The aim of this study was to analyze the effect of the application of dry and wet sucrose infusions, as pretreatments previous to air-and freeze-drying, on mechanical and physical properties of raspberries: water sorption, glass transition temperature (T g), molecular mobility, texture and rehydration properties. Different dry and wet sugar infusions were prepared using combinations of additives: sodium bisulphite, citric acid, sodium bisulphite and citric acid, and no additives. These specific pretreatments are often used to obtain better sensorial characteristics of fruits upon further drying. After the dehydration step (air-or freeze-drying), all the samples were in the supercooled state. Pretreated samples presented lower T g values and lower spin-spin relaxation times than control samples. Regarding texture, pretreated samples showed lower firmness than control samples. Also, freeze-dried pretreated samples showed higher firmness and lower deformability than air-dried pretreated ones. When considering the hygroscopicity, freeze-dried samples were more hygroscopic than air-dried ones. The fresh-like dried raspberries obtained could be directly consumed as snacks or incorporated in a composite food, such as a cereal mix. In this latter case, pretreated fruits would be more suitable, since their rehydration capacity at short times was relatively low.

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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. Freezedried 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.Fruit snacks from raspberries P. Sette et al. 314 Fruit snacks from raspberries P. Sette et al.

It is widely known that quality properties of fruits can be affected by drying processes. The approach was the quality improvement of dried cherry products through the application of combined technologies of drying and pretreatments. The objective of this work was to analyze the effect of blanching or sugar infusion prior to air-drying or freezedrying on quality properties such as color, bioactive compounds, and antiradical power of two cherry products (discs and dices). Air-drying caused darkening, whereas freezedrying provoked higher lightness of discs compared to fresh fruit (p<0.05). Cherry dices were lighter than the fresh fruit. A high retention of total anthocyanin (ACY) and phenolic content (TPC) was obtained in blanched freeze-dried discs (ACY = 165 ± 22 mg Cyd-3-glu/100 g d.w.; TPC = 739 ± 55 mg GAE/100 g d.w.). Sugar infusion pretreatment caused an important decrease in ACY (31-89 mg Cyd-3-glu/100 g d.w.) and TPC (222-271 mg GAE/100 g d.w.). When blanching was applied prior to air-drying, samples presented the highest antiradical power, similar to that observed in fresh fruit. In dices, the best quality attributes in terms of superficial color were found in control freeze-dried samples since they presented minor shifts in hue angle and a greater preservation of anthocyanin pigments (ACY=211 ±30 mg Cyd-3-glu/ 100 g d.w.). However, control air-dried dices presented the highest phenolic content (TPC=771±65 mg GAE/100 g d.w.). Regarding the possible application of the dry cherry products, discs could be directly consumed as snacks, while dices could be incorporated as ingredients in fruit bars, cookies, or muffins.

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