Abstract
High hydrostatic pressure processing (HHPP) was tested as means for controlling microbial contamination of chicken meat under the harsh Saudi environmental conditions. Samples of minced chicken were vacuum packaged and pressure treated at 300, 400, 450 and 500 MPa using a Stansted apparatus. Treated and untreated samples were then stored at 3 degrees C and microbial content as well as some chemical and physical properties were monitored. The microbial load of the untreated samples reached the spoilage level of 10(7) cfu/g in about one week, resulting in bad smell and dark brown color. The pressure treatments reduced total bacterial counts by 1.8 to 3.2 log(10) cycles and reduced counts of Enterobacteriaceae and Salmonella to non-detectable levels. The color of meat was slightly affected but pH, moisture content and the oxidation products of lipids were not substantially changed.
The treatment killed mainly gram-negative bacteria but also caused sub-lethal injury to part of the population resulting in prolonged lag phase. The population not killed by the 350 to 450 MPa treatments grew relatively slowly during storage and its load reached spoilage level in 4 to 6 weeks, while the load of the population treated at 500 MPa did not reach this level till the end of a storage period of 9 weeks. Interestingly, no signs of spoilage appeared on the pressure treated samples even when the microbial load reached the expected spoilage level. It can be concluded that HHPP can be successfully used for the control of microbial contamination of foods under Saudi and similar environmental conditions.