Friday, 29 May 2015

Chapter 78 – Dehydration of Basil Leaves and Impact of Processing Composition

Chapter 78 – Dehydration of Basil Leaves and Impact of Processing Composition


Both consumers and the food industry are increasingly interested in aromatic herbs, not only as flavoring agents, but also for their content in biologically active compounds. Sweet basil (Ocimum basilicum L.) is a very important culinary herb and a functional ingredient marketed fresh, dried, or frozen. At present, drying is by far the most widely used basil preservation method, thus ensuring microbiological safety and extending basil shelf-life. Nevertheless, during drying, a series of physical and chemical changes that may have an adverse effect on basil quality may take place. Such alterations include changes in its flavor and appearance, mainly caused by the loss of volatile components and the formation of new compounds. Both these aspects are important quality factors with a deep impact on the consumers’ acceptance of the product. In this chapter the most commonly used drying methods are described and their impact on the sensorial and nutritional properties of this raw material are analyzed.


  • Sweet basil (Ocimum basilicum L.);
  • Air-drying;
  • Microwave drying;
  • Freeze-drying;
  • Osmotic dehydration;
  • Experimental design;
  • Sensorial modifications

Chapter Points

Sweet basil (Ocimum basilicum L.) is a very important culinary herb and a functional ingredient mainly marketed dried to ensure microbiological safety and to extend shelf-life.
Decreased flavor, shrinkage, unappetizing texture, color damage, and browning effects are the most evident drawbacks of dried basil leaves.
As far as flavor is concerned, there is a decrease of the intensities of floral and herbaceous notes while there is an increase of spicy, earthy, and woody notes.
Adverse changes can be minimized by choosing among the mildest drying technologies and by appropriately designing the process conditions using design of experiments (DOE) in a comprehensive way, also considering pre-drying and post-drying processes.
Convective drying (CD) usually implies a significant reduction in the content of most of the volatiles together with a significant variation in their relative proportions according to changes in air temperature.
Convective pre-drying and vacuum-microwave finishing drying lead to high-quality dried products in terms of total volatiles in a relatively short time (about 250 min).
Osmotically dehydrated basil leaves show a higher quality than those treated with traditional methods.
Vacuum–microwave drying (VMD) often minimizes the leaf shrinkage and improves their texture.
Usually osmotic dehydration (OD) and freeze drying of herbs minimize the thermal damage to color by preventing enzymatic browning.
Nowadays, there are only a few studies on the effects of drying processes on the mineral content of basil leaves.