almidon generalidades 2014i

ALMIDON: ASPECTOS

FISICOQUMICOS Y

FUNCIONALES Dr. EDUARDO RODRIGUEZ

Docente Asociado

Universidad Nacional de Colombia

CONTENIDO

INTRODUCCIN

GRANULO DE ALMIDON

GELATINIZACIN

RETROGRADACIN

INTRODUCCIN

INTRODUCCIN

El almidn es utilizado en un amplio rango de productos porque funciona como espesante, agente gelificante, fuente de energa en una fermentacin, agente anti-pegajoso/pegajoso, etc.

GRANULO DE

ALMIDON

PARTCULA DE ALMIDN

La forma del almidn depende de la fuente botnica. Los grnulos ms pequeos (3 mm) y ms grandes (35 mm) del almidn de trigo tienen diferentes formas. Los grnulos de avena y arroz tienen pequeos grnulos individuales que conforman juntos un grnulo compuesto.

Starch granule shapes and sizes for wheat, corn, rice, and

potato viewed with scanning electron microscopy. (Courtesy of

C. McDonough, Cereal Lab, Texas A&M University, College,

Station,TX.)

COMPOSICIN

La amilosa y la amilopectica son los polisacridos predominantes en el almidn. Los componentes menores (protena, lpidos) pueden tener una gran influencia en las propiedades del almidn.

AMILOSA AMILOPECTINA cheng.cam.ac.uk

COMPOSICIN DE ALGUNOS

GRNULOS DE ALMIDN

Almidn Amilosa (%) Protena (g/100 g) Lpidos (g/100 g)

Yuca 17 0.1 0.1

Papa 21 0.06 0.05

Arroz 12.2-28.6 0.63-1.11

Arroz ceroso 0-2.32

Trigo 28 0.3 0.8

Cebada 25.3-30.1 0.68-1.28

Avena 25.2-29.4 1.35-1.52

Maz 25.8-32.5 0.3 0.61-0.82

Arveja 33 0.7 0.1

CRISTALINIDAD DEL ALMIDN

La cristalinidad del almidn se puede estudiar utilizando la tcnica de difraccin de rayos X.

Patrn A = Almidones de cereales

Patrn B = Almidones de races y tubrculos

Patrn C= Semillas y granos

Patrn V= Almidones gelatinizados con lpidos

Representacin esquemtica de la estructura granular del almidn: (a) un

grnulo con capas amorfas y semicristalinas, (b) vista expandida de la capa

semicristalina de un anillo creciente, (c) estructura de la amilopectina dentro

de la capa semicristalina (Tomado de Jacobs y Delcour, 1998)

ALMIDN DE YUCA NATIVO Y FERMANTADO

Starch granules from pea seed

jic.ac.uk

GELATINIZACIN

La gelatinizacin es el termino usado para describir eventos moleculares asociados con el calentamiento de almidn en agua, el cual cambia de una forma semi-cristalina (la cual no es digerible), a una forma eventualmente amorfa (digerible)

(Eliasson y Gudmundsson, 1996)

Representacin esquemtica de los cambios en el almidn

durante el calentamiento en exceso de agua. (Tomado de

Rooney y Huang, 2001)

VISCOGRAPH Pt 100

VISCOGRAPH E

AMYLOGRAPH

RVA

cwbrabender.com

MICRO VISCO AMYLOGRAPH

What Happens During the Temperature

Cycle of a Viscograph Test

Weipert Weipert

Weipert Weipert

At the beginning of the

measurement, viscosity is still very

low because the starch grains have

practically not yet swollen at all in

the cold water (a).

Weipert Weipert

When the temperature rises, the

starch grains start to absorb water

and, hence, begin to swell (b).

Weipert Weipert

Due to their enlarged volume, they

collide more frequently within the

crowd, rub each other, and the

viscosity as a measure for internal

friction increases (c).

Weipert Weipert

Besides, more and more particles

are dissolved from the starch grain,

so that the liquid becomes more and

more viscous and the starch grains

tend to stick within the liquid.

Consequently, viscosity rises further

(d).

Weipert Weipert

A maximum is reached when most of

the starch granules are swollen and

still intact, not destroyed.

Weipert Weipert

Chemical bonds are destroyed due to

the rising temperature. Swollen starch

grains and the surrounding gel are

broken by the mechanical action of the

stirrer (e). Consequently, the balance

tends from rising viscosity to

decreasing viscosity again. The

viscosity curve shows a maximum.

Weipert Weipert

This gelatinization maximum may

already be reached during the

heating phase, or during the

subsequent period of constantly

high temperature (f).

Weipert Weipert

During the last stage of the

measurement (cooling), the dissolved

and loosened molecules rearrange

into more regular forms

(retrogradation), and viscosity

increases again (g).

Evaluation of the

Viscogram Viscosity Temperature

Heating Constant Cooling

Beginning of Gelatinization

Beginning of gelatinization

(temperature when the

viscosity starts to rise).

Viscosity Temperature



Gelatinization Maximum

Evaluation of the

Viscogram

Gelatinization maximum (first

maximum of the curve with the

corresponding viscosity and

temperature). This point indicates,

e.g., which consistency a product

will reach during cooking.





Evaluation of the

Viscogram

The lower the gelatinization temperature,

the less energy is required during starch

treatment for obtaining complete

gelatinization.





Viscosity at the

end of the

heating phase Viscosity at the

beginning of the

cooling phase

Evaluation of the Viscogram

The change in viscosity in the

period of constantly high

temperature gives information

about the stability of the

gelatinized starch with regard to

temperature and shearing





Viscosity at the

end of the

heating phase Viscosity at the

beginning of the

cooling phase

Viscosity at the

end of the

cooling phase

Evaluation of the

Viscogram

Setback

The increase in viscosity up to the

end of cooling provides

information about the thickening

behavior of the starch tested.

RETROGRADACIN

La retrogradacin del almidn es un proceso que ocurre cuando las molculas en los grnulos de almidn gelatinizados comienzan a reasociarse en una estructura semi-ordenada. La perdida de la capacidad de retencin de agua, el incremento de la rigidez y la restauracin de la cristalinidad tambin se presentan durante el envejecimiento de los geles de almidn gelatinizados

Los factores que pueden afectar la retrogradacin son:

Temperatura

Contenido de agua

Composicin

Interaccin amilopectina y amilosa

Fuente botnica

almidon generalidades 2014i

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