Use of orange by-products (dry peel) as an alternative gelling agent for marmalade production: Evaluation of antioxidant activity and inhibition of HMF formation during different storage temperature

In this study, dry orange peel was added to an orange marmalade as an alternative for pectin. The product stability and the antioxidant effect on shelf life of this enriched marmalade were evaluated. In particular, the hydroxymethylfurfural formation in correlation with major bioactive compounds, antioxidant assay, total phenols and anthocyans were estimated during storage at 20 and 35 degrees C for 150 days. The level of phenols ranged from 73.65 to 147.67 mg/100 g for control samples and from 110.09-157.32 mg/100 g for enriched samples. The initial HMF content was 0.09 mg/100 g for the control marmalade and 0.16 mg/100 g for enriched samples and during storage, the level increased. Obtained data show that incorporation of orange peel in marmalade production can be a valid use of this by-product. After storage, the enriched samples at 20 degrees C maintained the analytical parameters better than the samples stored at 35 degrees C. Practical applicationsThe citrus fruit residues, which are usually discarded as waste can be used as nutraceutical resources. The utilization of these bioactive rich citrus residues can serve for the production of novel products or for the improvement of those already in use. Orange peel contains significant amounts of phenolic compounds especially phenolic acids and flavonoids, thus we can consider it a potential material for the formulation of nutraceuticals and food preservatives and may be used as a possible functional ingredient in alimentary products such as marmalade.