Characterization of by-products from the production of blackberry juice and liqueur

The growing preference for natural additives is driving the recovery of bioactive compounds from food industry by-products. The objective of this study was to characterize the powered products obtained from by-products from the blackberry juice and liqueur production industry and evaluate their antioxidant effects. The residues obtained from two types of by-product (blackberry juice or liqueur) were studied in two ways: as a whole (seeds plus skin, S+S) and considering only the seeds (S). Thus, four samples were analyzed based on the type by-product and the fraction studied: juice-S+S (JSS), juice-S (JS), liqueur-S+S (LSS), and liqueur-S (LS). The proximate composition, water activity (aw), pH, acidity, and polyphenols were determined. The capacity to inhibit fat oxidation (Rancimat method) was studied at three concentrations: 4%, 6%, and 8%. All the analyses were carried out in duplicate. ANOVA and Tukey's test were performed. The residues containing only seeds (JS and LS) were characterized by a higher fiber (81.6 - 83.5 %) and fat content (11.7 -12.5 %) and lower levels of sugars (10.6 -1.50 %) and acidity (0.474 -0.205 g citric acid/100 g), respectively, compared to the residues containing seeds plus skin (JSS and LSS, respectively), which showed the following contents of fiber (28.3 - 53.4 %), fat (4.3 -8.4 %), sugars (42.2 -24.4 %), and acidity (1.59 -1.43 g citric acid/100 g). The content of polyphenols (27.7 -28.4 mg GAE/ g) and anthocyanins (6.12 -2.21 mg cyanidin-3-glucoside /g) were higher in the seeds plus skin fraction (JSS and LSS) than in the seeds (polyphenol content: JS 27.2, LS 16.4 mg GAE/g; anthocyanin content: JS 0.752, LS no detected mg cyanidin-3-glucoside/g). The antioxidant activity and fat oxidation inhibition capacity was also higher in the JSS and LSS products. Therefore, the studied by-products could be used as functional ingredients in the development of healthier foods due to their high content of polyphenols with proven antioxidant activity.