First risk assessment report of aflatoxins in Egyptian tahini

Highlights

• 117 Tahini samples assessed for the aflatoxins levels.

• The unlabeled tahini samples from unknown sources containing more noteworthy concentration levels than branded samples.

• The estimated daily intake was 0.5 ng/kg b.w./day for children and 0.5 ng/kg b.w./day for adults.

Abstract

Aflatoxins are very dangerous natural toxins that are mainly produced by fungal organisms that are attracted to oil seeds, nuts and spices, where they are causing health and economic problems. Therefore, in this study, 117 samples of tahini (a product made from toasted sesame seeds) were collected from different Egyptian governments from already known brands and, moreover, from local unknown sources. Thus, there was a need to assess the level of contamination of aflatoxins and estimate the risk exposure according to the average daily intake. Results indicated that 67 % were free from aflatoxin B1 (AFB1), 21 % exceeded the maximum permitted limit (MPL) and 12 % were below MPL from the total samples, while the national MPL is 2 μg/kg for AFB1. The AFB1 mean concentrations for the samples reached 0.1 ± 0.2 and 13.0 ± 19.3 μg/kg for branded tahini samples and local unlabelled tahini samples respectively. The assessment revealed two different levels of exposure to AFB1 between adults and children and for branded and locally unlabelled made tahini. There was a higher estimated exposure from local unlabelled tahini than branded ranging from 0.001 to 0.1 ng/kg b.w./day for adults and from 0.004 to 0.5 ng/kg b.w./day for children.

Introduction

Two basic human needs are food security and safety. In recent years, they are considered to be important issues, not only for national organisation but also for international organisations. Currently, the most critical concerns are microbial and chemical food hazards. Among the food elements, mycotoxin attracted the world’s attention in terms of fungal invasion (Marin et al., 2013). Different fungus species produce aflatoxins which are one of the most dangerous secondary metabolites, which are derived from polyketides (Payne and Brown, 1998). Different entanglements could affect humans and animals as a result of fungal infection to cereal crops such as cotton, peanut, sesame, walnut, wheat and tree nuts (Jelinek et al., 1989). Aflatoxins are pale yellow to colourless crystals. AFB1 and AFB2 show a blue fluorescence in ultraviolet (UV) light while AFG1 and AFG2 exhibit green fluorescence. AFB1 melting point is 268–269 °C while AFB2 is 286–289 °C (Wogan, 1966; Kiermeier and Kroczek, 1974; Uwaifo et al., 1977).

Aflatoxins are freely soluble in organic solvents with moderate polarity, slightly soluble in water and insoluble in nonpolar solvents (Cole and Cox, 1981; Bennett, 1992). In the presence of oxygen, aflatoxin is unstable to UV light, moreover, it is unstable in the presence of the oxidising agent and to extremes of pH (< 3 or > 10) (Castegnaro, 1991). AFB1, AFB2, AFG1 and AFG1 structural formula are given in Fig. 1.

Production of aflatoxin is regulatory genes expression is influenced by changes in natural temperature (Schmidt-Heydt et al., 2010). Under specific conditions, aflatoxin will be produced by that fungus. Increasing the temperature to 37 °C alongside water stress and CO₂ presence, AFB1 production will be enhanced. While at the same temperature and water stress levels without CO₂ present, production of AFB1 will be reduced (Magan et al., 2011).

In the state of Gujrat and Rajasthan in India, about 106 deaths due to hepatitis were as a result of aflatoxin in 1975 (Krishnamachari et al., 1975). These comprised of fever, malaise and anorexia followed with abdominal pain, vomiting, and hepatitis as the early symptoms of hepatotoxicity of the liver, which is caused by aflatoxin. Aflatoxins are explicitly focused on the liver organ (Abdel-Wahhab et al., 2007); unfortunately, there are some cases of acute toxicity which are rare and exceptional. Chronic toxicity involves carcinogenic and immunosuppressive impacts (Etzel, 2002; Sargeant et al., 1961; Weidenbörner, 2001). Aflatoxins were found in oilseeds, spices, nuts and different types of cereals.

During harvest, transportation, and storage, or while in the field, fungal infection can occur (Kader and Hussein, 2009). Regulations have been set to limit aflatoxin production in many countries. Current guidelines, for the most part, concern the aflatoxins; however, guidelines for different mycotoxins are being quickly created. Analytical methodology, knowledge about the distribution of mycotoxins in commodities and, moreover, the availability of toxicological and survey data, are all factors that affect the decisions of setting limits for mycotoxins (Van Egmond and Jonker, 2004). According to the European Commission (EU, 2006) and Egyptian Standards (ES, 2007) a maximum permitted limit for aflatoxin (MPL) in oilseeds was set at 4 μg/kg for the sum of AFB1, AFB2, AFG 1 and AFG2, while 2 μg/kg for AFB1.

A critical perspective for the safety concern is the detection and quantification of aflatoxin in food and feed. One of the oldest techniques used to detect aflatoxin is thin layer chromatography (TLC) (Fallah et al., 2011). Currently, the most common techniques for detection are enzyme-linked immune sorbent assays (ELISA), high performance liquid chromatography (HPLC) and liquid chromatography–mass spectroscopy (LC–MS) (Tabari et al., 2011; Andrade et al., 2013; Sulyok et al., 2015).

Tahini sauce or sesame seed paste is made of hulled sesame seeds that are toasted and ground, which is well known in the Middle East (Abu-Jdayil et al., 2002). Egyptians are annually consumes in average of 8000 ton of tahini according to Egyptian Central Agency or Public Mobilization and Statistics. According to the Egyptian Organization for Standardization and Quality, which generates the Egyptian standard for tahini, it is the product of grinding roasted sesame seeds, in which humidity must not increase by 2% of the weight, furthermore, no fatty substance is allowed to be added other than sesame oil. The sauce is made from a mixture of sesame and peanut and any other seeds are illegal (ES, 2006). As a result of the health and culinary benefits of tahini, it has picked up popularity worldwide (Kahraman et al., 2010). Although tahini is rich in thiamine, niacin, proteins, carbohydrates, calcium, phosphate and lipids which form its high nutritive value, it has anti-nutritional properties and, moreover, it is highly susceptible to aflatoxin contamination (Kahraman et al., 2010).

In general, the point of a risk assessment is to give a scientific evaluation for risk management related to the need of further measures to reduce the risks posed by exposure to mycotoxins that are produced by several fungi found in cereals. The recurrence and amount of food consumption and the methodology utilised for evaluating dietary contaminant intake are factors that affect the level of risk associated with each contaminant (Vasanthi et al., 1997). The purpose of the present study is to estimate the daily intake (EDI) of AFB1 and AFB2 from the relationship between the daily tahini intake and the average body weight for an adult person by multiplying the average daily tahini consumption with the mean of AFB1 or AFB2 before dividing by the average body weight (WHO, 2009).