## 3 Results and Discussion
### CNC and LNP Characterization
Cellulose II is the most stable, while cellulose I is known to occur as a mixture of a triclinic I\(\alpha\) and monoclinic I\(\beta\) crystalline forms, being the I\(\beta\) prevalent in higher plants. Cellulose II can form upon treatment of cellulose I with strong bases or by its solubilization and precipitation [80]. Therefore, the presence of a certain amount of form II in HP CNC, compared to the 100% of I\(\beta\) crystalline form of HS CNC, may be the result of the extraction conditions employed, which may have favored the I\(\beta\) to II transition, even though different initial crystalline compositions between the two source materials cannot be ruled out. Moreover, because crystallinity index of both HP and HS CNC is nearly identical, the two extracts had a rather consistent calculated amorphous content of about 30% (Table 1). The obtained LNP were first observed by TEM. The negative staining process revealed an imperfectly spherical form for each LNP extraction step, with inconstant dimensions ranging from 50 to 200 nm (Figure 7). Microscopic observations also highlighted the presence of impurities and other substances that could play a role in promoting LNP aggregation when suspended after some time. Figure 6: X-ray powder diffraction profiles of CNC extracted from HP (**a**) and HS (**b**), in which the contributions of I\(\beta\) (green) and II (cyan) cellulose phases are shown. The amorphous contribution is also displayed (black line). The experimental profile is in red, the calculated one in blue, and the residual is shown at the bottom (pink). Extracts were freeze-dried and directly analyzed. While CNC from HS show patterns typical of a dominant I\(\beta\) crystalline phase, CNC from HP is a mixture of I\(\beta\) and II phases (see Table 1). As a confirmation, LNPs were also characterized in terms of size distribution by DLS. In general, LNPs were only partially colloidal due to a strong tendency to aggregate into large clusters. This is evident from the distributions in Figure 8, where in all cases aggregation produced micrometric populations and only LNP F from HP and LNP 100 from HS displayed nanosized populations. Such behavior seems uncorrelated with the production process itself, but it could rather be the result of the intrinsic instability of lignin particles that were not added with proper stabilizers or preservatives. Regarding the TPC of synthesized LNP, the Folin-Ciocalteu method revealed the following highly statistically significant (\(p\) < 0.01) results: 173, 102.6 and 162.8 GAE for the LNP, coming, respectively, from the first, the second and the final extraction step of  
Figure 8: Size distributions obtained by light scattering analysis of LPNs extracted from (**a**) HP and (**b**) HS using the three methods described. HP extracts show slightly higher colloidal populations than HS extracts. HS extracts show a higher degree of aggregated populations. Figure 7: TEM observation of different fractions of extracted LNP: (**A**) HP LNP 100; (**B**) HP LNP 70; (**C**) HP LNP F; (**D**) HS LNP 100; (**E**) HS LNP 70; and (**F**) HS LNP F.  
HP lignin, while LNP 100, LNP 70 and LNP F obtained from HS showed, respectively, 37.2, 33.5 and 114.3 GAE (Figure 9). The reported trend in TPC values for HP LNP is not linear with the extraction process: the most relevant TPC was noted in the first and in the third step. This behavior could be due to the complex composition of lignin, which is constantly rearranged and shaped by the different chemical and physical treatments. On the contrary, HS LNP showed a growing TPC: in fact, the LNP produced by the last extraction step had a higher content in polyphenols. Unlike the pruning residues, hazelnut shells present a much more complex structure, due to the high presence of waves and other lipid components [75; 76]. Such components, as it was assumed for CNC extraction, could play an important role in hampering the access of chemical reagents to the lignin fraction.