Food chemistry is the study of chemical processes in food. It explores how ingredients interact, react, and change during cooking, processing, and storage. Understanding these processes helps us create better, safer, and more nutritious foods.

This topic introduces the basics of food chemistry, including chemical composition, analysis techniques, and molecular interactions. It sets the stage for diving deeper into macronutrients and micronutrients in the rest of the chapter.

Chemical Composition and Analysis

Food Chemistry Fundamentals

• Food chemistry studies the chemical processes and interactions of all biological and non-biological components of foods
  • Focuses on the chemical composition, structure, and properties of foods and the chemical changes they undergo during processing and storage
• Chemical composition refers to the specific chemical components that make up a food, including water, carbohydrates, proteins, lipids, vitamins, and minerals
  • Understanding the chemical composition of foods is essential for predicting their behavior during processing, storage, and consumption (texture, flavor, shelf life)
• Nutrient analysis involves the identification and quantification of the nutrients present in a food
  • Includes macronutrients (carbohydrates, proteins, fats) and micronutrients (vitamins, minerals)
  • Nutrient analysis is crucial for determining the nutritional value of foods, developing food labels, and ensuring compliance with regulations

Analytical Techniques in Food Chemistry

• Various analytical techniques are used to determine the chemical composition and properties of foods
  • Spectroscopic methods (UV-Vis, IR, NMR) provide information about the molecular structure and functional groups present in food components
  • Chromatographic techniques (HPLC, GC) separate and identify individual compounds in complex food matrices
• Proximate analysis is a set of methods used to determine the major components of foods, including moisture, ash, protein, fat, and carbohydrates
  • Results of proximate analysis are used to calculate the energy content of foods and to ensure compliance with food composition standards
• Sensory analysis involves the evaluation of food quality attributes by human senses (sight, smell, taste, touch)
  • Provides valuable information about consumer acceptance and preference for food products

Molecular Interactions and Structure

Intermolecular Forces in Food Systems

• Molecular interactions play a crucial role in determining the physical properties and behavior of food components
  • Hydrogen bonding occurs between polar molecules (water, proteins) and contributes to the stability of food structures (gels, emulsions)
  • Hydrophobic interactions between non-polar molecules (lipids) drive the formation of lipid-based structures (micelles, bilayers)
• Electrostatic interactions between charged molecules (proteins, polysaccharides) influence the solubility, aggregation, and gelation of food components
  • pH and ionic strength can modulate electrostatic interactions and affect food texture and stability
• Van der Waals forces are weak attractive forces between molecules that contribute to the cohesion and adhesion of food components
  • Important for the formation of flavor complexes and the adsorption of molecules to surfaces (aroma retention, flavor release)

Food Structure and Functionality

• Food structure refers to the spatial arrangement of food components at various length scales (molecular, microscopic, macroscopic)
  • Determines the physical properties (texture, rheology) and sensory attributes (mouthfeel, flavor release) of foods
• Functional properties are the physicochemical characteristics of food components that determine their behavior in food systems
  • Solubility, emulsification, foaming, gelation, and water/oil binding capacity are important functional properties of proteins and polysaccharides
• Food processing operations (heating, cooling, shearing) can modify food structure and functional properties
  • Denaturation of proteins during cooking leads to changes in texture (egg white coagulation)
  • Gelatinization of starch during heating contributes to the thickening of sauces and puddings

Chemical Reactions in Food

Types of Chemical Reactions

• Chemical reactions in food involve the transformation of chemical compounds, leading to changes in food quality, safety, and shelf life
• Maillard reaction is a complex set of reactions between reducing sugars and amino acids that occurs during heating of foods
  • Produces brown pigments (melanoidins) and a variety of flavor compounds (caramel, roasted, nutty)
  • Responsible for the desirable flavors and colors of baked goods, coffee, and grilled meats
• Lipid oxidation is a major cause of food spoilage and off-flavor development
  • Involves the reaction of unsaturated fatty acids with oxygen, leading to the formation of hydroperoxides and secondary oxidation products (aldehydes, ketones)
  • Antioxidants (vitamin E, phenolic compounds) can inhibit lipid oxidation and extend the shelf life of foods
• Enzymatic reactions catalyzed by endogenous enzymes (amylases, proteases, lipases) can lead to both desirable (ripening of fruits) and undesirable (enzymatic browning of cut apples) changes in food quality
  • Controlling enzymatic activity through processing (blanching, pasteurization) is essential for preserving food quality and safety

Factors Affecting Chemical Reactions

• Temperature is a critical factor influencing the rate and extent of chemical reactions in foods
  • Increasing temperature accelerates most chemical reactions, including Maillard reaction and lipid oxidation
  • Refrigeration and freezing slow down chemical reactions and extend the shelf life of perishable foods
• pH affects the ionization of food components and the activity of enzymes
  • Acidic conditions (low pH) favor the Maillard reaction and inhibit enzymatic browning
  • Alkaline conditions (high pH) promote lipid oxidation and the degradation of vitamins
• Water activity (aw) is a measure of the available water in foods and influences the growth of microorganisms and the rate of chemical reactions
  • Low water activity (<0.6) inhibits microbial growth and enzymatic reactions, contributing to the stability of dry foods (crackers, powdered milk)
  • High water activity (>0.9) favors microbial growth and chemical reactions, leading to rapid spoilage of high-moisture foods (fresh fruits, meat)