Bread Baking Science Quiz
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Questions and Answers

What temperature range marks the pressure drops experienced during bread baking?

  • 60 °C to 90 °C
  • 30 °C to 50 °C
  • 40 °C to 70 °C (correct)
  • 50 °C to 80 °C

    • What role does water play in bread baking at the molecular scale?

  • Improves texture without any chemical change
  • Facilitates starch gelatinization (correct)
  • Enhances flavor
  • Stabilizes gluten structure

    • What is a consequence of the pressure build-up in bread during baking?

  • Reduction in CO2 release
  • Decreased crumb expansion
  • Increased dough stiffness
  • Rupture of crust (correct)

    • Which method is mentioned for monitoring water content profiles in baked products?

    <p>Nuclear magnetic resonance imaging (MRI)</p> Signup and view all the answers

    What contributes to spatial heterogeneity in crumb expansion during baking?

    <p>Uneven pressure distribution</p> Signup and view all the answers

    How does the release of CO2 affect bread baking?

    <p>It aids in aroma compound formation.</p> Signup and view all the answers

    Which factor is not mentioned as influencing water content in bakery products post-baking?

    <p>Air pressure during baking</p> Signup and view all the answers

    Which of the following is a consequence of water loss in baked products?

    <p>Collapse of the product</p> Signup and view all the answers

    What effect does steam injection have on the evaporation of water at the dough surfaces during baking?

    <p>It delays evaporation by condensation.</p> Signup and view all the answers

    What happens to the crust temperature as it approaches the dew point temperature during baking?

    <p>The rate of increase levels out.</p> Signup and view all the answers

    Which phenomenon occurs when the crust temperature is below the dew point temperature?

    <p>Condensation occurs.</p> Signup and view all the answers

    What is reported to enhance the porosity in the superficial layers of bread dough?

    <p>Intact starch granules.</p> Signup and view all the answers

    What is commonly believed about water condensation during baking?

    <p>It enhances the formation of glossy crusts.</p> Signup and view all the answers

    What limits water migration during baking in bakery products?

    <p>Low permeability of surface layers.</p> Signup and view all the answers

    What structural change in bakery products is observed when baked in a dry atmosphere?

    <p>A dull surface and harsh color.</p> Signup and view all the answers

    What effect does low permeability have on the baking process?

    <p>It limits gas development in the surface layers.</p> Signup and view all the answers

    What is the primary focus of the discussed figure related to wheat dough?

    <p>Viscosity of wheat dough as it relates to temperature</p> Signup and view all the answers

    Which deformation mode is associated with the term 'squeezing' in the context of the figure?

    <p>Biaxial deformation</p> Signup and view all the answers

    At which temperature range is the viscosity of wheat dough showing a significant decrease based on the provided data?

    <p>60-80°C</p> Signup and view all the answers

    Which water content percentage is associated with the tensile testing mode at 15°C/min?

    <p>44%</p> Signup and view all the answers

    What is implied about the temperature and viscosity relationship for squeezing at various rates?

    <p>Higher temperatures consistently lead to lower viscosity.</p> Signup and view all the answers

    Which of the following observations would NOT typically be drawn from the figure?

    <p>Viscosity remains static regardless of temperature in tensile mode.</p> Signup and view all the answers

    Based on the content, which author is linked to the squeezing mode at 4°C/min?

    <p>Lassoued-Qualdi</p> Signup and view all the answers

    What is the viscosity range indicated in the graph from the data?

    <p>$10^2$ to $10^4$ Pa.s</p> Signup and view all the answers

    What is the typical initial water content range for biscuit and crackers?

    <p>11 to 30%</p> Signup and view all the answers

    What hypothesis suggests that the crystalline structure of starch granules is lost due to hydration?

    <p>Hydration-facilitated melting</p> Signup and view all the answers

    How much lower is the water content in the bread crumb compared to the dough?

    <p>2–12%</p> Signup and view all the answers

    What is the final moisture range of a freshly baked biscuit?

    <p>1–5%</p> Signup and view all the answers

    What happens to the core crumb's moisture content just after baking?

    <p>Increases by 1–3%</p> Signup and view all the answers

    What contributes to the increase in viscosity during baking?

    <p>Swelling of granules and amylose exudation</p> Signup and view all the answers

    Which range of water content is typical for cake batter?

    <p>32–38%</p> Signup and view all the answers

    What effect does the concentration of soluble amylose have on amylose association?

    <p>Increases as soluble amylose concentration rises</p> Signup and view all the answers

    What was the main purpose of the research conducted by Mizukoshi and others in 1980?

    <p>To explore the impact of gas influx and outflux on dough structure</p> Signup and view all the answers

    During the experiments with biscuit dough, what significant physical phenomenon was observed on the surface of the dough?

    <p>Bubbles formation</p> Signup and view all the answers

    What was likely to happen to the biscuit dough if the influx of gas was lower than the outflux?

    <p>The porous structure would collapse</p> Signup and view all the answers

    What process is crucial for maintaining the dough's open porous structure until its setting?

    <p>Starch gelatinization</p> Signup and view all the answers

    In the study by Wagner and others in 2008, what method was used to monitor changes in local porosity during baking?

    <p>MRI scanning</p> Signup and view all the answers

    What does the net balance between influx and outfluxes determine in the context of dough heating?

    <p>The stability of the gas bubbles</p> Signup and view all the answers

    What was a significant characteristic of the dough as the internal temperature rose?

    <p>Formation of large bubbles</p> Signup and view all the answers

    How does the total thickness of the dough react over time during the baking process?

    <p>It initially increases before stabilizing</p> Signup and view all the answers

    What happens to the dough’s ability to retain gas as it reaches its maximum temperature?

    <p>It stabilizes and maintains its bubble structure</p> Signup and view all the answers

    Which region in the dough is most likely to contain the largest bubbles?

    <p>Region 4</p> Signup and view all the answers

    What phase is characterized by an almost linear increase in logarithmic viscosity between 55 and 75 °C?

    <p>Phase 2</p> Signup and view all the answers

    What phenomenon occurs as the dough is heated rapidly, affecting the minimum viscosity?

    <p>Finite rate of starch structure changes</p> Signup and view all the answers

    Which physical property transformation occurs during the cooling phase post-baking?

    <p>Formation of a three-dimensional network</p> Signup and view all the answers

    What is the range of extension rates associated with the decrease in dough viscosity during tensile mode measurement?

    <p>1 to 2 × 10–3 s−1</p> Signup and view all the answers

    What temperature range is associated with the observed decrease in logarithmic viscosity in phase 3?

    <p>75 to 100 °C</p> Signup and view all the answers

    What is the common outcome for dough viscosity in materials with no transformation during heating?

    <p>Decrease in viscosity at high temperatures</p> Signup and view all the answers

    What is a potential effect of the heating rate during baking on dough properties?

    <p>Influence on retrogradation processes</p> Signup and view all the answers

    What two processes are linked with the changes occurring in phase 2?

    <p>Starch gelatinization and protein coagulation</p> Signup and view all the answers

    Study Notes

    Baking

    • Heat and water transport during baking involves heat transfer modes into the dough, and measurement of temperature during baking.
    • Structural changes in starch and protein during baking lead to changes in dough/crumb mechanical properties.
    • Basic mechanisms of starch gelatinization affecting the extent of starch gelatinization include protein coagulation, and impact on dough viscosity during baking, and impact on mechanical properties of the crumb.
    • Spatial distribution of water content in bakery products is key in formation, overall collapse, and growth from gas nuclei.
    • Mechanisms affecting volume increase and limiting volume include starch gelatinization, cell expansion in the crust, cell collapse or coalescence, and total water loss.

    Heat and water transport during baking

    • Temperature is a key factor affecting product quality. It affects enzymatic reactions, volume expansion, starch gelatinization, protein denaturation, and water migration.
    • Time-course changes in baking temperature & its distribution in product (biscuit vs. bread) are determined by factors like product size, heat flow ratios (top, side, bottom), and expansion of cells impacting thermal conductivity and water vapor transport.
    • Heat is transferred through conduction, convection, and radiation from heating elements and hot metal parts in the oven.

    Heat and water transport during baking

    • Heat transfer in baking involves conduction, convection, and radiation.
    • Water vapor pressure gradients influence water movement between the dough core and surface, leading to evaporation-condensation processes.
    • Dough temperature and its distribution in baked products are affected by size, heat flow ratio, cell expansion (reducing thermal conductivity, but promoting water transport), and the evaporation of surface water and condensation in the core.

    Spatial distribution of water in bakery products

    • Moisture gradients exist in bakery products at the end of baking, affecting textural properties like crumb softness and crust crispness.
    • Water transport within the product during baking leads to distribution changes.
    • Initial water content varies greatly by product type (e.g., biscuits 11-30%, bread 38-48%).
    • Differences in final moisture contents are especially prevalent in the crust of bakery products.

    Cell expansion and squeezing, crumb formation, and overall collapse

    • During baking, the volume of bread, sponge cake, and biscuits can expand significantly (16–100%, 50–80%, and 100–300 % respectively).
    • Growth from gas nuclei is a prerequisite for inflation, achieved during mixing or whisking.
    • Specific mechanisms and factors limit volume increases, including starch gelatinization, cell wall ruptures, and cell collapse/coalescence.
    • Measuring water content in different bakery products and spatial distribution during baking process is a significant determinant of critical parameters.

    Mechanisms favoring volume increase in cell

    • Thermal expansion of occluded gases contributes to cell inflation by 10-15%.
    • Vaporization of dough components inside gas cells supports further dough expansion via vaporization of dough-interfacial substances that are hastened by temperature increase.
    • Dissolved gases such as CO₂ are released from the dough, increasing pressure in the gas cells.
    • Increased water vapor pressure supports gas release and accelerates cell expansion at the dough-interfacial region.
    • Starch gelatinization and/or protein aggregation contribute to dough hardening and limit cell expansion.

    Mechanisms limiting volume increase in cell

    • Multiple mechanisms limit further dough expansion, operating at different scales (molecular, microscopic, macroscopic).
    • Molecular-scale stiffening associated with starch gelatinization reduces the stretchability of cell walls and limits the increase of gas cell volume.
    • Microscopic ruptures in cell walls restrict further expansion.

    Measurement of temperature during baking

    • Accurate measurement of temperature in dough during baking is challenging due to variations and uneven temperature distribution due to oven rise and positioning of thermocouples.
    • Using optical fibers helps reduce errors and provides accurate measurements, even during oven rise.

    Crust formation

    • The crust, unlike crumb, is dry, dense, and contains elongated or small cells due to high temperature exposure.
    • Dehydration, through water loss, contributes to crust formation, texture, and reactions, and mechanical properties.
    • Water content and thickness of the crust depend on factors including dough porosity, baking time, drying intensity at surface, and cell collapse temperature.
    • Crust-crumb mass ratio is typically between 1 and 2 (Le-Bail and others 2011).

    Dehydration and its effect on reactions in and mechanical properties of the crust

    • The decrease in water content significantly affects the reaction mechanism and mechanical properties of the crust and affects the crispness of bakery products as well as interactions between mechanical properties and the process parameters.
    • The extent of starch gelatinization within the crust is influenced by water content.
    • The fast evaporation of water at dough surface due to elevated temperatures inhibits the complete gelatinization of starch in the crust, unlike the crumb.

    Role of steam injection on the crust formation

    • Steam injection delays water evaporation by condensation which occurs as long as crust temperature is below dew point.
    • Condensation delays water evaporation from the dough surfaces and moisture loss
    • It affects the crust formation by increasing the shelf-life of product.

    Total water loss

    • Moisture gradients exist in cooked products and are influenced by heat and mass transfer during baking.
    • Water content affects the final product quality, texture, and crispiness.
    • Spatial distribution of moisture in bakery products is determined during baking, affecting properties like crust and crumb.

    Factors affecting starch gelatinization and extent of starch gelatinization in bakery products

    • Presence of NaCl (sodium chloride) and sucrose results in slightly higher gelatinization temperatures.
    • However, the completeness of gelatinization is lower at lower concentrations.
    • The presence of fats and emulsifiers generally delays gelatinization.
    • Enzyme activity from a-amylase at 60–70°C breaks down gelatinized starch.

    Impact on dough viscosity during baking

    • Dough viscosity is affected by starch gelatinization and protein coagulation.
    • Dough viscosity changes predictably over a range of temperatures during baking.
    • Three distinctive phases in dough viscosity are observed at approximately 55, 75, and100°C.

    Impact on mechanical properties of crumb

    • Gelation occurs during cooling, creating a 3-D network embedding swollen starch granules. The granules associate and recrystallize, increasing firmness.
    • Heating rate and post-baking cooling rate influence retrogradation.
    • Mechanical properties of crumb are affected by the interplay between starch gelatinization and gluten matrix properties.

    Setting of the crust and its effect of cell collapse or coalescence

    • Crust setting acts as a macroscopic determinant of cell expansion during baking.
    • Cell expansion will be minimal when crust formation occurs quickly after dough expansion.
    • Pressure build-up caused by crust setting will affect the dough expansion; this will result in either decreased or increased volume.
    • Pressure build-up affects the rate of expansion of gas and causes cellular deformation.

    Factors affecting the crispiness of bakery products  and bread crust

    • Crispiness in cookies arises due to open-pore structure setting during baking
    • The setting of sponge structure in the final baking stage in crispy products like cookies determines their texture.
    • The mechanisms governing the opening of pores during baking have been studied extensively.
    • Water activity and moisture content directly relate to crispiness.

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    Baking: Chapter 19 - PDF

    Description

    Test your knowledge on the complex science behind bread baking. This quiz covers topics such as temperature ranges, the molecular role of water, and the effects of CO2 and steam in the baking process. Challenge yourself to understand the interactions that lead to the perfect loaf!

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