Detailed Notes on Enzymes and Their Functions in Food Production

Enzymes Overview

• Definition: Enzymes are proteins that act as catalysts in biochemical reactions, converting substrates into products.
• Catalytic Activity: They can accelerate reactions by factors ranging from $10^3$ to $10^{11}$ compared to non-enzymatic reactions.
• Specificity: Enzymes are highly specific to their substrates, meaning not all proteins function as enzymes.

Enzymes in Food Production

• Benefits:
  • Natural biological materials
  • Non-toxic
  • Highly specific actions, allowing precise control over reactions via temperature, pH, and enzyme concentrations.
• Most Common Types: Most food production enzymes are hydrolases, emphasizing the importance of hydrolytic reactions.

Enzyme Nomenclature (Enzyme Commission)

• EC Codes: Enzymes are categorized and assigned codes based on their function, consisting of four numbers (e.g., EC 3.4.15.1).
  • First Number: Major class - 1 (Oxidoreductases, 2 (Transferases), 3 (Hydrolases), etc.)
  • Subsequent Numbers: Provide subclassification and detailed enzymatic activity descriptions.

Main Classes of Enzymes

Mechanism of Enzyme Action

• Active Site: The specific region on the enzyme where substrates bind and react.
• Reaction Formula: E + S ightleftharpoons ES ightarrow E + P
  • E = Enzyme, S = Substrate, ES = Enzyme-Substrate complex, P = Product

Enzymatic Browning

• Definition: A color reaction affecting fruits, vegetables, and seafood caused by enzymes (notably Polyphenol Oxidase - PPO).
• Beneficial Effects: Enzymatic browning can enhance the color and flavor of foods such as tea, cocoa, and dried fruits.
• Detrimental Effects: Leads to significant economic loss in fresh produce, estimated over 50% for certain fruits.
• PPO Mechanism: Converts o-dihydroxyphenols to o-benzoquinones using O_2 , which then polymerize to form dark pigments (melanins).

Factors Affecting Enzymatic Browning

• Triggered by:
  • Oxygen presence
  • pH levels (optimal 6-7 for PPO)
  • Temperature (heat unstable)
• Control Methods:
  • Physical: Reduce temperature and oxygen levels using refrigeration, controlled atmospheres, or modified atmosphere packaging.
  • Chemical: Use acidulants to lower pH or reducing agents to revert o-benzoquinones back to substrates.
  • Common agents: Citric acid, ascorbic acid, cysteine, and sulfites (e.g., SO₂).

Carbohydrases

• Amylases: Enzymes breaking down starch into sugars.
  • α-Amylase: Attacks ext{α-1,4} bonds but not ext{α-1,6} bonds, yielding low molecular weight dextrins.
  • β-Amylase: Hydrolyzes ext{α-1,4} bonds to release maltose; significant for sweetness.
• Debranching Enzymes: E.g., Pullulanase, hydrolyze ext{α-1,6-glycosidic bonds} .

Importance of Enzymes in the Baking Process

• Role: Amylases facilitate dextrinization, producing fermentable sugars crucial for yeast fermentation during baking.
• Impact on Bread: Enzymatic activity can affect loaf volume, texture, and sweetness, emphasizing the importance of enzyme stability through the baking process.

Invertase and Lactase

• Invertase (EC 3.2.1.26): Hydrolyzes sucrose into glucose and fructose, enhancing sweetness.
• Lactase (β-D-galactosidase; EC 3.2.1.23): Reduces lactose in dairy, improving sweetness and solubility, beneficial for lactose-intolerant individuals.

Pectic Enzymes in Juice Clarification

• Types: Pectin methyl esterase and Polygalacturonases, which remove pectin polymers to clarify juice.
• Process: Enzymatic breakdown of pectic substances leads to reduced cloudiness, essential in juice and wine production.

Proteases

• Function to degrade proteins, introducing tenderness in meat and improving texture in baked goods.
• Utilization: Specific proteases used for meat tenderization, chill-proofing beer, and cheese-making.
• Enzyme Sources: Can be fungal, bacterial, or derived from animal sources (e.g., rennet for cheese).

Lipase and Glucose Oxidase

• Lipases (EC 3.1.1.3): Hydrolyze triglycerides, important in cheese ripening and flavor development.
• Glucose Oxidase (EC 1.1.3.4): Converts glucose to gluconic acid, utilized to prevent browning in various food products.

Conclusion

• Significance: Understanding enzymatic functions and their control methods is vital in optimizing food production processes and enhancing food quality.