Improvement in Texture of Pressure-Assisted Thermally Processed Carrots by Combined Pretreatment using Response Surface Methodology

The effect of pretreatment pressure (0.1 to
400 MPa), temperature (25 to 75 °C), and calcium chloride
concentration (0 to 1.5%) and their complex interaction on
hardness, residual pectinmethylesterase (PME) activity, and
diffused calcium content of pressure-assisted thermal
processed (PATP, 700 MPa, 105 °C for 15 min) carrot
have been studied using response surface methodology.
Predicted values of carrot hardness, calcium content, and
residual PME activity were found to be in good agreement
with experimental values as indicated by the high R2 values
of 0.98, 0.96 and 0.96, respectively. The optimum processing
conditions, namely, calcium chloride concentration
1.0%; pretreatment pressure ranging from 286 to 314 MPa;
pretreatment temperature varying from 53.8 to 58.3 °C,
fulfill the conditions to obtain the PATP carrot with hardness
≥145 N, calcium content≥2.5 mg/g, and residual PME
activity≥70%. These conditions resulted in more than
tenfold increase in the hardness of PATP carrot (14.08 to
145 N) as compared to PATP carrot without any pretreatment.
The study demonstrated that response surface methodology
can be used for modeling carrot quality parameters
of PATP.