Intermittent high-power short-time microwave-vacuum treatment combined with steam impingement for effective microbial decontamination of black pepper (Piper nigrum)

Black Pepper (Piper nigrum) also known as black gold is one of the most traded spices in the world. Recent instances have reflected increased numbers of export rejections due to the presence of Escherichia coli, Salmonella and a high load of microbes. This study presents the potential of a novel combination of microwave-vacuum–steam treatment that is capable of bringing down the high microbial load in the product at relatively low temperatures. The treatment has resulted in 7.59 log reduction for E. coli, 9.25 log reduction in Salmonella and around 3.28 log reduction in total mesophilic plate count. The optimized condition was found to be 4.19 W/g MW power density, 3 s steam time and 134 s process time. The process optimized and developed in this study with low microwave power density has the potential to be used industrially for bulk decontamination of spices.