UTJECAJ TEMPERATURE SUŠENJA SJEMENKI GROŽĐA NA KVALITETU ULJA
Sažetak
Sjemenke grožđa se sve rjeđe promatraju kao otpad prilikom proizvodnje vina, a sve češće kao vrlo vrijedna sirovina u mnogim područjima i industrijama, a najčešće se upotrebljavaju za proizvodnju jestivih ulja, kao izvor nutritivno vrijednih vlakana, u farmaceutskoj industriji, za proizvodnu biogoriva itd. Njihova visoka primjena rezultat je velikog udjela mononezasićenih i polinezasićenih masnih kiselina, od kojih je najznačajnija linolna kiselina (C18: 2) s udjelom od 72 do 76 %, ovisno o sorti grožđa. Sjemenke grožđa također sadrže određenu koncentraciju visokovrijednih fenolnih spojeva, uključujući flavonoide, karotenoide, fenolne kiseline, tanine i stilbene. Glavni polifenoli identificirani u ulju sjemenki grožđa su katehin, epikatehin, trans-resveratrol i procijanidin B1. Cilj ovog rada bio je utvrditi utjecaj tri različite temperature sušenja (20, 40 i 60°C) na kvalitetu hladno prešanog ulja sjemenki grožđa dobivenih od pet različitih sorata grožđa (Pinot crni, Pinot bijeli, Muškat žuti, Cabernet sauvignon, Graševina). Ovisno o razlikama kultivara, iz sjemenki grožđa mogu se dobiti različiti prinosi ulja. Kako bi se utvrdio utjecaj temperature sušenja sjemenki grožđa na njegovu kvalitetu, svim uzorcima ulja određene su vrijednosti kiselinskog broja koji je jasan pokazatelj hidrolize, postotak slobodnih masnih kiselina te peroksidni broj čijom vrijednošću je moguće dobiti uvid u koncentraciju nastalih produkata oksidacije. Vrijednosti peroksidnog broja povećavale su se s porastom temperature sušenja u svim uzorcima. Najviša vrijednost peroksidnog broja zabilježena je kod ulja dobivenog iz sjemenki sorte Graševina neovisno o temperaturi sušenja, dok su kod sorte Muškat žuti zabilježene najniže vrijednosti. Kiselinski broj, kao i udio slobodnih masnih kiselina karakteristični su za svaku sortu i neovisni o temperaturi sušenja.
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