Food Chemistry Study Notes PDF

1. Mayonnaise Key Concepts: Emulsification:Mixing two immiscible liquids (oil and water) to form a stable emulsion. Emulsifier:Egg yolk contains lecithin, a phospholipid that acts as an emulsifier, stabilizing the oil droplets in water. Acid-Base Reaction: Acids like vinegar or lemon juice lower the...

1. Mayonnaise Key Concepts: Emulsification:Mixing two immiscible liquids (oil and water) to form a stable emulsion. Emulsifier:Egg yolk contains lecithin, a phospholipid that acts as an emulsifier, stabilizing the oil droplets in water. Acid-Base Reaction: Acids like vinegar or lemon juice lower the pH, helping the proteins in egg yolk stabilize the emulsion. Factors Affecting Emulsion Stability: Oil Addition Speed: Adding oil too quickly can cause the emulsion to break. Temperature: Ingredients should be at room temperature to ensure stable emulsification. pH Levels: Different acids affect the stability and flavor of the emulsion. Common Issues and Fixes: Breaking Emulsion: Start with a new yolk and slowly incorporate the broken mixture. 2. Silken Tofu Key Concepts: Protein Coagulation: Proteins in soy milk coagulate when an acid or coagulant (e.g., vinegar or gypsum) is added. pH and Coagulation: The pH level affects the firmness and texture of tofu. Too high or too low pH can prevent proper coagulation. Fermentation (Optional): Sometimes used to enhance the flavor and texture. Factors Affecting Tofu Quality: Temperature: Coagulation occurs optimally at a certain temperature. Coagulant Amount: Too much or too little can affect the texture. Mixing Rate: Overmixing can break down the protein structure, leading to a less smooth texture. Common Issues and Fixes: Not Forming:Adjust the pH by adding more coagulant or changing the type of acid used. 3. Dough Key Concepts: Gluten Formation: Gluten proteins in flour form a network when water is added and the dough is kneaded, providing elasticity. Yeast Fermentation: Yeast converts sugars into carbon dioxide and alcohol, causing the dough to rise. Maillard Reaction: During baking, amino acids and reducing sugars react to form a brown crust and complex flavors. Factors Affecting Dough Quality: Salt Content: Enhances gluten structure and controls yeast activity. Kneading: Over-kneading can make the dough too tight; under-kneading can result in a weak structure. Temperature: Affects yeast activity and fermentation rate. Common Issues and Fixes: Not Rising:Check water temperature and yeast viability. Overly Sticky: Reduce hydration or knead more to develop the gluten structure. 4. Ice Cream Key Concepts: Emulsification: Similar to mayonnaise, fat is dispersed in water using emulsifiers like egg yolk. Freezing Point Depression: Sugar lowers the freezing point, preventing large ice crystal formation. Churning: Incorporates air and prevents ice crystals, leading to a smooth texture. Factors Affecting Ice Cream Quality: Sugar Content: Too much or too little effects texture and freezing point. Fat Content: Higher fat content leads to a creamier texture. Churning Speed and Time: Affects air incorporation and crystal size. Common Issues and Fixes: Grainy Texture: Increase fat content or reduce freezing time. Soft Consistency: Adjust emulsifiers or increase sugar to alter freezing point. Chemical Reactions and Their Roles: Maillard Reaction: Responsible for browning in baked goods and affecting flavor. Protein Denaturation and Coagulation: Key in tofu and egg-based products like mayonnaise. Fermentation: Increases volume and alters texture in dough; affects flavor in tofu. Emulsification: Stabilizes mixtures like mayonnaise and ice cream.