Effects of Post-Harvest Treatment Requirements on the Markets for Oysters

Article excerpt

Because of public health concerns, regulators are considering requiring post-harvest treatment of halfshell and shucked oysters by wholesalers and processors. Two recently developed post-harvest treatment technologies may actually reduce the costs of producing shucked oysters, but would increase the costs of halfshell oysters. An interregional model of the wholesale oyster industry is developed to estimate the effects of treatment requirements on prices, output, and employment. If post-harvest treatment is required for all Gulf oysters, price increases are estimated to be less than 20% and, in some cases, prices decrease. Results indicate producer and consumer losses in the halfshell market are partially or more than offset by gains in the shucked market.

Key Words: equilibrium displacement model, oysters, post-harvest treatment, Vibrio vulnificus

Regulators of the shellfish industries have been considering whether to require wholesalers and processors of oysters to use post-harvest treatment technologies because of concerns regarding illnesses and deaths due to Vibrio vulnificus. V. vulnificus is a bacterium that is naturally present in marine environments and is not associated with environmental contamination [Centers for Disease Control and Prevention (CDC), 2000a]. Although fewer than 100 cases occur each year, the CDC estimates V vulnificus bloodstream infections are fatal about 50% of the time (CDC, 2000b). Most cases are associated with consumption of raw shellfish, particularly Gulf-harvested oysters served raw on the halfshell. However, anecdotal evidence suggests some cases may occur when individuals consume shucked oysters in raw form (see Muth et al., 2000).

In June 1998, the Center for Science in the Public Interest (CSPI) petitioned the U.S. Food and Drug Administration (FDA) to require that all oysters intended for raw consumption be treated using a post-harvest treatment method proven to kill V. vulnificus bacteria (CSPI, 1998). In response to the petition, the Interstate Shellfish Sanitation Conference (ISSC) and the FDA are interested in determining the potential economic effects of requiring post-harvest treatment of oysters harvested from the Gulf region of the United States or for the entire United States.1

The available post-harvest treatment technologies include cryogenic individual quick freezing (IQF), cool pasteurization, and hydrostatic pressure.2 The companies currently using these technologies do so because they allow the companies to sell a differentiated (e.g., safer or longer shelf-life) product.

The cryogenic IQF process, which has been in use for over a decade, is employed by one large plant in Texas and two substantially smaller plants in Florida. For this process, oysters are opened and put on the halfshell, and are then passed through a freezer tunnel that rapidly cools the oysters using liquid CO2. However, the cryogenic IQF process has not been adapted for shucked oysters.

For the cool pasteurization process, which has been in use since 1997 by one plant in Louisiana, oysters are submerged in a computer-monitored tank of warm water, and then immediately cooled in a tank of cold water. Finally, the hydrostatic pressure process is a new technology, first used commercially in the summer of 1999 by one plant in Louisiana. In this process, oysters are loaded into a water-filled pressure chamber, which is then sealed and pressurized using an electric, 60 horsepower pump.3 For both the cool pasteurization and hydrostatic pressure processes, oysters intended for the halfshell market are banded prior to treatment, while oysters intended for the shucked market are immediately shucked and put into containers.

The objective of this study is to evaluate the potential economic effects of requiring post-harvest treatment of both raw halfshell and shucked oysters by processors and wholesalers of oysters. To evaluate the economic effects, we developed a simple aggregate deterministic model of the wholesale market for oysters. …