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Chemistry of Alcoholic Fermentation: Grape Harvest at IPAA

The students and teachers of IPAA Institute for Agriculture and Environment conducted a grape harvest on October 5th, 2016. After weeks of study and preparation, they were able to create their own hand-made wine, showcasing their knowledge of the chemistry behind alcoholic fermentation. This article traces the history of fermented drinks and explores the chemical process of fermentation. The students' hard work and dedication culminate in the joy of tasting the final product.

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Chemistry of Alcoholic Fermentation: Grape Harvest at IPAA

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  1. ERASMUS PLUS 2015-2017IIS LS Piccolo of Capo d’Orlando IIS Complex of IPAA Institute for Agriculture and Environment

  2. CHEMISTRY OF ALCOHOLIC FERMENTATION «October 5th 2016 GRAPE HARVEST AT IPAA»

  3. The students and the chemistry teachers of IPAA realised the «GrapeHarvest», on the 5th of October 2016. After weeks of study, preparation, theory and practice, finally the best fermentedproduct which the School isreallyproud of: hand made wine. The studentswerecarefullyprepared both in the rooms and «in the field», with a patient work of historical, chemicaland practical training. Allstarted with a brief shift in time……. …to discover the origins of a very special fermented drink…

  4. From the earliesttimes, fermenteddrinkshadalwaysbeenknown. Theyweresugarydrinksslowlytransformedintoinebriatingbeverages with gas bubbles. The Babylonianpeoples used to likebeer produced from barleyfermentation, Butcenturiesbefore, one of the mostknowndrinks was«Mead», obtained from the fermentation of water and honey.

  5. Information aboutwinetraced back to the Assyriantimes (about 3500 BC) and, from then on, wine spread throughout the wholeMediterraneanterritories. The transformation of sugarybeveragesinto alcoholicdrinks, and in particular, of the grape must intowine, wascalledfermentation ( from Latin fervere = to boil). The phenomenonattracetd the attention of Chemists, naturalists and alchemists in the Middle Ages And through the Still , first used by the Arabs in the II BC, itwaspossible to separate alcohol from wine.

  6. Onlythanks to the discovery of the magnifyingglass, scholarsstarted to analise the mystery of fermentation. In 1685 Antoni Van Leeuwenhoek managed to seemovingcorpuscles in the grape must through 150 diametermagnification of his compound microscope.

  7. In 1789 Lavoisierprovedthat sugar wastransformedintoalcohol duringalcoholfermentation. And in 1813 Gay-Lussac establishedthe processthrough the equation C6H12 O6 2C2 H5 OH + 2CO2 2C 2 Other information aboutalcoholfermentation werediffused in the XIX thcentury by the French Caignard-Latour (left) and the GermanSchwan (right) whobothlabelled the fermantation agent by the name of yeastcell, and lateryeast, from Latin levare = to ferment.

  8. Thisdiscoverytook the name of «VitalistTheory» of fermentation, verysoonfought by the mostfamouschemists of the time, asBerselius, whoopposedtheir«ChemicalTheory». According to the chemists, the transformation of sugar and alcohol in alcohol and carbon dioxidewas a chemicalreaction due to the moleculardisturbancecaused by microorganisms in decomposition. In 1858 the Vitalisttheoryhad a supporter in Luigi Pasteur whoprovedthat for eachkind of fermentationthereis a particularmicroorganism whichrapidlyreproduces in presence of oxigen (aerobiosis) and whichfeeds on sugar by transformingitinto water and carbon dioxide. On the contrary, in absence of oxigen ( anaerobiosis ), such a microorganism reproducesverylittle and sugar istransformedintoalcohol and carbon dioxide.

  9. In 1896, the BuchnerBrothersdiscovered a substance capable of fermentingsugarswithout the presence of yeasts. Itwascalledthe enzyme of the alcoholicyeasts, betterdefinedasalcoholiczimasis. Suchyeastessencesinvolved in the fermentation couldefficiently operate eveniftheywereremoved from theiroriginalcellularsites. At thispoint, the VitalistTheory (the yeastthatfeedsitself, reproduces and dies) and the ChemicalTheory (an enzymethattransforms the sugar moleculeintoalcohol and carbon dioxide) bothfindtheirexplanation. And the perfectresult of allthisis the alcoholicfermentation of grape must intowine!

  10. So after a long and patient season cycle of labour and sacrifices…

  11. time has come toreap the rewards of the students’ efforts. So they can feel the joy of theirownendeavour in the foodproducts comingfrom nature.

  12. The graperipeningisverified, with the perfect balance of all the components decreasing of acidity, increasing of sugarylevel, enriching of aromaticcomponents, softening of polyphenols – responsible of the redwine’stannicfeature –

  13. Nowstudents and teachers can proceed with the harvest and grapes are pickedmanually

  14. All the pickedgrapes are taken to the millstone

  15. Theycheck the sugarydegree of the grapes with a specifictool, the «Babo» must gauge in order to establish the probable future alcoholiclevel

  16. Thenthere come the treading maceration and pressing of the marcs

  17. At present, the must isiskept in specific containers for the fermentation, untilsugars are transformedinto alcool, thanksto yeasts (saccharomycetes). From 100 grams of sugar, in idealconditions of fermentation, 70 grams of ethylalcoholshould be obtained, according to the followingequation C6 H12 O6 2 CH3 – CH2OH + 2CO2

  18. Here is the teacher in the lab, whiletrying to determine the realsourness or PH of the wine of ourproduction by Amola Firmwith a «Pot-Potentiometer» method.

  19. Allisnaturalharmony: Studying, practicing, working, sweating, learning, joying, living! Waiting for the finalresults… In Nature, with Nature and for Nature. Activitiesrealisedbu the students of IPAA, IIS LS Piccolo Capo d’Orlando Informative material by Teachers Anita PaparoneGiuseppe Ricciardi and Antonino Carcione Power Point and English versionrealised by TeacherAglio Valentina

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