Quantum Cascade Laser Infrared Microscopy and In Situ Infant Formula Foam Wall Characterization

Quantum cascade laser (QCL) mid infrared (MIR) microscopy has been applied to the analysis of the composition of persistent foam generated by the reconstituted infant formula. A set of three infant formulae were examined. The set was composed of a reference formula, exhibiting acceptable foam dissipation, and two additional infant formulae, where the foam persists after reconstitution. The foam wall samples were measured immediately after reconstitution and without any destructive or composition altering preparation. The relative thickness of the foam wall produced by the samples was elucidated by the QCL transmission measurement. Fat in the form of globules was observed in the foam wall samples. Principal component analysis of hyperspectral data cubes extracted from the QCL measurements allowed for estimation of the fat globule diameter distribution and the fraction of the field of view occupied by fat globules. Multivariate curve resolution was applied to average MIR spectra calculated from the foam wall samples, and the relative macronutrient concentrations present were estimated. The foam wall thickness and water content provided the most useful data in relation to discussing the possible mechanisms driving the persistent foaming, and this is discussed with reference to the published data related to foam formation in aqueous dairy solutions.