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Abstracts
Workgroup: Public Health and Processing
Evaluating Consumer Attitudes and Preferences Toward Irradiated Oysters
Principal Investigator(s):
Linda Andrews, Mississippi State University-Coastal Research and Extension Center, lsa4@ra.msstate.edu
Co-Investigator(s):
Benedict C. Posadas, State University-Coastal Research and Extension Center
Funding Period: 9/99 to 9/02
Oysters were tolerant to irradiation processing <2.0 kGy absorbed dose. They maintained a normal shelf-life with no increase in mortality when compared with control (untreated oysters). At levels >2.0 the oysters showed increased mortality of 5-8% and at 3 kGy secreted a yellow unpleasant appearing exudate. Results of the initial irradiation response of pure broth cultures determined that V. vulnificus MO-624 (log 7/g oyster meat) was more sensitive to the irradiation exposure than the V. parahaemolyticus (log 7/g oyster meat) requiring 1.5 kGy and 2.0 kGy, respectively, to reduce each to non-detectable levels. That the V. parahaemolyticus 03:K6 was less sensitive to irradiation processing than Vibrio vulnificus was not surprising. Cook (2001) reported that the V. parahaemolyticus 03:K6 was the most resistant to processing of any of the Vibrios tested in his laboratory. Naturally incurred V.vulnificus (103/g oyster meat) was reduced to non-detectable levels with 0.75 kGy irradiation. Vibrios in control oysters and oysters exposed to very low doses of irradiation when stored under refrigeration (<40 C), V. vulnificus counts were reduced over time under these storage conditions. Pathogenic V.vulnificus (MO-624) was more resistant to irradiation processing than the naturally incurred strains and was reduced to non-detectable levels with 1 kGy absorbed dose. Note: This pathogen was also reduced over refrigerated storage. Artificially inoculated Vibrio parahaemolyticus 03:K6 TX-2103(log 4/g oyster meat) proved to be somewhat more resistant than the pathogenic V. vulnificus and required up to 1.5 kGy to reduce to non-detectable levels. The V.p were less sensitive to reduction during refrigeration than the V.vulnificus.
Two consumer panels were conducted. One in December, 2001, at the Coastal Aquaculture Unit Open House (Gulfport, MS) and the other at the Boston Seafood Show, March, 2002 (Boston, MA). There were 80 tests performed at the Open house and 66 tests performed at the Seafood Show. Consumer panelists were asked to perform a triangle difference test. Panelists were presented 3 oysters in random order. Of the three oysters, two were alike and one was different. Panelists were asked to pick the one they thought was the odd sample out of the three. Out of 146 tests conducted, 56 trials resulted in correct answers. By Chi-square statistical analysis this number was determined to be less than would be expected by random chance selection (Stone and Sidell, 1985). Therefore, there was no significant difference observed between the irradiated oysters and the control samples(p<0.001). An expert panel within the MSU community also tasted the oysters and reported that the irradiated oysters maintained a "raw like" quality, as was commented on by the consumer panelists. There were no flavor or visual changes noted. Oysters for sensory testing were irradiated within a dose range of 1-1.5 kGy gamma rays.
Consumer attitudes and preferences toward raw oysters in general, and irradiated oysters, in particular, were evaluated from results of consumer surveys conducted through personal and telephone interviews. Seventy-five personal interviews were conducted at the MSU-Coastal Aquaculture Unit (CAU) Open House in Gulfport, Mississippi on December 6, 2001. Another survey was conducted at the MSU-Coastal Research and Extension Center (CREC) booth and exhibit among 140 participants of the 2002 International Boston Seafood Show in Boston, Massachusetts on March 12-14, 2002.
Telephone interviews of adults living in the Baltimore and Houston were conducted in June 2002. Of the eligible respondents contacted in Baltimore, 610 completed the interview and 85 refused to participate. Of the eligible respondents contacted in Houston, 606 completed the interview and 67 refused to participate. The sampling error for the both surveys was no larger than " 4.0%. Respondents were asked whether they eat raw oysters or not, and if not, indicate the main reasons for not eating raw oysters. They were also asked about their primary food safety bacteriological concerns about raw oysters, frequency of eating raw oysters, and source of raw oysters. A series of questions was asked regarding their attitude toward radiation and irradiated oysters, interest in buying irradiated raw oysters, and willingness to pay for a dozen irradiated raw oysters if purchased in the supermarket. Respondents' characteristics including sex, marital status, age, household income, and educational attainment were also asked.
A higher proportion of the respondents interviewed personally than those interviewed by telephone reported eating raw oysters in 2001. More than 60 percent of the respondents at the Boston seafood show and Gulfport aquaculture open house ate raw oysters, while 28 percent of the respondents at the Baltimore and Houston telephone interviews reported eating raw oysters in 2001. More of the male respondents tend to consume raw oysters than female respondents. Among male respondents from Baltimore and Houston MSA's, about 40 percent stated that they ate raw oysters in 2001. A lower percentage of female respondents (20%) from the two MSA's reported eating raw oysters. Among male respondents at the Boston seafood show, 69 percent reported eating raw oysters in 2001. A lower percentage of female respondents (49%) at the seafood show indicated eating raw oysters.
IMPACTS and/or BENEFITS:
This project will benefit both the oyster consumer and the oyster industry. Consumers favorably accepted the irradiated oyster and could not differentiate an untreated from an irradiated oyster. The oyster industry will benefit from the exploration and acceptance of alternative post harvest treatments to reduce the risk of vibrio illnesses. Several Mississippi and Alabama processors have expressed interest in utilizing irradiation post harvest treatment upon approval by the US Congress.
PROJECT PUBLICATIONS:
Andrews, L.S., B. D. Posadas, M.Jahncke. 2002. Oyster irradiation: pathogenic Vibrio response and consumer difference testing. Proceeding 6th Joint Meeting, Seafood Science a& Technology Society of the Americas and Atlantic Fisheries Technology Society. Orlando October 9-11. (This is an extended abstract, not refereed journal article).
Posadas, B. and L.S. Andrews. 2002. Consumer preferences and attitudes toward irradiated oysters at the Boston International Seafood Show. Proceeding 6th Joint Meeting, Seafood Science a& Technology Society of the Americas and Atlantic Fisheries Technology Society. Orlando October 9-11. (This is an extended abstract, not refereed journal article).
Abstracts:
Andrews, L.S. and S. DeBlanc. 2002. Gamma irradiation processing to reduce the risk of vibrio infections from raw oysters. Sixty-sixth Annual Meeting Mississippi Academy of Sciences. Biloxi, MS. Feb. 2002.
Andrews, L.S., M. Jahncke, K. Mallikarjunan and C.D. Veal. 2002. Gamma irradiation processing to reduce the risk of vibrio infections from raw oysters. Seafood Technology Division, Instititute of Food Technologists. 2002 IFT Annual Meeting, Anaheim, Ca. June.
Andrews, L.S., B. D. Posadas. 2002. Oyster irradiation: pathogenic Vibrio response and consumer difference testing. Invited for presentation at the National Shellfish Association Meeting in New Orleans, April 2003.
Posadas, B. and L.S. Andrews. 2002. Consumer preferences and attitudes toward irradiated oysters at the Boston International Seafood Show. Invited for presentation at the National Shellfish Association Meeting in New Orleans, April 2003.
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