Drying of garlic (Allium sativum) and Its effect on allicin retention

Convective hot air-drying and freeze-drying were investigated as potential processes to preserve and concentrate allicin in garlic. Both temperature and air velocity had an important effect on hot air-drying kinetics. Sample size and temperature significantly affected the duration of freeze-drying, and thus the remaining moisture content of the garlic samples. Allicin content decreased with an increase of drying temperature in both convective hot air-drying or freeze-drying. Moderate air temperatures (40 and 50°C) allowed a better allicin retention than higher temperatures (60°C). However, retention of allicin was more important in garlic samples freeze-dried at a temperature of 20°C. The drying method did not show a significant impact on glass transition temperature values, indicating that garlic composition is a more important factor than internal structure. The predictions of the Gordon and Taylor model are in good agreement with the experimental data.