3.3. PEF-induced texture changes in carrot
The advantage of using PEF processing to inactivate AAO and POD in
carrot pieces has been shown in this study. Further investigation was
conducted to evaluate the cutting force required for PEF-treated carrots
(Fig. 4). The cutting force required to penetrate cross-section regions of
carrot epidermis to cortex, endodermis and xylem was investigated
before and after PEF treatment. In case of the reference sample for
untreated carrot pieces (refer to black line in Fig. 4), the cutting force
of approximately 55 N was required to penetrate the firm epidermis
(outer layer of carrot). Thereafter the cortex was cut through with elevating
force towards the endodermis region. The cutting force increased
when penetrating through cell regions with more pronounced cell density,
thus achieving the maximal cutting force when the cutting knife
reached the xylem region. As shown in Fig. 4a, when the cutting knife
reached the endodermis after 10 mm measured from the epidermis
region, the force increment was up to 94 N. Therefore this had led to
the breaking point of the carrot piece when reaching the outer xylem
at approximately 15 mm measured from the epidermis region. Consequently,
it was difficult to control the cutting accuracy since the carrot
started to break into half when the knife cut through the xylem region.
Overall, the maximum force needed to cut the raw (untreated) carrot
piece was averaged at 140.6 N. Nonetheless, it was rather apparent
that cutting raw carrots to obtain even cutting surface was indeed unattainable
(Fig. 4d, right)