Characterisation of food grade titania with respect to nanoparticle content in pristine additives and in their related food products

Figures & data

Table 1. Finished and semi-finished food test samples; * contained same type of E171.

Food Samples	Description
Custard cream	E171 homogenously dispersed in food sample
Candies A with liquorice core	E171 in the outer shell
Candies B with liquorice core	E171 in the outer shell
White sugar pearls	E171 homogenously dispersed in food sample (according to supplier’s specification, anatase crystalline phase and free of nanoparticles)
Yellow sugar pearls	Contained a pearlescent pigment; mica platelets (E555) coated with E171
Confectionery masses A	* Contained 0.375 % E171 (homogenously dispersed)
Confectionery masses B	* Contained 0.085 % E171 (homogenously dispersed)
Confectionery masses C	* Contained 0.1 % E171 (homogenously dispersed)

Figure 1. Raman spectra of pristine E171 starting sample materials (lower part) and rutile/anatase reference materials (upper spectra).

Figure 2. Transmission electron microscopy. Number-weighted size distributions of titanium dioxide particles in pristine E171 additives (starting materials) and extracted materials. Histograms of absolute frequency (counts) and cumulative functions.

Figure 3. Transmission electron microscopy. Number-weighted size distributions of titanium dioxide particles in pristine E171 additives (starting materials) and extracted confectionery masses. Histograms of absolute frequency (counts) and cumulative functions.

Table 2. TEM analysis: number of analysed particles, number-weighted mean size, D50 and relative frequency of particles in the nanoscale of pristine E171 additives and extracted particles.

Sample	Number of analysed particles	Number-weighted mean size [nm]	Number-weighted D50 [nm]	Relative frequency of particles ≤100 nm [%]
Custard cream
Pristine E171	3402	110	110.5	44.1
Extract	724	110	110.5	45.4
Candies A (with liquorice core)
Pristine E171	418	82.9	80	66.0
Extract	750	122	122.5	32.4
Candies B (with liquorice core)
Pristine E171	523	126	126.5	29.4
Extract	593	114	114.5	39.3
Confectionery masses
Pristine E171	1798	101	101	49.3
Extract A (0.375% E171)	380	84.9	85.5	58.2
Extract B (0.085% E171)	967	113	113.5	41.1
Extract C (0.1% E171)	1042	86.7	87.5	56.4
White sugar pearls
Pristine E171	2451	139	139.5	23.6
Extract	605	119	119.5	32.5

Figure 4. TEM images of pearlescent pigment used in yellow sugar pearls. (a) Lower magnification of pigment, (b) higher magnification of pigment surface, (c) extracted material, (d) energy dispersive x-ray analysis. Spectrum belonging to sub-figure (B).

Figure 5. TEM images of titania particles and matrix residuals (highlighted) in candy extracts.

Figure 6. Single particle ICP-MS – cumulative number distribution of titanium dioxide particles of four E171 pristine starting materials and the extract of white sugar pearls. The legend includes the number of analysed particles.

Table 3. Single particle ICP-MS analysis: number of analysed particles, median of the number-weighted size distribution and relative frequency of particles in the nanoscale of pristine E171 additives and particles extracted from white sugar pearls.

Sample	Number of analysed particles (± STDEV)	Number-weighted D50 Value (± STDEV) [nm]	Relative frequency of particles ≤100 nm (± STDEV) [%]
Candies (A) with liquorice core
Pristine E171	1666 ± 192	171 ± 6	18.8 ± 1.7
Candies (B) with liquorice core
Pristine E171	1308 ± 268	221 ± 4	11 ± 1
Confectionery masses
Pristine E171	909 ± 136	182 ± 7	17.2 ± 2.4
White sugar pearls
Pristine E171	2186 ± 53	191 ± 1	12.0 ± 2.7
Extract	2539 ± 39	180 ± 4	11.2 ± 2.6

Figure 7. Size distributions determined with CLS. (a) Absorbance-based/extinction-weighted size distributions for E171 particles extracted from different food products, (b) absorbance-based/extinction-weighted size distributions for E171 particles extracted from Candies A (three replicate measurements), (c) mass-weighted size-distribution of particles extracted from Candies A, (d) number-weighted size-distribution of particles extracted from Candies A.

Table 4. Surface areas (SSA), volume-specific surface area (VSSA) and TEM-based VSSA estimation (VSSA TEM) determined for six pristine E171 additives.

Extracted E171	SSA [m^2 g^−1]	VSSA [m^2 cm^−3]	RSD [%]	VSSA TEM [m^2 cm^−3]
Custard cream	9.28	35.64	2.5	34.06
Candies (A) with liquorice core	10.57	40.60	1.1	45.50
Candies (B) with liquorice core	8.28	31.78	2.2	36.46
Confectionery masses	8.38	32.18	1.7	32.04
White sugar pearls	8.43	32.35	2.0	31.39
Yellow sugar pearls	8.08	31.01^1	7.2	NA
		23.43^2

¹Calculated using the density of anatase (3.84 g cm⁻³).

²Calculated using the density of mica (2.9 g cm⁻³).