Start the clock at a named event
Choose a clear start such as cutting, pulping or the thermal outlet. Record actual sample time and temperature at each point, the previous thermal history and the interval before cooling. Do not compare unrelated lots using colour alone.
Control the observation conditions
Use the same sample depth, container, background and lighting; retain a colour reference where available. Record air exposure, mixing, headspace and storage conditions. A darker photo may reflect illumination rather than a process change.
Compare the complete history
Assess the selected puree or juice with its matched control and agreed colour method. Time-temperature records support investigation and product development; they are not microbial validation or a shelf-life validation.
