Optimazation of quality parameters from raspberries dehydrated by combined technologies: osmotic dehydration and convective drying.

SETTE, PAULA A.; SALVATORI, DANIELA; SCHEBOR, CAROLINA

Pirassununga

Seminario; Advances in Molecular Structuring of Food Materials; 2013

Universidad de Sao Pablo

Raspberries are an excellent source of bioactive compounds. Several studies have attributed many health benefits associated with consumption of these fruit, which has led them to incorporate in the formulation development of functional foods and nutraceuticals. The aim of this study was to analyze the quality parameters such as volumetric shrinkage, color, phenolic content and anthocyanin pigments in convective drying dehydrated raspberries (Tair: 60 ° C, RH = 10%, final aw 0.3), previously osmotically dehydrated. The pretreatments consisted in a dried (IS) and a wet infusion (IH), in both cases were studied the effect of adding additives. The experimental conditions were: no additives (IS, IH), with addition of sodium bisulfite (IS-B, IH-B), with addition of citric acid (IS-AC, IH-AC), with addition of sodium bisulfite and citric acid (IS-BAC, IH-BAC) and without pretreatment or control (C). Samples with IS pretreatments showed after dehydration, generally, lower values of a* and b*, which resulted in a decrease in the values of h*ab compared with IH samples. So, IH samples preserved better red hues, without significant differences from the control after drying. Dehydrated IH samples presented h*ab values superior to the control, especially IH-B. Likewise, the C*ab values from IS samples were generally lower with respect to the control mainly due to lower shrinkage of the matrix. Generally the brightness of the samples was similar to the control in all cases except the IH-B which were brighter. In these samples were checked also an increased tendency to yellow hues due to the interaction between anthocyanins and sodium bisulfite. These findings were reflected in the overall color change values being higher in raspberries IH-BAC. The bioactive compounds (polyphenols and anthocyanins) showed a marked decrease in all samples pretreated because of the dilution effect. The IH samples contained less anthocyanin pigments than the IS samples, being the IS-BAC the samples who increased the retention of this compounds after drying, which is consistent with the improved values of chromatic parameters. The volumetric shrinkage decreased by application of osmotic pretreatment. It was approximately 20% in comparison with the dried raspberry control. Samples with lower shrinkage were obtained by applying both infusions without additives (IH and IS). In conclusion, the application of osmotic dehydration as a pretreatment before convective drying produced a significant loss of anthocyanins and polyphenols in the samples, but it was possible to get dehydrated raspberries with very similar chromatic characteristics shape and volume to the original fresh fruit. The implementation of IS-BAC pretreatment allowed to optimize the quality of the convective dried raspberries.