Process optimization for microbial safety and sensory evaluation of high pressure processed hard clams (Mercenaria mercenaria)

Hard clams (Mercenaria mercenaria) are the most valuable commercially harvested clams in the United States. Among the various market grades of hard clams, littleneck and topneck are often eaten raw. Although most of the hard clams are harvested from approved waters under the guidelines of National Shellfish Sanitation Program, there are hard clams which are harvested from restricted waters under special permit. These restricted waters often have high levels of fecal coliforms (14-88 MPN). Clams harvested from these waters must undergo post harvest treatment either by relaying to clean waters or through depuration before entering the market. These treatments are time consuming and are not always effective in purging the bacteria and viruses. Thus, an alternate post harvest technology would benefit both the fishermen and the clam processors in terms of increased landings by accessing the special restricted areas and also by having a premium safe product in the market. High pressure processing (HPP) has been proven to be successful for reducing bacteria and viruses in oysters along with the retention of raw flavor. We investigated the effect of HPP on microbial safety of raw littleneck clams from restricted waters. Since the profitability of the process also depends on the preferences of consumers, we evaluated the impact of HPP process on the consumer acceptance of hard clams from approved waters. Littleneck hard clams from special restricted water were high pressure processed following a Response Surface Methodology (RSM) experimental design to optimize the pressure and hold time and then were evaluated microbiologically. The log reduction of the total bacterial count due to HPP was found to be primarily a function of pressure. Clams from approved waters were used for sensory evaluation. These clams were high pressure processed at 310 MPa for 3 minutes. A consumer panel sensory evaluation of these clams showed that consumers (n=60) equally preferred the HPP and the unprocessed clams. Consumers preferring the HPP clam (n=28) liked plumpness and saltiness of this sample more, whereas consumers preferring the unprocessed clam (n=32) liked the saltiness and chewiness of the unprocessed sample more. Thus, it was a taste driven preference.M.S.Includes bibliographical references (p. 66-68)