Effect of Osmotic Dehydration on Mechanical and Rheological Properties of Pumpkin Dried with Microwave Method in Reduced Pressure Conditions

Abstract

The objective of the research was to indicate the impact of sirup type used for osmotic dehydration and the microwaves power for microwave and vacuum drying on the selected mechanical and rheological properties of dried pumpkin. Pumpkin cultivar Rugosa was osmotically dehydrated in three concentrates: apple, aronia and cherry. Initially prepared material was dried with microwave method in the reduced pressure conditions which was within 6-4 kPa at the microwave power which was 240 and 480 W. Dried material was subjected to compression tests and stresses relaxation tests. Compression work values (Pś), cutting work (Pp) and indicators describing material elasticity (a and b) were computed. An initial treatment in the form of osmotic dehydration carried out before microwave drying in the reduced pressure conditions allows obtaining dried pumpkin with a raised resistance to compression and cutting and the decreased elasticity in comparison to dried material obtained from a pumpkin which was not subjected to the initial treatment. Microwaves power influences the values of compression and cutting of dried pumpkin.

Evaluation of process conditions on osmotic dehydration and quality indexes of pumpkin (Cucurbita moschata) and further polymeric film selection for packaging and refrigerated storage

“…It is a vegetable which is hard to store on account of fast and numerous changes in texture and chemical composition, which influence nutritive value as well as sensory properties (Bellocq, 2012). To this end, shelf life extension of vegetables and fruits can be obtained by osmotic dehydration (OD) as a first stage of a modified atmosphere refrigeration or of freezing (dehydrofreezing; Ramallo & Mascheroni, 2010; Bellocq, 2012; Dermesonlouoglou et al ., 2016) or combined with air, vacuum or microwave drying (Stępień et al ., 2016; Rodriguez et al ., 2015, 2017; Deng et al ., 2017). Moreover, their organoleptic and/or nutritional characteristics may be improved by the uptake of other components added to the osmotic solution, yielding a market product that is capable of satisfying the consumer demand for processed vegetables and fruits with sensorial characteristics similar to those of the fresh product (Bellocq, 2012; De Escalada Pla et al ., 2020).…”

“…However, most of the cited literature is about different varieties of pumpkin. Then, literature relative to OD of Anco pumpkin with or without later processing is very scarce (Castilho Garcia et al ., 2007; Lee & Lim, 2011; Derossi et al ., 2011; Arballo et al ., 2012; Bambicha et al ., 2012; Bellocq, 2012; Stępień et al ., 2016; Katsoufi et al ., 2017). That is why it is very important to characterise mass transfer during OD under specified working conditions, feasible to be adopted for industrial processing, as well as quality characteristics and its variation during refrigerated storage of OD pumpkin.…”