Assessment of the Microbiological Safety of Dried Spices and Herbs Commercialized in Spain
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- Sospedra, I., Soriano, J.M. & Mañes, J. Plant Foods Hum Nutr (2010) 65: 364. doi:10.1007/s11130-010-0186-0
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Spices and herbs are natural products or their blends that must be free of extraneous matter content. Conventional production of these products implicates a number of hygienic problems so spices and herbs may be exposed to a wide range of microbial contamination during pre- and post-harvest and they can present high microbial counts. In this study, we have analyzed the microbial quality of 53 samples of spices and dry herbs collected from Spanish markets detecting a contamination of samples of spices with mesophilic aerobic counts (10%) and Enterobacteriaceae (20%). The analysis from herbs showed that the percentage of contamination was 26% in both microbiological values. Pathogenic microorganisms like Staphylococcus aureus, Yersinia intermedia, Shigella spp., Enterobacter spp., Acinetobacter calcoaceticus and Hafni alvei were also isolated from spices and herbs. These unsatisfactory results showed a poor microbiological quality. Spices and dry herbs are used as ingredients in a variety of products prepared in different ways, this fact suggests the need to provide a control system to improve the quality of herbs and spices.
KeywordsHerbsShigella spp.SpicesStaphylococcus aureusYersinia intermedia
The term spices, which includes dried aromatic plants, relates to natural dried components or mixtures. The term applies equally to spices in the whole, broken or ground form . A spice is a dried seed, fruit, root, bark, leaf, or vegetative substance used in nutritionally insignificant quantities as a food additive. Spices and herbs are natural products or their blends that must be free of extraneous matter content. These products can be obtained from different parts of certain plants, from the root, rhizome, bulb, bark, leaves, stems, flowers, fruits or seeds. Spices are chiefly added to food due to their colouring, preserving or flavouring properties.
Since antiquity spices and herbs have been used throughout the world for different purposes. [29, 30, 37, 38]. During the time of the Greek civilization, the spice trade flourished between the Mediterranean region and the Far East. Spices were used extensively in the Roman Empire for culinary use, in medicines, and in luxury items such as perfumes, bath oils, and lotions. As the Roman civilization spread its influence through Europe, exotic spices were introduced to local tribes . Nowadays, there is a high demand of spices and their importance is still growing.
Spices are cultivated in various areas of the world, mainly in tropical countries. These differences and the production conditions in the cultivation areas may cause severe problems, which lead to an increased number of food-borne infections and intoxications . This fact may also affect food quality.
The collection and manipulation of spices is not always performed under rigorous hygienic conditions, which can lead to high microbial counts and the consequent damage to the food in which they are used . The presence of high levels of these microorganisms is unacceptable in ready-to-eat foods such as fresh and dry herbs, and these products may contain a high number of microorganisms, including pathogenic bacteria, mold and yeast, and, if they are not subjected to proper treatment, may cause rapid deterioration of the food. Spices can be recognized as the primary sources of alimentary intoxication when added to foods in which pathogen growth is favourable. The possibility of pathogen growth is higher when spices are used in foods that have not been subjected to complete thermal treatment, therefore particular attention needs to be paid to the application of spices to ready-to-eat foods which are not subjected to further heat treatments . Control processes based on steam or dry heat treatments to minimize the risk from pathogens must be applied by spice and herb suppliers.
The control of microbial contamination in these products lies in the application of good hygiene practices in the production/harvesting area, processing and personnel. During the last decade of the 20th century, food-borne infections and intoxications due to spices have increased in several European countries [3, 17].
There are not microbiological standards for dried spices and herbs in European Community legislation, however, the Codex Code of Hygienic Practice specifies that dried spices and herbs should be free from pathogenic microorganisms at levels that may represent a hazard to health and further requires that Salmonella should be absent in treated ready-to-eat spices . The European Spice Association (ESA) also specified that Salmonella should be absent in 25 g of spice , Escherichia coli to be present at less than 102 ucf/g, and other bacteria requirements to be agreed between buyer and seller .
The aim of this work was to analyze, at the first time, the microbial quality of spices and herbs commercialized in Spain.
Materials and Methods
Samples and Sampling
Dried spices (n = 27), herbs (n = 20), herbs mixture (n = 3) and spice blends (n = 3), elaborated according to the Code of hygienic practice for spices and dried aromatic plants , were collected from supermarkets, retails in street markets and little candy shops in Spain, aseptically in sterile bags and bottles (VWR International Eurolab, Barcelona, Spain) and analyzed in the same day. 48% of the samples collected were from Spain and the other 52% have an unknown origin but are commercialized in Spanish supermarkets.
Samples (25 g) were weighed and diluted with 225 ml buffered peptone water (BPW) (Oxoid, Unipath, Hampshire, UK). The homogenate from the sample preparation was used for the plating and incubation procedures. Four 10-fold dilutions were made with each sample, 1 ml of each step was inoculated in duplicate plate count agar standard (PCA) (Oxoid, Unipath, Hampshire, UK) at 30 °C for 72 h, according to ISO 4833 reference method  to determine the number of mesophilic aerobic plate counts (APC).
According to ISO 21528-2 , Enterobacteriaceae were determined using duplicate pour plates with 1 ml of each dilution in violet red bile glucose (VRBG) agar (Oxoid, Unipath, Hampshire, UK), over-layered with a further 10–15 ml of VRBG agar. The plates were incubated at 37 °C for 24 h. typical colonies were counted on all plates. Identification of Shigella, Yersinia, Acinetobacter and Hafni was done by a Rapid ONE System (REMEL Inc. Santa Fe, USA) for the colonies isolates form the VGBR agar. To isolate E. coli, the previous BPW tubes were inoculated onto CHROMagar ECC (CHROMagar Microbiology, Paris, France) at 37 °C for 48 h and confirmed by Rapid ONE System (REMEL Inc., Santa Fe, CA, USA) .
A volume of 0.1 ml of previous BPW was surface plated on Baird-Parker agar containing egg-yolk tellurite emulsion (Oxoid), and incubated at 37 °C for 24 h to enumerate S. aureus, according to ISO 6888-1 . Colonies with typical S. aureus morphology (i.e., black, convex and with or without halo on BP agar) were examined microscopically, Gram stained, tested for catalase reaction and confirmed with an agglutination Staphytect Plus test (Oxoid).
Isolation and identification of Salmonella spp., according the ISO 6579  was performed using the previous BPW being analyzed using Tetrathionate broth with Novobiocin (Oxoid) and Rappaport-Vassiliadis enrichment broth (Oxoid) for 24 h at 37 °C and 42 °C, respectively, and the positive cultures were finally streaked onto CHROMagar Salmonella (CHROmagar Microbiology). The confirmation was done with Rapid ONE System (REMEL Inc., Santa Fe, CA, USA).
To detect L. monocytogenes, according to ISO 11290-1  studied samples (25 g) were weighed into sterile stomacher bags, diluted and homogenized with 225 ml of Fraser broth (Oxoid). After being homogenized and precultured at 37 °C for 48 h, the positive broth was streaked Listeria Palcam agar (Oxoid) (37 °C, 48 h). Characteristic colonies were analyzed Gram stain, motility and oxidase and catalase tests followed by identification with the API Listeria system (BioMérieux, Mancy l’Etoile, France).
Moisture content was determined by drying approximately 10 g samples of spices at 105 °C to constant weight .
Data were analyzed by determining standard error of the mean, two way analysis of variance and simple correlation after converting the microbial counts to a logarithmic scale .
Moisture content and percentage of samples containing total enterobacteriaceae and aerobic mesophilic bacteria in retail spices from Spain
Moisture (g/100 g) Mean±SE
Aerobic plate counts
log cfu/g fresh weight
log cfu/g fresh weight
11.2 ± 1.58
9.6 ± 0.4
9.1 ± 1.26
Bay leaf powder
12.7 ± 0.73
11.2 ± 0.89
Black pepper powder
12.6 ± 2.05
12.7 ± 0.78
8.5 ± 0.42
9.8 ± 0.42
13.1 ± 0.33
11.1 ± 0.23
10.7 ± 0.41
10.9 ± 0.44
16.3 ± 0.93
Incidence of microbial flora in Spanish spices and herbs
Herbs (n = 23)
Spices (n = 30)
No bacterial contamination was detected in thyme, basil, cinnamon, clove, turmeric, ginger, aniseed and dry parsley. In our study, the analysis showed that 10 and 20% of total studied spices presented contamination with mesophilic aerobic counts and Enterobacteriaceae, respectively. In the case of the herbs, the analysis showed that the percentage of contamination was 26% in both cases, for mesophilic aerobic counts and Enterobacteriaceae. This frequency of contaminated samples indicates contamination from the environment or inadequate hygienic handling and unsanitary conditions, this usually occurs in samples bought at retail in street markets.
In both kinds of samples analyzed, spices and herbs, occur a high frequency of some pathogenic microorganisms like some species including S. aureus, Yersinia intermedia, Shigella spp., Enterobacter spp., Acinetobacter calcoaceticus and Hafni alvei (Table 2) which can cause health problems for consumers.
In analyzed samples considerable variations were observed in the microbial counts, even between samples of the same kind. This probably due to the production and cultivation conditions that are not the same. Schweiggert et al.  demonstrated than differences in spice technology can determine contamination levels. So, spices and herbs should not be grown or harvested where the presence of potentially harmful substances would lead to an unacceptable level of such substances in the final product. Cinnamon and basil samples were free from microbial contamination and it can be because according to the studies of Friedman et al. , cinnamon eliminates or reduces some microorganisms as E. coli, L. monocytogenes and Salmonella spp. Lachowicz et al. and Montes-Belmont [20, 26] also observed an antibacterial effect of basil essential oil against several microorganisms. Also thyme and oregano oils have presented antimicrobial activity in several studies .
In our study, thyme samples were not contaminated, thus it is possible that thyme inhibits the growth of some pathogens tested. Numerous studies demonstrated that the essential oil of thyme is among the most potent essential oils with regard to antimicrobial properties [8, 19, 24]. According to the study of Chen et al.  about the antimicrobial activity of Zingiberaceae plants, the ginger and turmeric samples analyzed were free of bacteria.
Otherwise, oregano samples were contaminated by different microorganisms. This fact can be because of the composition of the essential oil of herbs and spices can vary greatly depending upon the geographical region, the variety, the age of the plant and the method of drying .
In our samples, 11% were contaminated by Shigella spp., in a bay leaf sample the specie were S. somnei. The prevalence of this microorganism in food isolates is high. Since the year 2006, more than 70% of the laboratory-confirmed Shigella isolates reported to the Centers for Disease Control and Prevention (CDC) were S. somnei and more than 10% were unknown . Other samples studied were free of this bacteria and this fact is because several samples essential oil and their main constituents inhibit the growth of S. somnei .
Acinetobacter calcoaceticus has appeared with high frequency in our analyzed samples, which is generally considered nonpathogenic to healthy individuals. The study of Tharreau et al.  describes also the presence of this microorganism in French spices.
The prevalence of E. sakazakii and other Enterobacter spp. in infant food, milk powder, cereal products, spices, sugar and food production environments were studied . In spices samples, they did not find enterobacter presence but we have detected a high level of contamination of some Enterobacter species in herbs and spices samples. E. sakazakii has been also isolated from a wide range of foods [9, 15, 16, 21]. According to Soriano et al. , Enterobacter cloacae has been isolated from vegetable samples. We have also detected it in two spices samples, paprika and cayenne.
Considering the results obtained in the present study, the samples analyzed contain a high level of microorganisms. These results indicate that sanitary conditions in different production stages of condiments and spices must be improved to reduce health hazards. However, it is difficult to select a single microbial index for quality determination of these food additives because they are used as ingredients in a variety of products prepared in different ways. This fact suggests the need to provide a control system to improve the quality of herbs and spices.