Starch processing: During the liquefaction step, starch is converted to dextrins primarily by which enzyme?

Introduction:
Industrial starch conversion proceeds through liquefaction and saccharification. This question focuses on the liquefaction step that reduces viscosity by depolymerizing starch into shorter dextrins.

Given Data / Assumptions:

• Feed: gelatinized starch slurry.
• Goal: rapid viscosity reduction and dextrin formation.
• Operating conditions: elevated temperature suitable for thermostable amylases.

Concept / Approach:
α-amylase cleaves internal α-1,4 glycosidic bonds in amylose and amylopectin, generating dextrins and lowering viscosity. Cellulase acts on cellulose, and pectinase acts on pectins; neither targets starch polymers.

Step-by-Step Solution:
Gelatinize starch to expose α-1,4 linkages.Apply α-amylase to hydrolyze internal bonds, forming dextrins.Monitor viscosity drop as an indicator of liquefaction progress.

Verification / Alternative check:
Process control via dextrose equivalent and viscosity confirms that α-amylase action accomplishes liquefaction before saccharification by glucoamylase.

Why Other Options Are Wrong:
Cellulase: targets β-1,4 glucans in cellulose, not starch.

Pectinase: targets pectic substances, not starch.

All of these: cannot be correct because only α-amylase performs starch liquefaction.

Common Pitfalls:

• Equating any carbohydrate hydrolase with starch hydrolysis.
• Confusing liquefaction with saccharification stages.

Final Answer:
α-amylase