Physicochemical, antioxidant and antibacterial properties of peel and pulp of different grape varieties

The aim of the present study was to investigate the physicochemical, antioxidant, antimicrobial properties and mineral profile of peel and pulp of four distinct grape varieties. The grape varieties studied were two exotic (Fantasy Seedless and Thompson Seedless) and two local (Sahebi and Hussaini) varieties. The pulp of fantasy seedless variety had the highest total soluble solids (16.40 °Brix), total sugars (14.81 ​%), reducing sugars (9.06 ​%), and sweetness index (63.08). Generally, the pulps showed significantly higher values for these characteristics compared to the peels. Peels exhibited significantly higher levels of total phenol, flavonoid content and antioxidant properties for all grape varieties. Fantasy seedless peel showed the highest values of total phenolic content (5.38 ​mg GAE/g), total flavonoid content (0.68 ​mg QE/g) and antioxidant activity (70.40 ​% for the DPPH assay). Moreover, the antibacterial activity against both Gram-positive bacterium Staphylococcus aureus and Gram-negative bacterium Escherichia coli was evaluated using the disc diffusion method, revealing that grape peels possessed greater antibacterial efficacy than the pulp, with fantasy seedless peel exhibiting the most significant inhibitory effects in both cases. Enzyme activity analysis revealed that the fantasy Seedless peel had the highest polyphenol oxidase (PPO) activity (100.01 units/g/min). It was further contented from the results that thompson seedless peel exhibited significantly higher potassium (259.21 mg/100 ​g), calcium (50.20 ​mg/100 g), and phosphorous (29.90 mg/100 ​g) contents. These findings highlight the potential health benefits and functional attributes of grape peel extracts, particularly from the Fantasy seedless variety, and underscore their relevance in various applications, including food and pharmaceutical industries. • Pulp extract of all grape varieties had better physicochemical properties than peel. • Peels extract showed higher levels of antioxidant and antimicrobial properties than pulp. • Grape extracts inhibited more Gram-positive bacteria than gram-negative bacteria. • Among all grape varieties fantasy seedless variety showed best evaluated properties.