Pathogen elimination processes may impact spice quality

A study published in the Journal of Food Science examines the effect of pathogen inactivation processes on the quality of spices and herbs. Processing methods for spices and herbs include fumigation with ethylene oxide (EtO), irradiation, and vacuum-assisted steam. While fumigation with EtO has been shown to significantly reduce microbial populations on spices, some EtO-treated spices have been shown to undergo alterations in flavor and color. Vacuum-assisted steam processing has been used with greater frequency due to greater consumer acceptance of this process over EtO or irradiation. However, there may be a decrease in quality from the high temperatures typically used in this process. Finally, irradiation has been described as an effective, energy-efficient method for decontaminating spices, but higher doses of ionizing radiation have been shown to change the physical and antioxidative properties of food products. In addition, consumers have not been readily accepting of any product that has been treated with gamma rays, electron beam, and X-rays.

The researchers irradiated black peppercorn, cumin seed, oregano, and onion powder to a target dose of 8 kilograys (kGy). In addition, the researchers utilized ethylene oxide (EtO) fumigation and vacuum assisted-steam (82.22°C, 7.5 psia) on whole black peppercorns and cumin seeds. They then compared the treated and untreated spices/herbs (visual, odor) using sensory similarity testing protocols to determine if processing altered sensory quality. In addition, analytical assessment of quality (color, water activity, and volatile chemistry) was completed.

The researchers found that irradiation did not alter visual or odor sensory quality of black peppercorn, cumin seed, or oregano, but created differences in onion powder, which was lighter and redder in color, and resulted in nearly complete loss of measured volatile compounds. EtO processing did not create detectable odor or appearance differences in black peppercorn; however, visual and odor sensory quality differences, supported by changes in color (darker and more yellow) and increased concentrations of most volatiles, were detected for cumin seeds. Steam processing of black peppercorn resulted in perceptible odor differences, supported by increased concentration of monoterpene volatiles and loss of all sesquiterpenes. Meanwhile, steam processing only altered the visual appearance of cumin seeds. An important step in process validation is the verification that no effect is detectable from a sensory perspective.

The researchers concluded that “the progression of the relationship of spices and herbs beyond culinary contributions and toward developing relationships to health and wellness further establishes the importance of identifying effective processes that protect spice and herb quality.”

Abstract