Drying characteristics of yacon (Smallanthus sonchifolius) tubers

Bc. Barbora Motýlová

Master's thesis

Abstract:

Yacon (Smallanthus sonchifolius) is Andean crop harvested mainly for its sweet edible tubers. Although it is quite unknown, it has many to offer. Thanks to a high number of bioactive compounds such as fructooligosaccharides, inulin, and phenolics it has antioxidative, antimicrobial, antidiabetic, or anti-obesity properties and positive effect on weight management. In fresh state, yacon roots have a short shelf life and due to the high amount of water, tubers are fragile, heavy, and not easy to transport or store. Drying is an efficient preservation method to prolong the shelf life of food and dried yacon slices may be a promising product with economic potential. The yacon slices were dried at three different temperatures (40, 50, and 60 °C) and drying curves were constructed. Impact of various temperatures on final colour was measured using CIELAB colour space. The changes for each coordinate and the overall combined colour change (∆E) were calculated. The result shows that the temperature does not have an impact on the colour change during drying. Not much research has been done on the freeze drying of yacon slices or consumer perception. Therefore, two different methods of drying (hot-air drying and freeze drying) were examined and the best conditions were established. Consumer perception of these two drying methods was evaluated, resulting in a greater likability of the freeze dried sample. The change in colour was measured, and the lyophilized sample had a significantly lighter colour. Furthermore, different pretreatments using ascorbic acid, lemon, salt, and ginger were used to improve its organoleptic properties and sensory analysis was conducted. Also colour differences compared to control sample were measured. The results indicate that some pretreatments (like lemon) can improve consumer perception. On the other hand, some pretreatments (like salt and ginger) were not evaluated as positive. Furthermore, ginger significantly darkens the final product, which was also evaluated by panellists as unpleasant.

Keywords

freeze drying, yacon tubers, sensory analysis, drying pretreatments, Hot-air drying

Language used: English

Date on which the thesis was submitted / produced: 22. 4. 2022

Thesis defence

• Supervisor: prof. Ing. Jan Banout, Ph.D.

Czech University of Life Sciences Prague

Faculty of Tropical AgriSciences

Master programme:
Agri-food Systems and Rural Development