俄亥俄州大学：《食品科学》课程教学资源（PPT课件，英文版）FOOD ENZYMES

FOOD ENZYMES

FOOD ENZYMES

What is an enzyme? a biological catalyst that promoTes and speeds up a chemica| reaction withou叶t计sef being altered in the process Lowers the activation energies of a substance

What is an enzyme? ◼ A biological catalyst that promotes and speeds up a chemical reaction without itself being altered in the process. ◼ Lowers the activation energies of a substance

Energy Profile Ts catalyst E products reactants △H

Energy Profile reactants products H EA T.S. catalyst

Enzymatic Reactions Enzyme combines with a specific substrate to a form an enzyme substrate complex in a lock and key concept before forming new products

Enzymatic Reactions ◼ Enzyme combines with a specific substrate to a form an enzyme￾substrate complex in a lock and key concept before forming new products

Enzyme action substrate products enzyme

Enzyme action enzyme substrate products

Structure of an enzyme Contains both a protein and a nonprotein Nonprotein is either a coenzyme (usually a vitamin) or a cofactor (usually a mineral)

Structure of an enzyme ◼ Contains both a protein and a nonprotein. ◼ Nonprotein is either a coenzyme (usually a vitamin) or a cofactor (usually a mineral)

Factors influencing enzyme activity Operate under optimum conditions of pH and temperature Easily inactivated (denatured) it presence of inhibitors

Factors influencing enzyme activity ◼ Operate under optimum conditions of pH and temperature. ◼ Easily inactivated (denatured) in presence of inhibitors

Enzyme Nomenclature a Names usually end in -ase a Usually named after substrates they act upon e.g.urea urease lactose lactase or the resulting type of chemical reaction e.g. hydrolysis hydrolases oxidation oxidases This rule does not always apply. E.g ficin found in figs and papain in

Enzyme Nomenclature ◼ Names usually end in –ase. ◼ Usually named after substrates they act upon e.g. urea --- urease lactose --- lactase or the resulting type of chemical reaction e.g. hydrolysis --- hydrolases oxidation --- oxidases ◼ This rule does not always apply. E.g. ficin found in figs and papain in papayas

Enzyme Nomenclature cont a hydrolysis -- hydrolases oxidation oxidases This rule does not always apply E.g. ficin found in figs and papain In papayas

Enzyme Nomenclature cont. ◼ hydrolysis --- hydrolases oxidation --- oxidases ◼ This rule does not always apply. E.g. ficin found in figs and papain in papayas

Properties of enzymes a Control ripening Cause food spoilage(rotting) Responsible for changes in flavor color texture and nutritional roperties pr Can be inactivated by heat to extend storage stability of foods

Properties of enzymes ◼ Control ripening. ◼ Cause food spoilage (rotting). ◼ Responsible for changes in flavor, color, texture and nutritional properties. ◼ Can be inactivated by heat to extend storage stability of foods