Encimska hidroliza škroba v pšenični in riževi moki

Opara, Silva (avtor), Cigić, Blaž (mentor), Lušnic Polak, Mateja (komentor)

V okviru magistrske naloge smo preučevali encimsko hidrolizo škroba v pšenični in riževi moki, z namenom ovrednotenja vpliva dveh različnih encimov in procesnih parametrov na nastanek reducirajočih sladkorjev, ki bi lahko predstavljali alternativo dodajanju prostih sladkorjev v žitne izdelke. Hidrolizo smo izvajali pri različnih koncentracijah α-amilaze in amiloglukozidaze, pri temperaturah 60 °C, 65 °C in 70 °C, v trajanju 15 min, 30 min, 60 min in 120 min, večino pri masnem razmerju med moko in vodo 1:2. Stopnjo hidrolize smo določali spektrofotometrično na osnovi reaktivnosti s hidrolizo nastalih reducirajočih sladkorjev, kakor tudi z osmometrijo. Ugotovili smo, da v primeru pšeničnega škroba hidroliza poteka dobro tudi brez dodatka encimov, kar potrjuje vpliv endogene encimske aktivnosti pšenične moke. Dodatek alfa-amilaze (0,03 % glede na moko) je po 120 min tako pri 60 °C kot 70 °C rezultiral v cepitvi 38 % glikozidnih vezi v škrobu iz pšenične moke in 22 % glikozidnih vezi v škrobu iz riževe moke (določitev z osmometrijo). V primeru kombinacije alfa-amilaze (0,03 % glede na moko) in amiloglukozidaze (0,17 % glede na moko) je po 120 min pri 70 °C stopnja hidrolize škroba v pšenični moki dosegla 73 % in škroba v riževi moki 59 % (določitev z osmometrijo). Večanje razmerja med moko in vodo (do 1:1) je imelo negativen vpliv na hidrolizo škroba samo v riževi moki. Inkubacija testa (120 min, 70 °C) brez dodanih encimov je vplivala na veliko povečanje trdote in lepljivosti mase pri obeh mokah. Dodatek alfa-amilaze, ki ima endoglikozidazno aktivnost, je vodil do izrazitega zmanjšanja trdote in lepljivosti. Z opravljenimi eksperimenti smo potrdili, da lahko s primerno izbiro encimov in procesnih parametrov povečamo vsebnost sladkorjev v žitnih mešanicah, ne da bi sladkorje dodali.

• Jezik: Slovenski jezik
• Ključne besede: pšenična moka, riževa moka, škrob, encimska hidroliza, reducirajoči sladkorji, dekstrozni ekvivalent, DNS metoda, osmometrija, [alfa]-amilaza, amiloglukozidaza
• Vrsta gradiva: Magistrsko delo/naloga
• Tipologija: 2.09 - Magistrsko delo
• Organizacija: BF - Biotehniška fakulteta
• Založnik: [S. Opara]
• Leto izida: 2026
• PID: 20.500.12556/RUL-179498
• UDK: 664.2.0:577.15
• COBISS.SI-ID: 268496387
• Datum objave v RUL: 15.02.2026

Sekundarni jezik

• Jezik: Angleški jezik
• Naslov: Enzymatic hydrolysis of starch in wheat and rice flour

Izvleček

Within the framework of this masters thesis, enzymatic hydrolysis of starch in wheat and rice flour was investigated in order to evaluate the effects of two different enzymes and selected process parameters on the formation of reducing sugars, which could represent an alternative to the addition of free sugars in cereal-based products. Hydrolysis was carried out at various concentrations of α-amylase and amyloglucosidase, at temperatures of 60 °C, 65 °C and 70 °C, for reaction times of 15 min, 30 min, 60 min and 120 min, predominantly at a flour-to-water mass ratio of 1:2. The degree of reducing sugars formed during hydrolysis was determined spectrophotometrically, as well as by osmometry. The results showed that, in the case of wheat starch, hydrolysis proceeded efficiently even without the addition of exogenous enzymes, confirming the contribution of endogenous enzymatic activity present in wheat flour. The addition of α-amylase (0,03% relative to flour mass) resulted, after 120 min, in the cleavage of 38% of the glycosidic bonds in wheat flour starch and 22% of the glycosidic bonds in rice flour starch at both 60 °C and 70 °C, as determined by osmometry. When a combination of α-amylase (0,03% relative to flour mass) and amyloglucosidase (0,17% relative to flour mass) was applied, the degree of starch hydrolysis after 120 min at 70 °C reached 73% for wheat flour starch and 59% for rice flour starch (as determined by osmometry). An increase in the flour-to-water ratio up to 1:1, negatively affected starch hydrolysis just in rice flour. Incubation of dough systems (120 min at 70 °C) without added enzymes resulted in a pronounced increase in hardness and stickiness for both flours. In contrast, the addition of α-amylase, which exhibits endoglycosidase activity, led to a substantial reduction in both hardness and stickiness. The conducted experiments confirmed that, through an appropriate selection of enzymes and process parameters, it is possible to increase the sugar content of cereal-based mixtures without the addition of external sugars.

• Ključne besede: wheat flour, rice flour, starch, enzymatic hydrolysis, reducing sugars, dextrose equivalent, DNS method, osmometry, alpha-amylase, amyloglucosidase