ABSTRACT
Aims: Resistant starch (RS), kinetics of starch digestion, predicted glycemic index (pGI) and nutritional composition were determined in two improved rice varieties from Cameroun. Place and Duration of Study: Department of Bioresource Engineering, McGill University, Canada between December 2012 and March 2013. Methodology: Non-parboiled and parboiled samples of TOX 3145 and NERICA-3 varieties were involved in this study. An in vitro enzymatic starch digestion method was applied to measure starch digestibility parameters. Standardized methods were adopted for proximate and mineral contents evaluation. Results: The parboiled samples had significantly higher (P<0.05) resistant starch (8.35 - 11.07%) than the non-parboiled samples (3.81 - 4.84%). The values for pGI among samples ranged from 57.57 to 67.78%. Significantly higher values for protein, phosphorus and potassium were found among the parboiled samples (P<0.05). Nutritional composition was positively related to RS while pGI had inverse relationship with protein, ash, fat, phosphorus, potassium and RS. Conclusion: Starch digestibility of these rice varieties was associated to their nutritional composition.
ABSTRACT
O arroz (Oryza sativa L.) é consumido principalmente na forma polida, porém uma alternativa nutricionalmente melhor seria o arroz integral, que contém ao redor de 10% de farelo, rico em micronutrientes e compostos bioativos. Dentre esses destacam-se a vitamina E e γ-orizanol, aos quais se atribuem diversos efeitos benéficos à saúde. A literatura descreve vários estudos relacionados à presença desses compostos no arroz integral, porém pouco se sabe a respeito da sua estabilidade com o armazenamento, a parboilização e a cocção caseira. Pelo fato do arroz integral apresentar curta vida de prateleira, uma alternativa para aumentar o prazo para o consumo é o emprego da parboilização. A parboilização, que consiste em um processo hidrotérmico, provoca alterações estruturais no amido do grão e a literatura é controversa no que diz respeito à diminuição da digestibilidade do amido e consequentemente à redução do índice glicêmico (IG). Este trabalho teve como objetivos: avaliar os efeitos da parboilização sobre a disponibilidade do amido por meio da cinética de hidrólise do amido estimando o índice glicêmico (IG) em cultivares de arroz integral com diferentes teores de amilose; analisar o efeito da parboilização, do armazenamento por seis meses e da cocção caseira do arroz integral sobre a estabilidade dos compostos bioativos, e correlacionar os compostos bioativos com a atividade antioxidante do arroz, antes e após o processamento. Foram analisadas 36 amostras pertencentes a diferentes cultivares selecionadas de arroz integral e parboilizado integral das safras de 2007 e 2008 e outras três amostras de arroz integral e parboilizado integral, adquiridas no comércio local da cidade de São Paulo. A partir do índice de hidrólise (IH) in vitro, foi estimado o IG. A vitamina E e o γ-orizanol foram extraídos com metanol, separados por CLAE-fase reversa e quantificados por curvas padrão correspondentes. A atividade antioxidante foi avaliada pelos métodos de DPPH e ORAC...
Rice (Oryza sativa L.) is consumed mostly in the milled form. However, due to its content of bran, vitamin E and γ-oryzanol, the intake of brown rice has been recommended. Although previous studies ascribed some important health benefits related to these brown rice's compounds, information regarding the effect of cooking, storage and parboiling on these substances remains to be elucidated. Rice parboiling is a hydrothermal process consisting of soaking, heating and drying that provide technological and nutritional benefits to the consumer. Until now, if parboiling process decreases the starch digestibility and consequently reduces the glycemic index (GI) is unclear. The objectives of the present study were: to evaluate the effect of the parboiling process on starch digestibility through a GI estimation by the kinetics of starch hydrolysis in rice cultivars with different levels of amylose; to analyze the effect of traditional parboiling, cooking and storage for six months on the stability of bioactive components as well as to correlate the content of bioactive components of rice with its antioxidant activity before and after parboiling. Thirty-six samples of brown rice and parboiled brown rice harvested in 2007 and 2008 were analyzed. In addition, three commercial cultivars of both brown and parboiled brown samples from local market that were obtained in São Paulo were also studied. The glycemic index (IG) was estimated from the hydrolysis index (IH). Vitamin E homologues and γ-oryzanol were extracted simultaneously with methanol and analyzed by HPLC-RP/UV and fluorescence detection in a single run. Peak areas were converted to the corresponding by the standards of α- and γ-tocopherol, α- and γ-tocotrienol and γ-oryzanol. The antioxidant capacity was evaluated by both, DPPH and ORAC methods. The results indicated that starch digestibility from all rice samples was little affected by parboiling under the conditions employed in the present study. Samples with...
Subject(s)
Starch/analysis , Food Composition , Nutritive Value , Oryza/chemistry , Antioxidants , Chromatography, Liquid , HydrolysisABSTRACT
O amido é uma importante fonte energética podendo representar mais de 60% da ingestão calórica na dieta humana. A fração do amido, que é resistente à digestão enzimática, é denominada de amido resistente. Na parboilização de arroz ocorre a retrogradação do amido, com a formação do amido resistente tipo 3 (retrogradado), que apresenta efeitos benéficos à saúde, por atuar como prébiótico. Neste estudo, três amostras de arroz com alta, média e baixa amilose foram selecionadas, com o objetivo de avaliar o efeito de arroz convencional e parboilizado na glicemia de ratos Wistar. As amostras com alta e média amilose foram encharcadas durante 6h a 65°C e a amostra com baixa amilose durante 7h a 70°C, posteriormente foram autoclavadas em pressão 0,7 kgf.cm-2 durante 10 minutos. Utilizouse 6 ratos Wistar, machos, adultos por tratamento. Foram elaboradas 7 dietas experimentais, formuladas de acordo com AIN-93M, dieta controle e, dietas com substituição da fonte de carboidratos por arroz convencional e parboilizado. Determinou-se amido resistente nas dietas e a glicemia foi monitorada por leitura de glicofita, com sangue da parte distal da cauda do rato. Para a curva glicêmica as medidas de glicemia foram feitas em jejum, e ao longo de 90 minutos. Os resultados indicam que não foram encontradas diferenças significativas entre as dietas formuladas com arroz de alta, média e baixa amilose, parboilizado ou convencional na glicemia de jejum e pós-prandial de ratos Wistar.
The effect of parboiled rice on glycemia in Wistar rats. Starch is an important energy source and can represent more than 60% of the calories of the human diet. The starch fraction resistant to enzymatic digestion is called resistant starch. When rice is parboiled, the starch retrogrades with the formation of type 3- resistant starch (retrograded), which presents beneficial effects on the health, since it acts as a prebiotic. In the present study three types of rice were selected, with high, medium and low amylose contents, with the objective of evaluating the effects of conventional and parboiled rice on glycemia in Wistar rats. The samples with high and medium amylose contents were soaked for 6 h at 65ºC, and the low amylose sample for 7 h at 70ºC. The samples were subsequently autoclaved for 10 minutes at 0.7kgf.cm-2. Six male Wistar rats were used for each treatment. Seven experimental diets were elaborated, formulated according to AIN-93M, the control diet and diets substituting the carbohydrate source with conventional or parboiled rice. Resistant starch was determined in the diets and glycemia monitored using glucose paper strips, the sample being blood obtained from the distal part of the rats tail. For the glycemic curve, glycemia was measured in the fasting state and during 90 minutes post-prandial. The results indicated there were no significant differences between the diets formulated with high, medium and low amylose, parboiled or conventionally prepared, with respect to fasting or post-prandial glycemia in Wistar rats.