Fruit snacks from raspberries: influence of drying parameters on colour degradation and bioactive potential

Abstract

Raspberries were dehydrated using air and freeze-drying with wet and dry sugar infusion pretreatments. Product quality factors such as colour, bioactive compounds, antioxidant capacity and sensorial characteristics were analysed. Special emphasis was placed on the analysis of anthocyanin degradation and its relationship with colour deterioration and with polymeric compounds development and browning. Freeze-dried raspberries presented a higher retention of bioactive compounds and a lower content of polymeric compounds than air-dried ones. Dried samples without pretreatment (control) showed the highest retention of total phenolic content (freeze-dried ≈82% and air-dried ≈37% retention), but the lowest sensory acceptability. Although sugar infusion pretreatments caused an important loss of bioactive compounds (9–18% of TPC retention), a higher sensorial acceptability was obtained. Pretreatments with bisulphite and acid allowed obtaining the best quality attributes in terms of anthocyanin and polyphenol content, antiradical activity and colour retention. Polyphenol intake through pretreated dried raspberries (115–299 mg gallic ac./100 g intake) would be higher in some cases than that of usually consumed foods as vegetables, cereals and several fresh fruits.