Decontamination of Seeds for Seed Sprout Production by High Hydrostatic Pressure
Decontamination of Seeds for Seed Sprout Production by High Hydrostatic Pressure
Journal of Food Protection: Vol. 66, No. 6, pp. 918-923.
Elke Y. Wuytack,a Ann. J. Diels,a Katlijne Meersseman,a and Chris S W. Michielsa
aLaboratory of Food Microbiology, Katholieke Universiteit Leuven, Kasteelpark Arenberg 22, B-3001 Leuven, Belgium
ABSTRACT
Garden cress, sesame, radish, and mustard seeds immersed in water were treated with high pressure (250, 300, 350, and 400 MPa) for 15 min at 20°C. After treatment, percentages of seeds germinating on water agar were recorded for up to 11 days. Of the seeds tested, radish seeds were found to be the most pressure sensitive, with seeds treated at 250 MPa reaching 100% germination 9 days later than untreated control seeds did. Garden cress seeds, on the other hand, were the most pressure resistant, with seeds treated at 250 MPa reaching 100% germination 1 day later than untreated control seeds did. Garden cress sprouts from seeds treated at 250 and 300 MPa also took about 1 day longer to reach average sprout length than sprouts from untreated control seeds did, indicating that sprout growth was not retarded once germination had occurred. Garden cress seeds were inoculated with suspensions of seven different bacteria (107 CFU/ml) and processed with high pressure. Treatment at 300 MPa (15 min, 20°C) resulted in 6-log reductions of Salmonella Typhimurium, Escherichia coli MG1655, andListeria innocua, >4-log reductions of Shigella flexneri and pressure-resistant E. coli LMM1010, and a 2-log reduction of Staphylococcus aureus. Enterococcus faecalis was virtually not inactivated. For suspensions of the gram-positive bacteria, similar levels of inactivation in water in the absence of garden cress seeds were found, but the inactivation ofE. coli LMM1010 and S. flexneri in water in the absence of garden cress seeds was significantly less extensive. These data suggest that garden cress seeds contain a component that acts synergistically with high hydrostatic pressure against gram-negative bacteria.