Paramee Chumsri, Anchalee Sirichote, and Arunporn Itharat

pp. 133 - 139

Abstract

The present study aimed to: (a) study the physical and chemical properties of fresh roselle calyxes; (b) study the optimum conditions for water extraction of roselle; and (e) compare the methods of evaporation (vacuum, atmospheric) for processing of concentrated roselle extract. This study found that the L*, a* and b* values of fresh roselle calyxes were 0.09±0.01, 0.02±0.01 and 0.05±0.01. The pH, total acidity and total soluble solids content were 2.16±0.05, 4.20±0.01% as malic acid and 5.83±0.04°Brix, respectively. The yields of fresh and dried roselle calyxes production were 47.45±0.71% and 9.58±0.77%. The optimum conditions for fresh roselle calyxes, fresh calyxes to water ratio was 1:2, with the extraction temperature of 50°C for 30 min. For dried roselle calyxes, the optimum conditions were 1:10 ratio of dried calyxes to water and the extraction temperature of 50°C for 30 min. The method of evaporation under the vacuum of 44 cmHg at 70°C was an appropriate selected method for both concentrated fresh and dried roselle extracts. The pH, total acidity and total soluble solids contents of concentrated fresh roselle extract were 2.77±0.02, 12.73±0.09% as malic acid and 25.07±0.10°Brix, respectively. The total anthocyanin, total phenolic contents and EC₅₀ (DPPH radical scavenging assay) were 37.67± 0.02 mg/100 g fresh roselle calyxes, 31.26±0.75 mg gallic acid/g and 39.37±0.61 mg/ml (n=9). The pH, total acidity and total soluble solids contents of concentrated dried roselle extract were 2.89±0.05, 11.96±0.34% as malic acid and 25.07±0.10
°Brix. The total anthocyanin, total phenolic contents and EC₅₀ were 340.97±0.15 mg/100 g dried roselle calyxes, 31.18±0.62 mg gallic acid/g and 47.53±0.85 mg/ml (n=9), respectively.