# Metal Color, Marbling, and the Evaluation of Defects in Beef and Port at the Point of Purchase
## 1 Introduction  
Meat is the second largest food category in Serbia, affecting the average annual increase in food prices and accounting for approximately 23.9% of the total increase in these prices [1]. On a per capita basis, pork consumption is expected to increase globally, but to decline in European countries. On the other hand, global per capita beef consumption is projected to drop by up to 5% by 2030 [2]. Furthermore, it has been noticed that the focus in diets has shifted from pork to chicken and turkey meat [3]. Despite a predicted decline in beef and pork consumption, meat producers need to maintain a positive growth in long-term consumption trends and to gain a deeper understanding of consumers' behavior and preferences. By defining consumers' level of tolerance of certain meat characteristics, producers can avoid facing high failure rates and costs. Several authors have highlighted consumer attitudes and preferences towards attributes such as color and marbling [4; 5; 6; 7]. Meat color is one of the most critical traits for consumers intending to purchase beef and pork. Many factors, such as slaughter age [8], myoglobin concentration, and the chemical and physical parameters of meat [9], including light scattering and absorbing properties, affect meat color. It is also the result of many other factors, such as pH and the muscle type of the animal. After slaughtering, the pH becomes acidic (pH 5.4-5.7) within 18-24 h. After reaching the lowest point of acidic pH, the pH value will gradually increaseto the pH value of fresh meat, which is usually in the range of 5.5-6.2. Furthermore, meat color depends on the breed, age, and diet of the animal; meat from older animals will be darker in color because the myoglobin level increases with age [10]. Many studies provide results on differences in beef color according to different breeds [11]. Marbling is one of the primary carcass attributes used for quality assessment in most beef grading systems. From a technical point of view, marbling represents the content of intramuscular fat (IMF), considered one of the vital factors influencing beef's sensory quality including tenderness, juiciness, flavor, and color [12]. The most popular and used standards for the determination of the level of marbling are the AUS-MEAT Reference Standards [13], MSA (Meat Standards Australia) [14], the USDA Quality Grade and Yield Grade [15], and the Japanese marble score scale (BMS scale) [16]. In Europe, the current beef grading system is the EUROP grid, which is focused on carcass commercial value and carcass classification [9]. Although beef and pork producers are focused on producing meat that is free of quality defects, some classifications of defects have been made. According to previous research [17], the quality defects of beef that can be noted in the retail store are dark-cutting beef, lack of marbling, excess seam fat, too large or too small ribeye, and excessive external fat. Dark-cutting beef is abnormally dark-colored, lean, and less visually appealing to consumers [18]. The color can range from a dark cherry-red and extremely dark red to almost dark gray [19]. A lack of marbling is commonly linked to a greater variation in tenderness and juiciness. Although marbling is an important characteristic according to beef quality standards, seam fat content may be a more precise predictor of eating quality than visual marbling score evaluated by consumers [20; 21]. Dark firm and dry (DFD) meat [22], too much or too little marbling, excess seam fat [23], too much color variation in a single cut, and too much external fat are other examples of common defects. Thus, PSE lean meat not only refers to meat with a less intensive surface color but to meat with all preconditions to become gray or tan to brown. Meat processors have emphasized the production of consistent high-quality products. Products with quality defects are an economic burden to the industry as a whole and, at the same time, result in discounts of market prices or food waste.