Želatinizacija i likvefakcija kukuruznog škroba pomoću [alfa]-amilaze tijekom procesa ekstruzije = Continuous gelatinization and liquefaction of raw corn starch with a thermostable [alfa]-amylase in a twin screw extruder : disertacija - Ćurić, Duška (Zagreb : D. Ćurić, 1995)
Sažetak: Dosadašnja istraživanja procesa termomehaničke želatinizacije i enzimatske likvefakcije škroba u ekstruderu su ukazale na mogućnost korištenja ekstrudera kao sastavnog dijela kontinuiranog procesa hidrolize škroba. Cilj ovog rada je bio ispitati mogućnost proizvodnje maltodekstrina, glukoznog ekvivalenta DE]-10 iz nativnog kukuruznog škroba postupkom jednostepene, visokotemperaturne, kratkotrajne ekstruzije u prisustvu termostabilne [alfa]-amilaze Termamyl 120L. U prvom dijelu rada su prikazani rezultati istraživanja termomehaničke želatinizacije nativnog kukuruznog škroba u ekstruderu firme APV Baker, tip MPF 50:15.
Promatran je utjecaj masenog udjela vode u ekstruderu (25-45%), temperature želatinizacije (110-190 C) i broja okretaja pužnica (100-200 o/min) na: topljivost ekstrudata (%), stupanj želatinizacije ekstrudata (%), [alfa]-amilaznu probavljivost ekstrudiranog škroba "in vitro" i viskozitet ekstrudiranih škrobnih pasti (BJ). Topljiva suha tvar ekstrudata i stupanj želatinizacije škroba se povećava povećanjem temperature želatinizacije, smanjenjem masenog udjela vode u ekstruderu, povećanjem broja okretaja pužnica i povećanjem količine unešene specifične mehaničke energije.
Pri stalnoj dobavi suhe tvari škroba u ekstruder, 20 kg/h i zadanoj konfiguraciji pužnica, duljine L=750 mm, moguće je pri temperaturi želatinizacije, 110 C, masenom udjelu vode u ekstruderu, 45% i broju okretaja pužnica, 200 o/min, proizvesti ekstrudat čija je topljiva suha tvar veća od 35% i koji pokazuje maksimalnu [alfa]-amilaznu probavljivost "in vitro" (]-20). Određene su kinetičke konstante hidrolize termostabilne [alfa]-amilaze, Termamyl 120L, metodama po Bernfeldu (Vmax=1,587 mola maltoze/gEh i Km=1,19 g s.t. škroba/L) i Somogyu i Nelsonu (Vmax=0,678 mola glukoze/gEh i Km=0,74 g s.t. škroba/L).Istraživanje procesa termomehaničke i enzimatske likvefakcije nativnog kukuruznog škroba u estruderu je provedeno pri stalnoj koncentraciji [alfa]-amilaze Termamyl 120L u ekstruderu,10mL/kg s.t. škroba.
Promatran je utjecaj temperature kućišta zadnje sekcije ekstrudera (106-154 C), masenog udjela vode u ekstruderu (33-57%) i broja okretaja pužnica (170-230 o/min) na glukozni ekvivalent hidrolizata škroba na izlazu iz ekstrudera, ostatni enzimski aktivitet hidrolizata (%), temperaturu hidrolizata na izlazu iz ekstrudera ( C) i topljivost hidrolizata u hladnoj vodi(%). Pokusi su provedeni po Kompozicionom ortogonalnom planu pokusa, 2 3, i dobivene su jednadžbe koje opisuju odnose između mjernih i ispitivanih veličina. Najznačajniji utjecaj na mjerene veličine ima temperatura kućišta zadnje sekcije ekstrudera.
Maksimalna vrijednost glukoznog ekvivalenta, izmjerenu metodom po Bernfeldu (DEB=7,893) i metodom po Somogyu i Nelsonu (DES=5,631) imao je hidrolizat dobiven u slijedećim uvjetima ekstruzije: maseni udio vode u ekstrudatu, 55%; broj okretaja pužnica, 175 o/min; dobava suhe tvari škroba u ekstruder, 20 kg/h; koncentraciji [alfa]-amilaze Termamyl 120L u ekstruderu, 10 mLE/kg s.t.škroba. Optimalizacija procesa hidrolize nativnog kukuruznog škroba u ekstruderu, provedena po metodi Boxa i Willsona je pokazala da se maltodekstrini glukoznog ekvivalenta, DE]-10 i velike topljivosti u hladnoj vodi,75-85%, mogu proizvesti postupkom jednostepene visokotemperaturne kratkotrajne ekstruzije pri slijedećim uvjetima
- maseni udio vode u ekstruderu, 55%, temperatura kućišta zadnje sekcije ekstrudera,110 C; broj okretaja pužnica 175 o/min; koncentracija [alfa]-amilaze Termamyl 120L u ekstruderu, 20 mL/kg s.t. škroba; dobava suhe tvari škroba u ekstruder 20 kg/h; zadana konfiguracija pužnica duljine L=750 mm; promjer sapnica 5 mm; i - maseni udio vode u ekstruderu,55%, temperatura kućišta zadnje sekcije ekstrudera 110 C; broj okretaja pužnica 175 o/min; koncentracija [alfa]-amilaze Termamyl 120L u ekstruderu,10 mL E/kg s.t. škroba; vrijeme hidrolize ekstrudata na sobnoj temperaturi nakon izlaska iz ekstrudera,10 min; dobava suhe tvari škroba u ekstruder 20 kg/h; zadana konfiguracija pužnica duljine L=750 mm;promjer sapnica 5 mm. Ključne riječi:kukuruzni škrob,želatinizacija,likvefakcija, visokotemperaturna kratkotrajna ekstruzija, [alfa]-amilaza,maltodekstrini.
Summary: Recent investigations of thermomechanical gelatinization and enzymatic liquefaction processes of starch in the extruder have showed the possibility of using extruder as the integral part of continuous process of starch hydrolisis. The aim of this work was to find the possibility of maltodextrins production, the equivalent of glucose DE]-10, from native corn starch by onestage, high temperature short time extrusion in the presence of thermostable [alfa]-amylase, Termamyl 120L. In the first part of the work the results of termomechanical gelatinization investigations from native corn starch in twin-screw extruder (APV Baker, MPF 50:15) were showed.
The influence of mass ratio of water in the extruder (25-45%), gelatinization temperature (110-190 C) and screw speed (100-200 rpm) on soluble dry substance of extrudate (%), extrudate gelatinization degree (%), [alfa]-amylase digestibility of extruded starch "in vitro" and viscosity of extruded starch pastes (BU) were monitored. Soluble dry substance of extrudate and starch gelatinization degree are increasing with the increase of gelatinization temperature, decrease of mass ratio of water in the extruder, with speed screw increase and by increasing in quantity of specific mechanical energy coming into.
By constant feed rate of starch dry substance into extruder, 20 kg/h and determined screw configuration, the length is 750 mm, it is possible, at gelatinization temperature, 110 C, mass ratio of water in the extruder, 45% and speed screw of 200 rpm, to obtain extrudate with soluble dry substance higher than 35% and which exhibit the maximum of [alfa]-amylase digestibility "in vitro", ]-20. The kinetic constants of hydrolisis of thermostable [alfa]-amylase Termamyl 120L, were found and these [alfa]-amylases were used in all experiments of enzymatic liquefaction of starch in the extruder, implementing the methods by Bernfeld (Vmax=1.587 mole.maltose/gEh and Km=1.19 g d.s. of soluble starch/L) and Somogy and Nelson (Vmax=0.678 mole.glucose/gEh and Km=0.74 g d.s. of soluble starch/L).
Investigations of thermomechanical and enzymatic linquefaction of native corn starch in the extruder were carried out at the constant concentration of [alfa]-amylase Termamyl 120L in extruder, 10 mLE/kg d.s. of starch. The influence of barrel temperature of the last section of extruder (106-154 C), mass ratio of water in the extruder (33-57%) and speed screw (170-230 rpm) on the glucose equivalent of hydrolized starch at the outlet of the extruder were studied. The above mentioned hydrolized starch was defined by methods by methods of Bernfeld (DE B) and Somogy and Nelson (DE S). The influence of above mentioned parameters on residual enzymatic activity of hydrolozate (%), on the temperature of hydrolizate at the outlet from extruder ( C) and on solubility of hydrolizate in cold water (%) were also incvestigated.
The experiments were carried out in accordance by compositional orthogonal plan of experiment, 23 and the equotions were obtained which describe the interrelations between measured and investigated quantities. The most influential impact on the measured quantities has the barrel temperature of the last section of extruder. The maximum value of glucose equivalent measured by Bernfeld (DEB=7.893) and by Somogy and Nelson (DES=5.631) has hydrolizate obtained under the following conditions of extrusion: mass ratio of water in the extruder, 55%; barrel temperature of the last extruder section, 110 C; speed screw, 175 rpm; feed rate of dry substance of starch into extruder, 20 kg/h, concentration of [alfa]-amylase Termamyl 120L in extruder, 10 mLE/kg d.s. of starch.
Optimization of the process of native corn starch hydrolisis in extruder, carried out by the method of Box and Willson showed that malthodextrins of glucose equivalent DE]-10 and high solubility in cold water, 75-85%, could be produced by onestage, high temperature short time extrusion cooking at the following conditions: - mass ratio of water in the extruder, 55%; barrel temperature of the last extruder section, 110 C; speed screw, 175 rpm; concentration of [alfa]-amylase Termamyl 120L in extruder, 20 mLE/kg d.s. of starch; feed rate of dry substance of starch into extruder, 20 kg/h; determined screw configuration, length 750 mm; diameter of dies, 5 mm.
- mass ratio of water in the extruder, 55%; barrel temperature of the last extruder section, 110 C; speed screw, 175 rpm; concentration of [alfa]-amylase Termamyl 120L in extruder, 10 mL E/kg d.s. of starch; time of hydrolisis of extrudate on room temperature after the exit from the extruder, 10 min; feed rate of dry substance of starch into extruder, 20 kg/h; determined screw configuration, length 750 mm; diameter of dies, 5 mm. Key words: corn starch, gelatinization, liquefaction, high temperature short time extrusion, [alfa]-amylolysis, maltodextrins.
Sveučilište u Zagrebu, Prehrambeno-biotehnološki fakultet, Zagreb, 1995
Bibliografija: str. 190-198
Summary
Keywords: Kukuruzni škrob -- Ekstruzija