Enzymes produce precursors directly or indirectly involved in flavor forming processes  while yeast fermentation is responsible for the formation of a number of alcohols, acids, and esters . The biochemical activity of microflora in the sourdough, resulting in higher production of organic acid and flavoring compounds .
Higher extraction rate of flour results in higher production of lactic and acetic acids. The final acid values in sourdough made from whole meal flour are almost double the values in sourdough made from straight grade flours . The freshness of flat bread is the holistic attribute and is prized for its taste, aroma and texture. Because of the lean formula flat bread stale quickly during storage and shelf life is limited to few hours  , resulting from the physiochemical changes that lead to a loss of freshness with an increased firmness and an alteration of its organoleptic quality, and becomes difficult to chew which is considered objectionable in acceptance by consumers .
Due to an increasing consumer demand for fresh flat breads, new technologies and processing conditions have been developed to avoid these undesirable changes and to extend shelf life . One method involves the addition of particular components, such as emulsifiers, hydrocolloids, and enzyme preparations to the recipe . Another method applied to prevent bread staling consists of modifying the process conditions so as to offer the consumer fresh bread at any time.
Several works showed that bread staling was closely associated to starch retrogradation  . However, others have suggested a mechanism about bread staling dealing with the increase of interactions between starch molecules and gluten proteins . Later, it was shown that the addition of gluten in model systems did not change firming rate . Although considerable progress in dissecting the staling process has occurred, bread staling remains intensively studied, yet not well understood, phenomenon.
Even though starch seems to be a key player in the staling phenomenon, interactions between starch and other ingredients of the matrix seem to occur.
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The retrogradation of amylose occurs during the first hours following baking. Amylopectin retrogradation occurs in the long term and seems to be the major phenomenon involved in bread firming. Still, staling rate can be delayed by using specific ingredients such as shortening and emulsifiers that will delay the retrogradation of the starch components.
Staling involves hardening of the crumb that is a complex phenomenon in which multiple mechanisms operate. Factors affecting wheat bread crumb staling have been extensively investigated . However, many studies have shown that starch retrogradation is not the only factor responsible for crumb staling . Water plays a critical role in bread staling. When the retrogradation of amylopectin occurs, water molecules are incorporated into the crystallites and the distribution of water is shifted from gluten to starch linkages, thereby changing the nature of gluten network .
In addition to the molecular order of starch, water also plays an important role in crumb firmness due to its plasticizing effect on the crumb network .
Flat breads are consumed fresh as they stale rapidly on storage. With rapidly changing lifestyles, increasing urbanization and industrialization and changing socio-economic trends, there is an increase in the demand for convenience foods, which require less preparation time. Large-scale production of flat breads calls for mechanization and marketing of this flat bread in suitable unit packs. When it reaches the consumer, the packed flat breads should retain all the sensory characteristics of fresh bread .
The addition of emulsifiers has been also used by several authors to increase the shelf life of flat breads. Glycerol monostearate GMS and sodium stearoyl lactate SSL were used to retards the staling of starch in the Chapaties stored at ambient and refrigerated temperature . The percentage reduction of moisture content in glycerol monostearate-containing Chapati during storage at ambient was less as compared to control samples.
This is due to the ability of glycerol monostearate to form a complex with helical regions of starch, i. This change was attributed to the addition of SSL and GMS which reduced the extent of solubilisation of starch molecules upon heating in excess water . Surfactants have ability to form complexes with amylose and amylopectin linkages which leads to softening of bread  -. The higher degree of softness in the emulsified Chapaties compared to non-emulsified Chapaties is reported in literature .
Hydrocolloids have been also used for shelf life enhancement of flat breads. Among the hydrocolloids, guar gum increased the extensibility of fresh as well as stored Chapati . All the anti staling additives and water, play a role of plasticizer, thereby preventing the rigidity of macromolecular starch and gluten chains and hence enhancing the shelf life of flat breads.
Different wrapping materials have been used for the packaging of flat breads. Fresh Chapati was soft and extensible as indicated by low force values required to deform, low modulus of deformation and longer distances of extension before rupture. The Chapati stored for 24 h was hard and brittle as indicated by the high force values, high modulus of deformation and short distances of extension before rupture. The packaged Chapati was sealed decrease the extensibility could not be attributed to the loss in moisture but to recrystallization and retrogradation of starch in the Chapati, a very common phenomenon that occurs in bread .
There is a considerable potential for the large-scale manufacture and marketing of Parotha, as the demand for ready-to-eat convenience food products have been steadily increasing because of industrialization.
It calls for mechanization in the preparation and distribution in unit packs. For achieving the objective of commercial marketing, it is desirable that the Parotha should have adequate shelf-life. For extending the shelf-life of any product, knowledge regarding the changes taking place in the product during storage is necessary. For centuries, baked cereal products have been widely consumed throughout the world.
Among these, flat bread is the most popular because of its nutritional value, textural properties and easiness to produce. They are generally consumed fresh. However, flat bread is characterized by a relatively short life, resulting from physiochemical changes that lead to a loss of freshness with an increased firmness and an alteration of its organoleptic quality, thus becoming difficult to chew.
Due to an increasing consumer demand for fresh bread, new technologies have been developed to avoid or delay these undesirable changes and to extend the shelf life. The suitability of different wheat varieties and extraction rates have been assessed for the suitable flat bread production technology. They have also optimized on the basis of flour type, manner of sheeting or in the appearance of end product.
Different baking operations and formulations have been standardized to evaluate the flat breads. Food Chemistry, 77, Journal of Food Engineering, 55, Food Research International, 33, Food Chemistry, 68, Bulgarian Journal of Agricultural Science, 15, Food Research International, 29, Journal of Food Engineering, 65, Food Chemistry, 69, International Journal of Food Science and Technology, 38, Journal of Food Engineering, 19, Journal of Cereal Science, 35, Baking Industry Europe, London, Food Microbiology, 16, Journal of Applied Science, 22, Chemie Mikrobiologie Technologie der Lebensmittel, 17, Food Hydrocolloids, 21, Food Chemistry, , Journal of Food Engineering, 86, Journal of Food Science and Technology, 13, Cereal Chemistry, 78, Cereal Chemistry, 63, Lebensmittel-Wissenschoftund Technology, 26, American Association of Cereal Chemists, St.
Marcel Dekker, New York. Carbohydrate Polymers, 28, Food Chemistry, 67, Food Research International, 34, Journal of Food Science and Technology, 46, Journal of Food Science and Technology, 29, Food Hydrocolloids, 27, Cereal Foods World, 37, Journal of Cereal Science, 12, Journal of Cereal Science, 22, Journal of Cereal Science, 33, Carbohydrate Polymers, 21, Journal of Cereal Science, 48, Cereal Foods World, 33, Trends in Food Science and Technology, 14, Turkey Journal of Biology, 69, Journal of Cereal Science, 6, Journal of Texture Studies, 28, Bakers Digest, 53, The effect of germ and residue of date seed on dough rheology during mixing was examined with the Farinograph Brabender, Duisburg, Germany following official standard method 54— The determined parameters were:.
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Water absorption WA was defined as the amount of water required to centre the highest part of the mixing curve on the arbitrary BU Brabender units line. Arrival time AT was the time required for the curve to reach the BU line. Dough development time DDT was the time interval in min from the first addition of water until the curve reaches its maximum height. Stability was the time in minutes for which the top of the curve remains over line.
The gelatination temperature GT was defined as temperature at maximum consistency and determined with the Amylograph Brabender, Duisburg, Germany according to standard manner 22— This bread was produced using a standard method described by Pourfarzad et al. After cooling, bread samples were packed in polyethylene bags, stored at room temperature and evaluated. Quality analysis of fresh bread samples was carried out by measuring specific volume of the central slice rapeseed displacement.
Sensory analysis was carried out using a 5-point ranking scale with scores ranging from 1 least pleasure to 5 best pleasure. Sensory evaluation was performed by 10 trained panelists.
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Attributes of bread were selected according to the Iranian flat bread evaluation method, including bread form and shape; upper and bottom surface properties all undesirables bread features which has been created due to temperature changes in oven i. For each of the attributes, the average of the panelist scores was calculated. Staling phenomenon and its changes were evaluated by penetration test. Values for the Avrami model factors were estimated by fitting experimental points into the non-linear regression equation:.
Regression was done by using the CurveExpert 1. In order to assess significant differences among samples, a completely randomized design was performed. All statistical analyses were carried out using Minitab 16 software Minitab Inc. Results were reported as the average of three replications all treatments were evaluated in three batches. The characteristics of the flour are in the range of typical values of medium strong flour, suitable for Iranian Barbari flat bread. Date germ has a noticeable amount of protein and fat.
The fiber value of both fractions of date seed germ and residue is high, suggesting an important source of dietary fiber for enrichment of flat breads. The addition of germ and residue of germinated date seed could promote differences on the dough mixing behavior measured by the farinograph and amylograph.
Although the WA was not affected by residue, but addition of germ decreased it. The decrease of WA may be due to action of active enzymes of germ on the starch molecules hydrolyzing them to dextrins which have low water binding capacity Stauffer ; Gernah et al.
Similar results were observed in high protein, high fiber and low carbohydrate bread Dhinda et al. This result was similar to that reported previously Maeda et al.
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This tendency could be attributed to weakening of mixed doughs caused by the presence of a low molecular weight dextrin, which was produced from damaged starches by enzyme activity of germ Kim et al. The increase of stability may be due to the stabilizing action of components of both fractions such as protein. Also, the addition of defatted palm date seeds in dough increased stability. On the other hand, the MTI of dough samples increased with addition of date seed germ. Similar behavior was observed for DOS. The addition of 0.
But, no statistical difference was observed between control and dough supplemented with other levels of treatments concerning DOS. These results could be explained by enzyme activity of fractions and subsequently weakening of mixed doughs Kim et al. Results showed no significant effect of residue fraction for the GT among the samples. Volume of bread samples is a quality parameter as it indicates dough inflating ability and oven spring. This result led us to the hypothesis that the dilution effect of the non-protein components in germ and residue fractions of date seed does not fully account for the depression in loaf volume.
Thus, although both fractions of germinated date seed diluted gluten proteins, it does not appear to have affected the specific volume of the fresh bread. It might be due to the moderate level of protein in the treatments. Results showed no significant difference for the bottom surface property, cavity and porosity among the samples.
The form and shape and firmness of bread samples increased with addition of both date seed fractions in sensory analysis. The results perceived by the trained panelists showed a significant difference in chewing ability between the control and bread samples containing both fractions. This might be due to the crude fiber of date seed and effect of them on the mouth feel.
Odor and flavor are two of the important taste characteristics in food acceptance.
As it is difficult to determine a test profile by instrumental measurements, an investigation of the impact of germ and residue of germinated date seed on Barbari bread taste profile by sensory evaluation is necessary. This might be because of the germination and subsequently special produced aroma. With the exception of germ at the highest concentration 1. The high percentages of carbohydrate and protein in the germ, are the origin of high color intensity.
Brown crust in bread is a result of non-enzymatic browning reaction Maillard type between amino acids and reducing sugars Kent and Evers It can be concluded that germinated date seed fractions do not have any affect the sensory properties of fresh bread samples, except for germ at 1. Thus, it appears that both fractions may be successfully incorporated into bread without negatively impacting texture and overall acceptability, if we added the lower levels of germ.
Almana and Mahmoud and Kawka et al. Sensory characteristics of fresh Barbari bread containing fractions of germinated date seed. Crumb texture is critical to consumer acceptance of baked products. The kinetic of bread hardening was modeled using the Avrami equation as reported previously for describing crystallization kinetics during storage Cornford et al. This equation has been used for explaining bread staling based on starch retrogradation, despite the contribution of the other bread components Armero and Collar The resulting adjusted models provided information on the hardness of fresh breads and on the hardening kinetics.
Initial hardness T 0 of fresh breads could be accurately estimated and varied widely from Extreme values from the accurate estimation of limiting modulus were from Bread hardening kinetics strongly depended on both k and n. Breads containing germinated date seed fractions showed the lower constant k than the control samples, indicating slower rate for development of hardening during storage, related to the rate of crystals growing Torre et al. The hardness increase during storage has been attributed mainly to amylopectin recrystallization, although other phenomena, such as moisture diffusion between crumb and crust, and the starch—gluten interactions, has been proposed to additional players that contribute to hardness increase Zobel and Kulp In fact, flour replacement at different levels by dietary fibers from different sources significantly modifies the qualitative and quantitative thermal profile on starch gelatination and amylopectin retrogradation and kinetics during storage in different extend depending on the fiber source Santos et al.
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