Control by a Combination of Methods (Hurdle Concept) ◾ 531
QUESTIONS
1. Describe the principle of using a combination of factors, or the hurdle concept, in the preservation of “fresh-like” foods.
2. In combining two or more factors to preserve foods, what criteria need to be considered?
3. Give three examples to show how the combination of factors has been found to control the
growth of foodborne pathogens.
4. Spores of Clostridium laramie, associated with the spoilage of roast beef at refrigerated temperatures, were not destroyed by a UHP treatment of 80,000 psi for 20 minutes. In contrast,
when the spores were subjected to a UHP treatment at 20,000 psi for 10 minutes and then
treated with a bacteriocin containing biopreservatives and incubated at optimum temperature, no growth was observed. However, the pressurized samples without bacteriocin had
growth. Explain the possible causes for the difference.
5. How can microbial sublethal injury be advantageously used to control microbial growth in
food preserved by the hurdle concept?
6. Take a trip to your nearest supermarket and select six refrigerated foods that have been preserved (to control microbes) by using the hurdle concept.
References
1. Davidson, P.M., Critzer, F.J., and Taylor, T.M., Naturally occurring antimicrobials for minimally processed foods, Annu. Rev. Food Sci. Technol., 4, 163–190, 2013.
2. Tiwari, B.K., Valdramidis, V.P., O’ Donnell, C.P., Muthukumarappan, K., Bourke, P., and Cullen, P.J.,
Application of natural antimicrobials for food preservation, J. Agri. Food Chem., 57, 5987–6000, 2009.
3. Zhou, G.H., Xu, X.L., and Liu, Y., Preservation technologies for fresh meat: A review, Meat Sci., 86,
119–128, 2010.
4. Considine, K.M., Kelly, A.L., Fitzgerald, G.F., Hill, C., and Sleator, R.D., High-pressure processing:
Effects on microbial food safety and food quality, FEMS Microbiol. Lett., 281, 1–9, 2008.
5. Morris, C., Brody, A.L., and Wicker, L., Non-thermal food processing/preservation technologies: A
review with packaging implications, Packaging Technol. Sci., 20, 275–286, 2007.
6. Ray, B., Sublethal injury, bacteriocins and food microbiology, ASM News, 59, 285, 1993.
QUESTIONS
1. Describe the principle of using a combination of factors, or the hurdle concept, in the preservation of “fresh-like” foods.
2. In combining two or more factors to preserve foods, what criteria need to be considered?
3. Give three examples to show how the combination of factors has been found to control the
growth of foodborne pathogens.
4. Spores of Clostridium laramie, associated with the spoilage of roast beef at refrigerated temperatures, were not destroyed by a UHP treatment of 80,000 psi for 20 minutes. In contrast,
when the spores were subjected to a UHP treatment at 20,000 psi for 10 minutes and then
treated with a bacteriocin containing biopreservatives and incubated at optimum temperature, no growth was observed. However, the pressurized samples without bacteriocin had
growth. Explain the possible causes for the difference.
5. How can microbial sublethal injury be advantageously used to control microbial growth in
food preserved by the hurdle concept?
6. Take a trip to your nearest supermarket and select six refrigerated foods that have been preserved (to control microbes) by using the hurdle concept.
References
1. Davidson, P.M., Critzer, F.J., and Taylor, T.M., Naturally occurring antimicrobials for minimally processed foods, Annu. Rev. Food Sci. Technol., 4, 163–190, 2013.
2. Tiwari, B.K., Valdramidis, V.P., O’ Donnell, C.P., Muthukumarappan, K., Bourke, P., and Cullen, P.J.,
Application of natural antimicrobials for food preservation, J. Agri. Food Chem., 57, 5987–6000, 2009.
3. Zhou, G.H., Xu, X.L., and Liu, Y., Preservation technologies for fresh meat: A review, Meat Sci., 86,
119–128, 2010.
4. Considine, K.M., Kelly, A.L., Fitzgerald, G.F., Hill, C., and Sleator, R.D., High-pressure processing:
Effects on microbial food safety and food quality, FEMS Microbiol. Lett., 281, 1–9, 2008.
5. Morris, C., Brody, A.L., and Wicker, L., Non-thermal food processing/preservation technologies: A
review with packaging implications, Packaging Technol. Sci., 20, 275–286, 2007.
6. Ray, B., Sublethal injury, bacteriocins and food microbiology, ASM News, 59, 285, 1993.