Impact of Process Parameters and Recycling of Natural Deep Eutectic Solvent on the Physicochemical, Structural, and Gel Characteristics of Glucomannan

Porang glucomannan (PGM) is widely used as a functional ingredient in food and non-food products. However, the PGM industry still faces low PGM yield, which is a significant challenge in extracting PGM from porang flour (PF) using mechanical method (milling process aided by a wind-sifter). Natural deep eutectic solvents (NADES) are promising green solvents for glucomannan extraction. This study aimed to investigate the influence of stirring speed, PF particle size, filter pore size, and solvent recycling on characteristics of PGM using NADES composed of betaine and 1,2-propanediol at a 30% (W_water/W_total) hydration level (BPG14_70%). The PGM was characterized by glucomannan content, crystallinity, gel properties, morphology, and particle size distribution. The findings showed that increasing filter pore size and stirring speed improved the purity and viscosity of PGM. The PF particle size was the primary factor in glucomannan extraction, in which a smaller PF particle size reduced crystallinity and impurities surrounding the surface of PGM, resulting in higher purity and improved gel properties (firmer and springier gel). The suggested conditions for glucomannan extraction were a stirring speed of 800 rpm, a filter pore size of 149 μm, and a PF particle size of 257 μm. These conditions resulted in 76% PGM yield with a glucomannan content of 93% and strong gel properties. Additionally, after reusing five cycles, BPG14_70% could be recovered ranged 84–78%, producing PGM with a purity above 80%. Our findings offer an extraction technology to produce a high yield of purified PGM with a low environmental load.