An Environmentally Friendly Flow Injection-Gas Diffusion System Using Roselle (Hibiscus sabdariffa L.) Extract as Natural Reagent for the Photometric Determination of Sulfite in Wines

Abstract

In this work, a green and simpler method for photometric determination of sulfite based on a flow injection-gas diffusion (FI-GD) system using a natural reagent extracted from roselle (Hibiscus sabdariffa L.) was proposed. Despite the fact that the employed reaction is not selective to sulfite, its sensitivity is high, and the selectivity can be improved by coupling a GD unit to the FI system. The method involves monitoring a decrease in absorbance of the reagent solution that is used as an acceptor solution. When a standard solution or sample solution was injected into an acidic donor stream, the liberated sulfur dioxide diffuses through a gas-permeable membrane of the GD unit into the acceptor solution, causing color fading of the reagent. A linear analytical curve in the range of 5–100 mg L−1 was obtained with a detection limit of 2 mg·L−1. Relative standard deviations of 0.9%, 0.6%, and 0.6% were obtained for the determination of 30, 70, and 100 mg·L−1 SO32- (n = 11). The developed method was applied to wine samples, giving results that agreed with those obtained with the Ripper titrimetric method. The proposed method offers advantages of simplicity, cost-effectiveness, and being environmentally friendly such as reduced chemical consumption and less waste generation.

Valorization of pineapple processing residues through acetification to produce specialty vinegars enriched with red-Jambo extract of Syzygium malaccense leaf

“…The vinegar samples were analyzed for pH (pH meter), total acidity (504/IV method), mineral residues (incineration at 550 °C), reduced dry extract (509/IV method), density (specific weight at 20 °C) 24 , total sulfur dioxide content by the Ripper method 25 levels of acetic acid and ethanol (HPLC), total reducing sugars 19 total phenolics 20 , bioactive compounds (HPLC), antioxidant activity (ABTS, DPPH and FRAP methods), color by the CIELab system (L * a * b* color space).…”