Faculty of Food Technology and Biotechnology, University of Zagreb
Abstract
In order to measure the potential of apple pomace as a raw material for manufacturing food-related products (such as lactic acid, fiber-rich concentrates and pectin), samples from cider industry were assayed for composition and enzymatic digestibility. Alcohol-soluble compounds (monosaccharides, oligosaccharides and malic acid) accounted for 32–45 mass percent of oven-dry pomace. Glucose and fructose were the major components of this fraction. The alcohol-insoluble fraction accounted for 55–68 mass percent of oven-dry pomace and was mainly made up of neutral detergent fiber (62–69 percent of the mass fraction) and pectin (16.2–19.7 percent of the mass fraction). The feedstock content of N, P and metal ions (K, Mg, Fe and Mn) was favourable for further manufacture of lactic acid fermentation media. Apple pomace showed a high susceptibility to enzymatic hydrolysis: in media with a cellulase loading of 8.5 FPU/g of apple pomace and a cellobiase loading of 5 IU/FPU, about 80 % of the total glucan was converted into glucose after 15 h. Considering the low enzyme charge, liquor to solid ratio employed, reaction time needed to achieve the maximal sugars concentration and N, P and metal ion (K, Mg, Fe and Mn) content of samples, it can be concluded that apple pomace is a promising raw material for lactic acid production.Ispitani su sastav i enzimska razgradnja jabučnih otpadaka iz industrijske proizvodnje jabukovače radi mogućnosti njihove primjene u proizvodnji (mliječne kiseline, koncentrata bogatih vlaknima i pektina). Nakon sušenja otpadaka u pećnici, maseni je udio sastojaka topljivih u alkoholu (monosaharidi, oligosaharidi i jabučna kiselina) iznosio 32-45 %, od čega je najviše bilo glukoze i fruktoze. Ostatak od 55 do 68 % čine tvari netopljive u alkoholu, uglavnom neutralna detergentska vlakna (62-69 % masenog udjela) i pektin (16,2-19,7 % masenog udjela). Udio dušika, fosfora i iona metala (K, Mg, Fe i Mn) u sirovini povoljan je za daljnju fermentaciju mliječne kiseline. Jabučni se otpaci iznimno dobro razgrađuju enzimskom hidrolizom. U podlogama s 8,5 FPU celulaze po g jabučnih otpadaka i 5 IU/FPU celobiaze, od 80 % ukupnoga glukana nakon 15 sati dobiva se glukoza. Ako se uzme u obzir mala količina enzima, omjer tekuće i čvrste faze, vrijeme reakcije potrebno da bi se postigla maksimalna koncentracija šećera te udio dušika, fosfora i iona metala (K, Mg, Fe i Mn) u uzorcima, može se zaključiti da su jabučni otpaci prikladna sirovina za proizvodnju mliječne kiseline
