**Table 2.** Examples of protein-based methods for h. alal authenticity analysis. ¯

**Table 3.** Examples of genetic methods for h. alal authenticity analysis. ¯


The PCR amplification of pork mitochondrial genes (12S and 18Sribosomal RNA subunits and cytochrome b) and of the displacement loop region (D-loop) was successfully applied for the detection of pork derivatives and was found to be a suitable technique for routine food analysis and halal¯ certification [115].

In 2018, for the first time a tetraplex polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay to identify and discriminate rabbit, rat and squirrel meat in frankfurter formulation was developed and validated. The detection limit of the assay was 0.1% meat in frankfurter formulation. Moreover, results shown in this research assessed that variations in food processing treatments could not affect the stability of the optimized assay [92]. However, it should be considered that it is rather unlikely that rabbit or squirrel meat can be used as a substitute for chicken or beef, because their meat is certainly more expensive.

Nevertheless, although classical PCR and real time-PCR are the most frequently used methods, they usually target a limited pool of species, and usually the most used, such as pork, beef, horse and chicken, whereas the potential adulteration with exotic species often remains uncovered. For this purpose, Cottenet and colleagues [117] have recently developed a Next Generation Sequencing method for the identification of different species, both in pure meat samples, with optimal results, and in mixtures, where the species were correctly identified in spiked samples down to 1% (*w*/*w*). Together with the most common species, also yak, donkey, zebra, hare, fallow deer, reindeer, muskrat, fox, weasel, dog, cat pigeon and rat, and up to 46 different species were detected, amplifying and sequencing a mitochondrial DNA fragment of about 120 bp. Unfortunately, the method was less effective when applied to ground meat, suggesting that work is still required to improve the results.

Moreover, Lavelli has suggested a scheme of traceability implementation for the poultry meat supply chain: the author presented a case study to discuss both the advantages and difficulties of setting up a high-warrant traceability procedure conform to "generic" or "specific" traceability systems, depending on many different factors (technological and economical aspects, specific regulations and internal objectives) [125].

The genetic technologies, such as simple sequence repeat (SSR) and single nucleotide polymorphism (SNP) can be very reliable in the traceability management system of h. alal foods [ ¯ 126,127]. Some studies were carried out in order to select SNPs panel useful for traceability of h. alal beef [ ¯ 81,110].

A recent study reported about a particular pork peptide (signature sequence LVVITAGAR, from lactate dehydrogenase) that was not recorded in other meats; in this study, liquid based chromatography coupled with mass spectrometry (LC-MS) was used for the detection of the identified porcine-specific peptide as a thermostable marker of highly processed haram (that means proscribed by the Islamic law) meat products [99].

Interestingly, proton nuclear magnetic resonance (1H-NMR) has been applied together with HPLC as a high-performance approach to detect lard used to adulterate butter. In fact, the triacylglycerol (TAG) composition of lard can be used as chemical marker for h. alal authentication. More precisely, ¯ peaks recorded in the region of 2.60–2.84 ppm highlight specific characteristics present only in lard, and these frequencies can be considered specifically for the analysis [128].

A rapid, accurate, convenient, and eco-friendly analysis for the detection of porcine-based ingredients in food is the Electronic Nose (EN), employed to exclude possible contamination or fraud and also to investigate the oxidative status of meat products [85,86,101,102]. The ability to measure and identify the aroma and characteristics of persistent flavors of a product allows to obtain a variety of information, directly related to the acceptability and to nutritional and quality characteristics in terms of product health and safety. This consideration has led to a growing need and interest in non-destructive monitoring systems with high versatility, sensitivity, accuracy, cost-effectiveness, ease of use and above all rapidity of analytical response, such as electronic nose. This artificial olfactory systems can be used not only in the laboratory but also directly in the production plants for continuous monitoring of odors, from the raw material to the final product, analyzing the volatile compounds released from the matrix related to different aspects (sensory acceptability, deterioration, development of off-flavors, etc.). In our laboratories an electronic nose equipped with non-specific sensors arrays (porphyirins based) has been used to discriminate the lard presence in h. alal goat meat batter. First, four experimental batches of ¯ salami were manufactured with halal goat meat (70%) and fat (30%); each of the four batches had different levels of pork fat (batch 1, Control, with lard 0% *w*/*w* of total fat; other batches, with lard 5%, 10% and 20% *w*/*w* of total fat, respectively); then EN analyses were carried out after an equilibration step (for 30 min, at temperature of 41 ◦C). Principal Component analyses (PCA) scores (Figure 2) evidenced that porphyirins-based EN was able to discriminate the presence of lard even at the lowest experimental concentration (5%, *w*/*w*) [129].

Furthermore, a gas sensor array based on peptide modified gold nanoparticles deposited onto 20-MHz quartz crystal microbalances [102] has been also applied to discriminate the lard presence in h. alal meat products and investigate the shelf life of ¯ h. alal dry meat sausages (trials are still going on; ¯ unpublished data).

Finally, new approaches regarding h. alal authentication, including the latest biotechnological ¯ innovations, such as assays and the use of smartphones, are being also developed [130,131].

**Figure 2.** Principal component analyses (PCA) scores on porphyrins-based EN analysis on h. alal goat ¯ meat dough added with pork fat (0%, 5%, 10% and 20% of lard, *w*/*w*).

#### **5. Conclusions**

The quality assessment and authentication of h. alal products are issues raising a growing interest ¯ in European Community Countries (France, Sweden, Germany, Greece, Spain, Italy), Switzerland, Russia and other countries in the world (Asia, the UK, South and North America).

Considering that top producers of h. alal products (including meat) are countries where Muslims ¯ are a minority, future research should take into consideration h. alal standards, immigration and ¯ integration of qualified Muslim workers, as evidenced by a study recently carried out in Brazil [132]. As regards specifically halal salami, the origin of the animal raw meat, as well as ingredients and ¯

additives are the main concerns for consumers of Islamic faith. The pork matrix may be fraudulently present in processed meat, for both economic and technological purposes. In fact, the use of these raw materials (which are easier to find) has a lower cost; furthermore, it allows manufacturers to obtain final cured meat with better quality (sensory properties) and stability (especially with respect to oxidative reactions).

Many approaches have been proposed in the literature for the evaluation of the authenticity of salami and other meat products with h. alal certification. The research of accurate analytical methods for ¯ the differentiation of meat species is therefore of great importance for both companies and consumers, and important advances have been made in recent years, while analytical methods to distinguish the type of slaughter applied to obtain the meat are still difficult to optimize. Moreover, the literature is often focused on h. alal meat products, while comparisons with non ¯ h. alal analogue products are still ¯ scarce or even missing. Future researchers should carry out further studies on h. alal food in order to ¯ provide useful information about major factors related to quality and stability, especially for h. alal¯ dry cured meat products, such as salami. The market for h. alal products is evolving, considering ¯ that the non-Islamic consumer would seem to associate the h. alal brand with "superior" quality [ ¯ 133]. This would be very important to properly orient the companies that would like to diversify their production and also to guarantee food safety and consumer satisfaction.

**Author Contributions:** Conceptualization, M.M. and A.S.; methodology, M.M., A.S.; investigation, M.M., A.S.; resources, M.M., A.S.; data curation, M.M., A.S., D.M.; writing—original draft preparation, M.M.; writing—review and editing, M.M., A.S.; visualization, O.C., D.M.; supervision, M.M., D.M.; project administration, M.M.; funding acquisition, M.M. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Acknowledgments:** The authors would to thank Daniel Pizzoni for his helpful contribution for processing the data shown in Figure 2. This work is part of the project "Quality and shelf life of dry fermented goat sausage: a new perspective of market for companies of Abruzzo region" supported by funding from Cassa di Risparmio di Teramo (Italy).

**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

#### **References**


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