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Svrha je ovoga rada bila ispitati utjecaj dodatka prehrambenih vlakana iz različitih izvora (jabuka, bambus, indijski trputac i pšenica) i pektina masenog udjela 0,4 ili 0,5 g/100 g na fizikalno-kemijska svojstva pektinskih gelova za razvoj novog, zdravog proizvoda sličnog džemu. Da bi se konačni proizvod mogao deklarirati kao izvor vlakana, svakom pektinskom gelu dodano je 3 g/100 g vlakana. Udjel pektina, tip vlakna i njihova interakcija bitno su utjecali na viskoelastična i mehanička svojstva te sinerezu (gubitak vode) gelova. Sinereza gela s 0,4 g/100 g pektina bila je neprihvatljivo visoka, pa su daljnja ispitivanja provedena samo na gelovima s 0,5 g/100 g pektina. Dodatak vlakana poboljšao je viskoelastičnost gelova (pšenica>indijski trputac>bambus>jabuka). Kod gelova obogaćenih s indijskim trputcem nije došlo do sinereze, no imali su nepoželjna svojstva gumenosti, kao posljedicu male lomljivosti i čvrstoće te velike kohezivnosti. Zatim smo radi poboljšanja organoleptičkih svojstava gelova kombinirali izvore vlakana u omjeru 1:1. Kombinacija vlakana uglavnom je smanjila viskoelastična svojstva gelova. Međutim, miješanjem indijskog trputca s drugim vlaknima poboljšana su mehanička svojstva gelova, kod kojih je sinereza bila 0 g/100 g, što pokazuje da je najbolja formulacija za optimalnu stabilnost i čvrstoću proizvoda 0,5 g/100 g pektina, 1,5 g/100 g indijskog trputca i 1,5 g/100 g drugog izvora vlakana., The objective of this work is to evaluate the effect of the addition of dietary fibre from different sources (apple, bamboo, psyllium and wheat) and pectin mass fraction (0.4 and 0.5 g/100 g) on the physicochemical properties of pectin gels for the development of a novel, healthy product similar to a fruit confectionery jam. A mass fraction of 3 g/100 g fibre was added to each pectin gel in order to declare the final product as a source of fibre. It was evident that pectin content, type of fibre, and their interaction had a significant effect on the viscoelastic and mechanical properties, and syneresis (water loss) of the gels. Since syneresis of the gel with 0.4 g/100 g pectin was undesirably high, only studies of gels with 0.5 g/100 g pectin followed from this point forward. Fibre addition had a reinforcing effect on the viscoelastic properties of these gels (wheat>psyllium>bamboo>apple). Psyllium-enriched gels did not suffer any syneresis, although they showed an undesirable “gummy” property, caused by low fracturability, high cohesiveness and low hardness. Then, in order to improve the organoleptic properties of the gels, we combined fibre from different sources in pairs (1:1). In general, fibre combination decreased the viscoelastic properties of the gels. However, mixing psyllium with other fibre produced a desirable effect on the mechanical properties of the gels, keeping the syneresis at 0 g/100 g. This indicates that 0.5 g/100 g pectin and 1.5 g/100 g psyllium fibre with 1.5 g/100 g other fibre was the best formulation for the stability and texture of this product.

Two ber varieties differing in their shelf lives (Umran, 8 to 9 and Illaichi, 4 to 5 days) were analyzed for cell wall components, cell wall degrading enzymes and their isoenzyme profile at immature green, mature green, turning colour, ripe and overripe stages of ripening. Cellulose and pectin contents decreased during ripening in both varieties. This decrease was accompanied by a corresponding increase in pectin methylesterase, polygalacturonase and cellulase. The increase in the activity of pectin methylesterase was about 20- and 10-fold, that of polygalacturonase about 8.4- and 5.7-fold, and of cellulase 5.5- and 4.4-fold in Umran and Illaichi, respectively. The basal level of activities of all these enzymes was higher at all the stages of ripening in Illaichi variety, having short shelf life, as compared to Umran, with long shelf life. This was further confirmed by the intensity of isoenzyme bands of these enzymes. The isoenzyme profile also revealed that two isoenzymes of each, pectin methylesterase and polygalacturonase, and one of cellulase could be considered as isoenzymes responsible for the softening of cell wall during ripening and could be potential targets for manipulation to delay softening during ripening., U radu su ispitane dvije sorte voća Ziziphus mauritiana koje se razlikuju prema roku trajanja, i to sorta Umran (roka trajanja od 8 do 9 dana) i sorta Illaichi (roka trajanja od 4 do 5 dana). Analizirani su sastojci stanične stijenke, enzimi koji ju razgrađuju te njihovi izoenzimi u nezrelim zelenim, dozrelim zelenim plodovima i onima koji su promijenili boju, te u zrelim i prezrelim plodovima. Udjel se celuloze i pektina smanjivao tijekom dozrijevanja u obje sorte, što je uzrokovalo povećanje udjela pektin metilesteraze (u sorti Umran 20 puta, a u sorti Illaichi 10 puta), poligalakturonaze (8,4 i 5,7 puta) i celulaze (5,5 i 4,4 puta). U svim su fazama dozrijevanja voća osnovne aktivnosti tih enzima bile izraženije u sorti Illaichi, što potvrđuje i intenzitet njihovih izoenzimskih vrpci. Iz izoenzimskog je profila pektin metilesteraze, poligalakturonaze i celulaze vidljivo da ti enzimi razgrađuju staničnu stijenku tijekom dozrijevanja plodova, te da se njihovom inaktivacijom taj proces može usporiti.

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.