Introduction
Nowadays, food safety is of major concern since more and more chemicals are becoming a part of our environment.
Actually, food is an important route of exposure to contaminants such as dioxins, mycotoxins, heavy metals, pesticides, polycyclic aromatic hydrocarbons, drugs and hormones. Mycotoxins are a class of highly toxic compounds, secondary metabolites, produced under particular environmental conditions by certain fungi or moulds, developing in many foodstuffs. Despite concerted efforts in prevention, mycotoxins remain a problem of human health concern in several parts of the world including developed countries.
Many foods contain their own toxins. If these are ingested in large quantities or repetitively problems can arise. Toxins involved in food processing and storage include carcinogens such as nitrosamines, bleaching agents like methionine sulphoximine, solvent extraction by trichloroethylene and fumigation with ethylene oxide.
Natural toxins from plants may be both endogenous and exogenous. Cabbage and related vegetables contain glucosinolates which have goitrogenic activity although clinical symptoms are unlikely. Sweet potatoes or legumes may produce cyanogens thus producing neuropathy and mental confusion. Datura stramonium may produce atropine with resultant hallucinations. Bananas may produce pressor amines thus causing headache and hypertension. Solanin may be found in potatoes, especially when badly stored, which may result in headaches, incoherence, hallucination and dizziness.
Exogenous sources include peanuts and grains which may contain aflatoxins if contaminated with certain moulds. Aflatoxins can cause encephalopathy, hallucinations, and hepatic disease. Nitrites originating from endogenous nitrates may be present in some green vegetables including spinach with potential risk of headache, hepatic disease and methaemoglobinaemia. Conversion to nitrosamines results in potential risk of carcinogenic activity. Naturally occurring toxins from animals occur. Endogenous examples include fish which contain certain lipoproteins that may result in symptoms of vomiting, headache, and dizziness. Other examples include cheese which contains tyramine and can give headache and elevated blood pressure in susceptible individuals. Saxitoxin originating from dinoflagellates may be found in fish or shellfish possibly giving symptoms of dyspnoea, paralysis, or haemorrhage.
Patulin
Like other toxins, patulin is also one, which is present in many foods. Patulin is a mycotoxin that is produced by certain species of Penicillium, Aspergillus and Byssochylamys moulds that may grow on a variety of foods including fruits, grains, and cheese. Patulin is having molar mass 154.12 g mol-1, molecular formula C7H6O4 (Fig. 2) and is soluble in water. Patulin has been found to occur in a number of foods including apple juice, apples and pears with brown rot (Harwig, 1973, Brain, 1956), flour (Hasseltine and Graves, 1966), and malt feed (Ukai, 1954). However, given the nature of the food, the manufacturing processes, or consumption practices for many foods, patulin does not appear to pose a safety concern, with the exception of apple juice (Fritz and Engst, 1981). For instance, the rotten portions of most fruits and grains typically are removed prior to consumption. In foods such as cheese, the high cysteine content of the food interacts with patulin to render it inactive (Ciegler, 1977). Patulin is reported to be destroyed by fermentation and thus, is not found in either alcoholic fruit beverages or vinegars produced from fruit juices. Thermal processing appears to cause only moderate reductions in patulin levels, thus patulin present in apple juice will survive the pasteurisation processes (IARC, 1986, WHO, 1990, Harrison, 1989, McKinley and Carlton, 1991).
Fig1. An apple contaminated by Penicillium expansum
Fig2. 4-hydroxy-4H-furo[3,2-c]pyran-
History
Patulin was first isolated by Birkinshaw et al. in 1943 from Penicillium griseofulvum and Penicillium expansum. This was a part of the screening effort to find new fungal molecules with antibiotic properties, in the general enthusiasm following the discovery of penicillin by Fleming. Patulin fits well with Paracelces definition in his treatise -Von der besucht. "Every substance is a poison; only dose distinguishes a poison from drug." This compound was tested in clinical trials by a British company under the brand name - tercinin (Chalmers et al., 2004), however, the interest in this potential antibiotic soon waned due its toxicity to humans and animals. Today, patulin belongs to a short list of mycotoxins (aflatoxins, ochratoxin A, zearalenone, fumonisins and trichothecenes).
Microorganisms producing patulin
Patulin is isolated from several species belonging to Penicillium, Aspergillus, Paecilomyces and Byssochlamys. Among the Aspergillus species, the number of patulin producing species is limited to three of the Clavati group: Aspergillus clavatus, A. giganteus and A. longivesica (Varga et al., 2007). For the Penicillium genus, after checking a significant number of isolates from each species and re-identification of certain isolates, an overview determined 13 patulin producing species: P. carneum, P. clavigerum, P. concentricum, P. coprobium, P. dipodomyicola, P. expansum, P. glandicola, P. gladioli, P. griseofulvum, P. marinum, P. paneum, P. sclerotigenum, P. vulpinum (Frisvad et al., 2004). Among these species, P. expansum is responsible for the decay in pomaceous fruits (apples and pears) characterised by rapid soft rot and eventually by blue pustules (Fig 1). This species is considered as the main source of patulin in these fruits and consequently in apple derived products (McKinley and Carlton, 1991).
Occurrence
Occurrence of patulin in different fruit products had been determined and summarised here in table 1.
Table 1: Patulin concentrations in fruit products quantified in stable isotope dilution assays using GC/HRMS
Toxicology of patulin
During the last 60 years, several adverse health effects resulting from exposure to patulin have been described. Briefly, patulin is reported to be acutely toxic (McKinley & Carlton, 1991), genotoxic (Alves et al., 2000), cytotoxic, immunosuppressive, teratogenic and possible neurotoxic (Devaraj et al., 1982). Patulin has a strong affinity for sulphydryl groups, which causes the inactivation of enzymes. Although no specific studies on the mode of action of patulin have been performed, it is becoming clear that this ability of patulin to react with sulphydryl groups would explain the cytotoxic and some of the genotoxic effects (Speijers, 2004). However, it is unlikely that the toxicity is systemic since patulin is degraded quickly after penetrating the gastric wall. This degradation is caused partly by the reaction with glutathione and probably also by the reaction with proteins. However, the significant depletion of glutathione in gastric tissue can lead to local toxic effects (Rychlik et al., 2004). For many years patulin was believed to be carcinogenic, however the International Agency for Research on Cancer (IARC) concluded that there is inadequate evidence for carcinogenicity of patulin in experimental animals (IARC, 1986). A study on the combined effects of patulin on reproduction and long-term toxicity pointed to a safe intake of 43 g/kg body weight/day.
Safety assessment, risk management for patulin
FDA employed the "safety assessment" method as the risk assessment approach for considering the available safety data on patulin. FDA used the outcome of the safety assessment to evaluate whether processors should implement controls for patulin in apple juice, and to identify a level, (i.e., an "action level") at which FDA would consider taking legal action against apple juice products bearing patulin under Federal Food Drug and Cosmetic Act, which states that a food is "adulterated" if it bears or contains an added poisonous or deleterious substance which may render it injurious to health.
The safety assessment method (Lehman and Fitzhugh, 1954), introduced the use of 10-fold safety factors, which later also became known as "uncertainty factors," in assessing the safety of substances, e.g. contaminants, in food. Lehman and Fitzhugh described the application of the 10-fold safety/uncertainty factors as useful for establishing a "target" margin of safety. However, they concluded there were no scientific or mathematical means by which absolute values for these factors could be derived. Over the years these factors have been used routinely both in the US and internationally to ensure an adequate margin of safety (WHO, 1987).
Typically, for a contaminant in a food such as apple juice, where there is a potential for chronic exposure to the contaminant, FDA would determine the exposure level that would ensure an adequate safety margin from known adverse effects by applying two 10-fold safety factors (equating to a 100-fold safety factor) to the "no observed adverse effect level" (NOAEL) from lifetime animal feeding studies. One safety factor accounts for the extrapolation from animal data to humans (i.e., interspecies variation), and the second accounts for variation in sensitivity to the contaminant's effects within humans (i.e., intraspecies variation). This calculation yields a provisional tolerable daily intake (PTDI) or provisional tolerable weekly intake (PTWI) for the contaminant. An action level may be identified by calculating a maximum level for the contaminant in the food that will ensure that exposure to the contaminant results in an acceptable margin of safety, considering the PTDI or PTWI.
In deriving the action level for patulin, FDA considered consumption of apple juice by consumers of all ages who drink apple juice, and by consumers who drink apple juice among small children in two age categories, children less than one-year-old and children 1-2 years old. FDA considered the two age categories for children because they consume higher amounts of apple juice relative to their body weight than other age groups. Older children, e.g., 2-10 year olds, were not included as a separate group in FDA's assessment because consumption of apple juice on a "relative to body weight" basis declines substantially after age two. Therefore, there are no special risk considerations affecting older children that would need to be taken into account in a safety assessment.
Fig3. Illustration of how food safety control at a country level can link into food safety management at the operational level through a food safety objective set by a governmental competent authority on the basis of a public health goal (ALOP) established following the risk analysis framework
Source: Gorris (2005)
The Food Safety and Standards Authority of India (FSSAI) has been established under the Food Safety and Standards Act, 2006, as a statutory body for laying down science-based standards for articles of food and regulating manufacturing, processing, distribution, sale and import of food so as to ensure safe and wholesome food for human consumption. Various Central Acts like Prevention of Food Adulteration Act, 1954; Fruit Products Order, 1955; Meat Food Products Order, 1973; Vegetable Oil Products (Control) Order, 1947; Edible Oils Packaging (Regulation) Order 1988; Solvent Extracted Oil; De-Oiled Meal and Edible Flour (Control) Order, 1967; Milk and Milk Products Order, 1992; etc. will be repealed after commencement of FSS Act, 2006. The Act also aims to establish a single reference point for all matters relating to food safety and standards, by moving from multi-level, multi-departmental control to a single line of command. To this effect, the Act establishes an independent statutory authority the FSSAI with head office at Delhi. FSSAI and the state food safety authorities shall enforce various provisions of the Act.
Several countries have set limits for patulin concentrations in apple products. The World Health Organisation (WHO) recommended a maximum concentration of 50g/L in apple juice. In European Union, the limit is set to 50 micrograms per kilogram (g/kg) in both apple juice and cider, and to half of that concentration, 25g/kg in solid apple products and 10g/kg in products for infants and children. The Joint FAO/WHO Expert Committee on Food Additives set a provisional maximum tolerable daily intake of 0.4 g/kg body weight (JECFA, 1995). These limits came into force on November 1, 2003.
According to the FSSAI following are the proposed limits for crop contaminants and naturally occurring toxic substances including patulin
Conclusion
Toxin-producing microbial species are extremely common, and they can grow on a wide range of substrates under a wide range of environmental conditions. For agricultural commodities, the severity of crop contamination tends to vary from year to year based on weather and other environmental factors. Aflatoxin, for example, is usually worst during drought years; the plants are weakened and become more susceptible to insect damage. Toxins occur, with varying severity, in agricultural products all around the world. The estimate usually given is that one quarter of the world's crops are contaminated to some extent with toxins. Toxins can enter the food chain in the field, during storage, or at later points. Toxin problems are exacerbated whenever shipping, handling, and storage practices are conducive to mould growth. The end result is that toxins are commonly found in foods.
Nowadays, food safety is of major concern since more and more chemicals are becoming a part of our environment.
Actually, food is an important route of exposure to contaminants such as dioxins, mycotoxins, heavy metals, pesticides, polycyclic aromatic hydrocarbons, drugs and hormones. Mycotoxins are a class of highly toxic compounds, secondary metabolites, produced under particular environmental conditions by certain fungi or moulds, developing in many foodstuffs. Despite concerted efforts in prevention, mycotoxins remain a problem of human health concern in several parts of the world including developed countries.
Many foods contain their own toxins. If these are ingested in large quantities or repetitively problems can arise. Toxins involved in food processing and storage include carcinogens such as nitrosamines, bleaching agents like methionine sulphoximine, solvent extraction by trichloroethylene and fumigation with ethylene oxide.
Natural toxins from plants may be both endogenous and exogenous. Cabbage and related vegetables contain glucosinolates which have goitrogenic activity although clinical symptoms are unlikely. Sweet potatoes or legumes may produce cyanogens thus producing neuropathy and mental confusion. Datura stramonium may produce atropine with resultant hallucinations. Bananas may produce pressor amines thus causing headache and hypertension. Solanin may be found in potatoes, especially when badly stored, which may result in headaches, incoherence, hallucination and dizziness.
Exogenous sources include peanuts and grains which may contain aflatoxins if contaminated with certain moulds. Aflatoxins can cause encephalopathy, hallucinations, and hepatic disease. Nitrites originating from endogenous nitrates may be present in some green vegetables including spinach with potential risk of headache, hepatic disease and methaemoglobinaemia. Conversion to nitrosamines results in potential risk of carcinogenic activity. Naturally occurring toxins from animals occur. Endogenous examples include fish which contain certain lipoproteins that may result in symptoms of vomiting, headache, and dizziness. Other examples include cheese which contains tyramine and can give headache and elevated blood pressure in susceptible individuals. Saxitoxin originating from dinoflagellates may be found in fish or shellfish possibly giving symptoms of dyspnoea, paralysis, or haemorrhage.
Patulin
Like other toxins, patulin is also one, which is present in many foods. Patulin is a mycotoxin that is produced by certain species of Penicillium, Aspergillus and Byssochylamys moulds that may grow on a variety of foods including fruits, grains, and cheese. Patulin is having molar mass 154.12 g mol-1, molecular formula C7H6O4 (Fig. 2) and is soluble in water. Patulin has been found to occur in a number of foods including apple juice, apples and pears with brown rot (Harwig, 1973, Brain, 1956), flour (Hasseltine and Graves, 1966), and malt feed (Ukai, 1954). However, given the nature of the food, the manufacturing processes, or consumption practices for many foods, patulin does not appear to pose a safety concern, with the exception of apple juice (Fritz and Engst, 1981). For instance, the rotten portions of most fruits and grains typically are removed prior to consumption. In foods such as cheese, the high cysteine content of the food interacts with patulin to render it inactive (Ciegler, 1977). Patulin is reported to be destroyed by fermentation and thus, is not found in either alcoholic fruit beverages or vinegars produced from fruit juices. Thermal processing appears to cause only moderate reductions in patulin levels, thus patulin present in apple juice will survive the pasteurisation processes (IARC, 1986, WHO, 1990, Harrison, 1989, McKinley and Carlton, 1991).
Fig1. An apple contaminated by Penicillium expansum
Fig2. 4-hydroxy-4H-furo[3,2-c]pyran-
History
Patulin was first isolated by Birkinshaw et al. in 1943 from Penicillium griseofulvum and Penicillium expansum. This was a part of the screening effort to find new fungal molecules with antibiotic properties, in the general enthusiasm following the discovery of penicillin by Fleming. Patulin fits well with Paracelces definition in his treatise -Von der besucht. "Every substance is a poison; only dose distinguishes a poison from drug." This compound was tested in clinical trials by a British company under the brand name - tercinin (Chalmers et al., 2004), however, the interest in this potential antibiotic soon waned due its toxicity to humans and animals. Today, patulin belongs to a short list of mycotoxins (aflatoxins, ochratoxin A, zearalenone, fumonisins and trichothecenes).
Microorganisms producing patulin
Patulin is isolated from several species belonging to Penicillium, Aspergillus, Paecilomyces and Byssochlamys. Among the Aspergillus species, the number of patulin producing species is limited to three of the Clavati group: Aspergillus clavatus, A. giganteus and A. longivesica (Varga et al., 2007). For the Penicillium genus, after checking a significant number of isolates from each species and re-identification of certain isolates, an overview determined 13 patulin producing species: P. carneum, P. clavigerum, P. concentricum, P. coprobium, P. dipodomyicola, P. expansum, P. glandicola, P. gladioli, P. griseofulvum, P. marinum, P. paneum, P. sclerotigenum, P. vulpinum (Frisvad et al., 2004). Among these species, P. expansum is responsible for the decay in pomaceous fruits (apples and pears) characterised by rapid soft rot and eventually by blue pustules (Fig 1). This species is considered as the main source of patulin in these fruits and consequently in apple derived products (McKinley and Carlton, 1991).
Occurrence
Occurrence of patulin in different fruit products had been determined and summarised here in table 1.
Table 1: Patulin concentrations in fruit products quantified in stable isotope dilution assays using GC/HRMS
Toxicology of patulin
During the last 60 years, several adverse health effects resulting from exposure to patulin have been described. Briefly, patulin is reported to be acutely toxic (McKinley & Carlton, 1991), genotoxic (Alves et al., 2000), cytotoxic, immunosuppressive, teratogenic and possible neurotoxic (Devaraj et al., 1982). Patulin has a strong affinity for sulphydryl groups, which causes the inactivation of enzymes. Although no specific studies on the mode of action of patulin have been performed, it is becoming clear that this ability of patulin to react with sulphydryl groups would explain the cytotoxic and some of the genotoxic effects (Speijers, 2004). However, it is unlikely that the toxicity is systemic since patulin is degraded quickly after penetrating the gastric wall. This degradation is caused partly by the reaction with glutathione and probably also by the reaction with proteins. However, the significant depletion of glutathione in gastric tissue can lead to local toxic effects (Rychlik et al., 2004). For many years patulin was believed to be carcinogenic, however the International Agency for Research on Cancer (IARC) concluded that there is inadequate evidence for carcinogenicity of patulin in experimental animals (IARC, 1986). A study on the combined effects of patulin on reproduction and long-term toxicity pointed to a safe intake of 43 g/kg body weight/day.
Safety assessment, risk management for patulin
FDA employed the "safety assessment" method as the risk assessment approach for considering the available safety data on patulin. FDA used the outcome of the safety assessment to evaluate whether processors should implement controls for patulin in apple juice, and to identify a level, (i.e., an "action level") at which FDA would consider taking legal action against apple juice products bearing patulin under Federal Food Drug and Cosmetic Act, which states that a food is "adulterated" if it bears or contains an added poisonous or deleterious substance which may render it injurious to health.
The safety assessment method (Lehman and Fitzhugh, 1954), introduced the use of 10-fold safety factors, which later also became known as "uncertainty factors," in assessing the safety of substances, e.g. contaminants, in food. Lehman and Fitzhugh described the application of the 10-fold safety/uncertainty factors as useful for establishing a "target" margin of safety. However, they concluded there were no scientific or mathematical means by which absolute values for these factors could be derived. Over the years these factors have been used routinely both in the US and internationally to ensure an adequate margin of safety (WHO, 1987).
Typically, for a contaminant in a food such as apple juice, where there is a potential for chronic exposure to the contaminant, FDA would determine the exposure level that would ensure an adequate safety margin from known adverse effects by applying two 10-fold safety factors (equating to a 100-fold safety factor) to the "no observed adverse effect level" (NOAEL) from lifetime animal feeding studies. One safety factor accounts for the extrapolation from animal data to humans (i.e., interspecies variation), and the second accounts for variation in sensitivity to the contaminant's effects within humans (i.e., intraspecies variation). This calculation yields a provisional tolerable daily intake (PTDI) or provisional tolerable weekly intake (PTWI) for the contaminant. An action level may be identified by calculating a maximum level for the contaminant in the food that will ensure that exposure to the contaminant results in an acceptable margin of safety, considering the PTDI or PTWI.
In deriving the action level for patulin, FDA considered consumption of apple juice by consumers of all ages who drink apple juice, and by consumers who drink apple juice among small children in two age categories, children less than one-year-old and children 1-2 years old. FDA considered the two age categories for children because they consume higher amounts of apple juice relative to their body weight than other age groups. Older children, e.g., 2-10 year olds, were not included as a separate group in FDA's assessment because consumption of apple juice on a "relative to body weight" basis declines substantially after age two. Therefore, there are no special risk considerations affecting older children that would need to be taken into account in a safety assessment.
Fig3. Illustration of how food safety control at a country level can link into food safety management at the operational level through a food safety objective set by a governmental competent authority on the basis of a public health goal (ALOP) established following the risk analysis framework
Source: Gorris (2005)
The Food Safety and Standards Authority of India (FSSAI) has been established under the Food Safety and Standards Act, 2006, as a statutory body for laying down science-based standards for articles of food and regulating manufacturing, processing, distribution, sale and import of food so as to ensure safe and wholesome food for human consumption. Various Central Acts like Prevention of Food Adulteration Act, 1954; Fruit Products Order, 1955; Meat Food Products Order, 1973; Vegetable Oil Products (Control) Order, 1947; Edible Oils Packaging (Regulation) Order 1988; Solvent Extracted Oil; De-Oiled Meal and Edible Flour (Control) Order, 1967; Milk and Milk Products Order, 1992; etc. will be repealed after commencement of FSS Act, 2006. The Act also aims to establish a single reference point for all matters relating to food safety and standards, by moving from multi-level, multi-departmental control to a single line of command. To this effect, the Act establishes an independent statutory authority the FSSAI with head office at Delhi. FSSAI and the state food safety authorities shall enforce various provisions of the Act.
Several countries have set limits for patulin concentrations in apple products. The World Health Organisation (WHO) recommended a maximum concentration of 50g/L in apple juice. In European Union, the limit is set to 50 micrograms per kilogram (g/kg) in both apple juice and cider, and to half of that concentration, 25g/kg in solid apple products and 10g/kg in products for infants and children. The Joint FAO/WHO Expert Committee on Food Additives set a provisional maximum tolerable daily intake of 0.4 g/kg body weight (JECFA, 1995). These limits came into force on November 1, 2003.
According to the FSSAI following are the proposed limits for crop contaminants and naturally occurring toxic substances including patulin
Conclusion
Toxin-producing microbial species are extremely common, and they can grow on a wide range of substrates under a wide range of environmental conditions. For agricultural commodities, the severity of crop contamination tends to vary from year to year based on weather and other environmental factors. Aflatoxin, for example, is usually worst during drought years; the plants are weakened and become more susceptible to insect damage. Toxins occur, with varying severity, in agricultural products all around the world. The estimate usually given is that one quarter of the world's crops are contaminated to some extent with toxins. Toxins can enter the food chain in the field, during storage, or at later points. Toxin problems are exacerbated whenever shipping, handling, and storage practices are conducive to mould growth. The end result is that toxins are commonly found in foods.
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