Influence of inulin on bread: Kinetics and physico-chemical indicators of the formation of volatile compounds during baking

The influence of inulin on the formation and release of white bread volatiles was studied during baking, using an innovative on-line baking extraction device. Kinetic studies were performed to follow the development of crust physical properties and the formation of volatiles responsible for the flavour of breads having different amounts of inulin. It was demonstrated that inulin accelerated the formation of the bread crust and the Maillard reaction. It led to breads with an overall quality similar to that of non-enriched breads, but baked for a shorter time. Correlations between some crust properties and the amount of Maillard volatiles were determined. They showed that crust water activity, moisture and clearness could be good indicators of the Maillard reaction during the baking of bread.     

Physico-chemical changes in breads from bake off technologies during storage

Quality of several bread specialties from frozen partially baked breads was assessed to define main quality features. Loss of crust freshness shortly after baking was also determined. Quality parameters that characterize bread crust and crumb were determined by instrumental methods in nine different (regarding to formulation and bake off duration) bread types obtained from frozen partially baked breads. Principal component analysis (PCA) allowed discriminating among bread specialties. Quality parameters that enable the differentiation of wheat bread types were crust mechanical properties together with specific volume, crumb hardness and structure. Crust flaking barely represented a problem in the studied types of bread. Crust mechanical properties were rapidly lost during the first 4 h after baking and the rate of the process was greatly dependent on the bread type. The force to promote crust fracture underwent increase up to 6 h after baking and those changes occurred in the Aw range of 0.50-0.74 or moisture content 9-15 g/100 g.     

Wheat bran particle size effects on bread baking performance and quality

Commercial hard red spring, hard red winter, soft white and durum wheat brans were used to evaluate the particle size effect of wheat bran on bread baking performance and bread sensory quality. Three different particle size bran samples were obtained from each bran by grinding, not by sifting, the bran samples. The bran samples were similar in chemical composition, but different in particle sizes. Results of baking experiments showed that breads containing fine bran had lower specific loaf volume and darker crumb colour than breads containing coarse or medium size bran. Sensory test panellists found that fine bran contributed smoother crust appearance and less gritty mouthfeel than the coarse bran. The sensory panel also indicated that breads containing soft white wheat bran had significantly better flavour and mouthfeel than breads containing hard red spring wheat bran. © 1999 Society of Chemical Industry     

Gas chromatographic–mass spectrometric characterisation of the Italian Protected Designation of Origin “Altamura” bread volatile profile

Dynamic headspace extraction technique coupled to the gas chromatography–mass spectrometry analysis was applied to characterize volatile compounds of both crust and crumb of the Protected Designation of Origin Italian durum wheat sourdough “Altamura” bread. Volatile compounds of crust and crumb were characterized and statistically compared and their relative abundance was also calculated. A total of 89 compounds belonging to different chemical classes were identified in the crust. More abundant compounds detected in the crust were ethanol (20 ± 6%), 2-furfural (14 ± 7%) and 3-methyl-1-butanol (9 ± 5%). A lower number of volatile compounds (74) was identified in crumb, among which ethanol (32 ± 7%), 3-methyl-1-butanol (23 ± 6%) and 3-pentanol (7 ± 3) were the most abundant. The influence of different baking modes (wood- or gas-fired) on volatile compounds, macroscopic appearance and selected physico-chemical parameters (colour and texture) of bread samples were also evaluated.

Samples baked in wood-fired oven showed larger amount of volatile compounds such as furans and aldehydes that could positively influence the flavour of the product.

Crust of wood-fired breads showed higher amounts of compounds from Maillard reaction, resulting in harder and browner breads than gas-fired samples. Macroscopic appearance of crumb of wood-fired breads showed higher percentages of larger pores, being also less hard and cohesive than gas-fired samples.     

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.     

间歇性添加蒸汽对餐包品质的影响

通过测定餐包升温曲线、质构、丙烯酰胺含量及风味物质等参数,研究了焙烤时蒸汽添加频率(低、中、高频率,对应添加蒸汽的时间间隔分别为4、2、1 min)对餐包品质的影响。结果发现,相比无蒸汽组,蒸汽的加入使餐包中心升温速率总体更加平缓。较之无蒸汽组,中高频率引入蒸汽餐包的烘焙损失率降低(P<0.05)。随着蒸汽频率增高,餐包表皮中心的L*值和b*值上升,而a*值下降,通过质构测定,加入蒸汽使餐包表皮硬度和餐包硬度均显著降低(P<0.05),其耐咀嚼度和回复性随蒸汽频率增高呈先下降后上升的趋势。蒸汽的引入使醇类、壬醛和3-羟基-2-丁酮等物质的相对含量升高,而糠醛的相对含量降低,使面包在具有更加浓厚的香气的同时,减少焦糊味。同时,蒸汽的引入改变了餐包表皮的微观结构,降低了餐包整体及其表皮的丙烯酰胺生成量,其中表皮由350 μg/kg降低为218、141、83 μg/kg(依次为低、中、高频率组),整体由74 μg/kg降低为59、55、41 μg/kg(依次为低、中、高频率组)。餐包表皮赖氨酸的残留量显著增加(P<0.05),由无蒸汽组的0.97 g/kg增加至高频率组的1.58 g/kg。最后结合感官评价得出,当蒸汽加入时间间隔为2 min时,餐包色香适中且营养安全品质较优。     

Protein profile and sensorial properties of rye breads

The protein profile of four types of traditional rye breads formed on rye flours with the extraction rate of 100, 95, 85 and 70% and baked at 260 °C for 40 min was investigated as a nutritional quality indicator. A fractionation process was applied to discriminate high-molecular- (HMW >3 kDa) and low-molecular weight compounds (LMW <3 kDa) present in extracts of rye bread and its crumb and crust. The content of soluble proteins, available lysine, carbohydrates and total phenolic compounds was analysed before and after ultrafiltration in both retentates (HMW >3 kDa) and filtrates (LMW <3 kDa). The dependence between sensory quality of rye breads and composition on soluble proteins, available lysine, carbohydrates and total phenolic compounds was provided. Baking caused a decrease in rye bread protein content. The content of available lysine was the lowest in crusts and it was dependent on the rye flour extraction rate taken for rye bread making. The SDS-PAGE analysis showed that the primary structure of the rye bread proteins was modified in the highest extent in the crust’s bread of all types. The analyses of both retentates and filtrates after ultrafiltration demonstrated that the most of carbohydrates and phenolic compounds were incorporated into the HMW fraction suggesting their conjugation with proteins due to the Maillard reaction. Compounds able to react with Folin Ciocalteu reagent were also detected in filtrates of crust’s extracts (MW ≤3 kDa) from all breads indicating their distribution between LMW and HMW fractions. About 22.5, 27, 11.2 and 46.8% of the phenol compounds forming crusts of breads based on the flours with extraction rates of 100, 95, 85 and 70% were recovered in the corresponding LMW fractions.The sensory analysis of the four types of rye breads indicated for a high correlation between overall quality of breads and their content of carbohydrates. The highest correlation was noted for a rye bread formed on flour with extraction rate of 95%. This finding suggested that the content of carbohydrates as a substrate for Maillard reaction has had an influence on palatability by consumers of rye bread formed on flour with the extraction rate of 95% which had also the highest overall quality.     

Shelf-life stability of artisanally and industrially produced durum wheat sourdough bread (“Altamura bread”)

Physico-chemical properties and volatile compounds of three commercial Altamura breads were evaluated during storage at 25 °C. Two protected denomination of origin (PDO) artisanally produced Altamura breads (Bari, Italy), characterized either by high (High A) or low (LowA) loaf, and an industrial product, commercialized as “Altamura like” (IndA), were studied.HighA and LowA breads had a tick crust that was also detached from the crumb creating an air cushion between crust and crumb. IndA products had a thinner crust, a more homogeneous crumb structure as well as a more homogeneous water distribution among the different portion of the bread loaf than HighA and LowA. A more pronounced water gradient characterized the artisanal breads. Crust and under crust portion of all breads, and crumb for IndA product, underwent a significant reduction of moisture content and a_w during storage. Both artisanal breads were subjected to a more significant crumb hardening than IndA sample. Fresh crusts of artisanally produced breads were also significantly harder than IndA. Fresh IndA samples were significantly less cohesive and less springy than artisanal products; cohesiveness significantly decreased in all samples during storage. A more complex gas chromatographic profile was found in the artisanal bread as a larger amount of volatile compounds was present as compared to the IndA bread. Volatile compounds originated both from microbial activity and non-enzymatic browning. Larger amount of volatile compounds characteristics of yeast fermentation was found in IndA. Volatiles decreased over storage in both samples, more significant in the IndA product.     

Sensory Crispness of Crispy Rolls: Effect of Formulation, Storage Conditions, and Water Distribution in the Crust

ABSTRACT:  Crispness is an important sensory quality parameter that strongly influences the acceptability of cellular solid foods such as the crust of many types of breads. Crispness of the bread crust depends particularly on its water content. In this study, the relationship between sensory crispness of crispy rolls and the average water content of the crust was studied for different bread formulations (control, amylase, glucose-oxidase, and protease) and storage conditions (40% and 80% RH). From the different formulations used, only protease treatment increased the crispness of the crust and its retention at both storage conditions. The positive effect of the protease treatment was due to a lower water content of the crust of these breads compared to the other formulations. The relationship between sensory attributes, formulation, and storage conditions was found to be dominated by the dependence on storage conditions. When combining data for low and high humidity storage it showed that crusts with equal water contents could exhibit different scores for crispness. The results led to the hypothesis that a gradient of water content exists within the crust. At high humidity, the crust will take up water from both crumb and environment and a relative smaller gradient of water will exist within the crust. At low humidity on the other hand, the crust will take up water from the crumb only, resulting in a larger gradient of water within the crust.     

Physical properties of breads containing hydrocolloids stored at low temperature. I. Effect of chilling

Different bread types, some of them containing also hydrocolloid stabilizers, were cold stored for evaluating the final quality of breads after storage. Dough (DB), semi-baked products (SB) and full-baked (FB) breads were used. After storage their physical characteristics were measured, data grouping was performed using PCA analysis and correlations among the properties measured were found. Fresh samples presented some similarities to DB or SB breads, but FB breads had a completely different behaviour. Crust characteristics were found to be important for the quality characterization of breads, as crust textural characteristics; its colour and moisture content were correlated to other properties. Furthermore, crust viscoelastic characteristics gave an indication of bread staling. Porosity was the only physical property not correlated to other bread characteristics. Differences were noticed according to the bread type before storage and the hydrocolloid used, but the main differences were determined by the baking stage before storage. Furthermore, hydrocolloids addition could result in different final bread properties according to the baking stage before storage. The crumb of FB breads was relatively viscous despite of hydrocolloid addition. Hydrocolloids seem to be more effective as stabilizers in DB and SB breads.     

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.     

Effect of temperature and time on the formation of acrylamide in starch-based and cereal model systems,flat breads and bread

Dry starch systems, containing varying amounts of asparagine and glucose, freeze-dried rye-based flat bread doughs, flat bread and bread, were baked at varying temperatures and times according to central composite designs. In the starch-based model system the amount of acrylamide went through a maximum when the level of asparagine increased. No such maximum was found for glucose. In the starch system, freeze-dried flat bread doughs and flat breads, the amount of acrylamide formation went through a maximum at approximately 200 °C, depending on the system and the baking time. The amount of acrylamide was reduced at long baking times. However, in bread crust, the amount of acrylamide increased with both baking time and temperature in the interval tested.     

Influence of Final Baking Technologies in Partially Baked Frozen Gluten‐Free Bread Quality

The effect of final baking in convection oven (FBC), microwave oven (FBM), and microwave oven with susceptor packaging material (FBMS) on partially baked (PB) frozen gluten‐free bread characteristics was investigated. Specific volume and crust color of loaves were measured at day 0. Bread moisture, water activity, and crumb and crust texture (at 15, 45, and 90 min after baking) were analyzed at day 0 and after 28 d of frozen storage (?18 °C). Volatile compounds from breads baked in convection oven or microwave oven with susceptor packaging material were also evaluated. Bread finally baked in convection oven or in microwave oven with susceptor packaging increased crust browning. Crumb and roll hardness increased with time after final baking (measured at 15, 45, 90 min) and after 28 d of frozen storage. Bread finally baked in microwave oven was the hardest, due to high water losses. At day 0, bread finally baked in convection oven had softer crumb than bread finally baked in microwave oven with susceptor packaging but, after 28 d of frozen storage, there were no differences between them. Moreover, FBC and FBMS rendered gluten‐free breads that could not be distinguished in a triangular test and had the same volatile compounds profile. In conclusion, FBMS could be an alternative to FBC.     

STEAMED BREADS MADE FROM COLORADO GROWN WHITE WHEATS

Seven Colorado grown white wheats and a commercial all-purpose flour were used to prepare Chinese steamed bread. Steamed bread doughs were made from 41.8% flour (200g per batch), 0.7% instant active dry yeast, and 57.5% water. Steamed breads were evaluated for specific volume (cm³/g), color of crumb and crust, texture using a texture analyzer, and by a subjective sensory evaluation.
Specific volume of steamed bread ranged from 3.3 to 3.6 cm³/g. There was no statistical significant difference in crust and crumb color among breads from all flour samples. Low peak force and area texture measurements which indicate softness, were correlated with high specific volume. Overall, the flours from Colorado grown white wheats were desirable for making steamed bread with one exception. The all-purpose commercial flour was found to be desirable for making steamed bread.     

Furosine is a useful indicator in pre‐baked breads

There is increasing demand for pre‐baked bread. Bakers can meet consumer requirements for breads of specific flavour and colour by pre‐baking an amount of bread in the morning and completing the baking process in the afternoon. This type of product is of special interest to sandwich bars, restaurants and large communities. In order to obtain an indicator of utility to monitor the processing of pre‐baked bread, the browning indicators furosine, hydroxymethylfurfural (HMF) and glucosylisomaltol were analysed in two independent assays of bread pre‐baked at 175 °C for between 5 and 30 min. No furosine was detected in raw or fermented dough. In the pre‐baking stage, furosine increased from 1.5‐ to 5‐fold between 5 and 30 min. The furosine values obtained in the two independent experiments were similar. HMF and glucosylisomaltol were only detected after 15 min, which is the time period commonly used for processing by the industry. Thus, among these indicators, furosine is the only one with utility for monitoring the pre‐baking process. On the other hand, a study of the baking of pre‐baked bread at 220 °C showed that HMF and glucosylisomaltol can be used to monitor the latter process. Copyright © 2004 Society of Chemical Industry     

Effect of Baking Procedure and Storage on the Pasting Properties and Staling of Part-Baked and Rebaked White Pan Bread Crumb

In this investigation, the white pan breads were part-baked for 10, 15, 20 minutes at 230°C with and without calcium propionate (0.2%), were stored at room temperature (20°C) for 3, 5, 7 days wrapped with two polyethylene bags. After storage, baking time of part-baked breads was completed to the baking time of control breads (25 minutes). Breads were subjected to softness analysis and pasting properties of bread crumb were determined using the Brabender Amylograph. Addition of Ca-propionate decreased softness value of crumb of bread rebaked after part-baked, while the peak, holding end and cooling end viscosities increased. The increase in initial baking time resulted in a decrease in the pasting temperature and softness value and an increase in the bump area and viscosity of the rebaked bread crumb. Bump area, water activity, softness value and peak, holding end and cooling end viscosities of crumb of the rebaked bread after part-baking decreased with longer (intermediate storage) time. Peak viscosity and water activity significantly correlated with softness of bread crumb rebaked following part-baking and storage at room temperature. Rebaking bread for 10 and 15 minutes after storage of 3 and 7 days at room temperature resulted in softer crumb than the control group.     

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.     

Identification of bitter compounds in whole wheat bread

Bitterness in whole wheat bread can negatively influence product acceptability and consumption. The overall goal of this project was to identify the main bitter compounds in a commercial whole wheat bread product. Sensory-guided fractionation of the crust (most bitter portion of the bread sample) utilising liquid–liquid extraction, solid-phase extraction, ultra-filtration and 2-D offline RPLC revealed multiple bitter compounds existed. The compounds with the highest bitterness intensities were selected and structurally elucidated based on accurate mass-TOF, MS/MS, 1D and 2D NMR spectroscopy. Eight bitter compounds were identified: Acortatarins A, Acortatarins C, 5-(hydroxymethyl)furfural(HMF), 2,3-dihydro-3,5-dihydroxy-6-methyl-4(H)-pyran-4-one (DDMP), N-(1-deoxy-d-fructos-1-yl)-l-tryptophan (ARP), Tryptophol (TRO), 2-(2-formyl-5-(hydroxymethyl-1H-pyrrole-1-yl)butanoic acid (PBA) and Tryptophan (TRP). Based on the structures of these compounds, two main mechanisms of bitterness generation in wheat bread were supported, fermentation and Maillard pathways.     

Effects of flour from different barley varieties on barley sour dough bread

Twenty flours from 16 different barley varieties cultivated in 1990 and 1992, and a Swedish reference flour, were fermented by Lactobacillus plantarum A1 to sour doughs. Barley breads (40% barley/60% wheat flour) from each flour type were baked with and without an admixture of barley sour dough in order to investigate how the sour dough admixture would affect the baking properties. A trained panel carried out sensory evaluation by conventional profiling on breads made from three of the barley varieties and the Swedish reference flour, made with and without sour dough admixture.

The barley varieties influenced both the sour dough properties and the properties of the barley bread. The pH of bread with sour dough ranged from 4.6 to 4.8 as compared to 5.4 to 5.6 in bread without sour dough. The acidity of the breads with sour dough ranged from 4.1 to 5.0 ml NaOH/ 10 g bread crumb as compared to 2.4 to 3.6 in breads without sour dough. In 14 of the twenty bread types an addition of sour dough lowered the bread volume. Breads with a sour dough admixture scored higher for total taste and acidulous taste than breads without sour dough. The β-glucan content of the flours had no significant influence on the sour dough or the sensory characteristics of the bread, except for the breadcrumb colour.     

Effect of prebaking and frozen storage on the sensory quality and instrumental texture of bread

The effect of part‐baking, freezing, frozen storage, thawing and rebaking on the quality of bread has been investigated. Quality evaluation of the stored bread was done using sensory analysis, instrumental texture profile analysis (TPA) and cutting tests of the crumb and crust. It was found that frozen bread with 71% fraction of baking time showed high stability of sensory features and rheological parameters during the entire storage period (11 weeks) and, after thawing and rebaking, had superior quality in comparison with its frozen and thawed full‐baked (100%) counterpart. Second‐order regression showed that the optimal time for the initial prebaking lies within the wide range from 74 to 86% of the time needed for the full‐baking of unfrozen bread. It is therefore a good method for preventing the staling process and obtaining a product of a quality close to that of fresh, not frozen bread. It has also been shown that a fraction of baking time equal to 43% was too small to ensure desirable sensory and textural features of bread after its frozen storage and rebaking. © 2002 Society of Chemical Industry