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
Heating Constant Cooling
Beginning of Gelatinization
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.
Viscosity Temperature
Heating Constant Cooling
Beginning of Gelatinization
Gelatinization Maximum
Evaluation of the
Viscogram
The lower the gelatinization temperature,
the less energy is required during starch
treatment for obtaining complete
gelatinization.
Viscosity Temperature
Heating Constant Cooling
Beginning of Gelatinization
Gelatinization Maximum
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 Temperature
Heating Constant Cooling
Beginning of Gelatinization
Gelatinization Maximum
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