ABSTRACT
Food authenticity is a major necessity to meet the demands of conscious consumers and to reassure them regarding the origin and content of their food, and also to ful‘ll the needs of manufacturers to enable them to comply with government regulations and labeling obligations for their products. The determination of food authenticity, particularly meat species identi‘cation, has great importance in food quality control and safety. Fraudulent substitution or undeclared adulteration of meat species in comminuted and highly processed meat products is a widespread problem in retail markets. Undesired practices in general include replacement of cheaper or undesired meats with higher commercial value meat species and the nondeclaring of proportion of meat species used in the production. These cases have led to the suggestion of some analytical techniques for the qualitative and quantitative determination of such replacements in meat mixtures. These methods include different protein-based techniques and related methods such as electrophoretic techniques, enzyme-linked immunosorbent assays (ELISA), and isoelectric focusing (IEF). However, these methods have been reported to be sometimes inadequate or less sensitive for the species identi‘cation of thermally processed foods due to the denaturation of proteins. DNA-based
12.1 Introduction .................................................................................................................................. 249 12.2 Spectroscopic Techniques ............................................................................................................ 250 12.3 Chromatographic Techniques .......................................................................................................251 12.4 Electrophoretic Techniques .......................................................................................................... 252
12.4.1 PAGE and SDS-PAGE ..................................................................................................... 252 12.4.2 Isoelectric Focusing ......................................................................................................... 252 12.4.3 Capillary Electrophoresis ................................................................................................ 253
12.5 Immunoassays .............................................................................................................................. 254 12.6 DNA-Based Methods ................................................................................................................... 255
12.6.1 DNA Hybridization ......................................................................................................... 255 12.6.2 PCR-Based Techniques ................................................................................................... 256
12.6.2.1 Sequencing of PCR Products ........................................................................... 257 12.6.2.2 Species-Speci‘c PCR ...................................................................................... 257 12.6.2.3 Species-Speci‘c Multiplex PCR ...................................................................... 258 12.6.2.4 PCR-Restriction Fragment Length Polymorphism .......................................... 259 12.6.2.5 PCR-Random Ampli‘ed Polymorphic DNA .................................................. 259 12.6.2.6 PCR-Single-Strand Conformation Polymorphism .......................................... 260
12.6.3 Real-Time PCR ................................................................................................................ 260 12.6.3.1 Intercalating Dyes .............................................................................................261 12.6.3.2 Oligoprobe-Based Chemistries ........................................................................ 262
12.7 Conclusion .................................................................................................................................... 267 References .............................................................................................................................................. 268
techniques could offer a potential to identify the animal species because of the higher stability of DNA molecules in thermal processing conditions compared to proteins and their high speci‘city to all types of cells. Polymerase chain reaction (PCR) is a fast, sensitive, and highly speci‘c technique, and it could be an alternative to the protein-based methods. However, when a conventional PCR technique is used, it only allows qualitative identi‘cation of the species, not quantitative identi‘cation. Nowadays, real-time PCR technique is a very popular tool for the species identi‘cation and quanti‘cation because of its high sensitivity and speci‘city, larger dynamic detection range, and less carryover contamination. In this respect, real-time PCR method now appears to be the most effective and robust technique for the identi-‘cation and quanti‘cation of trace quantities of different animal species, even in complex foods. Consequently, advances in analytical techniques constantly offer new possibilities for meat species identi‘cation. However, the recognition of such techniques by food control laboratories is inŽuenced by several factors such as their sensitivity, speci‘city, cost, rapidity, reliability, etc. In this chapter, we will describe a wide range of techniques, some of which are currently in practice.
