Nanomaterials in food
Characterization techniques in food.
Published on: Mar 3, 2016
Transcripts - Nanomaterials in food
CURRENT CHARACTERIZATION TOOLS FOR ENM FOR FOOD APPLICATION
When analysing ENMs in food matrices, obtaining representative samples can be a very
When the ENM is incorporated into the food matrix, changes in pH, ionic strength, ionic
composition, cooling or heating as well as mechanical stress during food production and
digestion can lead to the alteration of the ENM.
Food constituents can interact with nanoparticles and alter their properties.
So, techniques should be sensitive enough to measure low concentrations
WHY IS THIS PROBLEM SO DIFFICULT TO ANALYZE?
ELECTRON MICROSCOPE (SEM , TEM)
It is a microscopy technique that produces images of a sample with a
focused beam of electrons.
The electrons interact with atoms in the sample, producing signals that
can be detected
Gives information about the sample's surface topography and
composition which includes information about the state of aggregation,
dispersion, sorption, size , structure and shape.
Materials to be viewed under an electron microscope need sample
Electron microscopy can achieve resolution better than 1 nanometer.
Scanning electron microscope
A SAMPLE VIEWED BY SEM, AFM AND TEM:
Zno dispersed in distilled water, allowed to dry. Obtained size- 50-70nm.
DYNAMIC LIGHT SCATTERING
A technique used to determine the size distribution of
small particles in suspension or polymers in solution.
Rayleigh scattering phenomenon is observed in the
Due to laser, the scattering intensity fluctuates over
time. This fluctuation is due to Brownian motion, so
the distance between the scatterers in the solution
constantly changes with time.
This scattered light then undergoes either constructive
or destructive interference by the surrounding particles.
Interferences can be caused by dust particles can have a
great influence on the scattering intensity and therefore
on the sizing result
Schematic of DLS
INDUCTIVELY COUPLED PLASMA MASS SPECTROMETER (ICP-MS)
A type of mass spectrometer capable of detecting metals and
several non- metals at concentrations as low as one part in
1012 (part per trillion)
Achieved by ionizing the sample with inductively coupled
plasma and then using a mass spectrometer to separate and
quantify those ions
Example: TiO2 levels in food can be determined by purchasing
white-colored foods and personal care products. Food samples
first to milder digestion with hydrogen peroxide and nitric acid
only, then passing through nylon filters with a pore size of 450
nm and then analyzed .
This shows that a significant fraction (about 36%) of the TiO2
particles deliberately added to the tested foods were of
Schematic of Spectrometer
SURFACE PLASMON RESONANCE ASSAYS
It is a physical surface phenomenon whereby collective
oscillations of electrons on a material’s surface (called
plasmons) come into resonance with the natural oscillation of
SPR has been used in the development of biosensors that can
directly monitor the interaction between an analyte and ligand
present on a sensor chip.
For example: Use of a human-metallothionein-based SPR
sensor chip to detect and measure AgNPs in food and
environmental samples. The hypothesis was that if AgNPs are
present in the test matrix, they will bind to the protein and
induce a change in the SPR response of the gold chip surface.
It was observed that the sensitivity of the sensor increased as
the size of the AgNPs increased, due to the enhancement of
the SPR signal, which is proportional to the mass of the
Change in mass concentration at the sensor surface alters the
refractive index and angle at which an SPR signal is generated.