A canela é uma especiaria pertencente ao gênero Cinnamomum da família Lauraceae e é amplamente utilizada em várias culturas ao redor do mundo [ 15 ]. O nome “canela” é derivado da palavra grega, que significa “madeira doce” [ 16 ]. É uma árvore perene que pode atingir alturas de 7 a 10 m, embora também possa ser cultivada como arbusto, podendo atingir menos de 3 m de altura. A canela prospera em climas tropicais, quentes e úmidos e fica pronta para a colheita após cerca de três anos de crescimento. Possui folhas verde-escuras, pequenas flores branco-amareladas e frutos roxos que contêm uma única semente [ 3 ].

Cerca de 250 a 350 espécies de canela foram identificadas e distribuídas na América do Norte, América Central, América do Sul, Sudeste Asiático e Austrália. Dentre essas espécies, quatro são consideradas de maior importância e são comumente utilizadas para obtenção da especiaria: Cinnamomum zeylanicum Blume (também conhecida como C. verum ), Cinnamomum Aromatum (ou C. cassia ), nativa da China, Cinnamomum burmannii , nativa da Indonésia e Cinnamomum loureiroi , nativo do Vietnã [ 17 , 18 ].

Seu consumo está associado a benefícios à saúde, como atividade antimicrobiana [ 19 ], propriedades antioxidantes [ 20 ], efeitos anticancerígenos [ 21 ] e controle da glicose no diabetes [ 22 ]. A canela é utilizada em alimentos, temperos, cosméticos e medicamentos, e está disponível em diversas formas, como integral, moída, extratos ou óleos essenciais obtidos das folhas e cascas. No entanto, o consumo de canela também pode causar efeitos adversos à saúde. O trans -cinamaldeído, também conhecido como cinamaldeído, principal componente da casca da canela, pode resultar em sensibilização da pele e causar dermatite de contato [ 23 ]. O ácido cinâmico também é conhecido por induzir hipersensibilidade ao contato [24 ].

A canela verdadeira nativa do Sri Lanka, também conhecida como canela do Ceilão , inclui as espécies C. verum e C. zeylanicum , e a canela falsa, que tem origens diversas como China, América do Sul e Indonésia, e inclui a espécie C. cassia , C. aromático , C. burmannii e C. loureiroi [ 25 ] ( Tabela 1 ).

O aroma e o sabor da canela verdadeira são suaves e doces, e sua cor é marrom claro, enquanto a canela falsa é mais escura, além de possuir sabor mais forte, adstringente e picante [26 ] . Além disso, possuem características distintas quanto à composição de compostos fenólicos, sendo a canela verdadeira rica em compostos aromáticos e fenólicos, como cinamaldeído e eugenol, enquanto a canela falsa possui maiores quantidades de cumarina (2.000 a 5.000 mg/kg), aproximadamente um mil vezes superiores aos encontrados na canela verdadeira (2 a 5 mg / kg) e taninos na casca, o que explica o sabor adstringente [ 25 , 27 , 28 , 29 ].

A cumarina é um agente anticoagulante que pode representar sérios riscos à saúde devido aos seus efeitos hepatotóxicos e carcinogênicos em animais. Por esse motivo, os órgãos de saúde estabeleceram restrições quanto à ingestão diária tolerável de cumarina, determinando assim a ingestão diária de 0,1 mg/kg/dia e, consequentemente, o consumo de C. cassia , garantindo seu uso seguro [ 31 , 32 ].

O Regulamento Europeu (CE) n.º 1334/2008 [ 33 ] estabeleceu limites máximos específicos de cumarina como segue: 50 mg/kg para produtos de panificação tradicionais e/ou sazonais com canela mencionada na sua rotulagem, 20 mg/kg para cereais de pequeno-almoço, incluindo muesli , 15 mg/kg para produtos de panificação fina (excluindo produtos de panificação tradicional e/ou sazonal com canela na rotulagem) e 5 mg/kg para sobremesas.

Em geral, C. loureiroi contém altos níveis de cumarina, o que pode causar efeitos colaterais adversos ao consumidor, incluindo danos ao fígado. A canela verdadeira, por outro lado, é altamente vulnerável a fraudes devido ao seu valor agregado e maior qualidade em comparação à canela falsa [ 34 ].

C. verum é uma especiaria muito apreciada e considerada superior à falsa canela, que é comumente encontrada e mais barata. Visualmente, a casca da canela aparece na forma de cilindros enrolados. Porém, a canela verdadeira apresenta coloração marrom-avermelhada clara enrolada em várias camadas, enquanto as demais são em tons marrom-avermelhados escuros, duras e enroladas em apenas uma camada [30 ] .

As diferentes partes da casca, folha ou pó da canela apresentam diferenças na composição ( Figura 1 ), que podem ser utilizadas para controle de qualidade. A casca, por exemplo, contém antioxidantes naturais, enquanto os galhos são utilizados no tratamento de doenças inflamatórias. O pó da casca de canela, quando adicionado a outros medicamentos, pode retardar o processo de deterioração de algumas doenças cardíacas [ 35 , 36 , 37 ].

CEOs are complex mixtures of aromatic products from the secondary metabolism of plants, normally produced by secretory cells or groups of cells from different parts of the plant, such as stems, roots, leaves, flowers, and fruits [38,39]. The essential oil content may vary according to the species, physical form of the sample, part of the plant used (Table 2), geographical origin, and stage of development of the plant [3].

The constituents of CEOs can belong to several classes of compounds, with emphasis on terpenes and phenylpropenes, which are the classes of compounds commonly found. Monoterpenes and sesquiterpenes are the most frequently found terpenes in EOs, as well as diterpenes, and minor constituents [40].

Different parts of cinnamon, bark, leaves, branches, fruits, and roots can be used for the production of essential oils by distillation and oleoresins by solvent extraction [41]. The volatile components of the EO are present in all parts of the plant (Table 2) and can be classified into monoterpenes, sesquiterpenes, and phenylpropenes, with main constituents such as trans-cinnamaldehyde (bark), eugenol (leaves), and camphor (root) [3,42].

Cinnamaldehyde is a yellowish oily liquid responsible for the strong odor and sweet taste of cinnamon [17] and the main constituent of EO. It is recognized as safe by the United States Food and Drug Administration and the Association of flavor and extract manufacturers, receiving status A, that is, it can be used in food [45]. Its commercial use is limited due to its low solubility in water and sensitivity when exposed to light and air for prolonged periods [46]. Friedman; Kozuke; Harden [47] evaluated the stability of trans-cinnamaldehyde present in EO at different temperatures and observed that around 60 °C the compound was decomposed. Das, Gitishree et al. [48] report that cinnamaldehyde has a biological effect and is quickly oxidized into cinnamic acid, and as a product of its degradation, benzoic acid is excreted by the urinary system.

Due to cinnamic acid and cinnamaldehyde, cinnamon has protective effects against cardiotoxicity produced by the compound isoproterenol [49]. In addition, cinnamon is associated with the inhibition of fatty acids such as arachidonic acid, which has an inflammatory effect. The compound eugenol, identified in cinnamon extracts, has an antioxidant effect, helping to inhibit lipid peroxidation and the generation of reactive oxygen species [50].

Eugenol is the main volatile compound of OECF [51]. It is an aromatic substance with a pleasant odor and taste, belonging to the class of phenylpropanoids [52]. It is usually found as a yellowish oily liquid [53]. Like cinnamaldehyde, eugenol is also recognized as a safe food by the Food and Drug Administration [54]. Eugenol has antimicrobial [4,5], antifungal [6,7], anti-inflammatory [9,10], and antioxidant [11,12] activities. Despite having good biological properties, eugenol has low solubility in water [55], and sensitivity to light [54].

CEO contains some vital bioactive components in the form of terpenes and aromatic compounds, giving it remarkable biological properties. Thus, CEO has been widely used as a raw material in the medicine industry, as natural additives, condiments, and flavorings in the food industry, and in perfumery [42,56].

The main responsibility for the biological activities is often attributed to the major compounds present in the oil, such as the volatile fraction and the phenolic compounds [57]. In addition, biological activities can also be related to the joint contribution of different compounds, with minor components producing a synergistic effect with the others [3,58]. Table 3 provides an overview of the diverse biological activities associated with various species of Cinnamomum. The compounds found in cinnamon have demonstrated a wide range of biological effects, including antimicrobial, anti-inflammatory, antioxidant, insecticidal, and antidiabetic activities. This compilation highlights the multifaceted potential of Cinnamomum in various fields, from traditional medicine to modern pharmaceutical research, pest control, and diabetes management.

CEO can be used in culinary preparations due to its sweet and spicy aroma and flavor. It is generally used in seasonings for meat, fish, sauces, roasts, and beverages; in bakery and pastry products as an alternative to preservatives [13]; and in chewing gum as a flavoring agent [14]. With the growth in demand in the food, perfumery, and cosmetics industries, the market for natural aromatic raw materials is expanding exponentially to meet your needs. To meet this search for aromatic products, research has focused on compounds from biotechnological processes used in the production of aromas and fragrances from other plant origins [80].

With the growth in demand in the food, perfumery, and cosmetics industries, the market for natural aromatic raw materials is expanding exponentially to meet your needs. To meet this search for aromatic products, research has focused on compounds from biotechnological processes used in the production of aromas and fragrances from other plant origins [80].

Intentionally altered products with hidden properties or quality and incomplete and unreliable information define adulteration. In general, counterfeiting involves actions that deteriorate the specific properties of the products while maintaining their characteristic indicators, such as appearance, color, consistency, and aroma [81].

Currently, the authenticity of food and food ingredients is a major challenge, as it is often related to fraud. Food adulterations have been occurring for a long time, with the difference that they have been improved over the years, accompanying or even advancing in the field of research into new methods. A greater number of adulterations among raw materials are found in spices, edible oils, honey, milk and its derivatives, fruits and fruit juice, coffee, flour, and meat products [26].

Among the raw materials, cinnamon is one of the spices commonly adulterated. These adulterations can include species (mixing different species of Cinnamomum), origin (incorrectly labeling the country of origin), additives and fillers (adding other substances such as starch, sawdust, or other spices), and oil (adulterating EOs derived from cinnamon with synthetic or cheaper oils).

Due to its high added value and high cost, true cinnamon is highly prone to adulteration with false cinnamon species, which are of lower quality and cheaper, causing potential health risks and making the product unsafe for the consumer. This practice is usually carried out in powder form, which makes it difficult to discriminate between cinnamons as their characteristics are lost during the process [29].

Furthermore, true cinnamon can be adulterated with other types of spices, such as clove and chili powder, and clove and cinnamon oil, as reported by Gopu et al. [82]. Cinnamon fraud triggered research for the development of new, more accurate, reliable, and sensitive analytical methods in order to identify and quantify potential adulterants in true cinnamon more quickly and efficiently, ensuring food safety. Among the methods developed, chromatography is based on the determination of the main active compounds of cinnamon or adulterants, called marker compounds, such as cinnamaldehyde, eugenol, linalool, and coumarin, among others [82].

Cinnamon adulterations do not only occur in the form of powder, frauds are also found in CEO by mixing other compounds or even false cinnamon species. Through physical–chemical and instrumental analyses, the CEOs purity can be proven through qualitative and quantitative analyses, that is, determining the constituents or identifying the compounds present in the oil, respectively [81].

To prevent the entrance of adulterated cinnamon products into local markets, the regulatory sector takes several steps: product testing and certification are performed by implementing regular product testing to verify the authenticity and quality of cinnamon products; certifying authentic products with recognized standards can help consumers identify genuine products; labeling regulations require accurate information about the species, country of origin, and any additives or fillers in the product; clear and transparent labeling helps consumers make informed choices; traceability systems that track the supply chain of cinnamon products from production to market, which can help identify and eliminate adulterated products at different stages; import controls and inspections to ensure that products entering the country meet regulatory standards, which includes checking for proper documentation and compliance with labeling regulations; public awareness and education about the different types of cinnamon and their characteristics—informed consumers are less likely to purchase adulterated products; penalties and enforcement for those found guilty of adulteration, and rigorous enforcement of these penalties, which can act as a deterrent to unethical practices; collaboration with industry and associations to establish self-regulation practices and codes of conduct that promote authenticity and quality; and international cooperation with international regulatory bodies and other countries to share information and best practices in combating cinnamon adulteration, especially when products are imported.

For the regulation of EOs, the molecules must come from the raw material of the reference plant to be considered and labeled as 100% pure and natural [80]. Adulteration of CEOs can be divided into four types [81]: essential oil diluted with a solvent that has similar physicochemical characteristics, such as vegetable oils or organic solvents; cheaper CEO, but similar in origin or chemical composition, mixed with authentic CEO; unique natural or synthetic compounds added to mimic aromatic characteristics or composition; and/or substituting with low-value or blending CEOs.

As they are complex matrices, the EOs need to be analyzed by different techniques to ensure quality, safety, and authenticity, in addition to ensuring safety for consumers. As a result, a wide range of techniques have been reported, including organoleptic, physical, and chemical methods. However, these techniques, for the most part, require specialized people, have a high investment cost, are time-consuming, and some degrade the samples [81,83].

Molecules produced from natural reagents, also known as semi-synthetic compounds, can be used to adulterate specific EOs [80]. Cinnamaldehyde molecules can be produced from the benzaldehyde found in bitter almonds and used as an adulterant [84]. There are several scams associated with bitter almond and CEO, and since the false origin is cheaper than the Ceylon origin, blends between these CEOs are common. Despite this, it is possible to detect this type of adulteration by analyzing differences in composition between EOs or by spectroscopic analysis [26,28,80].

As adulterações ao longo da cadeia alimentar representam um perigo para a saúde e a vigilância contínua é fundamental em termos de segurança alimentar, no que diz respeito à investigação e desenvolvimento de métodos analíticos para detectar adulterações e contaminações nos alimentos a partir das matérias-primas utilizadas [26 ] .