Impact of Food Adulteration on Food Quality, Safety, and Market
The consequence of food adulteration is that the consumers do not obtain the food products as described in their labels. This can potentially result in health risks of consumers and economic loss to the local food industry (Manning and Soon, 2016; Reid et al., 2006; Spink et al., 2019).
Potential Health Risks to Consumers
Generally, most food adulteration incidents do not necessarily affect public health. However, there are still some cases where the health and well-being of consumers have been compromised. In 1981, the oils contaminated by fatty acid esters of 3-(N-phenylamino)-l,2-propanediol (PAP) was sold and consumed as olive oil in Spain, leading to an outbreak of a previously undocumented condition that became known as the 'toxic oil syndrome' (TOS) (Giuliani et al., 2015), with clinical symptoms of severe myalgia, peripheral eosinophilia and pulmonary infiltration. Approximately 20,000 people were finally affected, among which 300 people died shortly after the consumption and many suffered from developed chronic diseases. Similarly, the methanol wine scandal in Italy, in 1986, resulted in the food poisoning of hundreds of people. Ninety victims were hospitalised, 23 died and many suffered from blindness and nerve damage (Gelpi et al., 2002). In 2008, mineral oil-contaminated sunflower oil (~ 1,000 mg/kg mineral oil-saturated hydrocarbons) was exported from Ukraine to several EU countries (Grundbock et al., 2010). Although the discrepancy between the toxicological evaluation and the mineral oil content observed in foods is not necessarily indicative of a health problem, it was regarded as an alert by the authorities to adjust the toxicological levels.
In the above-mentioned 2008-milk scandal, due to widespread melamine, the pollution of human food and animal feed by melamine has become a serious public health problem. Melamine was detected in many types of products, including powdered infant formula, powdered milk products, liquid milk, yoghurt, frozen dairy products, and snack foods, with a wide range of adulterant concentrations (Everstine et al., 2013). It is believed that melamine and its congeners have been toxic to humans and animals for decades, depending on the rate of exposure (Chaisson and Martinson, 2008). The median dietary exposure of melamine based on the consumption of melamine-adulterated infant formula in 2008-Chinese scandal was estimated to be in the range of 8.6-23.4 mg/kg body weight per day, according to the report provided by the Chinese Center for Disease Control and Prevention (Chen, 2009). Based on the outcomes of risk assessment for melamine, many countries have introduced limits for this plasticizer in infant formula and other foods, for example, CODEX issued the limits for melamine in powdered infant formula (1 mg/kg) and in other foods (2.5 mg/kg) for food safety purposes (Sharma and Paradakar, 2010).
Another example of an adulterated food product can be tea. Since the start of tea trade in the 19th century, the adulteration of this product has never stopped. Generally, tea adulteration can be divided into four categories: (1) intentional addition of weighting substances to tea, since their cost is lower; (2) intentional addition of dyes, aimed at improving the color of tea; (3) intentional addition of flavored tea leaves, in order to increase the pungent astringency of tea and change the aroma, and (4) partial substitution of new tea using old tea leaves (Collins, 1993; Johnson, 2014). Sometimes, multiple types of adulteration methods are applied within the same batch of tea products. The dyes used for tea adulteration purpose include graphite, indigo, prussian blue, turmeric, female yellow (Chinese yellow), clay, soapstone, chrome yellow, Venetian red, copper carbonate, potassium chromate and potassium dichromate, etc. most of which are toxic and can seriously harm the health of the consumers (Sumar and Ismail, 1995).
Food adulteration also causes consumers to suffer economic loss, particularly when they believe that they have purchased the genuine product at a high price but received adulterated low-grade products (Manning and Soon, 2014; Roberts and Turk, 2017). Food adulteration can have some significant negative consequences for local food industries, including product recall, loss of sales and/or dramatically reduced price of food products for domestic and overseas markets (Jha et al., 2016; Manning and Soon, 2014; Roberts and Turk, 2017; Zach et al., 2012).
The adulteration of olive oil is notorious and is more associated with the economic losses of consumers, rather than health. Generally, these adulterated olive oil products are manufactured in two ways:
(i) intentional addition of other lower-grade dietary vegetable oils (such as hazelnut, sunflower, peanut, rapeseed and soybean oil) into olive oil and the subsequent sale with high price and/or (ii); intentional addition of lower-grade virgin olive oil or even olive pomace oil into extra-virgin olive oil (Azadmard-Damirchi, 2010; Johnson, 2014). Because the oil used for adulteration of olive oil is generally edible oil (although with lower commercial grade), the health risks to the consumers are quite limited in most cases. For the authentication of olive oil, chromatography, spectroscopy, and other technologies have been developed, among which gas and liquid chromatography are most widely used (Azadmard-Damirchi, 2010; del Coco et al., 2012; Poulli et al., 2006, 2007; Wojcicki et al., 2015). Meanwhile, spectroscopic techniques such as infrared, Raman, fluorescence, and ultraviolet spectroscopy exhibited the advantages such as ease in operation, low cost and rapid non-destructive detection (Jha et al., 2016), so they are quite promising methods for screening purposes. Although NMR technology exhibited high sensitivity, the use of this technology in olive oil authentication is still limited due to the high cost of analysis/instrument. It is worthwhile to notice that the results of these methods are mostly spectrum; further data analysis and processing are required. Therefore, the data analysis program to interpret the data also plays an important role (Azadmard-Damirchi, 2010; Riedl et al., 2015; Zhang et al., 2011).
The main components of honey are sugars, within which the content of monosaccharides (glucose and fructose) accounts for more than 70 per cent. In addition, honey also contains amino acids, vitamins, inorganic salts, organic acids, trace elements, and other nutrients (Hong et al., 2017; Won et al., 2008). It has been accepted that honey not only has high nutritional value but also exhibits many pharmacological benefits, such as anti-bacterial, anti-oxidational and improvement in immunity (Da Silva et al., 2016). As mentioned above, the adulterants in honey nowadays are mainly some syrups, which contain similar components as honey, such as corn, high-fructose corn, malt, sucrose, and rice syrup
- (Zabrodska and Vorlova, 2014). The high-fructose corn syrup exhibits a significantly lower cost (may differ by several to more than ten times) and a quite similar chemical composition compared to honey, making it a candidate for honey adulteration (Wang et al., 2015). In 2011, the average bulk price for honey was about US$ 0.384/kg, while high fructose corn syrup was US$ 0.071 /kg. With this five-fold difference in price, it is not that surprising for some manufacturers to resort to adulteration (Strayer et al.,
- 2014). Since these syrups are also commonly used as food ingredients, the impact of adulterated honey on consumers' health is also limited. However, the economic loss to both the consumer and the industry is huge. In 2018, around 20 per cent of honey products in the Australian market were found to be adulterated. Ritten et al. (Ritten et al., 2019) suggested that fraudulent practices in the international honey market affect 10 per cent of products.
Food production and consumption are decentralized. Thus, incomplete information and information asymmetry can easily occur between manufacturers and consumers (Chen et al., 2014). Briefly, the food supply chain is a food production-and-supply network composed of related companies in agricultural, food processing, retail and logistics industries (Manning, 2016). A complete food supply chain includes planting and breeding, food production and processing, food retail and food logistics. The most fundamental cause of food-safety problems is information asymmetry in the food supply chain (Ellis et al., 2015). Food adulteration results in loss of transparency and control of the supply chain; therefore, it may hinder traceability of the products (Zach et al., 2012) and the occurrence of food scandals may damage consumer confidence in the food market.