Abstract
In sugar industry there is a problem of the presence of undesirable macromolecules compounds such as pectin in sugar beet juice. The affinity of calcium ions commonly used in the sugar industry for the removal of pectin from the sugar beet juice is relatively small. Coagulation and precipitation of pectin can be performed by process of discharging that is chemically induced. Compounds with di- and trivalent cations such as pure CuSO4, Al2(SO4)3 or their mixtures can be applied for clarification of pectin colloidal systems. According to data from the order of pectin selectivity to divalent metal ions, Cu2+ ions are the first order of ion binding. Also, aluminum sulfate is commonly used in the waste water treatment. Two model solutions of pectin whose concentration corresponds to the concentration of these macromolecules in sugar beet juice (0.1% w/w) are investigated. Using a method of measuring zeta potential, it was proven for both investigated pectin that fewer quantities of Cu2+ ions compared to the values of Al3+ ions are needed to reach zero zeta potential. In all the investigated coagulants and their mixtures, zeta potential has changed the sign. In experiments with mixtures has been shown that pure salts showed better coagulation properties. The reduced strength of binding of cations in the case of most of the applied mixture of Cu2+ and Al3+ ions, can be explained by the mutual competition of these ions for the adsorption site (COO- groups) on the surface of macromolecules. Mixture with approximately equal shares of ions Cu2+ and Al3+ had the most unfavorable coagulation ability (ion antagonism). Mechanism of discharge as well as the model of double electric layer surrounding pectin macromolecules in the presence of mixtures of Cu2+ and Al3+ ions are suggested. However, due to possible undesirable effects of CuSO4 on food processing, Al2(SO4)3 is proposed instead of traditional coagulant CaO, not only because of lower consumptions of coagulants but owing to protection of the environment.
Highlights
In sugar industry there is a problem of the presence of undesirable macromolecules compounds
The affinity of calcium ions commonly used in the sugar industry for the removal
relatively small. Coagulation and precipitation of pectin can be performed by process
Summary
Čišćenje sirovog soka u preradi šećerne repe je važna operacija kojom se odstranjuju nesaharozne materije radi dobijanja što kvalitetnijeg finalnog proizvoda – konzumnog belog šećera. Koagulaciona moć i afinitet vezivanja kalcijuma sa makromolekulima soka šećerne repe je jako mali. Pre svega pektina ovo naelektrisanje je nastalo disocijacijom funkcionalnih grupa i adsorpcijom jona iz okolnog rastvora [2,3,4]. Afinitet vezivanja dvovalentnih metalnih jona, proučavan je na pektinima i derivatima pektina limuna i šećerne repe. T.A. KULJANIN i sar.: UTICAJ BAKARNIH I ALUMINIJUMOVIH JONA NA IZDVAJANJE PEKTINA IZ ŠEĆERNE REPE. Cilj ovog rada je ispitivanje mogućnosti primene jedinjenja Al2(SO4) čistog ili sa dodatkom male količine CuSO4 za prečišćavanje soka šećerne repe. Gouy–Chapman–Stern-ov (GCS) model dvojnog električnog sloja sa označenom pozicijom ravni smicanja i zeta potencijalom ζ [5]. Eksperimentalno je potvrđen GCS model dvojnog električnog sloja kod pektina šećerne repe u prisustvu jona Cu2+ [6]. Promena zeta potencijala pektinskih makromolekula proporcionalna je količini Cu2+ dodatih u
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