Effect of Ultra High Pressure Under Argon and Temperature on the Volatiles and Piperine Content and Microbiological Quality of Black Pepper (Piper Nigrum L.)

Abstract

In the search of effective decontamination methods of herbal spices, combined action of high pressure under argon at various temperatures has been applied. Ground black pepper (Piper nigrum L.) samples were exposed to hydrostatic pressure of 1 000 MPa under argon for 30 minutes at elevated temperature (60 °C, 80 °C, 100 °C and 140 °C). Under all experiments conditions vegetative cells of bacteria were totally inactivated. Under conditions of 1 000 MPa and temperature 60 °C 84.3% of moulds spores were killed. The total destruction of vegetative microorganisms was observed at 1 000 MPa in 140 °C. For inactivation of 99.9% of aerobic bacterial spores it was necessary to apply pressure of 1 000 MPa and 140 °C under argon.These results indicate that microorganisms present in ground black pepper, which is the product of low water activity, are very resistant to treatment with pressure and temperature. Changes in the essential oil and piperine content as well as changes in the volatile constituents by means of GC and GC-MS were studied. The essential oil content decreased significantly in all treated samples, the losses increased with temperature. Piperine content significantly (ca. 20%) decreased only in samples pressurised at 100 0C and 140 °C. Volatiles composition changed after all kind of treatment. Decrease of most of the monoterpenes, minor decrease of sesquiterpenes and increase of a-and y-terpinene and 1-terpinen-4-ol were observed.