Table 2 In vitro tests design: main factors affecting bioaccessibility results

Gastric pH

+++

- IVBA ↑ when pH ↓

- Check the pH increase at the end of the G phase.

[69, 81–84]

Intestinal pH

+++

- ↓ IVBA as compared to gastric IVBA

^- Adjust intestinal IVBA to Pb salt solubility during the intestinal phase

[65, 67, 85, 86]

- Major ↓ IVBA from pH 4 to 6

- Increase in solubility of bile/pancreatin-Pb complexes at pH 7.5

- Slight ↑ IVBA at pH 7.5 compared to pH 6.0-7.0

Temperature

-

- No impact between 20°C and 37°C

- May be important when enzymes are added

[84]

Phases simulated

+++

- Gastric IVBA > Intestinal IVBA

- Adjust intestinal IVBA to Pb salt solubility during the intestinal phase

[67]

Extraction

+

- IVBA ↓ in the range: centrifugation > microfiltration > UF

- No difference between 0.2 and 0.45 μm filtration

[84, 87]

Fluid composition

+

- Contradictory results (↑ or ↓ IVBA)

- Physiologically based fluids may be important when food is added

[55, 67, 85, 88–90]

- Physiologically based fluids do not seem important for the G phase

- Bile/pancreatin would create soluble complexes with Pb

Retention time

++

- IVBA ↑ when gastric phase time ↑

- Lower impact on more soluble Pb forms: IVBA plateau reached after 20–30 min

[55, 74, 88, 91]

- No information on intestinal extraction time effect

Mixing

++

- Aggressive mixing (Ar gas) ↑ IVBA

- End-over-end agitation adapted to maximize solid/fluid contact, but not too aggressive

[69, 74, 84]

S/L ratio (g/mL)

+++

- IVBA ↓ with high S/L > 1/100

- High S/L ↑ the effect of TM on pH ↑

[83, 84, 92]

- No effect between low ratio 1/100 and 1/5000

Food addition

+++

- IVBA ↓ with food, except powdered milk

- Effect variable depending on food type

[62, 87, 88, 93]

- Fed tests linked to lower recovery rates