Candying process for enhancing pre-waste watermelon rinds to increase food sustainability

This work describes two alternative laboratory methods ’candying fruit’ methods of fresh mesocarp of Crimson sweet watermelon, a typical waste and unappetizing material. Our experimental candying process was conducted by slow osmosis, lasting 24 weeks at room temperature. It was activated with granular sucrose according to our two alternative laboratory methods, WET and DRY. Fresh watermelon rinds were transformed into candied fruit with excellent flavor and aromas. The aromatic profile of all the materials was characterized with HS-SPME-GC– MS technique. The results highlighted some significant differences in the Volatile Organic Compounds fraction, probably attributable both to the cultivar and to the two candying methods, as verified also by a panel test. The class of alcohols remains almost constant in all the samples. Terpenoids are highly present in FRESH samples, while they disappear in DRY candied ones. Acetate esters are absent in FRESH rinds, they reach the maximum level in WET, and stop at the middle in DRY samples. The trend of the values relating to the class of acids is opposite: absent in the FRESH aromatic profile, maximum and average for DRY and WET samples, respectively.