The role of betel (Piper betle) leaf extract and glycerol on physical properties of bioplastic based on sago starch

Abstract

Starch-based bioplastic from sago is one of the potential sources in Indonesia. Since it is made from natural ingredients, it is easier to absorb water and susceptible to the activity of microorganisms. Betel leaf extract is one of natural antimicrobial agent that rich of tannin and flavonoid. This study aims to investigate physical properties and antimicrobial activity of sago (Metroxylon sp.) starch-based bioplastic. The betel leaf was extracted by using the ultrasonication method with ethanol as a solvent. Betel leaf concentrated extract is diluted using aquadest with a concentration of 2 g/100 mL (2%) to be applied as an antimicrobial agent in bioplastics. The compositions of glycerol were varied from 10-30% whereas betel leaf extract from 3-9%(v) in the manufacture of bioplastics. The results show that the highest density of 1.5 g/cm3 was achieved at the composition of glycerol and betel leaf extract, respectively, 30%(v) and 9%(v). The highest water absorption percentage was shown by sample with 30%(v) glycerol without addition of betel leaf extract, that was 83.31%. The antibacterial activity showed that the addition of betel leaf extract to bioplastics was able to inhibit the activity of bacteria (Bacillus cereus). The best inhibition were shown in bioplastics with a variation of 20%(v) glycerol and 9%(v) betel leaf extract addition. However, all variation did not show their inhibition with fungal activity (Aspergillus niger).