Effects of High Hydrostatic Pressure Shucking on Inherent Microbiota and Adductor Muscles in Live Triploid Eastern Oyster (Crassostrea virginal)

Authors: WU, YUWEI - Mississippi State University; CHANG, SAM - Mississippi State University

Submitted to: Institute of Food Technology
Publication Type: Abstract Only
Publication Acceptance Date: 2/26/2021
Publication Date: N/A
Citation: N/A

Interpretive Summary: Our research found that for live triploid Atlantic oysters, the high hydrostatic pressure treatment at about 43,500 pound per square inch (psi) for 2 minutes was sufficient to facilitate shucking oysters and reduce the inherent bacteria. Further increases in the pressure and processing time did not produce a better effect on shucking and sterilization. Instead, high pressures changed the appearance of muscles and protein molecular changes more significantly. Mathematical equations were used to show how oysters could be processed to reduce bacteria. The results provided the engineering data for killing bacteria using proper pressure and processing time.

Technical Abstract: Triploid Atlantic oyster (Crassostrea virginica) was processed by hydrostatic pressure processing (HHP) with combinations of pressure (100, 200, 300, 400, 500, and 600 MPa) and time (1, 2, 3, 4, and 5 min) at 20 ±1 °C in our processing laboratory. Aerobic plate counts (APC) were performed to indicate extent of bacteria inactivation. Appearance and protein profiles of adductor were compared between untreated oysters and those treated by HHP at 100, 200, 300, 400, 500, 600 MPa for two and four minutes. Changes in protein patterns of the adductor muscle were studied with native and sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis (PAGE) with and without ß-mercaptoethanol (MCE, a reducing agent) treatments. The adductor muscle's opaque portion changed color after HHP processing with pressure over 300 MPa. Oysters released adductor muscle from the oyster shell after processing at 300 MPa for two min. Gradient electrophoresis gel showed five distinct bands with molecular mass higher than 140 kDa, which had never been reported in the adductor muscle of oysters. Protein aggregations caused by HHP were observed when comparing electrophoresis gel with and without MCE. Under native PAGE without MCE, the upper parts of the lanes corresponding to HHP treatments from 400 to 600 MPa were smeared, while the smeared bands almost disappeared with the inclusion of MCE. Whole shell oysters processed under conditions of 300 MPa HHP for two min had a much lower APC (log CFU g-1) than those treated with one min, but processing at this pressure for 3, 4, and 5 min did not significantly reduce the bacteria further. The Baranyi's model and bi-phasic model's overall performance had a better fit (higher R squre value) than the linear model for the inactivation rate estimated from our HHP processing experiment.