Sara López-Sanz1, F. Javier Moreno1, Antonia Montilla1, Rodrigo Moreno2, Mar Villamiel1
1Instituto de Investigación en Ciencias de la Alimentación, CIAL (CSIC-UAM)
C/Nicolás Cabrera 9, 28049 Madrid, Spain
2Instituto de Cerámica y Vidrio, ICV (CSIC), C/ Kelsen 5, 28049 Madrid, Spain.
Introduction
In the last few years, the increasing interest toward prebiotic carbohydrates as functional food ingredients has
promoted the enzymatic synthesis of commercial galactooligosaccharides (GOS) and new lactose derivatives such as
those derived from lactulose (OsLu) [1]. GOS are known oligosaccharides that can be used in a number of
applications due to their nutritional, bioactive and technofunctional properties [2]. OsLu are new oligosaccharides
having potentially better bioactivity than GOS, as it has been demonstrated by recent in vitro and in vivo studies.
However, the development of novel bioactive oligosaccharides will be of commercial interest only if they are
formulated into foods and placed in the market. In this sense, the different formed structures determine not only the
physiological effects of the commercial preparations, but also their physicochemical properties and, consequently,
their applications. To the best of our knowledge hardly any information is available on the rheological properties of
GOS and, in the case of OsLu, no investigation has been done on their technological properties.
Materials and methods
Effect of share rate (𝜸)
Results and discussion
Figure 1. Flow and viscosity curves of Vivinal®GOS at 35ºC.
Phase 1: 𝛾 = 0 to 10 s-1 in 30 s, T = 25 ºC.
Phase 2: 𝛾 = 10 s-1 and T = 25 to 80 ºC in
3600 s.
Phase 3: 𝛾 = 10 to 0 s-1 in 30 s, T = 80 ºC.
Effect of temperature (T)
T = 25 ºC
Phase 1: 𝛾 = 0 to 10 s-1 in 30 s.
Phase 2: 𝛾 = 10 s-1 during 600 s.
Phase 3: 𝛾 = 10 to 0 s-1 in 30 s.
Effect of time of share (t)
Effect of share rate (Figure 1 and 2)
At 4°C, in the shear rate range applied (0-10
s-1), the flow and viscosity curves of GOS
and OsLu were very close to Newtonian,
whereas at temperatures higher than 25°C
in the shear rate range applied (0-500 s-1),
became pseudoplastic, suggesting structural
changes of the sample. Viscosity of OsLu
was higher than that of Vivinal®GOS,
probably ascribed to the differences in the
chemical composition.
To
study
the
rheological behavior of both
ingredients, Vivinal®GOS
and OsLu, including the
flow and viscosity curves
and the effect of temperature
and time on viscosity.
Phase 1: 𝛾 = 0 to 500 s-1 in 180 s.
Phase 2: 𝛾 = 500 s-1 in 60 s.
Phase 3: 𝛾 = 500 to 0 s-1 in 180 s.
T = constant (4, 25, 35, 50 and 70 ºC).
Vivinal®GOS // OsLu
- Rheometer rotational
Haake MARS in controlled
shear rate mode.
- Measurement system:
plate-plate (PP35), ø = 35
mm and distance = 1 mm
- Temperature regulated
with thermostatic bath
Objetive
Figure 2. Flow and viscosity curves of OsLu at 35ºC.
Effect of share time (Figure 3)
An increase in viscosity was observed in
both ingredients, indicating their rheopexy.
This demonstrates that shearing promotes
the formation of a network structure
associated with the modification of the
sample.
Figure 3. Variation of viscosity with time at constant share rate
(10 s-1) and temperature (25 ºC).
Effect of temperature (Figure 4)
A decrease of viscosity was observed in
both ingredients. OsLu seemed to be more
stable than Vivinal®GOS, because in the
latter, more irregular behaviour was found.
Figure 4. Variation of viscosity with temperature at constant
share rate (10 s-1) during 1 h.
Conclusions
-
The rheological behaviour of both ingredients, Vivinal®GOS and OsLu, is strongly influenced by the shear rate, shear time and temperature.
These data provide important information on the application of prebiotic carbohydrates in food processing, because better rheological characteristics
could give rise to an equivalent functionality with smaller amount of ingredient, helping in the reduction of cost production.
References: [1] Moreno F.J. et al. (2014) Analysis, structural characterization, and bioactivity of oligosaccharides derived from lactose. Electrophoresis. 35, 1519-1534.
[2] Lamsal. (2012) Production, health aspects and potential food uses of dairy prebiotic galactooligosaccharides. Journal of the Science of Food and Agriculture 92, 2020–20
Acknowledgments: Project AGL2011-27884