engleski

Characterization of Red Raspberry (Rubus idaeus L.) Quality Attributes Affected by Freeze Drying and CO2 Drying

The aim of this study was to evaluate and compare the bioactive and nutritional profile of red raspberry (Rubus idaeus L.) affected by two non-thermal drying techniques, freeze drying and CO2 drying. In that order, optimization of CO2 drying conditions with the aim of achieving the highest quality of the final product was conducted. UV/Vis spectrophotometric methods were employed to determine the content of total polyphenols and flavonoids, as well as antioxidant capacity evaluated by 2, 2-diphenyl-1-picrylhydrazyl (DPPH) and 2, 2-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) free radical scavenging assays. Since anthocyanins are among the most important quality indicators of red raspberries, and their contribution to the appearance and visual acceptability is crucial, individual anthocyanins were identified and quantified by means of reversed phase high performance liquid chromatography, which was also applied to determine the ascorbic acid and sugar contents of differently dried red raspberries (HPLC-PDA, -RID). By comparing the drying efficiency of freeze drying and CO2 drying, both techniques resulted with deterioration of bioactive compounds and antioxidant capacity, where freeze drying provided better preservation efficiency, while degradation tendency in CO2 drying depended on processing conditions. Comparison of freeze drying and the best CO2 drying condition showed that freeze drying provided only slightly better preservation of bioactive compounds and better preservation of the antioxidant capacity. Five individual anthocyanins were determined, among which cyanidins where more abundant (cyanidin-3- sophoroside, cyanidin-3-rutinoside, cyanidin-3-glucoside), while pelargonidins (pelargonidin-3-rutinoside, pelargonidin-3-glucoside) were present in a much lower content, in both fresh and dried red raspberry samples. Among sugars, fructose, glucose, and sucrose were identified in all raspberry samples. According to the obtained results, CO2 drying with the most suitable processing parameters may be regarded as a good alternative to freeze drying.

Bioactive profile; CO2 drying; Freeze drying; Raspberry

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