## 1 Introduction  
Inulin is a kind of mixture consisting of oligosaccharidesadides and polysaccharides. Inulin structure can be divided into two types: (1) mainly \(\mathrm{F_{n}}\) type, which consists of \(\beta(2\!\to\!1)\) fructosyl-fructose links [1]; and (2) eventually \(\mathrm{GF_{n}}\) type with a glucose unit at the end of fructan chain [2]. Although inulin exists in several plants, such as garlic, onion, asparagus leeks, and banana, the ideal raw materials for industrial inulin production are mainly chicory root and _Jerusalem artichoke_ root [3; 4]. Nowadays, inulin has attracted more and more attention from both food industry and researchers due to its unique functional properties as a natural resource. In food industry, inulin has been widely used for production of healthier products based on its potential as fat replacer since it has similar technological functions and sensory characteristics compared to animal fat or oil [5; 6]. Moreover, inulin with high degree of polymerization (DP) can be used as texture modifier, due to its lower solubility and enhanced viscosity [7; 8]. Apart from food applications, inulin has been recently investigated to produce biofuels, thus having the potential for saving non-renewable fossil fuels. For example, inulin can be hydrolyzed by exo-inulinase, thus removing the terminal fructose residues from the non-reducing end of the inulin molecule and producing fructose and glucose, which can be easily converted into ethanol by _S. cerevisiae_[9]. Due to its wide applications and important functions, both inulin extraction and quantification are essential for inulin-rich plants valorization and its functional properties investigation. Among various extraction intensification methods, ultrasound assisted extraction (UAE) has been reported as an efficient tool to recover valuable compounds from plants, mainly due to the cavitational effect generated by the ultrasonic waves [10; 11; 12]. Previous studies showed that UAE effectively enhanced polysaccharide, polyphenol and pigments extraction from plant food matrices, wastes and by-products [10; 11; 12]. Since inulin is a mixture of molecules with different DP, no single method provides a complete and quantitative analysis of all its forming compounds. Normally, inulin content determination requires a first step of hydrolyzing inulin long chains to fructose and glucose by chemical and enzymatical methods, followed by fructose and glucose analysis [4; 13; 14]. From a literature review, it was observed that several techniques are available for the analysis of inulin. For instance, enzyme-assisted hydrolysis of inulin, for quantification, is one of the most commonly used methods. In this line, [PERSON] et al. [15] determined inulin content extracted from _Jerusalem artichoke_ by using Megagzyme fructan assay kit, according to AOAC Method 999.03 and AACC-32.32. Inulin was mainly hydrolyzed to d-fructose and d-glucose with a mixture of highly purified endo- and exo-inulines. Then, d-fructose and d-glucose were measured with a \(p\)-hydroxybenzoic acid hydrazide (PAHBAH) method. [PERSON] et al. [16] applied inulininase and novozyme to hydrolyze inulin from chicory for its quantification. From these studies, it was concluded that enzyme-assisted hydrolysis techniques present some important benefits as they are not time consuming and can be used under mild reaction conditions. However, the main drawback is their high cost. On the other hand, other several methods consisting of the hydrolysis of inulin using chemical reagents have also been widely used. [PERSON] et al. [4] determined inulin content by evaluating the difference between total carbohydrates and reducing sugars. Total carbohydrates were determined using the phenol-sulfuric acid method [17], and the reducing sugars were determined by the dinitrosalicylic acid method [18]. This method was applied by several researchers to quantify inulin in chicory [19] and _Jerusalem artichoke_[20] extracts, due to its easy operation and the use of economic reagents.