Efficacy of combinations of high pressure treatment, temperature and antimicrobial compounds to improve the microbiological quality of alfalfa seeds for sprout production

The effect of combined treatments of pressure, temperature and two disinfectant agents (hypochlorite and carvacrol) applied on alfalfa seeds, on their germination capability as well as on the reduction of the native microbial load of sprouts developed from treated seeds was evaluated by using response surface methodology (RSM). The germination percentage decreased as pressure and carvacrol concentration increased, while calcium hypochlorite concentration had no significant impact on seed viability. The counts of total aerobic mesophilic bacteria, total and faecal coliforms and moulds and yeast were reduced with increasing pressure and hypochlorite and carvacrol concentrations. The optimal conditions for improving the microbiological quality of alfalfa seeds (reductions between 4.5 and 5 log CFU/g) for sprouts production were 200 MPa and hypochlorite concentration of 18,000 ppm. On the contrary, the process parameters of the combined treatment HP/carvacrol that ensure the microbial safety of sprouts (250 MPa and 1500 ppm of carvacrol) reduced the germination percentage to unacceptable levels.