Food quality has always been a concern to human being especially in developing countries. The results of the present study showed that the three types of ready-to-eat sesame (sweet dehulled sesame, salted dehulled sesame and raw sesame) harbor microorganisms such as total flora, thermotolerant coliforms and yeast and mould up to 72% in sesame sweet dehulled sesame, 44% in salted dehulled sesame and 89.33% in raw sesame.
Raw sesame had the highest counts of thermotolerants coliforms, total aerobic mesophilic bacteria and yeast and mould as compared to dehulled sweet and dehulled salted sesame. The means were 4.26 log10UFC.g− 1; 5.39 log10UFC.g− 1 and 4.55 log10UFC.g− 1 respectively for thermotolerants coliforms, total aerobic mesophilic bacteria and yeast and mould. Raw sesame was followed by sweet dehulled on which the means of thermotolerants coliforms, total aerobic mesophilic bacteria and yeast and mould were respectively 3.83 log10UFC.g− 1; 4.74 log10UFC.g− 1 and 2.89 log10UFC.g− 1. The lower contaminated was salted dehulled sesame with the average of 1.23 log10UFC.g− 1; 3.65 log10UFC.g− 1 and 1.6 log10UFC.g− 1 respectively for thermotolerants coliforms, total aerobic mesophilic bacteria and yeast and mould. Based on recommended microbiological criteria for dehydrated foods use in this study [13] [14] (Table 2); 50.67% of the ready to eat sesame are satisficing while 17.33% are acceptable and 32% are not satisficing. The discrepancies between the numbers of microorganisms of these three types of ready-to-eat sesame may reflect differences of food handler’s hygiene management and the final product conservation. The flowchart of ready-to-eat sesame processing (Fig. 4) showed clearly that no heating step is involved in the production of raw sesame. This is what probably justifies its high load in microorganisms and which makes it one of the most contaminated and risky foods. [15] found out an average of 4.53 log10UFC.g− 1 (3.4x104); 4.83 log10UFC.g− 1 (6.9x104); 4.36 log10UFC.g− 1 (2.3x104) respectively for coliforms, aerobic plate counts and yeast and mould while assessing the microbial quality of tahini (Sesame Paste) in Lebanon. In the other hand, [16] found out an average of 1.44 log10UFC.g− 1 (2.8x10); 4.63 log10UFC.g− 1 (4.3x104); 3.88 log10UFC.g− 1 (7.6x103) respectively for coliforms, aerobic plate counts and yeast and mould while assessing the microbiological and chemical quality of tahini halva in Turkey. The obtained results in this study are slightly different of these two-research finding. Indeed, all these products are sesame-based product and the presence of microbes according to [15] has been attributed to a number of reasons including, the microbial quality of sesame seeds, poor hygiene and sanitation, and improper processing and storage conditions.
Published papers reported that sesame-based products such as Tahini and Halva (Helva) has been linked to salmonella infections outbreak [16] ; [17] ; [18]. The causes of these contaminations are mainly due to contaminated ingredients or unhygienic processing. It believed that contamination of sesame based products is deeply linked to the quality of the raw materials. [19] exhibited 24.6% of salmonella contamination of raw sesame submitted to exportation from 2007 to 2017 in Burkina Faso. According to [5], in Burkina Faso, sesame based products processing is run by artisanal and semi-artisanal processors who are individuals, companies, associations and some pastries.
Therefore, there is a need as stipulated by the [17] to design and to setup proper Hazard Analysis Control Critical Point (HACCP) system and Good Manufacturing Practices (GMP) as the contributing factors for reduction of microbial contamination in low-moisture foods.
Indeed, the processing methods used to transform raw sesame into dehulled sweet and dehulled salted sesame should normally reduce drastically the microorganism population. We can hypothesize that the presence of microorganisms could then be linked to post contaminations. Our hypothesis was clearly confirming by the presence of thermotolerant coliforms in 32 out of 75 samples (42.70%) including heat treated sesame. Most of them were found particularly in 89,33% of the raw sesame samples (17 out of 25). The presence of thermotolerants coliforms indicates the presence of fecal material from warm-blooded animals [20]. The thermotolerants coliforms (fecal coliforms) group is restricted to organisms that grow in the gastrointestinal tract of humans and other warm-blooded animals and includes members of at least 3 genera: Escherichia. Klebsiella, and Enterobacter [21]. The process used to obtain the three types of ready-to-eat sesame involved some critical points as showed in Fig. 4 in red color. These critical points could be the ways through which microorganisms could reach the final product and cause public health issue. Controlling these critical points is essential to improve the quality of the final product. During the processing of sweet and salted dehulled sesame, a large amount of sugar and salt were added to give the sweet taste and dirt but also to improve the conservation of these products. Even thought, some sesame samples seem to have high number of microorganisms. According to [4], the addition of large amounts of salt or sugar can also be regarded as a simulated drying process, as it results in a reduction of the amount of water available for microbial growth. The dehulled sweet sesame after caramelization undergoes a manual kneading operation in order to give the desired shapes (circles, heart, lozenge…) to the final products (Fig. 4). This could be one of the reasons for its high coliform load. Sanitation and personal hygiene, especially during home-based food processing, needs improvement. According to [22], the tendency at present is to market dried fruits in the packaged form, the principal chances for contamination after drying would be from the hands of the person filling the package, if filling is done by hand, or from the package itself. Furthermore, there is a variation between the sesame samples in terms of visual quality. Some are more grilled, more sweet or more salted within the same group of samples. This suggested a lack of quality standards in sesame processing conditions. Therefore, it seems necessary to setup and respect Good Manufacturing practices (GMP), Good Hygiene Practices (GHP) and Good Standard Processing (GSP) by training the actors as the processing system of this field still artisanal.
In general, survival, growth and multiplication of microorganisms in food depend on various factors which may be classified simply into those that are intrinsic or associated with the food material and those that are extrinsic or associated with the environment surrounding the food [23]. Therefore, all materials used for processing should be clean immediately in order to ensure the quality of the next production as the total aerobic mesophilic bacteria is high in almost all the sample (92%) and varies from 3x10 to 6.12x105 CFU g− 1. Aerobic mesophilic bacteria are fermentative bacteria involved in food degradation and contribute to lowered the merchantable quality of food.
The presence of possible pathogenic organisms in these foodstuffs suggest a potential public health hazard to consumers. Fortunately, no Salmonella spp neither E. coli were found in any of our samples. It was expected to find those pathogens in the raw samples as no heating step are involved in this process. Biochemical tests used to confirm suspected E. coli was found to be some Klebsiella and Enterobacter species. Further molecular investigations are deeply needed to understand why no Salmonella spp neither E. coli were not found even in high load of thermotolerants coliforms. Indeed, raw sesame and sesame-based products are known to harbor sometimes Salmonella species. Previous studies on food quality in Burkina Faso raised the circulating pathogens such as E. coli, Salmonella and Campylobacter. [24] ; [25] highlight the presence of S. enterica, Campylobacter and E. coli in raw meat, poultry feces and carcasses in while [26] raised E. coli and Salmonella strains in milk and [27] isolated E. coli in Organic Waste Products from Cattle’s Markets.
Statistical analysis revealed that there is correlation between the three different parameters (p-value ˂ 0.05) and the strength of this correlation, according to Pearson were 46.3%, 47.7% and 75.4% respectively between the total aerobic mesophilic bacteria and yeasts and moulds; between total aerobic mesophilic bacteria and the thermotolerant coliforms and finally between the thermotolerant coliforms and yeasts and moulds.
Sesame is a dehiscent dry food that low moisture allowed it to be store at ambient temperature without any treatment. In the absence of sesame safety standards, weak conditioning systems can favor microbial growth to unacceptable levels even supplement such as sugar have been added.