Effects of high-pressure processing on the quality of green beans

High-pressure processing is a mild preservation method, currently applied for pasteurization of foods. In this work a pulsed high-pressure method for achieving sterilization of whole intact products was under investigation. The effects of several high-pressure processes on the product quality of intact green beans were compared to conventional preservation techniques. The effects of these preservation technologies on texture, color and ascorbic acid content were evaluated. In addition reduction of natural flora was determined, also after storage of green beans. High-pressure conditions, 500 MPa at 20degreesC, showed inactivation of vegetative cells, only spores remained. Two-pulse pressure treatment, 1000 MPa at 75degreesC, showed a reduction of all natural flora below the confidence threshold. After one month storage there was no significant outgrowth of microorganisms. Both 500 MPa high-pressure and two-pulse high-pressure treatment showed a large retention of firmness for green beans compared to conventional preservation methods. High-pressure and two-pulse pressure treatments resulted in changes in greenness (a*-value). 500 MPa high-pressure treatment at ambient temperature showed no effect on ascorbic acid content, whereas two-pulse high-pressure treatment, 1000 MPa, 75degreesC showed a small decrease.