Influence of preliminary osmotic dehydration on drying kinetics and final quality of carrot (Daucus carota L.)

Abstract

This paper concerns convective drying of carrot preliminary dehydrated in aqueous solutions of three types of osmotic agents (sucrose, fructose, glucose). Three solution concentrations (20, 40 and 60%) were examined to work out efficient conditions of osmotic dewatering. The parameters such as water loss (WL), solid gain (SG) and osmotic drying rate (ODR) indicating the real efficiency of osmotic dehydrations (OD) were determined. The samples dehydrated with osmotic solutions underwent further convective drying to analyze influence of dehydration process on drying kinetics and final products quality. The quality of products was assessed on the basis of visual appearance of the samples and colorimetric measurements. It was found that osmotic pretreatment improves significantly the final product quality as the samples were less deformed and their colour was better preserved compared to samples, which had not been preliminarily dehydrated. Preliminary dehydration, however, did not influence significantly the overall drying time of the samples.

Quality Aspects of Fruit and Vegetables Dried Convectively with Osmotic Pretreatment

“…However, most vegetables and fruits contain more than 80% water and therefore are highly perishable (Pabis and Jaros, 2002). Because of putrefaction processes, long-term storage of fresh vegetables and fruits is not possible (Kowalski and Mierzwa, 2011;Mujumdar, 2007). One of the ways of their preservation is to convert perishable food into stabilised products, and thus to enable their storage for extended periods of time and to reduce their postharvest losses.…”

Apple juice concentrate impregnation enhances nutritional and textural attributes of the instant controlled pressure drop (DIC)‐dried carrot chips

“…Although the un‐pretreated samples had an initial moisture content (8.34 g g –1 , db), which was much higher than the osmotic samples (2.45 g g –1 , db), all of the carrot samples reached the same moisture content of 0.40 g g –1 db at around 150 min. This could be a result of the impact of sugar blocking moisture diffusion and reducing the superficial water activity . As noted in the Materials and methods, the moisture content of all the samples should be controlled to 0.50 g g –1 db before DIC drying.…”

Hybrid Drying of Carrot Preliminary Processed with Ultrasonically Assisted Osmotic Dehydration

“…On the other hand, changes in the material structure, followed by the action of ultrasonic waves may also influence the quality parameters of the material. In our previous research (15,16,36) the relationship between the amount of solute, which penetrates the material during osmosis, and the changes in the colour of the final products was found. Moreover, as it was stated in the literature (7,37), the change of material structure (e.g.…”

“…Water permeates through the cell membrane from the plant tissue to the solution, while soluble solids penetrate the cell wall from the solution to the interior of the plant cell (13,14). In this way, even 50 % of water initially present in the material can be removed at a relatively low expenditure of energy (15,16). According to Lewicki and Lenart (17), convective drying needs about 5 MJ per kg of evaporated water, whereas osmotic dehydration needs only 0.1-2.4 MJ per kg of removed water.…”