Optimization of ultrasound assisted extraction of polysaccharides from plant waste material

In this study, effects of ultrasound on extraction of polysaccharide were evaluated theoretically and experimentally. Effects of parameters of ultrasound assisted extraction system on end product and system components were investigated in the scope of this study. For extractions, probe type high power ultrasound was used, and selected material, which is appeared after roasting process as a waste, was skin of hazelnut. Hazelnut is high in traditional value and highly produced in our country. Extractions were applied to the pretreated hazelnut skins and distilled water was selected as a solvent. Extracts obtained from hazelnut skin, which is one of heat treated waste, were characterized to investigate the effects of sonication on extracts. Additionally best fitted mass transfer kinetic model parameters and heat transfer model were determined in this study. Statistical modelling was carried out by using Response Surface Methodology (RSM). For this purpose both of the designs called Box Behnken Design (BBD) and central Composite Design (CCD) were applied. While experimental designs were evaluated by running Design Expert software, other calculations such as curve fitting practices and mathematical model assessment processes were implemented by using MATLAB software. Selected model parameters were temperature, time and amplitude for ultrasound assisted extraction and corresponding responses were extract yield, carbohydrate content, average molecular weight and total energy requirement for applied processes. As a consequence, it was presented that there were no adverse chemical effect for selected levels of sonication parameters on extracted material. Although physical changes were observed at the end of applications, these effects were on positive side for extracts. Influence of sonication on heat transfer rate in reactor, particle velocity and mass transfer parameters were investigated. It was found that there is an important relation between mass transfer parameters and particle velocity. Average molecular weight of extracts and their thermal stabilities have positive correlation with each other. Each of two optimization procedures gave similar results and obtained values resemble experimental results that were obtained from evaluated levels for validation. On the other hand, while having high desirability and smallest deviation (1%), optimum condition obtained by BBD (28.7 min, 31.5oC, 69.1% amplitude) is the most successful one for the polysaccharide yield maximization.