Physical changes in garlic and its relation with the loss of allicin during convective drying

The retention of allicin and its relation to changes in the structural properties:
apparent density (b), true density (p), porosity (𝓔) and shrinkage (Sb) during garlic drying were evaluated. Drying kinetics, structural properties (SP) and allicin content (AC) were determined in garlic slices subjected to drying temperatures of 50 and 60 °C with an airflow of 1.5 m/s. To calculate structural properties, experimental data volume of the solid were determined using volumetric displacement and gas stereopycnometer methods.
The AC was determined using the dinitrophenylhydrazine method. Data were correlated using Pearson's equation. The results showed a strong inverse relationship between AC and Sb, p and b, while a weak relation to the Ɛ was found for both temperatures. The kinetics showed two stages, the first showed a rapid increase in the p, b and Sb, according with the loss of allicin. In the second, the increase of p, b and Sb remained without significant losses of allicin. The results suggest that a denser structure prevents the penetration of oxygen through the solid reducing the degradation of bioactive compounds. Both, the temperature and changes in the SP affect the retention of allicin.
Drying temperatures of 60°C can induce more rapid shrinkage, dense structures, and partially inactivate the enzyme allinase.