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.     

Effect of HPMC addition on the microstructure, quality and aging of wheat bread

The effect of hydroxypropylmethylcellulose (HPMC) addition on a basic bread formulation is described. The effect of HPMC as bread improver and antistaling agent was analysed in terms of microstructure. Bread quality was assessed by physical parameters (volume, width/height ratio, moisture content and hardness), crumb grain structure (number of air cells, cells area and the ratio between cells area and total area) and sensory evaluation (appearance, aroma, taste and texture). Bread staling was determined by following both the hardness increase and the starch retrogradation during storage. The microstructure was analyzed by cryo scanning electron microscopy (cryo-SEM). The results confirm the ability of the HPMC for improving fresh bread quality and for delaying staling. The presence of HPMC decreased the hardening rate of the bread crumb and also retarded the amylopectin retrogradation. The microstructure analysis revealed the possible interaction between the HPMC and the bread constituents, which could partially explain the antistaling effect of this hydrocolloid.     

馒头老化指标的初步研究

研究了馒头在储存过程中物理化学特性的变化并进行了相关性分析，初步确定馒头芯的硬度与弹性、馒头瓤上清液中干物质和蛋白质含量以及上清液与碘试剂络合吸光度为馒头老化的代表指标。     

Functional effects of xanthan gum on composite cassava-wheat dough and bread

The use of composite flour for bread making is gradually gaining prominence worldwide due to some economic and nutritional reasons. However, studies on the application of functional ingredients purposely to improve composite bread quality are very few. This paper examines the functional role of xanthan gum (XG) on the properties of dough and bread from composite cassava-wheat flour. The viscoelastic properties of dough and gas retention characteristics of batter as well as the fresh and storage properties of bread from the composite flour (90% wheat plus 10% cassava) were studied. The crumb cell structure was also studied using digital image analysis technique. Inclusion of XG had significant effects on the dough tenacity and extensibility and sensory acceptability of fresh composite bread. The oven spring, specific volumes of bread loaf and crumb softness were higher at 1% XG content. Also, addition of XG made the composite bread samples had more open crumb structure and better sensory acceptability. However, moisture loss and crumb firming during bread storage were best reduced when 1% XG was added to bread formulation.     

Influence of in-situ synthesized exopolysaccharides on the quality of gluten-free sorghum sourdough bread

The majority of gluten-free breads on the market are of poor sensory and textural quality. Exopolysaccharides (EPS) formed from sucrose during sourdough fermentation can improve the technological properties of gluten-free breads and potentially replace hydrocolloids. In this study, the influence of in situ formed EPS on dough rheology and quality of gluten-free sorghum bread was investigated. Dextran forming Weissella cibaria MG1 was compared to reuteran producing Lactobacillus reuteri VIP and fructan forming L. reuteri Y2. EPS containing bread batters were prepared by adding 10% and 20% of sourdough. As control served batters and bread containing sourdoughs fermented without sucrose and batters and bread without sourdough addition. The amount of EPS formed in situ ranged from 0.6 to 8.0 g/kg sourdough. EPS formed during sourdough fermentation were responsible for the significant decrease in dough strength and elasticity, with in situ formed dextran exhibiting the strongest impact. Increased release of glucose and fructose from sucrose during fermentation enhanced CO? production of yeast. Organic acids in control sourdough breads induced hardening of the bread crumb. EPS formed during sourdough fermentation masked the effect of the organic acids and led to a softer crumb in the fresh and stored sorghum bread. Among EPS, dextran showed the best shelf life improvements. In addition to EPS, all three strains produced oligosaccharides during sorghum sourdough fermentation contributing to the nutritional benefits of gluten-free sorghum bread. Results of this study demonstrated that EPS formed during sourdough fermentation can be successfully applied in gluten-free sorghum flours to improve their bread-making potentials.     

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.     

Bread crumb quality assessment: a plural physical approach

The aim of this study was the assessment of pan bread crumb quality attributes of commercial samples using a plural physical approach to better match consumer awareness. Static (texture profile analysis, firmness AACC and relaxation test) and dynamic (innovative oscillatory test) deformation techniques, image analysis, sensory analysis and colour measurements (colorimeter and Photoshop system) were used for white/whole commercial pan bread quality evaluation over 10 days of storage. Static (k ₁, k ₂, cohesiveness, springiness, hardness, chewiness and resilience) and dynamic (stress) bread crumb rheological properties were correlated illustrating that both techniques can be useful in evaluating crumb physical characteristics. In addition, sensory perceiveness with regard to softness and overall acceptability exhibited dependence with either dynamic stress or static firmness. Despite the fact that empirical measurements are closely linked to macroscopic features whilst dynamic tests are strongly linked to molecular characteristics, the obtained results support that both techniques are complementary since derived instrumental parameters are related to some sensory attributes. As data achieved using the proposed novel approaches might be better linked to the consumer awareness than those obtained from classical analyses, the obtained results are promising for a proper bread crumb quality assessment.     

添加改性麸皮对含麸皮面包结构及消化特性的影响

采用酶解-高压湿热处理对小麦麸皮进行改良,将改良后的小麦麸皮回添至高筋粉中获得不同麸皮含量的面粉,制作含麸皮面包,研究改良麸皮添加量对含麸皮面包的结构及消化特性的影响规律。结果表明：改良后的小麦麸皮中脂肪酶残余酶活降至0,不溶性膳食纤维含量从37.38%降低至15.64%,持水力升高了41.26%。与改良前的含麸皮面包相比,改良后的含麸皮面包香气浓郁,比容、硬度、弹性都得到了明显的改善。随着改良麸皮添加量增加,面包的老化程度降低、比容降低、硬度增加、弹性降低、感官品质降低。添加改良麦麸的含麸皮面包抗性淀粉含量增加,淀粉水解率降低。此外,改良麦麸显著降低了面包血糖生成指数。     

Improvement and stabilization white of bread flavour

Effect of adding the model system mixture (D,L-lysine · HCl, L-proline and D-glucose) on the sensory properties and volatile components of fresh bread and bread stored for 3 days were investigated. The results showed that the model system mixture improved the crust colour and flavour of fresh bread and kept the freshness, retarded the staling and improved the quality of the bread samples stored for 3 days. Analysis of the crust aroma of the bread samples showed that 2-acetyl pyrazine, 2-acetyl pyridine and 2-methyl-3-ethyl pyrazine, which may be responsible for bread crust aroma, were determined at high concentration in the bread sample containing 0.24% model system mixture. The concentration of pyrazine derivatives increased during storage whereas the carbonyl, pyrrol and furan derivatives decreased.     

小麦麸皮的品质改良及含麸皮面包焙烤品质的研究

本研究采用微波辐照联合复合酶法对小麦麸皮进行改良,将改良后的小麦麸皮添加至高筋粉中得到不同小麦麸皮含量的含麸皮面粉并制作含麸皮面包。结果表明:改良后小麦麸皮中脂肪酶残余酶活和脂肪氧化酶残余酶活降低至0和10.34%、粗纤维含量降低至3.21%、还原糖含量上升至3.79 g/100 g。与改良前的全麦面包相比,改良后的全麦面包组织结构得以改善、全麦面包储藏7d后吸热焓值降低了14.70%、全麦面包中酮基、羰基、醛基含量增多。改良后的全麦面包比容增加了26.40%、硬度降低了32.90%、弹性增大了6.90%。随着改良麸皮添加量的增加,含麸皮面包组织结构变得粗糙多孔,含麸皮面包吸热焓值逐渐降低,酮基、羰基、醛基含量增多,含麸皮面包芯亮度逐渐变暗、比容逐渐降低、硬度逐渐增加、弹性逐渐减小、感官品质降低。与未稳定化麸皮含量16%的全麦面包相比,稳定化全麦面包的稳定性、贮藏性和质构得到明显提高。     

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 chitosan on physical and chemical processes during bread baking and staling

The objective of this research was to investigate the effect of chitosan on the interaction of water with bread ingredients and on the rate of staling. The changes in freezable bound water and total water contents in bread crumb were assessed by differential scanning calorimetry from water melting and evaporation endothermic peak areas. It was found that freezable water content and total water content in bread crumb decrease during staling more rapidly in the presence of chitosan. The weak interaction of freezable water with protein and starch polymeric chains in bread crumb becomes stronger, but the interaction of nonfreezable bound water with protein and starch molecules in bread crumb becomes weaker in the course of staling during bread storage. Two stages of bread crumb staling were indicated. Chitosan increases the rate of bread staling during both stages. It was suggested that during bread staling chitosan increases water migration rate from crumb to crust, prevents amylose-lipid complexation, and increases dehydration rate both for starch and gluten.     

High-Protein Oat Flour Functionality Assessment in Bread and Sausage

The effectiveness of high-protein oat flour, a by-product of an oat starch process, was studied in bread baking and sausage processing. Its impact on sensory properties of products was assessed. High-protein oat flour enhanced water absorption and mixing stability of the dough. Some weakening of dough was found as indicated by a decrease in extensibility and resistance. Addition of oat flour increased loaf volume, enlarged grain size and darkened crumb color. It also caused some off-odors assessed as a decrease in “cleanness” of aroma. Sausages containing high-protein oat flour formed an external gel-like layer under the casing during processing, probably caused by the low pH of the flour. In sensory analyses the sausages were judged less firm and juicy than the control. The “cleanness” of odor and flavor of the sausages was distinctively diminished. Cereal products should be considered the primary products for utilization of high-protein oat flour.     

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.     

Effect of carrot (Daucus carota) antifreeze proteins on texture properties of frozen dough and volatile compounds of crumb

The effects of concentrated carrot protein (CCP) containing 15.4% (w/w) carrot (Daucus carota) antifreeze protein on texture properties of frozen dough and volatile compounds of crumb were studied. The sensory quality and texture profile analysis results of bread with CCP supplementation were similar to those of the control. Meanwhile, CCP supplementation brought some beneficial effects in holding the loaf volume. Results of texture property analysis showed that the hardness of dough with CCP supplementation was softer and steadier than that of the control during frozen storage, mainly due to the lower freezable water content. Furthermore, solid phase micro-extraction (SPME)-GC-MS analysis showed CCP supplementation did not give negative influence on volatile compounds of crumb and brought a pleasant aroma felt like Michelia alba DC by trans-caryophyllene simultaneously. In conclusion, CCP could be used as a beneficial additive to frozen dough.     

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.     

Effect of zein protein and hydroxypropyl methylcellulose on the texture of model gluten‐free bread

The influence of zein protein and hydroxypropyl methylcellulose (HPMC) on the texture and volume of gluten‐free bread was investigated. The addition of HPMC to starch affected the dough viscoelasticity and it improved the bread volume during baking since it acts as an emulsifier. The addition of zein protein to gluten‐free bread increased the crumb firmness and reduced the crust hardness within the range of concentrations investigated. No zein protein network could be observed in the bread crumb. The zein protein, cold mixed at low concentration, did not enhance the dough elasticity. Due to the lack of a protein network noncovalent interactions may stabilize the bubble structure stabilization within the crumb, rather than covalent links of the protein chain. With an optimized amount of zein protein and HPMC hydrocolloid, the gluten‐free bread showed similar texture and staling behavior to that of model wheat bread. The optimized recipe, compiled into a spreadsheet, is available in the supporting information. The microstructural observations suggest that zein could be replaced with another protein for this recipe resulting in a similar bread texture.