  Context: In a freeze drying (FD) process, an accurate observation and control
of the process parameters at critical stages are at high importance.
Particularly accurate and timely identification of the critical temperature
(TC) at the end of primary drying phase would lead to heating energy cost
reduction and product waste elimination by ending the process before the
product's micro-collapse stage. Aim: Within this work, a combination of novel
techniques optical technique called Intelligent Laser Speckle Imaging (ILSI) in
association with product image texture analysis, coupled to an electrical
impedance technique called through vial impedance spectroscopy (TVIS) has been
applied onto the real-time product states observation process to identify the
specific structural product surface/subsurface characteristics and hence the
micro-collapse stage. Method: 2 cycles - one providing a profile for standard
approach (non-collapsed) and another with a temperature ramp through TC to
micro-collapse, TVIS provides an assessment of the onset of micro-collapse
through the assessment of the acceleration in drying rate whereas the ILSI with
pattern recognition detects the change in microstructure
