation enthalpies and total crystallinity values of breads did not show significant differences with baking type.The replacement of rice flour with chestnut flour and addition of xanthan–guar gum blend–DATEM mixture in formulations significantly delayed staling of gluten-free breads by decreasing moisture loss, hardness, retrogradation enthalpy, and total mass crystallinity.     

High-Legume Wheat-Based Matrices: Impact of High Pressure on Starch Hydrolysis and Firming Kinetics of Composite Breads

The significance of high hydrostatic pressure (HHP) processing on the physico-chemical—techno-functional and firming kinetics—parameters and nutritional properties—nutritional composition and “in vitro” starch digestibility—of highly replaced wheat flour breads by chickpea, pea and soybean flours was investigated, and the power/effectiveness of HHP in partially replacing structural agents (gluten and/or hydrocolloids) was discussed. Incorporation of pressured legume slurries (350 MPa, 10 min) at 42% of wheat replacement into bread formulation provoked a general increase in initial crumb hardness and browning of the crust with a concomitant explicit reduction of moisture, whiteness of the crumb and bread specific volume, but a slower in vitro starch digestibility with prominent formation of slowly digestible starch and resistant starch, compared to their counterparts prepared by using a conventional gluten/carboxymethyl cellulose (CMC)-added breadmaking recipe/process. Pressured breads with no gluten but 3% CMC in the formulation kept higher sensory ratings, softer initial texture and lower firming profiles on ageing than pressured breads with no gluten nor CMC. HHP has proven to be an effective technology to partially replace structuring agents (CMC and/or gluten) in high-legume wheat-based matrices providing sensorially acceptable breads with medium physico-chemical quality profile but enhanced formation of nutritionally relevant starch fractions and slower crumb firming kinetics on ageing.     

Gluten-free Bread Based on Tapioca Starch: Texture and Sensory Studies

In the present work, gluten-free formulations for breadmaking, destined to celiac people, were studied. A base blend of tapioca starch and corn flour (80:20) and typical bread ingredients such as yeast, salt, sugar and water were utilised. Ingredients such us vegetable fat, hen egg, and soybean flour were incorporated in different levels by means of an experimental design of three factors. Bread quality was analysed throughout physical (specific volume, weight loss percentage) and textural (firmness, elasticity and firmness recovery) parameters. The optimum bread selected, the bread with highest levels of fat and soybean flour and one egg, presented low values of firmness (≤100 N) and elasticity (>65%) and the lowest variation of these parameters with storage. Overall acceptability of this bread was 84% for habitual consumers of wheat bread and 100% by celiac people. Therefore, tapioca starch-based breads with spongy crumb, high volume and a good sensory acceptance were obtained.     

Effect of baking conditions and storage with crust on the moisture profile,local textural properties and staling kinetics of pan bread

To investigate the impact of baking conditions on staling kinetics and mechanical properties, pan breads were baked at 180 °C/34 min and 220 °C/28.6 min using a ventilated oven and metallic moulds. After baking, bread slices were stored with and without crust at 15 °C in hermetic boxes for 9 days. This investigation provides a textural and physical analysis by examining the Young's modulus, crumb density and crust/crumb ratio during storage. In order to understand the relationship between firmness and moisture content, a moisture profile and a Young's modulus profile were determined during the storage of bread. To fit the staling, a first order model was used. It was found that the kinetics were faster for samples baked with a fast heating rate than for those baked with a slow heating rate. Moreover, the staling rate of bread stored with crust was faster than for bread without crust and the outer crust area staled more rapidly than the centre of the bread slice. These results suggest that the firming of the crumb is related to moisture distribution between the crumb and crust and to the impact of local baking conditions on local firmness.     

Impact of microbial transglutaminase on the staling behaviour of enzyme-supplemented pan breads

The effects of microbial transglutaminase (TGM) when added singly and in combination with amylolytic (-amylase, NMYL) and non-amylolytic (xylanase) enzymes on the textural profile of fresh pan beads and pan breads stored for up to 20 days have been investigated in samples made with low and high extraction rate wheat flours following a sponge-dough process. White and whole-wheat enzyme-supplemented bread samples evidenced a similar sensory firming profile but a different quantitative instrumental staling pattern during storage. Two groups of samples with different staling behaviour can be defined according to the absence (faster staling kinetics) or the presence (slower kinetics) of NMYL in the bread formula, the separation being particularly clear for hardness, cohesiveness and resilience in white bread samples. TGM when added to NMYL-supplemented doughs induced synergistic beneficial effects on fresh bread quality and staling kinetics retardation. The binary combination led to breads with softer and less chewy fresh crumbs, increased initial crumb cohesiveness and resilience, and slower crumb staling kinetics and sensory deterioration during storage, particularly for samples made with white flour.     

Value Added of Resistant Starch Maize-Based Matrices in Breadmaking: Nutritional and Functional Assessment

The ability of white (W) and yellow (Y) maize flour as basic ingredients to make nutritious and healthy breads meeting functional and sensory standards is investigated. Resistant starch (R) and common wheat flour (WF) were incorporated into formulations as single and associated extra ingredients, and dough machinability, bread nutritional and functional profiles, starch hydrolysis kinetics and keeping behaviour were assessed in blended maize matrices and compared with the maize and wheat flour counterparts. Simultaneous replacement of maize flour samples by R and WF at 40 % significantly modified textural profile, crumb grain features and firming kinetics, and free polyphenol pattern of breads thereof compared to the respective Y or W maize counterparts. Bigger specific volume (+28 % Y-R-WF, +36 % W-R-WF), softer crumb bread (?64 % Y-R-WF, W-R-WF), more aerated structure and homogeneous crumb grain, and lower and slower staling kinetics are observed in composite Y and W maize-based breads, respectively. Nutritional information on maize-based blended breads showed most appealing nutritional quality than WF breads, in terms of lower digestible starch (up to ?21 % in Y-R-WF, W-R-WF, WR) and rapidly digestible starch (up to ?37 % in W-R-WF), higher slowly digestible starch (up to three times in WR) and resistant starch contents (from five to six times in Y-R-WF, W-R-WF, W-R, Y-R) of medium-high sensorially rated bread matrices. All single and blended maize-based breads can be labelled as high-fibre breads (6 g dietary fibre (DF)/100 g food). According to health-related benefits and prebiotic dosage of resistant starch a daily intake of 100 g of single Y-R, W-R, W-R-WF and W-R-WF provides enough resistant starch to positively affect postprandial glucose and insulin levels, while 170 g covers the amount necessary to enhance health.     

Influence of Gluten-free Flours and their Mixtures on Batter Properties and Bread Quality

Gluten is a major component of some cereals and is responsible for flour technological characteristics to make bakery products. However, gluten must be eliminated from the diet of celiac patients because its ingestion causes serious intestinal damage. The objectives of this study were to assess the effect of different flours and their mixtures on thermal and pasting properties of batters, and to study the quality parameters and staling rate of gluten-free breads. Starch gelatinization temperatures and enthalpies depended on batter composition. Soy flour addition had a higher effect on rice than on corn starch, indicating some differential interaction between starch and proteins. Inactive soy flour incorporation improved all bread quality parameters in both corn- and rice-based breads. Higher batter firmness of formulations with soy addition (extrusion force was doubled in rice/soy and rice/corn/soy batters with regard to rice and rice/corn batters) partially explained higher specific volume (rice breads: 1.98 cm³/g; rice/soy 90:10 2.51 cm³/g, corn/soy 90:10: 2.05 cm³/g, whereas corn/soy 80:20: 2.12 cm³/g), as these batters retained more air during proofing. The staling rate was decreased by soy flour incorporation on rice (staling rate of rice breads with 10% soy diminished 52%, and with 20% of soy addition, 77%, both regarding to 100% rice breads) and corn formulation (the staling rate of corn/soy 80:20 breads was 5.9% lower than corn/soy 90:10) because of the high water-holding capacity of soy proteins and the interactions established with amylopectin that could retard the retrogradation process. Breads made with rice, corn, and soy flours showed the best quality attributes: high volume, good crumb appearance, soft texture, and low staling rate.     

The impact of baking time and bread storage temperature on bread crumb properties

Two baking times (9 and 24 min) and storage temperatures (4 and 25 °C) were used to explore the impact of heat exposure during bread baking and subsequent storage on amylopectin retrogradation, water mobility, and bread crumb firming. Shorter baking resulted in less retrogradation, a less extended starch network and smaller changes in crumb firmness and elasticity. A lower storage temperature resulted in faster retrogradation, a more rigid starch network with more water inclusion and larger changes in crumb firmness and elasticity. Crumb to crust moisture migration was lower for breads baked shorter and stored at lower temperature, resulting in better plasticized biopolymer networks in crumb. Network stiffening, therefore, contributed less to crumb firmness. A negative relation was found between proton mobilities of water and biopolymers in the crumb gel network and crumb firmness. The slope of this linear function was indicative for the strength of the starch network.     

High-Amylose Resistant Starch as a Functional Ingredient in Breads: a Technological and Microstructural Approach

Resistant starches (RS) are important functional fibers with high potential for the development of healthy foods. The technological, nutritional, and commercial possibilities of introducing type 2 RS in white breads were studied. Four levels of maize RS (HM) as wheat flour replacement were evaluated: 0%, 10%, 20%, and 30% (control, HM10, HM20, and HM30, respectively). Thermal transitions experiments were assessed on doughs prior to breadmaking. The bread quality was studied by specific volume, color of crust and crumb, porosity, and texture of the crumb. The microstructure of the crumb was analyzed by environmental scanning electron microscopy (ESEM). Proximate composition and in vitro starch digestibility were performed to characterize the nutritional profile of breads and estimate the glycemic index (GI). Consumer acceptability of breads was also evaluated. Breads with HM showed great performance up to 20% replacement in the specific volume, the crumb porosity, and the texture. Replacement up to 30% caused major damage to those parameters. Differential scanning calorimetry runs demonstrated that HM starch did not gelatinize under the baking conditions, as confirmed by ESEM. The presence of increasing levels of native starch is thought to have the greatest influence on reducing the crust browning, increasing the crumblier texture and decreasing starch digestibility. With respect to the control, a high and progressive reduction in the estimated GI and an outstanding increase of fiber with increasing levels of HM were found. The sensory evaluation of HM20 bread showed that this level of substitution has great consumer acceptance, giving it the chance to become a healthy substitute of white bread.     

The effect of dairy and rice powder addition on loaf and crumb characteristics,and on shelf life (intermediate and long-term) of gluten-free breads stored in a modified atmosphere

Many commercially available gluten-free breads are inferior in quality to their gluten-containing counterparts. They also have a relatively short shelf life. The current study investigated the effects of 3% milk protein isolate and 3% novel rice starch addition to a gluten-free bread formulation, and on the intermediate (8 days) and long-term (43 days) staling profile of both gluten-free bread formulations, packed in an 80% CO₂\20% N₂ atmosphere. Dairy protein and rice starch addition increased loaf volume and the loaves were preferred to a control sample by an untrained panel. The most notable changes in crumb hardness occurred in the early days of the testing periods for the control gluten-free bread in both the intermediate and long-term studies.     

Staling in Starch Bread: the Effect of Gluten Additions on Specific Loaf Volume and Firming Rate

Hypotheses on the role of gluten in bread staling range from gluten having an anti-firming effect, or no effect on firming, to gluten-starch interactions being essential for bread firming. To test these hypotheses, the firming rate of starch bread made from protein-free synthetic flour was compared with that of starch-gluten breads made from synthetic flours containing 1–15% gluten (Fig. 1). Only loaves of similar specific loaf volume and crumb moisture content were compared to eliminate these parameters as variables that might influence firming rate. The starch breads clearly increased in firmness up to six days, indicating that gluten was not essential to the firming process, starch alone causing bread to firm with time. The starch-10% gluten breads and starch-15% gluten breads had very similar specific loaf volumes, moisture contents and firming rates to that of the starch breads. This indicates that protein possibly has some role in firming, because if only starch has a role in firming then adding gluten would effectively dilute the starch and reduce the rate of firming. We propose that increasing bread firmness results from glucan chains of partially leached amylose and amylo-pectin attached to swollen starch granules forming hydrogen bonds with other starch granules and, to a smaller extent, with gluten fibrils.     

Partial-Baking Process on Gluten-Free Bread: Impact of Hydrocolloid Addition

The objectives of this work were to assess the impact of partial-baking process on gluten-free bread, and to study how carboxymethylcellulose (CMC) and xanthan gum addition affected this process. As different from the conventional baking which involves only one baking step (40 min), the part-baking process consisted in an initial-baking step (25 min), storage (7 days, 4°C), and final-baking step (15 min). Bread-specific volume (SV), crumb hardness, and image analysis were assessed on final products of both processes and intermediate products of part-baking process. Breads were stored at room temperature for 72 h and crumb firming and amylopectin retrogradation were monitored. Freezable water (FW) fraction was determined on fresh and stored samples by using differential scanning calorimetry. Part-baked breads showed lower SV and higher crumb hardness. No SV diminution was observed during cold storage. Hydrocolloids, especially CMC, had a positive effect on these parameters, and during bread storage at room temperature, the increase in crumb hardness was mitigated by hydrocolloid addition. Part-baked breads showed smaller cell area than full-baked ones. Overall, crumb structure was more homogeneous for CMC breads. FW showed no significant differences among processes, formulations, or storage time. Amylopectin recrystallization was higher for part-baked breads. Interrupted-baking process affected the final bread quality, but negative effects could be diminished by hydrocolloid addition. Part-baking process is suitable for obtaining gluten-free breads, stored for a week at 4°C, turning them appropriated for home consumption.