Global Perspective of Sensors for the Detection of Food Adulterants

Introduction

Food is vital as a nutritional supplement for all living organisms and it should be essentially rich in proteins, lipid, carbohydrate, minerals, vitamins for growth, repair, and other vital metabolic processes. Human invasion in the climatic or environmental zone has led to the addition of various chemical substances in the environment which are dangerous for human consumption. Inedible or non-foods items are organic and inorganic items that are not recognized as food because of sensory unattractiveness, anticipated negative physiological effect, predominantly non-nutritive properties, or cultural aversion (Rozin et al., 1997).

The basic definition of adulterants is all chemical substances that are added intentionally or unintentionally, leading to contamination of food products. Food adulteration has emerged as a serious issue that is needed to be investigated for maintaining food safety and public health (Sumar et al., 1995). According to the Food Drug and Administration (FDA), economically motivated adulteration is defined as "the fraudulent, intentional addition of a foreign substance in any food mainly for reducing the cost of the final product or increasing its apparent value'' (USFDA, 2009). Since the last few years it has become very common to hear, read or observe about food being adulterated and consumption of this food may cause serious health issues among the people. Food Safety and Standards Act of India (FSSAI) defines an adulterant as "any material which is or could be employed for making the food unsafe, or sub?standard, or misbranded, or containing extraneous matter" (FSSAI manual). The process of making profit by adding undesirable substances to food of similar appearance and color to the original product, is known as adulteration. According to the Annual Public Laboratory Testing Report (2014-15) by FSSAI, out of 49,290 samples of food tested, nearly one-fifth, (8,469), were found to be adulterated and misbranded. Adulterants lower the quality of food by substituting the important components of food with some inferior foreign particles. Furthermore, food products are mixed with foreign agents as adulterants for different reasons, like increase in demand, urbanization, economy, quality, volume of food article for trade, cost reduction for market competition, lack of effective food laws, government initiative, and, above all, customer awareness. Some adulterated food contains natural toxin and prolonged consumption of these compounds affects the health by causing allergy and nutrient unavailability like Lathyrus sativus (neurotoxinP-N- oxalyl-amino-L-alanine) consumption leads to a crippling disease known as lathyrism or Amanita mushroom which contains toxins like phalloidin that damages the liver and kidney (Bansal et al., 2015).

Food Adulterants

The food is said to be adulterated if it is replaced with cheap and inferior substances, or poisonous substances, prohibited color, preservative, rotten or decomposed material and insects. There are mainly three types of food adulterants, i.e., incidental, intentional, and metallic adulterants (FSSAI,

2012). When foreign substances are added to a food product as a result of lack of knowledge, or due to any accidental reason, or due to negligence, ignorance or lack of proper facilities, it is considered as incidental adulteration, which can be of acquired type, like contamination of food by bacteria, fungi, pesticide residues, rodents, larvae, dust, stones, packing harmful residues. Further, they can be of different types, like chemicals, organic compounds, radicals or naturally occurring toxic varieties of pulses, mushrooms, vegetables, fish and sea foods (Bansal et al., 2015). Intentional adulteration is when inferior materials are added to a food product with the prime intention to make profit out of it; for example, sand, stones, marble chips, talc, chalk powder, mineral oil, mud. Such an adulterant can cause serious health issues, like indigestion, acidity, ulcers, cancer, and kidney disorder (Trivedi et al., 2009). Metallic adulteration is considered when addition of heavy metals takes place either intentionally or incidentally, for example, with lead, arsenic, tin, mercury, in water from pesticide, cans, chemical industry and effluents, etc. (FSSAI, 2017) (Table 1). The common food color toxicants are metanil yellow, orange II, rhodamine B, blue VRS, auramine and malachite green (Kobylewski et al., 2013). The poisonous chemicals, like calcium carbide (ripen fruits like mangoes, bananas), copper sulphate (fruit ripener), oxytocin (faster growth of pumpkin, watermelon,

Table 1. Tabulated permissible limit of metals in different food products.

Table 1 contd....

...Table 1 contd.

brinjal, gourd, cucumber), wax (for shine on apples, pears), saccharin (sweeten fruits, like watermelon), pesticides and herbicides (growth of fruits and vegetables). All these chemicals cause serious health problems, like digestive disorder, eyes- and liver-related issues, vomiting and diarrhoea in children, kidney failure, and brain damage (specially by oxytocin). The most common adulterants present in food samples are tabulated in Tables 2 and 3.