Effect of pretreatments on carrot texture after thermal and pressure-assisted thermal processing

The effect of various physical and chemical pretreatments such as pressure (100-400 MPa), temperature (50-70 degrees C), calcium chloride (0.5-1.5% w/v), and their combinations on carrot texture was studied after pressure-assisted thermal processing (PATP) and thermal processing. Untreated PATP and thermally processed samples without any Pretreatment served as controls. Individual pretreatments were effective to a limited extent in improving the product quality. Pressure (200 MPa), heat (60 degrees C) and calcium chloride (1.0%) pretreatments increased product hardness by 1.2, 2.0 and 2.4 times after PATP and 2.7, 3.6 and 2.4 times, respectively, after thermal processing. Combined pretreatments increased the hardness of the samples by 9.16 times (from 14.08 to 129.07 N) and 13.22 times (from 4.36 to 57.63 N), respectively, in comparison to untreated PATP or thermally processed samples. The calcium content of the samples was found to have a positive influence in preserving hardness. The microstructure analysis of PATP carrots indicated that the combined high pressure, heat, and calcium pretreatments better preserved cell structure. This combined pretreatment process could serve as an effective toot in preserving the quality of PATP as well as thermally processed carrot. (c) 2008 Elsevier Ltd. All rights reserved.