Comparison of microscopy techniques for the examination of the microstructure of starch-containing imitation cheeses

Cryo-scanning electron microscopy (cryo-SEM), environmental scanning electron microscopy (ESEM), light microscopy (LM) and Fourier transform infrared (FT-IR) imaging techniques were assessed to see which was most appropriate for the examination of the microstructure of starch-containing imitation cheeses. Cheeses (54% moisture) containing four starches at 10% w/w (native, pre-gelatinised, resistant or waxy corn) were manufactured using a Farinograph-E®. Cryo-SEM produced high-resolution images making the measurement of fat globule size possible, whereas ESEM images allowed detailed visualisation of the protein matrix. FT-IR imaging and LM were both useful in specifically distinguishing the different components of the cheese. Starch type greatly influenced cheese microstructure. Resistant starch did not gelatinise and the intact starch particles were observed to have little interaction with the protein matrix, whereas pre-gelatinised and native corn starch gelatinised during cheese manufacture at 80 °C, and so interacted more with the protein matrix.