Milk powder samples, representing dry food, were used directly without any treatment, whereas, other samples containing higher water activity were replaced with previously samples ash which had been tested using ICP-MS. Transmission electron microscopy (TEM) was conducted using a JEOL JEM-2000FX attached to an Oxford Instruments INCA energy dispersive X-ray system.
For TEM analysis, samples were prepared by dilution of orange juice samples in UPW (2e3 drops of the solution) on a copper grid and dried at room temperature after concentrating the solution using filter paper.