الملخص الإنجليزي
Garlic has potential to be used in food products as a natural preservative, flavoring agent and medical or functional food. Generally garlic is commercialized as a fresh product, but recently numbers of other products are being developed by drying, distillation, maceration in oil, hydroalcoholic short extraction, and hydroalcoholic long maceration. However, drying is the most widely used method in developing garlic products. In developing dried products it is important to know the stability or loss of the active functional components and to know the drying kinetics in order to design the drying process. Drying kinetics was developed by drying 5 mm thick slices in air, vacuum, and modified atmosphere drying. The drying coefficient and lag factor were estimated from the slope and intercept of the moisture ratio plot based on the Dincer Hussain's model. Both drying coefficient and lag factor increased with the increase of drying temperature. Moisture diffusivity and external mass transfer coefficient were estimated from the drying coefficient and lag factor as suggested by Dincer-Hussain model. Similarly moisture diffusivity was also estimated by commonly used Fick's law of diffusion and it increased with the increase of drying temperature. The diffusivity estimated from the Fick's law of diffusion and Dincer-Hussain's models differed since Fick's law assumed negligible external mass transfer coefficient whereas Dincer Hussain model considered both internal and external mass transfer resistance. Allicin is one of the most biologically active compounds in garlic and it is rapidly produced by the action of allinase on alliin when crushed. Air dried samples at 50°C, vacuum dried samples at 50 and 60°C, modified atmosphere dried samples at 40°C showed lowest loss of allicin potential. In general the loss of allicin increased with the increase of drying temperature and drying below 50°C could be the best drying condition for the retention of allicin potential. This could be due to retention of allinase activity during lower temperature drying. The loss of allicin potential decreased with the increase of slice thickness. This may be due to the fact of lower structural damage in the case of thicker slices.
