IMPROVING THE SAFETY OF HARD CLAMS, MERCENARIA MERCENARIA, THROUGH POST HARVEST TREATMENT WITH HIGH HYDROSTATIC PRESSURE PROCESSING (HHP)

NON-TECHNICAL SUMMARY: Hard clams are sometimes consumed raw but they may contain harmful bacteria and viruses. This project will evaulate the effect of high hydrostatic pressure on getting rid of these harmful bacteria and viruses.

OBJECTIVES: 1)Establish optimal physical processing parameters for applying HHP technology to hard clams. 2)Assess the HHP processing through a microbiological shelf life study, including work on viruses. 3)Carry out preliminary studies to evaluate the sensory characteristics of the HHP processed clams. 4)Educate the public about this new food preservation process and evaluate their perceptions.

APPROACH: High Hydrostatic Pressure (HHP) processing is a novel food processing method that destroys food borne bacteria and viruses, and inactivates deleterious enzymes which affect food quality, without using heat. During HHP processing, pressures up to 145,000 pounds per square inch (psi) may be applied on a food product. HHP processing offers a new way to produce safe, value-added, and high quality products, with minimum detrimental effects associated with heat processing such as loss of original flavor, color, texture, and nutritional value. In our proposed work, we will apply HHP to process hard clams Mercenaria mercenaria to improve the food safety aspects of these raw shellfish.

PROGRESS: 2006/09 TO 2010/09

OUTPUTS: In an effort to gauge public perception about the acceptability of High Hydrostatic Pressure (HHP) processed hard clams, the marine extension agent (Flimlin) used the Information taken from the sensory evaluation tests done at Rutgers Department of Food Science to develop both educational point of sale information and for live presentations for wholesalers and retailers. The process was set up to educate seafood managers and then customers. Information must be understood by those selling the HHP clams first, so that they can educate others down-line. Education programs are necessary to institute change in the mindset and buying habits of seafood consumers who have been previously educated that dead raw shellfish are unacceptable. A tri-fold brochure was developed which explained the, how shellfish responded to it, and the benefits of the processing. These were aimed at the consumer, not the scientific field. There were 2500 of these brochures printed, some which were used immediately in public demonstrations, and some which will be used over time for future educational opportunities. The extension agent took the processed clams out to several entities to explain the process and show the product. He went to Rastelli's Seafood in Egg Harbor City, and did a demonstration for the owner, sales manager, and corporate chef. He demonstrated the finished product for McCarthy's Clams, one of the suppliers of product for our experiments to gauge his concept of the product. He took clams to the Atlantic County Chapter of the American Culinary Federation/Professional Chef Association of South Jersey. This event involved professional chefs, food distributors, food sales personnel, Chef Educators and culinary students. An informal taste test was done and an in-depth demonstration and explanation of the HHP process was done for the 85 attendees for that event. Samples were left with the restaurant's own chef to experiment with. Two seafood distributors there expressed interest in the process. In order to reach the general public, the agent contacted the President of Food Circus Super Markets, part of the Super Foodtown chain. Mr. Louis Scaduto allowed the agent to do 6 demonstrations in 6 different Foodtown markets. Three demos were done on each of two days. He spoke with at least 95 seafood customers and 79 filled out a brief questionnaire following an educational talk about the HHP clam, and a taste testing. The results were impressive. 96% liked the Aroma 95% liked the Appearance and Plumpness 76% liked the Saltiness 94% liked the Firmness (or Mouth Feel) 100% liked the Ease of Opening 100% liked the Overall Taste and Acceptance 97% said they would be likely to purchase this type of clam. 81% said they would pay more for this ease of opening over self opening of a regular clam 63% said that it didn't matter that the clam was not alive. Consumers were obviously impressed with the product safety, form and edibility characteristics of the HHP clam. This combined with our initial sensory evaluations at the University indicate both controlled and real world tests of the efficacy of the reduction of food-borne illness associated with raw molluscan shellfish. PARTICIPANTS: Mukund V. Karwe George E. Flimlin Donald W. Schaffner Beverly Tepper Shalaka Narwankar Gabriel Mootian TARGET AUDIENCES: Researchers Extension Specialists Seafood processors Seafood vendors Regulatory PROJECT MODIFICATIONS: Not relevant to this project.

IMPACT: 2006/09 TO 2010/09

In this project, the effect (HHP) processing on the total plate count (TPC) from littleneck hard clams harvested from special restricted waters in New Jersey was investigated. A response surface methodology (RSM) was used to find optimum pressure and time conditions for microbial inactivation. Based on the experimental design a total of 12 pressure and time combinations were evaluated, which were between 386 to 545 MPa and hold time of between 1 and 7 min. Total plate count (TPC) analysis was done before and after processing. The results of the RSM showed that at least 480 MPa pressure was needed to achieve a 1 log reduction (90%) in TPC. Consumer acceptability of HHP clams was evaluated. A panel of 60 regular raw clam eaters tasted both pressure processed and unprocessed hard clams from approved waters. The results showed that consumers equally preferred the processed and unprocessed hard clams. However, two subgroups of consumers emerged; those who preferred the plumpness of the processed clam and those who liked the aroma of the unprocessed clam. We then studied the physical changes in clam meat as a result of HHP using instrumental analysis. Specifically, changes in volume, texture and color of meat were evaluated. In addition to the physical effects of high pressure on clam meat, the effect of HHP on Vibrio parahaemolyticus, a human pathogen associated with shellfish borne gastroenteritis, were also evaluated. Textural changes were determined by performing a compression test on clam meat with a 50 mm diameter probe while color changes were determined using Hunter colorimeter. Volume measurements were done using 0.5 mm diameter glass beads. The results showed that HHP processed clam meat was firmer compared to unprocessed meat; however clams processed at 552 MPa were softer than clams processed at 276 MPa. Processed clam meat also had a glossy appearance and was pale red in color, consistent with increased values of lightness (L) and reduced values of redness (a). Volume of meat (in shell) also increased by 150%. This occurred simultaneously with a reduction in clam liquor surrounding the meat. The plumpness was thus determined to be the result of absorption of the clam liquor during pressurization. A scanning electron microscope analysis of processed meat was conducted in an effort to explain the textural and volume changes due to HHP. The SEM micrographs showed muscle fibers separated from one another after high pressure. The impact of HHP against Vibrio parahaemolyticus was evaluated by inoculating live hard clams through natural bioaccumulation with a cocktail culture of 5 outbreak strains of Vibrio parahaemolyticus. Contaminated clams were processed at pressure and time conditions of 250 MPa to 450 MPa at hold times between 2 and 6 min. Treatment conditions of 350 MPa for 6 min and 450 MPa for 4 min were found to reduce the concentrations of Vibrio parahaemolyticus in clams to below the limit of detection(