Comparison of Traditional and Novel Drying Techniques and Its Effect on Quality of Fruits, Vegetables and Aromatic Herbs

Abstract

Drying is known as the best method to preserve fruits, vegetables, and herbs, decreasing not only the raw material volume but also its weight. This results in cheaper transportation and increments the product shelf life, limiting the food waste. Drying involves the application of energy in order to vaporize and mobilize the moisture content within the porous products. During this process, the heat and mass transfer occurs simultaneously. The quality of dehydrated fruits, vegetables, and aromatic herbs is a key problem closely related to the development and optimization of novel drying techniques. This review reports the weaknesses of common drying methods applied for fruits, vegetables, and aromatic herbs and the possible options to improve the quality of dried products using different drying techniques or their combination. The quality parameters under study include color, bulk density, porosity, shrinkage, phytochemicals, antioxidant capacity, sugars, proteins, volatile compounds, and sensory attributes. In general, drying leads to reduction in all studied parameters. However, the behavior of each plant material is different. On the whole, the optimal drying technique is different for each of the materials studied and specific conditions must be recommended after a proper evaluation of the drying protocols. However, a novel or combined technique must assure a high quality of dried products. Furthermore, the term quality must englobe the energy efficiency and the environmental impact leading to production of sustainable dried products.

Artichoke by Products as a Source of Antioxidant and Fiber: How It Can Be Affected by Drying Temperature

“…The air drying tests were performed at atmospheric pressure using an air velocity of 1 m/s and at five different temperatures (40, 60, 80, 100 and 120 °C). This range of temperature and air velocity is usually applied in the drying of agro-food products [ 13 , 14 , 15 ]. The relative humidity remained below 10% in every experiment carried out.…”

“…However, the influence of temperature on the drying rate depends on the products and sometimes, shortening the drying time could not compensate the increase of energy consumption, which the increase of temperature causes. Moreover, the thermal treatment promotes organoleptic and nutritional changes in food products that may cause quality degradation [ 15 ] or even the formation of new compounds [ 16 ]. According to the author’s knowledge, the drying of the main artichoke by-products, bracts and stems, has never been studied independently.…”

The Effect of Plant Additives on the Stability of Polyphenols in Dried Black Chokeberry (Aronia melanocarpa) Fruit

“…Convection pre-drying enables the removal of the unbound part of water. Microwave drying in a vacuum allows significantly increasing the efficiency and shortening the processing time [ 11 , 12 ].…”

Flavor and Aroma Analysis as a Tool for Quality Control of Foods

“…In the second topic of studies of different processing and conditions, six manuscripts have been published [ 4 , 5 , 6 , 7 , 8 , 9 ]. The authors provide an overview of recent advances made in the field of food processing establishing the best processing conditions in order to obtain food based products with a high quality in terms of aroma, flavor and, consequently, consumer satisfaction.…”

“…From a sensory point of view, the best drying treatment was vacuum-microwave drying at 240 W because it produced dried samples most resembling the fresh material with high intensities of key sensory descriptors such as hemp flower ID, fresh vegetables, citrus, balsamic and anise and therefore this drying treatment and conditions can be recommended as the best option for hemp flower drying. The sixth and last manuscript of this second topic by Calín-Sánchez et al [ 9 ] is a review manuscript that compared traditional and novel drying techniques and describes their effect on the quality of fruits, vegetables and aromatic herbs. The quality of dehydrated fruits, vegetables and aromatic herbs is a key problem closely related to the development and optimization of novel drying techniques.…”