The oven drying method for determination of the moisture content of rice and soybean seeds

O presente trabalho teve como objetivos: a) comparar o m??todo oficial de determina????o do grau de umidade de sementes de arroz e soja utilizados no Brasil (Estufa a 105??C/24 horas) com o m??todo de refer??ncia Estufa a 103??C/17 horas, adotado pela ISTA, e b) verificar a possibilidade de determina????o do grau de umidade das sementes de arroz e soja em tempo inferior a 24 horas. Estudo pr??vio foi realizado para verificar a influ??ncia da posi????o da amostra na estufa com a finalidade de reduzir a varia????o na determina????o do grau de umidade das sementes analisadas. Foram utilizadas sementes de arroz e de soja, com graus de umidade obtidos pelo m??todo de Estufa a 105??C/24 horas de 9,0%; 17,6% e 7,5%;16,8%, respectivamente. Foram determinados os graus de umidade das sementes inteiras de arroz e soja, em estufa do tipo mec??nico de ar for??ado, submetidas ??s temperaturas de 70, 103, 105 e 130??C por um per??odo de 1, 3, 5, 7, 17, 24, 48, 72 e 96 horas, para cada uma das temperaturas utilizadas. Foram utilizadas sementes mo??das, segundo crit??rios da ISTA, para a determina????o do teor de ??gua pelo m??todo de refer??ncia (Estufa a 103??C/17 horas), e para a determina????o do grau de umidade pelo m??todo alternativo para sementes de arroz Estufa a 130??C por 2 horas. O m??todo de Estufa a 105??C/24h subestima o teor de ??gua das sementes de arroz e soja com grau de umidade inferior a 10% e superestima o teor de ??gua das sementes quando for igual ou superior a 17,6%. ?? poss??vel determinar o teor de ??gua das sementes de soja em tempo inferior a 24 horas, utilizando sementes inteiras e temperatura de 130??C, dependendo do teor de ??gua das sementes.The aim of this work was to a) compare the standard official methodology in Brazil for the determination of the moisture content of rice and soybean seeds (i.e. oven dried at 105??C for 24 hours) to the ISTA standard method (103??C for 17 hours), and b) test the possibility to determine whether the moisture content (MC) of rice and soybean seeds can be accurately estimated drying for a period shorter than 24h. Previously, a study was performed to establish the influence of the sample position within the oven, aimed to reduce the variation of the results on MC among different seed samples. The rice and soybean seeds tested in the experiment showed MC as determined by oven drying at 105??C/24h of 9.0%; 17.6% and 7.5%; 16.8%, respectively. The MC of whole rice and soybean seeds was estimated through oven drying at temperatures of 70, 103, 105 e 130??C for periods of 1, 3, 5, 7, 17, 24, 48, 72 and 96 hours for each level of temperature. Following ISTA standards, ground seeds were employed to determine their MC through the standard procedure (oven dried at 103??C/17h), whereas for the alternative procedure rice seeds were oven dried at 130??C for two hours. It was concluded that drying at 105??C/24h either underestimate the MC of rice and soybean seeds, when the MC was under 10% and overestimate when was equal or superior of 17,6%. It is possible to estimate its value in whole soybean seeds by drying them at 130??C for less than 24h depending of the seeds MC