RESUMO
BACKGROUND: Protein composition, amino acid profile and nutritional value of the lotus seed and its Osborne fractions were investigated. The seed was rich in protein with 19.85%, and showed well balanced amino acid composition compared with FAO/WHO pattern, Its nutritive properties were similar to those observed in the reference soybean protein. Phenylalanine, tyrosine, leucine and lysine were the limiting amino acids in the seed proteins. The albumin and globulin were the main protein fraction, the amino acid profile and nutritional value were close to the seed protein. RESULTS: Changes in transition temperature and thermal stability were observed through different solvent extractions. Albumin possessed the predominant thermal stability (81.4 °C) followed by globulin (74.49 °C), prolamin (69 °C) and glutelin (65.6 °C). So, solvent compositions influence the profile of AAs and their nutritive value, and aqueous solvent with 0.1 mol L⻹ NaCl was an efficient protein solubiliser. CONCLUSION: The results indicated that the extraction processes influenced the lotus seed protein quality and thermal stability. Overall, the study revealed that the lotus seed protein was nutritionally well-balanced protein and might be of significant importance in the formulation of diets for humans.
Assuntos
Aminoácidos/análise , Proteínas Alimentares/análise , Nelumbo/química , Proteínas de Armazenamento de Sementes/química , Sementes/química , Albuminas/análise , Albuminas/química , Albuminas/isolamento & purificação , Aminoácidos Essenciais/análise , Varredura Diferencial de Calorimetria , Fenômenos Químicos , China , Proteínas Alimentares/isolamento & purificação , Globulinas/análise , Globulinas/química , Globulinas/isolamento & purificação , Glutens/análise , Glutens/química , Glutens/isolamento & purificação , Humanos , Valor Nutritivo , Extratos Vegetais/química , Extratos Vegetais/isolamento & purificação , Prolaminas/análise , Prolaminas/química , Prolaminas/isolamento & purificação , Estabilidade Proteica , Proteínas de Armazenamento de Sementes/análise , Proteínas de Armazenamento de Sementes/isolamento & purificação , Solubilidade , Solventes/química , Temperatura de TransiçãoRESUMO
Following the sequential Osborne extraction procedure, the proteins of lotus seeds were classified. The secondary structures of albumin, globulin, prolamine and glutelin fractions were determined by Fourier transform infrared spectroscopy (FTIR). The FTIR images of amide I and III bands from the four protein fractions were analyzed using Fourier deconvolution and curve-fitting technique. The results showed that there were minor differences in every corresponding peak position and peak area percent of secondary structure between albumin and globulin as well as between prolamin and glutelin. But there were differences in every corresponding peak position between albumin (or globulin) and prolamin (or glutelin). Especially the area percents of the corresponding nonrandom structures (alpha-helix and beta-sheet) of albumin and globulin were significantly larger than those of prolamin and glutelin. The contents of nonrandom structures of albumin and globulin extracted with 0.1 mol x L(-1) NaCl solution were about 55% and those of prolamine and glutelin fractions were only at round 40%, indicating that the secondary structures of the salt-extraction protein were ordered and stable.
