Combined Effects of Mild Acidification and Thermal Treatment on Color and Texture of Green Beans

Hurdle technology combining mild acidification (4.6 < pH < 5.0) and reduced thermal treatment could be a potential preservation technique for the production of high-quality processed canned vegetables once it has been microbiologically validated. Freshly harvested green beans were acidified in pre-prepared brine using one of three acidulants (lactic acid [LA], glucono-delta-lactone [GDL], or fermented dextrose containing organic acids), hermetically sealed in cans, and thermally processed in a pilot-scale water-immersion retort. Eight levels of acidulant concentration (0.01-19.5 g/kg) and five levels of desired lethality (0.01-2.74 min) were applied through uniform shell experimental design (Doehlert network method). The color and texture properties of blanched green beans (control samples) and thermally processed green beans with and without prior acidification were evaluated. Statistical analysis showed that acid concentration had a significant effect on color characteristics, and that lethality had a significant effect on texture indices (p < 0.001). Regression models were developed for the prediction of both color and texture properties of thermally processed acidified green beans with two independent parameters: acidulant concentration and lethality.