Reducing microbial contamination of black pepper by microwave-generated low pressure plasma
- Publikations-Art
- Kongressbeitrag
- Autoren
- Müller, J; Argyropoulos, D; Romano, G; Meissner, K; Heindl, A; Bolkenius, N; Voesgen, W; Leins, M; Schulz, A; Walker, M; Stroth, U
- Erscheinungsjahr
- 2012
- Tagungsname
- 7th International CIGR Technical Symposium “Innovating the Food Value Chain”
- Tagungsort
- Stellenbosch, South Africa
- Tagungsdatum
- 25 - 29 November 2012
The typical post-harvest processing of black pepper involves blanching prior to traditional sun drying followed by cleaning, grading and packaging. However, improper drying causes subsequent microbial contamination of the product during packaging, storage and transport. To reduce microbial count to consumer safe levels an alternative method i.e. the application of partially ionized gas at low-pressure (non-thermal, “cold” plasmas) was investigated for inactivation of microorganisms in black pepper as an example for temperature-sensitive materials. The main mechanisms of the plasma treatment are UV light and radicals, which causes lethal damage to the cells of bacteria. The peppercorns are evenly distributed in a cylindrical drum made of stainless steel which is rotated on its horizontal axis in the chamber where two linear plasma sources are mounted. The operating low pressure is generated by a pump connected through a flange to the main body of the sealed chamber. The surface temperature of the product is continuously measured during the plasma treatment by an infrared pyrometer. Pepper with a high original microbial contamination was used for the tests. Microbial count, moisture content, essential oil yield and color of the peppercorns were measured before and after treatment. Microbial count was reduced by four orders of magnitude from 107 to 103 colony forming units without affecting the quality of pepper. Based on the positive results a continuous treatment device for in-line application in food processing industry can be developed.