This study investigated the amino acid composition of eight local and three imported rice varieties frequently consumed by consumers in the capital of Sri Lanka. Investigation included twenty free amino acids (FAAs) analysed using liquid chromatography-tandem mass spectrometry (LC-MS/MS) and sixteen protein bound amino acids analysed using high performance liquid chromatography with diode array detection (HPLC-DAD). The mean total amino acid (TAA) in rice ranged between 64.5 ± 1.9 g/kg and 96.0 ± 5.1 g/kg on dry basis (db). Ponni, Basmathi, Rathu Nadu and Fragrant rice which were parboiled varieties, reported the overall highest mean TAA contents while imported Ponni and Basmathi exhibited the highest mean essential amino acid (EAA) contents depicting high quality protein. Red rice varieties of Nadu, Kekulu and Kekulu Samba reported signifi cantly (p < 0.05) higher mean TAA contents than their white counterpart varieties. The parboiled varieties; Rathu Nadu, Sudu Nadu, Keeri Samba and Samba reported the overall highest gamma amino butyric acid (GABA) contents (0.9 ± 0.3-5.0 ± 1.7 mg/100g). Completely polished Sudu Kekulu reported the overall lowest mean TAA, EAA and GABA contents. Except for unanalysed tryptophan, fi ndings revealed that disregarding the nutritional loss encountered during cooking irrespective of variety, consumption of approximately 100 g of raw rice (after cooking) three times a day will provide an average adult (of 50 kg body weight) more than 50 % of the daily intake of essential individual amino acids recommended by the Food and Agricultural Organization (FAO).

Adaptable to any routine laboratory, the study presents the validation results of a simple, accurate and reliable method developed for the analysis of total amino acids (TAAs) in rice using reversed-phase high-performance liquid chromatography-diode array detection (RP-HPLC-DAD). Exhibiting excellent selectivity with resolution (Rs) ≥ 2 for seventeen amino acids, the method was proven accurate against the analysis performed on the certified reference material (CRM): NIST 3233. Percentages of recoveries were in the range 86%-100% with percentage relative standard deviation (%RSD) ≤ 6% for all amino acids. Limit of detection (LOD) and limit of quantification (LOQ) values were within 0.024-0.069 g/100 g and 0.025-0.078 g/100 g respectively. A wide working range with satisfactory linearity having regression coefficients ≥ 0.999 were reported for all the amino acids. Complying with international guideline requirements, this validated method can be successfully applied for the determination of seventeen TAAs including all essential amino acids in rice.