Development of instant jelly powder from elephant foot yam (Amorphophallus oncophyllus) and roselle (Hibiscus sabdariffa L.) as a functional food for diabetes mellitus patients

Elephant foot yam (Amorphophallus oncophyllus) is one of Indonesia’s most widely grown agricultural commodities. It has a myriad of benefits, especially as a functional food for people with diabetes mellitus. Roselle (Hibiscus sabdariffa L.) is a flowering herb rich in polyphenols and anthocyanins with antioxidant and antidiabetic potentials. Therefore, the aim of this study was to create a functional food that is suitable for diabetes mellitus patients. In this study, a functional food product in the form of instant jelly powder was developed from the yam and roselle. Glucomannan extract, obtained from the yam flour by leaching, was tested using a Fourier-transformed infrared (FTIR) spectrophotometer (qualitative) and determined the content. Three formulas with different amounts of glucomannan and iota carrageenan were developed to determine the most optimized formulation. The most optimized formulation was determined based on organoleptic characteristics and the results of the gel strength and hardness, total phenolic content (TPC), and antioxidant activity tests using the ABTS (2,2'-azino-bis(3 ethylbenzothiazoline-6-sulfonic acid) assay. Glucomannan extraction produced a 92.40% yield, with 46.32% glucomannan content. The spectrophotometric analysis indicated the presence of glucomannan in the extract, and further tests showed it increased with the decrease in gel strength and hardness. It was found that formula I produced the best jelly texture with a total phenolic content of 0.30% GAE (formula II 0.13% GAE; formula III 0.27% GAE) and an ABTS radical scavenging activity of 90.51% (II: 73.49%; III: 88.16%). In conclusion, formula I containing 6.35 g of carrageenan, 2.12 g glucomannan, 1.5 g roselle, 0.03 g citric acid, and 0.003 g sucralose has the best composition to create the most elastic and firm jelly texture with the highest phenolic content and radical scavenging activity.