《Food Safety and Home Food Preservation》课程教学课件（PPT讲稿）Food Enzymes

FOOD ENZYMES

FOOD ENZYMES

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

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 reactants products H EA T.S. catalyst

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 enzyme substrate products

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) in presence of inhibitors

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

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 ◼ 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. ◼ 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 ◼ 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

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