## 1 Introduction  
Red chili is a spice, fruit, and vegetable consumed across the globe from ancient times as fresh, dried, crushed, or in powdered form. It has also been widely used in different sauces and medicines. The quality of red chili is characterized based on its color and pungency. Capsaicinoids are the main component in red chili, which cause a sensation of burning when they come in to contact with body tissues and the level of burning sensation is measured in Scoville Heat Units (SHU). The color of red chili is due to the presence of carotenoids, which come in different isomeric forms and derivatives. This makes it difficult to measure the color of red chili. However, the American Spice and Trade Association (ASTA) has devised a mechanism for measuring red chili color by calculating the absorbance at 460 nm [1]. In a natural environment, carotenoids in red chili are well protected but storage conditions highly impact the carotenoid content. [PERSON] et al. reported that the amount of carotenoids loss varies from 9.6% to 16.7% during storage with and without illumination, respectively [2]. Other studies examined different factors (like temperature, humidity, and water) of storage conditions and their impact on the color of red chili [3,4]. Similarly, the process of drying also affects the carotenoids content in red chili. [PERSON] et al. reported that drying of red chili at mild temperature provides the time for necessary metabolic activities which increases or retains the number of carotenoids [5]. In general, to preserve the color or carotenoids content of red chili, several measures including closed storage, lower temperature, and humidity are required. However, instead of ensuring these measures, traders have found another alternative of deceiving the customers. To enhance the color or increase the value of the inferior product, Sudan dyes that are characterized as a carcinogen [6] and banned worldwide as a food additive were found in grounded red chili and products that contain red chilies like sauces, cuisines, and frozen meat. Sudan dyes are insoluble in water but can be dissolved in fats and some organic solvents [7]. However, there is very little information available about their solubility in the literature. The main reason for adding Sudan dyes in red chili instead of approved food color is its insolubility in water. This property helps traders in hiding their fraud as food colors are soluble in water and can change the color of the food in which color-adulterated red chili is added. Being insoluble in water, Sudan dyes do not alter the color properties of food. Moreover, as Sudan dyes are available in powdered form and cannot be added directly in grounded red chili, they are usually dissolved first in oil and then mixed in grounded red chili. Although the oil used is mostly edible, it is still harmful to someone who is allergic to the oil or facing specific health conditions. Moreover, oil without any Sudan dye also changes the color properties of red chili as shown in Figure 1.  
Although Sudan dyes were banned as food additives in 1973 by a joint committee of the Food and Agriculture Organization (FAO) and World Health Organization (WHO) on food additives due to its toxicity [8], their usage has continued in different foods like palm oil, red chili, and others. This issue came to the surface in 2003 when a lab detected Sudan dye in red chili imported from India, and the European Union then took emergency measures and published a list of authorized food color [9]. As a result, in 2005 the United Kingdom Food Safety Agency (FSA) analyzed over 400 products and found some to be contaminated with Sudan dye [10]. Similar incidents were observed in India, China, Pakistan, and South Africa, forcing countries to implement safety measures and develop detection methods for illegal dyes in their food [11; 12; 13].