Effect of thermal and high pressure pre-treatments and of high pressure shift freezing on green peppers firmness

Abstract

Industrially, bell peppers are usually fiozen, after being thermally blanched, to be consumed in salads after thawing. However, texture tend to decrease after this process. Therefore, several thermal (55°C) and thermalhigh-pressure (200MPa, 25°C and 55°C) pre-treatments, with and without calcium (0.50%, wlv) addition, were studied for their possible effect on texture improvement of green bell peppers. The temperature-pressure-calcium conditions revelead a significant (P<0.05) enhancement on the firmness of peppers. Peppers pre-treated at the conditions that caused the best firmness improvements were used to fürther study the effect on firmness of fieezing at atmospheric pressure and of high-pressure shift fieezing (HPSF). Only the pre-treated samples that were fiozen by HPSF (200MPa, -18°C) showed no detrimental effect on f m e s s p0.05), while those fiozen at atmospheric pressure (-l8"C, -40°C) presented a significant decrease on firmness (PK0.05). The pretreated samples showed no changes on firmness (P>0.05) after overnight storage, but after 2.5 months storage, only the high pressure pre-treated peppers showed no decrease in firmness (P>0.05), clearly indicating the beneficial effect of the high pressure pre-treatrnents to retain fmess. These results illustrate the potential of thermal, pressure, combined thermalíhigh-pressure pre-treatments on firmness improvement of green bell pepper and of HPSF to retain firmness during fieezing and frozen storage.