Mangoes are an abundant local fruit. Mango seed is a biowaste material that only becomes an environmental problem. Therefore, a study was conducted to utilize one of the compounds contained in mango seeds particularly the seeds of the Arummanis (Mangifera indica L.) from Indonesia, namely flavonoids. One of the most optimum methods is used for extraction with a variety of solvents, namely ethanol, methanol, and hexane. Determination of total flavonoid content is based on the AlCl3 method with total flavonoids content expressed in QE (Quercetin equivalent) at a maximum wavelength of 425 nm. The results showed that the most optimal total flavonoid content was from ethanol extract with the reflux method of 3.234 mg QE/g extract.

Hydrogels are three-dimensional (3D) polymer networks that are water-absorbent, insoluble, flexible, and biocompatible. The freeze-thaw technique is a physical cross-linking method for hydrogel synthesis, which can form a stable structure and non-toxic materials. Biopolymer hydrogel is a solution to environmental pollution due to synthetic polymers, which have been widely used as hydrogel base materials. This paper uses starch composite as precursor solutions for the preparation of hydrogels. The precursor solution ratios (potato starch/gelatin) of 20:0, 20:1, 20:2, 20:3, and 0:20 were labeled as SCG1, SCG2, SCG3, SCG4, and SCG5, respectively. Morphological results showed a cross-linking between polymer chains (solid area) and porosity (liquid area). During the freeze-thaw process, gelatin interfered with a cross-linking process of the hydroxyl group so that the solid phase decreased and the pore size was irregular and enlarged. The swelling degree increased with the gelatin composition, while the weight loss showed the opposite result. SCG1 showed the highest swelling degree value of around 319.39 ± 35.05a % and lower weight loss of about 19.26 ± 9.91a %, which showed a higher degradability. SCG1 has good mechanical properties with Young Modulus, onset strain, and onset stress of about 1.4 ± 0.33a KPa, 145.11 ± 47.28b %, and 1.62 ± 0.08c KPa, although the highest compressive strength was shown by SCG5 of 25.63 ± 2.75a KPa. In general, we found that the physical properties of starch hydrogels showed a potential to be used as a functional food matrix: higher swelling degree, modulus elasticity, and degradability. For gelatin hydrogels, it is necessary to modify the process to become a potential matrix as a media delivery.