In Vitro Bioaccessibility of Bioactive Compounds of Freeze-Dried Orange Juice Co-Product Formulated with Gum Arabic and Modified Starch

Abstract

The large amount of waste generated by the orange juice industry has sparked the interest of many researchers in incorporating recycling systems and following a much more sustainable circular economy model. This work proposes the valorization of the co-product generated in the orange juice extraction industry after freeze-drying for its subsequent reuse as a natural ingredient in the food industry. In addition, the possible protective effect of gum Arabic and corn starch esterified with octenyl succinic groups, in proportions optimised in previous studies 0.25 and 0.45 g/g orange co-product dry solutes, on the main bioactive compounds of orange peel during the freeze-drying process has been studied. The samples were characterised for their content of vitamin C (ascorbic and dehydroascorbic acids), flavonoids (hesperidin and narirutin), total phenols and total carotenoids, as well as their antioxidant capacity (DPPH and FRAP assays). In addition, samples were digested, mimicking the human enzymatic oral gastro-intestinal digestion process, and the bioaccessibility of the bioactive compounds was evaluated. It was observed that the addition of both biopolymers improved the stability of the hydrophilic compounds during freeze-drying. This conservative effect was more remarkable for higher biopolymer concentrations. However, no protective effect on carotenoid compounds was observed. This trend was reflected in the antioxidant activity of the different samples. In addition, the incorporation of biopolymers improved the bioaccessibility of the bioactive compounds studied. In conclusion, the results supported the feasibility of the freeze-dried orange juice co-product as a natural, sustainable source of health-promoting compounds.

Keywords: antioxidant capacity; carotenoids; citrus industry; co-product; in vitro digestion; total phenols; vitamin C.

Figure 1

Vitamin C (sum of ascorbic acid (AA) and dehydroascorbic acid (DHAA)) of the orange juice co-product before (OJC) and after freeze-drying (OJC-FD), and those freeze-dried orange co-products formulated with gum Arabic and starch modified with octenyl succinic anhydride, at 25 and 45 g/100 g co-product dry solutes (GA25, GA45, OSA25, OSA45, respectively). Results are expressed as mg of bioactive/100 g of orange coproduct dry solutes (ds). Different letters indicate different homogeneous groups established by Tukey HSD ANOVA (p < 0.05) between samples: ^a–d for AA and ^A–E for DHAA.

Figure 2

Antioxidant capacity measured by DPPH (a) and FRAP (b) of the hydrophilic and lipophilic fractions of orange co-product before (OJC) and after freeze-drying (OJC-FD), and those freeze-dried orange co-product samples formulated with gum Arabic and starch modified with octenyl succinic anhydride, at 25 and 45 g/100 g co-product dry solutes (GA25, GA45, OSA25, OSA45, respectively). Results are expressed as mmol Trolox Equivalent (TE)/100 g of orange coproduct dry solutes (ds). For each fraction, different letters indicate different homogeneous groups established by Tukey HSD ANOVA (p < 0.05) between samples: ^A–E for the hydrophilic fraction; ^a–c for the lipophilic fraction.