## 7 Emerging Research and Innovations  
### Nanocellulose Extraction from Grape Pomace  
Cellulose is a natural, biodegradable biopolymer made up of \(\beta\)-anhydro-D-glucose units. While traditionally sourced from forest wood, agro-industrial by-products like fruit peels and husks are now recognized as valuable sources of cellulose. Recycling these materials can significantly reduce the environmental impact of food waste in agricultural and industrial activities [75]. Agro-industrial wastes offer low-cost and sustainable options for nanocellulose due to their consistent availability. This approach not only helps minimize disposal pollution but also promotes economic viability [75]. The extraction of cellulose and nanocellulose typically involves several steps, including pre-treatment, purification, acid hydrolysis of amorphous regions, and mechanical treatment to achieve nanoscale sizes. Acid hydrolysis and mechanical methods are widely used in industrial recovery [75]. Extraction techniques range from conventional methods with toxic chemicals like sodium hydroxide and sulfuric acid to newer approaches that aim for higher purity cellulose. Pre-treatment steps, such as hot water washing, are essential for quality recovery but are often neglected in reports [75]. The physico-chemical properties of nanocellulose from different sources need to be characterized. Nanocellulose exhibits enhanced properties compared to micro- and macrocellulose, including an improved fiber-matrix interface and good dispersion in matrices. Nanocellulose suspensions are transparent due to their smaller and homogeneous fiber size. Important properties evaluated include the crystallinity index and thermal stability. Techniques such as X-ray diffraction (XRD), \({}^{13}\)C nuclear magnetic resonance (NMR) spectroscopy, and infrared (IR) spectroscopy are used to assess crystallinity, with XRD being the most commonly employed method. Recovered nanocellulose typically exhibits an increase in crystallinity index and a higher thermal decomposition temperature compared to the raw source material [75]. Nanocellulose's abundance, non-toxic nature, mechanical properties, and biodegradability make it attractive for various applications. Some of the applications are summarized in Table 6. Nanocellulose applications. Adapted from [75]. Extensive grape pomace produced from red wine-making can seriously pollute the environment and represents a waste of resources. Although active constituents, such as polyphenols or vitamins, are sometimes extracted, much of the grape pomace, rich in cellulose, is often treated as waste [76]. An eco-friendly method for extracting Cellulose Nanocrystals (CNCs) from grape pomace can be achieved using a simple and environmentally friendly deep eutectic solvent (DES). The green DES used had a composition of lactic acid and choline chloride in a 2:1 molar ratio. The extraction process involved pretreating crushed grape pomace to remove impurities, lignin, and hemicellulose, resulting in cellulose. This cellulose is then hydrolyzed using the DES. A key advantage of DES is its eco-friendliness and ease of preparation. The components of the DES (lactic acid and choline chloride) and ethyl acetate used for separation can be recycled, offering a sustainable and straightforward preparation method [77]. The extracted CNCs successfully obtained are rod-like crystals with an average length of 241.5 \(\pm\) 45.3 nm and a diameter of 22.0 \(\pm\) 3.9 nm. They show higher crystallinity (95.2%) than the original cellulose (89.6%), indicating the successful removal of amorphous regions. FT-IR and electric conductivity titration confirmed the presence of carboxylic acid groups (0.63 mmol/g) on the CNC surface, resulting from