Dynamic mechanical analysis was employed to explore the development of carrot parenchyma softening
during heating in the range of 30e90 C. Results indicated that compared with raw carrots the toughness
of carrots at 60 C decreased significantly (P < 0.05) at 0.5 C/min while there was no significant
deference (P > 0.05) at 2 C/min. Samples at 0.5 C/min finally obtained the lower toughness. Besides,
both loss tangent (LT) and two negative peaks on the temperatureeslope plot were heating rate
dependent. At 0.5 C/min, distinct increases of LT started at about 48 C while at about 67 C at 2 C/min.
With increasing rate, LT effect decreased obviously. Increasing rates caused a shift of both peaks from low
temperatures (49e60 C) to high ones (67e75 C). Values of both peaks were significantly higher
(P < 0.05) at 0.5 C/min than at 2 C/min. Furthermore, the microstructure of samples at 0.5 C/min was
more rigid and irregular shrinkage, accompanied by more small pores as well as bigger cracks in comparison
to that at 2 C/min. And cell walls of samples at 0.5 C/min seemed to thinner. Therefore, the
development of carrot parenchyma softening during heating was both temperature and heating rate
dependent. We suggested that the breakdown of pore proteins and middle lamella in cell walls induced
the dramatic loss of cell turgidity and the subsequent changes of elastic modulus, collectively causing
tissue softening.