# Antimicrobial and Odour Qualities of Alkylpyrazines Occurring in Chocolate and Cocoa Products
## 4 The Quantification of the Impact of Alkylpyrazine Compounds on the Aroma of Cocoa and Chocolate
### Pyrazine Content Differences in Cocoa, Dark and Milk Chocolate  
It is common practice to combine cacao beans from various sources while making chocolate. The origin of chocolate is distinguished by a distinct flavour and scent that come from the cocoa beans used, which are primarily influenced by the location of the plantation. Flavour volatiles are one of the most significant factors influencing the acceptability of cocoa beans and chocolate, which is essential to the popularity of cocoa beans and cocoa-based goods like chocolate.  
According to the study conducted by [PERSON] et al. [15], single-origin and blend chocolate with various quantities of the cocoa mass showed substantial variances in the overall level of alkylpyrazines. These findings imply that the final odour potential, which was not specified for these products, is greatly influenced by the properties of the raw materials utilized as their origin. Comparing chocolates of different origins, samples from different blends revealed variations in the content of fragrance components. For example, the content of tetramethylpyrazine varied from 60.31 mg/kg in the blend sample and 285.74 mg/kg in the Madagascar single-origin sample, which was found to be the highest concentration of alkylpyrazines, namely tetramethylpyrazine. Additionally, trimethylpyrazine (15.01-81.39 mg/kg), 2,5-dimethylpyrazine (1.99-10.18 mg/kg), 2,3-dimethylpyrazine (2.74-15.11 mg/kg) and 2,6-dimethyl-3-ethylpyrazine (0.98-6.77 mg/kg) were spotted at high concentrations.  
Pyrazines are a sign of a healthy fermentation process and can be used to evaluate the quality of dried fermented beans. In the research by [PERSON] and [PERSON] [30], which were comparing pyrazine content in cocoa mass and milk chocolate, some compounds demonstrated very noticeable variations in their odour activity, especially 2-methoxy-3-isopropylpyrazine (FD = 64--milk chocolate, FD = 512--cocoa mass) and 2-ethyl-3,6-dimethylpyrazine (FD = 32--cocoa mass, FD = 512--milk chocolate), which may be explained by the theory that these fragrance molecules may partially evaporate during the conching process.  
Chocolates, dark and milk, have been classed depending on their formula, and one of the most crucial ingredients in the production of milk chocolate, milk powder, can significantly alter the physical and organoleptic qualities of chocolate. Although the aroma of milk chocolate may be enhanced by the addition of dairy products, the presence of milk fat caused a notable reduction in the release of volatile substances. In a study by [PERSON] et al. [21], it was proven that the release of alkylpyrazines is considerably reduced by chocolate's enhanced particle size distribution and fat content.  
By using GC-MS, [PERSON] et al. [19] evaluated the amount of the key aroma-active chemicals in cocoa liquid, dark and milk chocolate, and compared them using GC-O-MS (gas chromatography-olfactometry-mass spectrometry), AEDA and sensory assessment. Strecker aldehydes, pyrazines, pyrroles and carboxylic acid made up 76% of the entire value of odourants with FD factors 81 in the dark chocolate, but milk chocolate only contained about 37.5% of this indication. Dark chocolate had substantially higher concentrations of all six pyrazines (2.654 mg/kg) than milk chocolate (0.619 mg/kg) and slightly more than cocoa liquid (2.2213 mg/kg). Numerous pyrazines, including 2,5-dimethylpyrazine, 2-ethyl-6-methylpyrazine, trimethylpyrazine, 3-ethyl-2,5-dimethylpyrazine and 3,5-diethyl, 2-methylpyrazine increased in comparison with the cocoa liquid during the manufacturing process. This was consistent with the fact that during conching, low volatile pyrazine concentrations considerably increase. The significant difference in these chemicals between the two kinds of chocolate also suggested that the milk chocolate's lower pyrazine concentration was due in part to its distinct conching conditions.