Grapes are one of the largest fruit crops in the world, while their processing into juice is definitely a minor reality compared to wine-making. In 2013 the world wine production was 27.42 Mton, with 57 % of production in Europe, followed by Americas (25.7 %), Asia (7.5 %), Oceania (5.4 %) and Africa (4.5 %). The top five wine producers resulted France (4.29 Mton), Italy (4.11 Mton), Spain (3.20 Mton), USA (3.22 Mton) and Chile (1.83 Mton).
Either for wine or juice production, grapes processing generates huge amount of residues. At the primary production level, vine shoots (or vine prunings or trimmings) derive from in-field interventions for both the productions, even though different cultivation systems may lead to different amounts of shoots.
At the processing level, also the destemming step is carried out for both juice and wine line, with generation of a second residue: the grape stalks, often referred to as stems. At this point, the grape juice is extracted through pressing and the residue grape marc (often referred to as grape pomace) is obtained.
In the case of grape juice and white wines (with a few exceptions), grape marc is immediately discarded. In the case of red wines (and for some white wines), grape marc is not promptly removed but left with juice (from this point called must in the wine-making process) for a certain fraction of the fermentation period, in order to enhance the extraction of grape constituents (mainly phenolic compounds and pigments).
After this maceration step, grape marc can be taken away from the must, pressed and discarded. After completion of fermentation, the lees are removed (generally by decanting) and the following steps (the whole or only some, depending on the wine type) are carried out: second fermentation (for sparkling wines), ageing (in stainless tank or wooden barrels), clarification, filtration, cold stabilisation (detartration) and bottling. Additional residues are generated from the filtration and stabilisation steps, which are carried out also in the grape juice manufacturing.
Read full article here.
Handbook of Grape Processing By-Products: Sustainable Solutions covers the most recent advances of grape processing by-products management in the name of sustainability. It fills the gap of transfer knowledge between academia and industry by providing a reference for all the wine makers, professionals and producers activated in the field, trying to optimize wineries performance and reduce their environmental impact.