Agregação de valor ao resíduo de melão: caracterização, avaliação de atividade antioxidante, antiproliferativa, potencial prebiótico e produção de enzimas

Abstract

The use of food processing residues is a strategy to contribute to reducing waste and adding value to new products. Melon is a fruit consumed worldwide and its high consumption accompanies large amounts of residues, such as peel and seeds. The objective of this thesis was to add value to melon peel and seeds (Cucumis melo var. reticulatus), evidencing its nutritional properties, antioxidant capacity, anti-tumor effect, prebiotic potential and its capacity for enzyme production. Flours of melon peel and seed were elaborated using experimental design 22 to evaluate the factors of drying time and temperature, and the responses moisture, water activity and flour yield. Flour characterization was carried out using centesimal composition (moisture, ash, proteins, lipids, dietary fiber), fibrous fractions of cellulose, hemicellulose, lignin and pectin. Flours were evaluated for their in vitro prebiotic properties using Bifidobacterium lactis in submerged fermentation and bile salt tolerance. The potential of the flours in the production of cellulases in semi-solid fermentation using Aspergillus oryzae fungus was also evaluated. For the accomplishment of the analyzes of antioxidant and antiproliferative power, aqueous extracts, hydrometanolic and hydroethanolic of the flours were prepared, characterized as monosaccharide composition, analysis of total sugars and proteins. For antioxidant evaluation, the total phenolic compounds, total flavonoids, total carotenoids and tannins were determined. Phytochemical evaluation of the extracts was carried out by Thin Layer Chromatography. The antioxidant capacity evaluation was verified by the following in vitro tests: total antioxidant capacity, reducing power, iron and copper metal chelation, sequestration of DPPH, hydroxyl and superoxide radicals, and evaluation of the oxygenated radicals absorption capacity. The antiproliferative activity was evaluated using the tumor cell lines (SiHa, HeLa, 786-0 and HT29) by colorimetric test of cell viability evaluation. The results for the drying experimental design showed that the temperature factor significantly influenced the yield response of the flours, being the test of 80 ºC for 24 h which presented better yield. Data showed that the melon residues had important nutritional characteristics for human consumption, with emphasis on dietary fiber content (51.75% for seed, 40.57% for peel), proteins (22% for seed; 18% for peel) and lipids (24% for seed). The residues can be characterized as cellulosic material, with values of 35% cellulose for melon seed and 19% for peel. Satisfactory percentages of pectin were detected, being 28.96% for seed and 32.65% for melon peel. As for the prebiotic potential of the flour, it was observed that the fructo-oligosaccharide standard showed a growth of bifidobacteria of 12 LogUFCmL-1, after 12 hours of fermentation, and the melon seed flour promoted bifidobacterial growth reaching 9.9 LogUFCmL- 1, after 8 hours of culture, indicating prebiotic properties, with tolerance to the action of bile salts for up to 8 hours of fermentation. The melon peel did not provide growth of bifidobacteria. Melon peel and seed proved to be a good substrate for enzyme production. The best CMCase activity (1.045 U / g) was verified on six days of fermentation and FPase (0.190 U / g) after 96 h of fermentation with medium containing the peel and seed flours. In the evaluation of the extracts obtained from the melon residues, phytochemical analysis indicated the presence of compounds characteristic of phenolics, terpenes and saponins. Total phenolic compounds in aqueous, hydrometanolic, and hydroethanolic extracts of melon residue were quantified and expressed as gallic equivalents, highlighting peel extracts (1.016 mg 100g- 1). Total carotenoids, total flavonoids and tannins were also detected in extracts of melon residues, with emphasis on 96 μg of total carotenoids per gram of melon peel, 491 μg of catechin equivalents and 309 μg of catechin equivalents in 100 g extract dried of melon peel. The tests to evaluate the antioxidant activity revealed that all extracts presented antioxidant capacity. In the test of total antioxidant capacity (expressed as equivalent in ascorbic acid), hydroethanolic and methanolic extracts for peel and seed presented values of 89.74 and 83 mg / g, respectively; 50.56% and methanolic 67.7% for melon peel. Reducing power and chelating abilities of copper and iron metals presented relevant data for both melon peel and seed, demonstrating an excellent antioxidant potential. The aqueous extract of the peel showed the ability of in vitro of copper ions chelation (84%) and iron ions chelation (61%). Scavenging activity of the DPPH radical was significant only for extracts of melon peel (29.5%).The cell viability test allowed us to observe that the extracts were able to extract the organic extracts, to significantly decrease the viability of the HeLa, SiHa and 786-0 cancer cells. Aqueous seed extracts at the 1.0 mg / mL concentration inhibited the proliferation of SiHa cells by 80% and the peel hydroethanolic extract (0.25 mg / mL) inhibited by 80% the viability of HeLa cells. For human renal tumor cells (786-0) all extracts at the concentration of 1.0 mg / ml inhibited cell proliferation by more than 50%. The extracts evaluated did not present significant inhibition activity of HT29 cells. All melon peel and seed extracts weakly inhibited the proliferation of normal 3t3 fibroblasts (25% inhibition). It is concluded that melon peels and seeds have antioxidant potential in vitro and antiproliferative effects in tumor cells. Flours of melon peel and seed may be substrates for the production of cellulolytic enzymes, in addition the seed flour showed in vitro prebiotic indication.