アルファ化でんぷん

WordNet

feature as the star; "The movie stars Dustin Hoffman as an autistic man"
a plane figure with 5 or more points; often used as an emblem
an actor who plays a principal role (同)principal, lead
(astronomy) a celestial body of hot gases that radiates energy derived from thermonuclear reactions in the interior
any celestial body visible (as a point of light) from the Earth at night
mark with an asterisk; "Linguists star unacceptable sentences" (同)asterisk
be the star in a performance
stiffen with starch; "starch clothes"
a complex carbohydrate found chiefly in seeds, fruits, tubers, roots and stem pith of plants, notably in corn, potatoes, wheat, and rice; an important foodstuff and used otherwise especially in adhesives and as fillers and stiffeners for paper and textiles (同)amylum
a commercial preparation of starch that is used to stiffen textile fabrics in laundering
foodstuff rich in natural starch (especially potatoes, rice, bread)

PrepTutorEJDIC

『星』;恒(fixed star) / 『星形のもの』;星章,星標(*)(asterisk) / 『スター』,花形 / (人の運勢を左右するといわれる)運星;《しばしば複数形で》運勢,運,星回り / (星印で示した)等級 / 《文》実現不可能な逆標(願望) / 星の / 花形の,主役の;卓越した,すぐれた / …を星(星形の物)で飾る;…‘に'星印をつける;(…を)…‘に'のようにちりばめる《+『名』+『with』+『名』》 / …‘を'主役にする / 主役を務める,主演する
〈U〉でんぷん / 〈U〉〈C〉でんぷん食品 / 〈U〉のり(糊) / 〈U〉堅苦しさ / …‘に'のりをつける,‘を'のりづけして堅くする

Wikipedia preview

出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2016/10/22 11:07:23」(JST)

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Starch gelatinization is a process of breaking down the intermolecular bonds of starch molecules in the presence of water and heat, allowing the hydrogen bonding sites (the hydroxyl hydrogen and oxygen) to engage more water. This irreversibly dissolves the starch granule in water. Water acts as a plasticizer.

Three main processes happen to the starch granule: granule swelling, crystal or double helical melting, and amylose leaching.

During heating, water is first absorbed in the amorphous space of starch, which leads to a swelling phenomenon.^[1]
Water then enters via amorphous regions the tightly bound areas of double helical structures of amylopectin. At ambient temperatures these crystalline regions do not allow water to enter. Heat causes such regions to become diffuse, the amylose chains begin to dissolve, to separate into an amorphous form and the number and size of crystalline regions decreases. Under the microscope in polarized light starch loses its birefringence and its extinction cross. ^[2]
Penetration of water thus increases the randomness in the starch granule structure, and causes swelling, eventually soluble amylose molecules leach into the surrounding water and the granule structure disintegrates.

The gelatinization temperature of starch depends upon plant type and the amount of water present, pH, types and concentration of salt, sugar, fat and protein in the recipe, as well as starch derivatisation technology used. Some types of unmodified native starches start swelling at 55 °C, other types at 85 °C.^[3] The gelatinization temperature of modified starch depends on for example on the degree of cross-linking of the amylopectin, the degree of acid treatment, acetylation. Gel temperature can also be modified by genetic manipulation of starch synthase genes.^[4] Gelatinization temperature also depends on the amount of damaged starch granules. These will swell faster. Damaged starch can be produced, for example, during the wheat milling process, or when drying the starch cake in the starch plant.^[5] There is an inverse correlation between gelatinization temperature and glycemic index.^[4]

Gelatinization improves the availability of starch for amylase hydrolysis. So gelatinisation of starch is used constantly in cooking to make the starch digestable or to thicken/bind water in roux, sauce, or soup.

Retrogradation

Cooked, unmodified starch, when cooled for a long enough period, will thicken (or gel) and rearrange itself again to a more crystalline structure; this process is called retrogradation. During cooling, starch molecules gradually aggregate to form a gel. Molecular associations occur: Amylose-Amylose ; Amylose-Amylopectin; Amylopectin-Amylopectin. A mild association amongst chains come together with water still embedded in the molecule. Due to the tightly packed organization of small granule starches, retrogradation occurs much more slowly compared to larger starch granules. High amylose starches require more energy to break up bonds to gelatinize into starch molecules, leading to a rigid and stiff gel. A mild association amongst chains come together with water still embedded in the molecule.

Due to strong associations of hydrogen bonding, longer amylose molecules will form a stiff gel.^[6] Amylopectin molecules with longer branched structure, increases the tendency to form strong gels. Granule size do not directly impact starch performance, but it is one of the main factors affecting starch gelatinization and retrogradation. High amylopectin starches will have a stable gel, but will be softer than high amylose gels.

Retrogradation restricts the availability for amylase hydrolysis to occur.

Pregelatinized starch

Pregelatinized starch is starch cooked and then dried in the starch factory on a drum dryer or in an extruder making the starch cold-water-soluble. Also spray dryers are used to obtain dry starch sugars and low viscous pregelatinized starch powder.

Determination

Diagram illustrating the appearance of various thermal transitions on a DSC curve

A simple technique to study starch gelation is by using a Brabender Viscoamylograph. It is a common technique used by food industries to determine the pasting temperature, swelling capacity, shear/thermal stability and the extent of retrogradation. Under controlled conditions, starch and distilled water is heated at a constant heating rate in a rotating bowl and then cooled down. The viscosity of the mixture deflects a measuring sensor in the bowl. This deflection is measured as viscosity in torque over time vs. temperature, and recorded on the computer. The viscoamylograph provides the audience with the beginning of gelatinization, gelatinization maximum, gelatinization temperature, viscosity during holding, and viscosity at the end of cooling.^[7]

Differential scanning calorimetry (DSC) is another method industries use to examine properties of gelatinized starch. As water is heated with starch granules, gelatinization occurs, involving an endothermic reaction.^[8]

The initiation of gelatinization is called the T-onset. T-peak is the position where the endothermic reaction occurs at the maximum. T-conclusion is when all the starch granules are fully gelatinized, and the curve remains stable.

References

^ Jenkins, P J, and A M. Donald. "Gelatinisation of Starch: a Combined Saxs/waxs/dsc and Sans Study." Carbohydrate Research. 308 (1998): 133-147. Print.
^ Zobel, H. F. (1988), Starch Crystal Transformations and Their Industrial Importance. Starch - Stärke, 40: 1–7. doi:10.1002/star.19880400102
^ Hans-Dieter Belitz, Werner Grosch, Peter Schieberle, Food chemistry, Edition 3, Springer, page: 318-323, year: 2004, ISBN 3-540-40818-5, ISBN 978-3-540-40818-5
^ ^a ^b US application 20080201807A1, Robert James Henry & Daniel Lex Ean Waters, "Gelatinization Temperature Manipulation", assigned to SOUTHERN CROSS UNIVERSITY, Rural Industries Research and Development Corporation
^ Stanley P. Cauvain, Linda S. Young, Baking problems solved, Woodhead Publishing, page: 25-26, year: 2001, ISBN 1-85573-564-4, ISBN 978-1-85573-564-4
^ Hegenbart. S.. Understanding starch functionality. Food product. Web. 1996 http://www.foodproductdesign.com/articles/1996/01/understanding-starch-functionality.aspx
^ http://www.brabender.com
^ http://www.siint.com/en/documents/technology/thermal_analysis/application_TA_006e.pdf

External links

Food Resource, Starch, Oregon State University
Corn starch gelatinization, filmed with microscope, Youtube

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English Journal

Temperature and dietary starch level affected protein but not starch digestibility in gilthead sea bream juveniles.

Couto A, Enes P, Peres H, Oliva-Teles A.SourceDepartamento de Biologia, Faculdade de Ciências da, Universidade do Porto, 4169-007, Porto, Portugal, acouto@fc.up.pt.
Fish physiology and biochemistry.Fish Physiol Biochem.2012 Jun;38(3):595-601. Epub 2011 Jul 5.
A study was carried out with gilthead sea bream juveniles to assess the effect of water temperature (18 and 25°C) and dietary pregelatinized starch level (10, 20 and 30%) on digestibility of protein and starch and on the activity of proteolytic and amylolytic enzymes. ADC of pregelatinized starch w
PMID 21728054

Utilization of Smoked Salmon Trim in Extruded Smoked Salmon Jerky.

Kong J, Dougherty MP, Perkins LB, Camire ME.SourceAuthor Kong is with Abbott Laboratories, Columbus, OH 43219, U.S.A. Authors Dougherty, Perkins, and Camire are with Dept. of Food Science and Human Nutrition, Univ. of Maine, 5735 Hitchner Hall, Orono, ME 04469-5735, U.S.A. Direct inquiries to author Camire (E-mail: Mary.Camire@umit.maine.edu).
Journal of food science.J Food Sci.2012 May 16. doi: 10.1111/j.1750-3841.2012.02717.x. [Epub ahead of print]
During smoked salmon processing, the dark meat along the lateral line is removed before packaging; this by-product currently has little economic value. In this study, the dark meat trim was incorporated into an extruded jerky. Three formulations were processed: 100% smoked trim, 75% : 25% smoked
PMID 22591245