Comparative chemical characteristics of hydrochloric acid- and ammonium oxalate-extracted pectin from roselle (Hibiscus sabdariffa L.) calyces

Recent research suggesting the existence of potential source of pectin from roselle calyces. Pectin was successfully extracted from seven different varieties of roselle calyces. Pectin extraction was conducted using hydrochloric acid (HCl, 0.03 N, pH 1.5) or ammonium oxalate (0.25% w/v, pH 4.6) at 85°C for 1 h. Chemical characteristics of the HCl- and ammonium oxalate extracted pectin were compared. Results indicated that ammonium oxalate exhibited greater efficiency in pectin extraction than HCl. Highest pectin yield at 18.7% was obtained by ammonium oxalate extraction of roselle calyx variety Acc.6 compared to only 9.77% by HCl extraction. The lowest pectin yield at 11.3% and 5.78% were observed respectively in ammonium oxalate and HCl extractions of roselle calyx variety UKMR-3. Some important characteristics of ammonium oxalate extracted pectin of roselle Acc.6 were 5.98% moisture, 3.81% ash, 4.64% methoxyl content, 42.24% anhydrouronic acid (AUA) and degree of esterification (DE) 60%. This study suggested that the high DE% roselle pectin is an alternative source of pectin for food industry.