SummaryThe use of X-rays to evaluate food microstructure has developed considerably in recent years. In this work we used X-ray micro tomography (XMT) to visualize the microstructure of loose-packed and compacted samples of spray-dried skim milk powder (SMP) and whole milk powder (WMP) and to quantify the proportion of both interstitial and occluded air voids in each sample. Visual scrutiny of the acquired XMT images showed details of the microstructure of the milk powders such as the spherical morphology of the particles, the size of the particles and internal air voids of various sizes. Within loose-packed powders, the proportion of air voids was higher (13% average) in WMP than in SMP. This was reversed in the compacted powders, in which the proportion of air voids was higher in SMP. The disparity in the proportion of air voids in both loose-packed and compacted samples of SMP and WMP was attributed to the size, shape and surface properties of the particles.

Raman confocal microscopy is an increasingly useful technique when applied to food samples. It has the unique ability to interrogate the chemical structure, aligned with the same confocality capability that is available when using standard confocal microscopy. In this research, we used Raman confocal microscopy to investigate the effects of maturation on the microstructure of cheddar cheese. Statistical analysis of the spectral data showed significant protein structural changes as the cheese matured. The results illustrate the potential of Raman confocal microscopy in conjunction with spectroscopy and imaging to understand chemical changes in complex dairy matrices.