Danila Amendola

Autohydrolysis and organosolv process for recovery of hemicelluloses, phenolic compounds and lignin from grape stalks.

A combination of two environment-friend processes for hemicelluloses and lignin recovery from red grape stalks were investigated: an autohydrolysis pretreatment at 180°C for 30 min followed by a non-catalysed ethanol organosolv step at 180°C for 90 min. Hemicelluloses were precipitated by ethanol addition to autohydrolysis liquor, while lignin was tentatively precipitated by acidification of liquors from both the processes. Results suggest that stalks hemicelluloses can be easily hydrolysed requiring a milder treatment to reduce sugar degradation, while the organosolv process did not give a consistent delignification. Autohydrolysis allowed a recovery of 2% (on stalks d.m.) of total phenols in the liquor. Organosolv liquor had a higher concentration of phenols (corresponding to 0.72% of stalks d.m.) which almost completely precipitated with lignin.

Microwave-Assisted Extraction of Phenolic Compounds from Dried Waste Grape Skins

Abstract Microwave-assisted extraction (MAE) was investigated for recovering of total phenolic compounds from dried waste grape skins using a domestic microwave oven. Influence of vessel geometry, irradiation cycles, irradiation power and time was investigated. The results in terms of phenolics yield, antioxidant capacity and energy consumption were compared with a reference solid–liquid extraction (SLE) carried out for 2 h at 60°C. Equivalent yield of total phenolics as in SLE was achieved with a MAE extraction time of 1,033 sec (corresponding to 83 sec of irradiation at 900 W, 83% saving in extraction time compared to SLE and with a 70% energetic efficiency). Pre-maceration of samples and solvent pre-heating are proposed for large-scale industrial processes to enhance phenolics extraction and process efficiency.

Screening of four different agro-food by-products for the recovery of antioxidants and cellulose

Carried out under the European Project SusFoFlex, this study aimed the investigation and selection of different agro-food by-products for the recovery of antioxidants and cellulose to be further exploited for application in the development of innovative and sustainable food packaging materials. Based on literature data and partners’ countries availability, four by-products were considered: brewers’ spent grains, wheat straw, hazelnut shells and orange peels. A common process for the production of antioxidant extracts (a two-step hydro alcoholic solvent extraction) and another for the fractionation of cellulose (an acid hydrolysis step followed by an alkali hydrolysis and, then, an oxidative bleaching step) was applied to all the materials with the objective of selecting ideally a unique by-product for the production of both antioxidants and cellulose. The extracts were characterised in terms of total phenols content (based on Folin assay and expressed as gallic acid equivalents) and antioxidant activity (evaluated with both the radical ABTS test and the Ferric Reducing/Antioxidant Power assay).The highest total phenols recovery was obtained for orange peels (9.50±0.66 mg per g of dried by-product), while the yields for the other byproducts were not statistically different and < 2 mg/g. Regarding the antioxidant activity, all the extracts showed very similar results with the ABTS assay, whereas orange peels extract exhibited the highest level of FRAP activity. The obtained cellulose residues were analysed for the total cellulose content and the level of lignin and hemicellulose impurities. In this case, the best by-product resulted wheat straw, with the recovery of 45 % of the original cellulose, a cellulose content (purity) of 84 % and residual impurities of hemicelluloses and lignin of 2 % and 12 %, respectively.