Effect of irradiation on the microbiological status and flavouring materials of selected spices

Abstract

Spices from Egyptian local markets were irradiated with different recommended doses (0, 5, 10, 20 and 30 kGy). The spices tested included dried leaves of marjoram (Majorana hortensis Moench), rhizomes of ginger (Zingiber officinale Roscoe) and powdered hot pepper (Capsicum annum L.). The study included the isolation and identification of micro-organisms in spices following their irradiation, as well as gas chromatographic (GLC) chemical analysis for the presence and structure of volatile oils, pungent and pigment materials. The results showed that hot pepper was contaminated more (9.2 x 10(5)/g) than marjoram (4.2 x 10(3)/g) and ginger (14.3 x 10(3)/g) with respect to total aerobic bacterial content. The total contents of moulds were 4.8 x 10(3)/g, 5.7 x 10(3)/g and 19 x 10(3)/g in the same spices, respectively, but the pathogenic moulds and bacterial strains differed according to the type of spice. Irradiation at 10, 20 and 30 kGy caused complete elimination of micro-organisms, whereas 5 kGy was less effective. With the GLC method chosen 18 and 50 compounds could be detected in the extracts of marjoram and ginger, respectively; gamma-terpinen and zingiberen being the major compounds in marjoram and ginger, respectively. A noticeable reduction was observed in the amount of terpenes present in irradiated marjoram; they were converted to monoterpenesalcohols. Ginger was more sensitive to irradiation, especially at high doses, but moderate changes were detected at low doses (5 and 10 kGy). A slight, but significant effect on the capsaicin (pungent compound) in hot-pepper was observed following irradiation, whereas no changes in total pigments resulted at any dose. These results prove that 10 kGy is a sufficiently high dose to eliminate the micro-organisms in spices, causing only slight changes in the flavouring materials.

Postirradiation changes of the microbiological quality, aflatoxin, capsinoids, volatile oils, and the color of red pepper powder

“…Therefore, it is obvious that γ‐irradiation was efficient in decontaminating red pepper of microorganisms, and a linear relationship existed between the radiation dose and the microbial load (Sung, ). As a result of the high frequency of Bacillus in red pepper powder and based on different types of red pepper powder, a dose of 16–20 kGy might be required (Ahmed Farag et al, ) to efficiently reduce the Bacillus population.…”

“…This contamination by bacteria and fungi may be due to cultivation, harvest, storage, processing and technology. Commercial red peppers are generally contaminated with bacteria at a level of 10 5 –10 8 cfu·g −1 (Ahmed Farag, Haliem Aziz, & Ali Attia, ; Rico et al, ). At the same time, chillis are also susceptible to attack by fungi (Horváthová, Suhaj, & Polovka, ; Mandeel, ; Sádecká, ), which produce mycotoxins (e.g., aflatoxin, citrinin, zearalenone, and T‐2 toxin).…”

“…Irradiation, as a new decontamination method, has been gradually recognized and accepted in at least 51 countries, with a maximum average dose of 10 kGy (Listed, ). However, doses of 3–10 kGy can only reduce the viable cells of total aerobic bacteria to 10 3 −10 4 cfu·g −1 , which does not meet the hygienic standard (≤ 10 2 cfu·g −1 ) of commercial irradiated spice (Ahmed Farag et al, ). Therefore, some countries (USA, China, and Australia) have raised the irradiation dose to 30 kGy without any apparent harmful effects (Ahmed Farag et al, ; Rico et al, ; Sádecká, ).…”

“…However, doses of 3–10 kGy can only reduce the viable cells of total aerobic bacteria to 10 3 −10 4 cfu·g −1 , which does not meet the hygienic standard (≤ 10 2 cfu·g −1 ) of commercial irradiated spice (Ahmed Farag et al, ). Therefore, some countries (USA, China, and Australia) have raised the irradiation dose to 30 kGy without any apparent harmful effects (Ahmed Farag et al, ; Rico et al, ; Sádecká, ). Irradiation at a dose of 10 kGy reduced the population of total aerobic bacteria by up to 4–5 logs and showed a perfect decontamination effect on fungi in hot pepper powder (Ahmed Farag et al, ; Rico et al, ).…”

“…Therefore, some countries (USA, China, and Australia) have raised the irradiation dose to 30 kGy without any apparent harmful effects (Ahmed Farag et al, ; Rico et al, ; Sádecká, ). Irradiation at a dose of 10 kGy reduced the population of total aerobic bacteria by up to 4–5 logs and showed a perfect decontamination effect on fungi in hot pepper powder (Ahmed Farag et al, ; Rico et al, ). However, previous studies did not refer to the elimination effect of irradiation on existing aflatoxin.…”