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Foam Formation and Starch Gelatinization with Alpha-Crystalline Emulsifiers

Richardson, Gisela LU (2003)
Abstract (Swedish)
Popular Abstract in Swedish

I bageriindustrin används emulgatorer i så kallad alfaform för att tårtbottnar ska kunna vispas i ett steg och ändå få en stor luftvolym. Avhandlingen fokuserar på vissa av emulgatorns effekter i produkter såsom kaksmet: Hur skumbildningen påverkas av emulgatormolekylernas packning, hur emulgatorer ändrar svällningen av stärkelsekornen i mjölet, och vilka effekterna blir i den verkliga produkten. Emulgatorerna som studerades var antingen alfageler, vilket betyder att molekylerna packat sig i skikt med vatten emellan vilket ger en mjuk och smidig konsistens, betakristaller, vilka är stora korn av tätt packade molekyler, eller miceller, vilket innebär att de bildar små bollar (vanligt i disk- och... (More)
Popular Abstract in Swedish

I bageriindustrin används emulgatorer i så kallad alfaform för att tårtbottnar ska kunna vispas i ett steg och ändå få en stor luftvolym. Avhandlingen fokuserar på vissa av emulgatorns effekter i produkter såsom kaksmet: Hur skumbildningen påverkas av emulgatormolekylernas packning, hur emulgatorer ändrar svällningen av stärkelsekornen i mjölet, och vilka effekterna blir i den verkliga produkten. Emulgatorerna som studerades var antingen alfageler, vilket betyder att molekylerna packat sig i skikt med vatten emellan vilket ger en mjuk och smidig konsistens, betakristaller, vilka är stora korn av tätt packade molekyler, eller miceller, vilket innebär att de bildar små bollar (vanligt i disk- och tvättmedel där man innesluter smuts och fett i dessa aggregat). Förutom kaksmet, som ju innehåller en stor mängd ingredienser, användes sockerskum och stärkelseblandningar som modellsystem för att undersöka emulgatorernas effekter. Skummen vispades, antingen med en visp eller i ett tryckkärl, och undersöktes med olika sorters mikroskop. Stärkelselösningarna värmdes under omrörning, och prover undersöktes i ljusmikroskop efter värmning till olika temperaturer.



Den viktigaste slutsatsen av arbetet var att emulgatorerna i alfaform har väldigt speciella egenskaper just på grund av den molekylära packningen. De fördelar sig lätt över nya bubbelytor och de har även en ”klistrande” effekt, dvs de får luftbubblorna att hänga ihop så att skummet blir stabilt, vilket inte t.ex emulgatorn i micellform klarar. De har även en speciell effekt på stärkelsekornen under värmning, pga att alfagelerna kan fördela sig i blandningen redan vid rumstemperatur medan t.ex. den kristallina formen är olöslig upp till 50-60°C. Alfagelerna hindrar kornen från att svälla redan vid låga temperaturer, medan betakristaller bara hindrar svällning över ca 60°C. Skillnaden i den tidiga svällningen ger en annorlunda konsistens på den färdigvärmda blandningen vid 95-97°C.



Det visades också att emulgatorer i allmänhet kan förhindra att stärkelsekornen går sönder förrän vid ca 90°C. Normalt sker detta mycket tidigare. De hindrar också amylos från att läcka ut ur kornen. Amylos är den del av stärkelsen som gör att en kräm stelnar till när den kallnar. När amylosen hindrades från att läcka ut kontinuerligt under värmningen, så ändrades också fördelningen av den, vilket också kan påverka konsistensen på den slutliga produkten. Istället för att bilda ett nätverk i lösningen, vilket är det normala beteendet som ger en mer trögflytande kräm, så klumpade amylosen ihop sig till små bollar och krämen förblev lättflytande. Socker, som ju är vanligt i bakverk, gjorde att stärkelsekornen gick sönder vid ännu högre temperaturer. En överdosering av socker kan därför leda till att en kaka inte blir färdigbakad. (Less)
Abstract
In the baking industry, emulsifiers in the alpha-gel state are used for foam formation. This thesis focuses on some parts of the effects of the emulsifier: how the foam formation and foam stability are influenced by the physical state of the emulsifier, how emulsifiers change the gelatinization and gel formation of starch, and the impact that these factors may have in a true product such as a sponge cake. The emulsifiers studied were either alpha-gels with a varying amount of vesicle structures, beta-crystals, or micelles. In addition to the study of the effects in a sponge cake batter, a sucrose foam was used as a model system for the foam stability studies, and a starch paste was used for the gelatinization studies. The foams were... (More)
In the baking industry, emulsifiers in the alpha-gel state are used for foam formation. This thesis focuses on some parts of the effects of the emulsifier: how the foam formation and foam stability are influenced by the physical state of the emulsifier, how emulsifiers change the gelatinization and gel formation of starch, and the impact that these factors may have in a true product such as a sponge cake. The emulsifiers studied were either alpha-gels with a varying amount of vesicle structures, beta-crystals, or micelles. In addition to the study of the effects in a sponge cake batter, a sucrose foam was used as a model system for the foam stability studies, and a starch paste was used for the gelatinization studies. The foams were whipped, either with a mixer or in a pressurized vessel, and the foam formation and stability were measured with density measurements, TEM (transmission electron microscopy), CLSM (confocal laser scanning microscopy), and oscillatory rheological measurements. The starch pastes were heated in a Brabender viscometer, smeared onto a slide, stained with iodine and examined with light microscopy. Cooled gels were also embedded and studied with TEM.



The main conclusion was that the alpha-gel has specific properties that influence the foam formation, the foam stability, and the starch gelatinization. In a foam, the main advantage of the alpha-gel was that it seemed to have an attractive bridging effect, which stabilized the structure. This led to better dispersion, with smaller bubbles, and a more stable foam, since drainage and creaming decreased. During starch gelatinization, the alpha-gel interacted with the starch granules at low temperatures and restricted the granule swelling below 50°C. Solid beta-crystals did not have this effect on the starch before they melted. Although both the alpha-gel and the beta-crystals transformed into other states above a temperature of about 60°C, this difference in swelling during the early heating was shown to give other rheological properties of the paste at 95-97°C.



This thesis also showed that emulsifiers were able to hinder granule swelling, amylose leakage and granule rupture up to 90°C. The rupture temperature did not depend on the emulsifier concentration. When the temperature became too high, the granules disrupted completely without initial leakage of the soluble molecules, which resulted in a different distribution of the components. In combination with sucrose, the granules could be kept intact even longer. It was also shown that emulsifiers changed the microstructure of the amylose gel formed during cooling. At moderate emulsifier concentrations, the amylose aggregated into thicker and more rigid strands than normal, and at high concentrations the amylose gathered into spherical aggregates without any network connecting them. These changes were further pronounced in gels with whole starch granules. (Less)
Please use this url to cite or link to this publication:
author
opponent
  • Professor Larsson, Kåre, Bjärred, Sweden
organization
publishing date
type
Thesis
publication status
published
subject
keywords
Food and drink technology, Livsmedelsteknik, image analysis., rheology, microscopy, amylose-lipid complex, gelatinization, dynamical arrest, amylose, starch, sponge cake, foam, emulsifier, alpha-gel, physical state
pages
52 pages
publisher
SIK - Svenska Livsmedelsinstitutet
defense location
Hörsalen, SIK, Göteborg, Sweden
defense date
2004-01-23 10:15
ISBN
91-628-5941-2
language
English
LU publication?
yes
id
95f2ea71-3cc4-4a2b-8f07-84cf736d3f6a (old id 466577)
date added to LUP
2007-10-14 14:34:42
date last changed
2016-09-19 08:45:14
@misc{95f2ea71-3cc4-4a2b-8f07-84cf736d3f6a,
  abstract     = {In the baking industry, emulsifiers in the alpha-gel state are used for foam formation. This thesis focuses on some parts of the effects of the emulsifier: how the foam formation and foam stability are influenced by the physical state of the emulsifier, how emulsifiers change the gelatinization and gel formation of starch, and the impact that these factors may have in a true product such as a sponge cake. The emulsifiers studied were either alpha-gels with a varying amount of vesicle structures, beta-crystals, or micelles. In addition to the study of the effects in a sponge cake batter, a sucrose foam was used as a model system for the foam stability studies, and a starch paste was used for the gelatinization studies. The foams were whipped, either with a mixer or in a pressurized vessel, and the foam formation and stability were measured with density measurements, TEM (transmission electron microscopy), CLSM (confocal laser scanning microscopy), and oscillatory rheological measurements. The starch pastes were heated in a Brabender viscometer, smeared onto a slide, stained with iodine and examined with light microscopy. Cooled gels were also embedded and studied with TEM.<br/><br>
<br/><br>
The main conclusion was that the alpha-gel has specific properties that influence the foam formation, the foam stability, and the starch gelatinization. In a foam, the main advantage of the alpha-gel was that it seemed to have an attractive bridging effect, which stabilized the structure. This led to better dispersion, with smaller bubbles, and a more stable foam, since drainage and creaming decreased. During starch gelatinization, the alpha-gel interacted with the starch granules at low temperatures and restricted the granule swelling below 50°C. Solid beta-crystals did not have this effect on the starch before they melted. Although both the alpha-gel and the beta-crystals transformed into other states above a temperature of about 60°C, this difference in swelling during the early heating was shown to give other rheological properties of the paste at 95-97°C.<br/><br>
<br/><br>
This thesis also showed that emulsifiers were able to hinder granule swelling, amylose leakage and granule rupture up to 90°C. The rupture temperature did not depend on the emulsifier concentration. When the temperature became too high, the granules disrupted completely without initial leakage of the soluble molecules, which resulted in a different distribution of the components. In combination with sucrose, the granules could be kept intact even longer. It was also shown that emulsifiers changed the microstructure of the amylose gel formed during cooling. At moderate emulsifier concentrations, the amylose aggregated into thicker and more rigid strands than normal, and at high concentrations the amylose gathered into spherical aggregates without any network connecting them. These changes were further pronounced in gels with whole starch granules.},
  author       = {Richardson, Gisela},
  isbn         = {91-628-5941-2},
  keyword      = {Food and drink technology,Livsmedelsteknik,image analysis.,rheology,microscopy,amylose-lipid complex,gelatinization,dynamical arrest,amylose,starch,sponge cake,foam,emulsifier,alpha-gel,physical state},
  language     = {eng},
  pages        = {52},
  publisher    = {ARRAY(0x91f0340)},
  title        = {Foam Formation and Starch Gelatinization with Alpha-Crystalline Emulsifiers},
  year         = {2003},
}