Grape (Vitis vinifera L.) marc has long been utilized as a compost feedstock. However, this process takes an extended period of time due to the phytotoxic chemical composition of the marc. Removal of these compounds presents an opportunity to utilize the grape marc as a growing medium. Following a water-based extraction procedure to remove polyphenolic compounds of interest, analysis of the depleted marc showed a decrease in the content of these compounds, and in nutrient and trace element levels. Carrot (Daucus carota L.) and corn (Zea mays L.) seedling emergence in the depleted marc and blends with compost were not adversely affected, demonstrating its effectiveness for growing plants at all ratios. A 50:50 blend of compost and depleted grape marc resulted in plant growth equivalent to the compost alone. This combined with the observed water holding capacity suggests that depleted grape marc, when blended with compost, can be a suitable alternative to peat or coconut coir for seedlings.

Intermolecular interactions and molecular dynamics in thin films of highdensity polyethylene (HDPE) containing a high loading of Grape Marc Extract (GME) were analyzed by solid-state NMR. Optical microscopy (OM), Scanning Electron Microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) studies were used to corroborate the findings. The OM and SEM images and 1 H-13 C RAMP CP/MAS (ramped amplitude cross-polarization/magic-angle spinning) spectra of HDPE, HDPE-GME, and GME confirmed the incorporation of the GME into the HDPE structure. The results were compared to those for an unfilled HDPE film. The influence of GME on enhancing the amorphous nature of HDPE, altering the crystalline melting behavior and possible intermolecular interactions were evident from the DSC and FTIR. The NMR spin-diffusion and T 1 (1 H), T 2 (1 H), T 1ρ *(13 C), T 1ρ (1 H) relaxation and variable contact time experiments revealed the interactions and dynamics at the sub-micron level.

Food spoilage is a major global concern, and solutions involving green active packaging are being actively sought. Grape marc is a by-product of the wine industry, and is rich in tannins with antioxidant and antimicrobial activity. For use in melt blending with plastics such as polyethylene, the impact of heating a grape tannin extract to 150°C was evaluated. While there was a loss in total phenolic content after heating, this did not lead to a loss in functionality. There was an improvement in antioxidant activity from 65.3 ± 0.6% to 70.8 ± 1.3% DPPH radicals scavenged, and a significant improvement in antimicrobial activity. Against E. coli, the activity improved by 35%, while against S. aureus there was improvement of 60%. FT-IR analysis showed no degradation of the extract when heated to 150°C, other than some disruption of hydrogen bonds within the condensed tannin network.