Admixture of costly coffee beans with comparatively cheap beans is a very common practice. The two commercially important species, Arabica coffee (Coffea arabica) and Robusta coffee (Coffea canephora) are different in quality and botanical characteristics. Arabica coffee is costlier and has greater acceptability than robusta coffee due to its organoleptic properties. As a blend of these two varieties is also available in the market, the valid representation and labelling as pure Arabica is often susceptible. It is possible to distinguish these two types of beans through visual inspection; however, for coffee in ground and roasted form, it is not possible to distinguish in such a way. Similarly, other commercially valued high quality and rare coffee species, such as Kona coffee grown in Kona Island, Blue Mountain, Tanzanian Peaberry, and Indonesian palm civet coffee (Kopi luwak), are often substituted by coffee beans with cheap species. Foreign fillers and coffee byproducts are also admixed with pure coffee products.
Animal protein, such as egg, gluten, and porcine gelatin are often added to meat products to increase the apparent protein content. Soybean proteins and cereal flours are used in sausages to recover the desired all-meat properties, such as emulsifying capacity, emulsion stability, and water-binding capacity. Plasma protein is a complex mixture of serum albumin, globulins, and fibrinogen that possesses the ability to produce and stabilize foams and emulsions and to form heat-induced gel. It is utilized by the food industry to control the texture and desired structure of processed meat products. Enzymes such as fibrinogen and thrombin are used as blood-based binding agents both in chilled and raw states to give a desired mass and shape to processed meat products. Thrombin is used in conjunction with blood plasma as meat binders to give the desired shape in minced meat products. Collagen and its denatured form known as gelatin casing, is considered an important molecule. It offers excellent uniformity of appearance and strength and is usually used to fix the size and shape of processed meat products. Gelatin solution is often injected into cured meats, which solidifies and increases water retention and resistance to cutting. Again, being a potential source of cheap and high-quality protein, chickpea flour added to comminuted meats increases cooking varieties and provides a softer texture that becomes commercially more valuable. Addition of organic compounds, such as melamine, milk, and urea, are also reported.
Milk protein, which is considered a precursor of many bioactive peptides with antimicrobial activity, is not only a good source of calcium, zinc, copper, and phosphate ions but also helps in the absorption of many other nutrients. Compounds with high nitrogen content can mimic a high protein concentration. As the non-protein nitrogen cannot be distinguished by Kjeldhal and Dumas methods used for the determination of total protein content, the addition of various nitrogenous compounds in dairy products to increase the apparent protein content is quite frequent. In this case, melamine, urea, and whey are the most reported agents.
Addition of urea has also been reported several times. A low concentration of urea is naturally present in milk that generally comes from the grass or feed given to dairy cattle. Due to being comparatively cheaper than other alternatives, it is extensively used to increase the apparent protein content. If the amount of urea is found greater than the permissible limit of 10–16 mg/dL, it simply indicates an external addition.
Whey, being produced in large volume as a cheap byproduct of cheese and caseinates manufacturing, is added to liquid milk as whey protein to increase both the protein content and the total volume. The fraudulent addition of rennet whey solids has been reported several times. As cheese whey costs four to five times less than milk and does not affect the sensory properties, it is a lucrative option for dishonest traders.
Vegetable proteins, such as low-grade soya powder, pea, and wheat also contribute to increasing the protein content of milk and are a convenient option due to being cheap and easily available. Rice and almond proteins are sold as milk supplements for consumers possessing lactose intolerance.
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