Modeling of the oxidative stability alterations and some selected chemical properties of black Cumin seeds’ oil influenced by microwave pretreatment and screw rotational speed

Abstract

Black Cumin seed (Nigella sativa L.) as one of the novel edible oil resources used commonly these days for seasoning in food product industries and with considerable medicinal properties and high nutritional impacts has been noticed. Oil extraction by pressing method as an approach compared to other methods including solvent extraction is more faster, safer and cheaper. In the oil extraction process, the preparation of the seeds is a substantial stage for obtaining oil with high quality and efficiency. Microwaves are electromagnetic waves that have a frequency ranged from 300 MHz to 300 GHz with corresponding wave lengths ranged from 1 mm to 1 m.On the other hand the artificial neural network as a powerful predictive tool ina wide scale of process parameters has been studied on an industrial scale in this research in order to achieve a simple, rapid, precise as well as effective model in the oil extraction of Nigella sativa L. Materials and methods: In the present study Black Cumin seed after preparation including cleaning and passing resistant test against air and moisture penetration have been shifted and preserved in a plastic bag until the experiments. Then, they have been pre-treated with microwave within different processing times (90, 180 and 270 S) and powers (180, 540, and 900 W). Afterwards, seeds’ oil have been extracted by screw rotational speed levels approach (11, 34 and 57 rpm), then different selected parameters including extraction efficiency, oil acidity value, colour and oxidative stability have been detected. To predict the alterations trend, the artificial neural network (ANN) design in MATLAB R2013a software has been used. Results and Discussion: According to MSE and R2 values presented in these tables, feed forward neural network with transfer function sigmoid hyperbolic tangent and Levenberg- Marquardt learning algorithm with topology of 3-10-5 (input layer with 3 neurons– a hidden layer with 10 neurons – output layer with 5 neurons) were selected as the optimal neural network with R2 more than 0.995 and MSE equal to 0.0005. Also, the results of the optimized and selected models were evaluated and these models with high correlation coefficients (over 0.949), were able to predict the changes' trend. According to the complexity and multiplicity of the effective factors in food industry processes and the results of this research, the neural network can be introduced as an acceptable model for modeling these processes. By determined the activation function in neural networks which was a function of sigmoid hyperbolic tangent in this study and also, with having the amounts of weight and bias, the connections created by the neuro-fuzzy model can be extracted. By defining this simple created mathematical equation, in a computer software such as Excel, we can have a useful, simple and accurate program for predicting the desired parameters in the process of oil extraction by using microwave pre-treatment. Due to high accuracy of neural model we can trust the prediction of these models with high confidence, and this model can be used to optimize and control the process, which can lead to saving in energy and time, and on the other hand, can create a better final product.