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Hop (Humulus lupulus) is cultivated to harvest female flowers that lend a deep flavor, aroma, and bitter taste to beer. However, the rest of the plant is burned or land filled as agro-industrial waste. This work upcycles hop stems (HS), which contain 44% cellulose, and demonstrates their suitability as raw materials for the isolation of cellulose nanofibers (CNFs). The Wise method followed by alkaline pretreatment removed lignin and hemicellulose. 2,2,6,6-Tetramethylpiperidine-1-oxyl radical-mediated oxidation fibrillated CNFs from pretreated and non-pretreated HS. A uniform height distribution was inferred from atomic force microscopy, with a median of ∼2 nm for pretreated and non-pretreated HS-derived CNFs. Solid-state nuclear magnetic resonance and X-ray diffraction characterizations indicated that the pretreatment enhanced the purity and crystallinity of the CNFs, though traces of triacylglycerols and calcium oxalate monohydrate remained. The two CNF samples exhibited similar two-step thermal degradation at 255–260 and 300 °C, though less char residue was produced by the pretreated CNFs.

It is important to understand the structural characteristics of triacylglycerol (TAG), polysaccharides and trace elements in coffee beans, so that residues can be reutilized in applications including biodiesel oils. Here, we performed 1 H and 13 C solid-state NMR measurements on Indonesian green beans, roasted beans, and spent coffee grounds (SCGs). In the NMR spectra, there were liquid-like TAG containing linoleic acids based on observed signals of-CH=CH-CH2-CH=CH-group in an acyl chain, which play a role in decreasing TAG's melting point. We have found TAG was still abundant in the SCGs from NMR spectra. After lipids were removed from SCGs, the intensity of the TAG signal decreased considerably, with approximately 64% of the TAG was successfully extracted. We described the chemical structure of TAG in coffee beans and demonstrated that it is possible quantify the amount of extracted TAG using solid-state NMR.

Magnetic resonance imaging (MRI) relaxometry and diffusion methods were used to highlight the instability mechanisms of oil-in-water Pickering emulsions stabilized by cellulose nanofibers (CNFs). Four different Pickering emulsions using different oils (n-dodecane and olive oil) and concentrations of CNFs (0.5 and 1.0 wt %) were systematically investigated over a period of one month after emulsification. The separation into a free oil, emulsion layer, and serum layer and the distribution of flocculated/coalesced oil droplets in several hundred micrometers were captured in MR images using fast low-angle shot (FLASH) and rapid acquisition with relaxation enhancement (RARE) sequences. The components of the Pickering emulsions (e.g., free oil, emulsion layer, oil droplets, and serum layer) were observable by different voxelwise relaxation times and apparent diffusion coefficients (ADCs) and reconstructing in the apparent T 1, T 2, and ADC maps. The mean T 1, T 2, and ADC of the free oil and serum layer corresponded well with MRI results for pure oils and water, respectively. Comparing the relaxation properties and translational diffusion coefficients of pure dodecane and olive oil obtained from NMR and MRI resulted in similar T 1 and ADC but significantly different T 2 depending on the sequence used. The diffusion coefficients of olive oil measured by NMR were much slower than dodecane. The ADC of the emulsion layer for dodecane emulsions did not correlate with the viscosity of the emulsions as the CNF concentration increased, suggesting the effects of restricted diffusion of oil/water molecules due to droplet packing.