Quantitative analysis of organic acids in aqueous extracts of Tamarindus Indica pulp and preparation of tamarind powders

Abstract

Tamarind (Tamarindus indica L.) has long been used in traditional medicine for several purposes such as antipyretic, antimicrobial and especially as a laxative for constipation. Organic acids in tamarind pulp are the laxative active component. This study aimed to quantitatively determine organic acids in tamarind pulps and prepare tamarind powder from tamarind pulp extracts with tamarind seed polysaccharide (TSP) as carrier. Organic acid contents in sour and sweet tamarind pulps were determined by HPLC. The results showed that tartaric acid was a major acid in sour tamarinds while tartaric acid and L-malic acid were the major acids in sweet tamarinds. The other minor organic acids were oxalic, citric, succinic and fumaric acids. High content of tartaric acid was found in sour tamarinds, “Priao-Yak” from Phetchabun (P) province and “Priao” from Nakhon Ratchasima (Khorat/K), whereas sweet tamarind “Sithong-nak” from Nakhon Ratchasima (Khorat/K) province contained the lowest content of tartaric acid. Tartaric acid contents in tamarind pulp between different tamarind cultivars were significantly different (P<0.05). The sweet tamarind “Sithong-nak” contained the highest content of oxalic acid, L-malic acid, fumaric acid and succinic acid; these values were significantly higher (P<0.05) than those of sour tamarinds. Tamarind pulp polysaccharide was extracted from tamarind pulp with hot water extraction, followed by acid-alcohol precipitation and Tamarind seed polysaccharide (TSP) was extracted from tamarind seed kernel with hot water, followed by ethanol precipitation. Sugar composition analysis of polysaccharide was determined by acid hydrolysis and HPLC. Tamarind pulp polysaccharide showed the presence of galacturonic acid rhamnose, xylose, arabinose, fructose and glucose/galactose, while tamarind seed polysaccharide showed the presence of xylose and glucose. FT-IR pattern of tamarind pulps polysaccharide was similar to that of commercially available pectin. TSP of sour and sweet tamarind at a concentration of 2% w/v in water exhibited a pseudoplastic flow behavior, increasing shear rate resulted in decreasing viscosity. Tamarind pulp extracts and tamarind seed polysaccharides were formulated to prepare tamarind powder by spray-drying technique. Tamarind powder formulation contained extracts of “Priao-Yak” and “Khantee” 15 g/L each, 1.35 g/L fructose, 0.45 g/L NaCl, 25 g/L maltodextrin, 5 g/L TSP and 0.3 g/L silicon dioxide in 1 L of DI water was prepared by spray drying. The product obtained was light yellow powder with 8.05+-0.02 %. moisture content. Tamarind powder product (10 g) was completely dispersed in 100 mL hot water in 10 minutes.