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Foods ; 8(8)2019 Jul 24.
Artigo em Inglês | MEDLINE | ID: mdl-31344943


The aim of this study was to investigate the effect of a pretreatment, performed by a combined method based on blanching, ultrasound, and vacuum application, on the kinetics of osmotic dehydration and selected quality properties such as water activity, color, and bioactive compound (polyphenols, flavonoids, and anthocyanins) content. The pretreatment was carried out using blanching, reduced pressure, and ultrasound (20 min, 21 kHz) in various combinations: Blanching at reduced pressure treatment conducted three times for 10 min in osmotic solution; blanching with reduced pressure for 10 min and sonicated for 20 min in osmotic solution; and blanching with 20 min of sonication and 10 min of reduced pressure. The osmotic dehydration was performed in different solutions (61.5% sucrose and 30% sucrose with the addition of 0.1% of steviol glycosides) to ensure the acceptable taste of the final product. The changes caused by the pretreatment affected the osmotic dehydration process by improving the efficiency of the process. The use of combined pretreatment led to an increase of dry matter from 9.3% to 28.4%, and soluble solids content from 21.2% to 41.5%, lightness around 17.3% to 56.9%, as well as to the reduction of bioactive compounds concentration until even 39.2% in comparison to the blanched sample not subjected to combined treatment. The osmotic dehydration caused further changes in all investigated properties.

Ultrason Sonochem ; 56: 1-13, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31101243


A lot of effort is put to decrease the energy consumption of drying. This effect might be achieved by shift of a drying technology e.g. from a hot-air to a microwave-vacuum method. Moreover, an unconventional pre-treatment such as ultrasound or pulsed electric field may modify a cellular tissue, what influences drying kinetics of plant tissue. The aim of the study was to analyse the quality of microwave-vacuum dried, osmodehydrated (OD) cranberries processed by the means of blanching and ultrasound (US) or blanching followed by pulsed electric field and sonication (PEF + US) in comparison to traditionally treated material. Physical, chemical and sensorial properties of cranberry fruits were assessed. What is more, the impact of aforementioned unconventional treatments on the kinetics of microwave-vacuum dried cranberries was studied. Microwave-vacuum drying process was very short (25-38 min) in comparison to convective drying, which lasted several hours (13.2 h). Most of the samples subjected to US and PEF + US treatments before OD and drying were characterized by similar or a higher amount of bioactive compounds such as polyphenols, anthocyanins and flavonoids, and better colour and taste, as compared to cut osmodehydrated cranberry fruits subjected to convective drying (reference samples).