FSSAI Food Chemistry: Carbohydrates Overview

FSSAI Food Chemistry

• This book is for food safety officers and technical officers
• It covers food chemistry topics including carbohydrates, proteins, lipids, vitamins, minerals, pigments, flavours, enzymes, and antinutritional factors.

Carbohydrate

• Food: Any solid/liquid consumed for nourishment
• Food Chemistry: Study of food composition, properties, and structure
• Carbohydrates are photosynthesis products
• Chemical formula: Cx(H2O)y
• Provide 4kcal/g of energy

Classification

• Monosaccharide: Simplest carbohydrates
  • Glucose, fructose, galactose are aldohexose
  • Fructose is a ketohexose
  • Mostly have a sweet taste
  • Water soluble
• Aldopentose:
  • Ribose, arabinose, xylose, lyxose
• Aldotriose:
  • Glyceraldehyde
• Isomerism:
  • D configuration: -OH carried on the asymmetric carbon is to the right of the plane
  • L configuration: -OH carried on the asymmetric carbon is to the left of the plane
• Anomers: Alpha and Beta sugars

Oligosaccharides

• Composed of 2-10 monosaccharide units
• Disaccharides:
  • Maltose: two glucose units bonded via a 1,4 glycosidic linkage
  • Lactose: glucose & galactose joined by a β 1,4 glycosidic linkage
• Trisaccharides: Composed of three monosaccharides
  • Raffinose: glucose is a monosaccharide bridge between galactose and fructose

Polysaccharides

• Homo-polysaccharides: Starch, Glycogen, Cellulose, Inulin

• Hetero-polysaccharides: -Pectin, gums, agars, carrageenans, algin, dextran, xanthan

• Starch: Glucose polymers, important source of energy for plants & humans

  • Amylose (20%): Linear glucose units linked by α (1,4) glycosidic bonds
  • Amylopectin (80%): Branched glucose units, linked by α (1,4) linkages with branching via α (1,6) linkages.

Caramelization

• Browning reaction of sugars at high temperatures (above 165°C) producing caramel flavours.
• Involves release of volatile compounds, like diacetyl.
• Involves the removal of water and breakdown of sugar.

Maillard Reaction

• Reaction between reducing sugars and amino acids at temperatures of about 140-165°C.
  • Results in the formation of complex brown compounds (melanoids).
• Improves colour, flavour, and aroma of baked foods

Enzymes

• Biological catalysts that speed up chemical reactions in living systems without being consumed in the process
• Usually proteins with specific 3D structures
  • Active site: Specific region where substrate bind
• Factors affecting enzyme activity: Temperature, pH, substrate concentration, presence of inhibitors
• Types of enzymes: Oxidoreductases, transferases, hydrolases, lyases, isomerases, ligases

Proteins

• Macromolecules made of amino acids
• Structure of Proteins:
  • Primary Structure: The linear sequence of amino acids in a polypeptide chain.
  • Secondary Structure: Local folding patterns of the polypeptide chain (e.g., alpha-helices, beta-sheets) stabilized by hydrogen bonding.
  • Tertiary Structure: Three-dimensional arrangement of the entire polypeptide chain, stabilized by interactions between amino acid side chains.
  • Quaternary Structure: Structure of proteins that consist of more than one polypeptide chain.

Lipids

• Insoluble in water
  • Simple Lipids: (e.g., triglycerides, waxes) esters of fatty acids with alcohols.
    • Triglycerides: Formed from glycerol and 3 fatty acids. Important energy storage molecules
    • Waxes: Esters of long-chain fatty acids and long-chain alcohols.
  • Compound Lipids: (e.g., phospholipids, glycolipids) Fatty acids combined with other groups such as phosphorus or carbohydrates.
  • Derived Lipids: (e.g., fatty acids, steroids, fat-soluble vitamins) Derivatives of simple and compound lipids

Vitamins

• Essential organic compounds required in small quantities for normal growth, health and reproduction.
• Classification:
  • Water-soluble (B-vitamins, Vitamin C)
  • Fat-soluble (Vitamins A, D, E, K)
• Functions vary depending on vitamin type

Minerals

• Inorganic elements necessary for various bodily functions
• Types:
  • Macrominerals: Required in relatively large amounts (e.g., calcium, phosphorus, sodium, potassium, magnesium, and sulfur)
  • Micronutrients (trace minerals): Required in smaller quantities (e.g., iron, zinc, copper, iodine, manganese, selenium, and molybdenum)

Pigments and Colors

• Naturally occurring substances that impart color to foods
• Chlorophyll: Green pigments in plants vital for photosynthesis, responsible for green color in plant-based foods. Chlorophyll A and B are important.
• Anthocyanins: Water-soluble pigments giving red, purple, and blue colors to plants.
• Carotenoids: Yellow, orange, and red pigments (e.g., beta-carotene) found in various fruits and vegetables.

Flavours

• Taste and smell properties of food, resulting from a mix of components
• Flavonoids: Contribute to the flavor of fruits (e.g., orange, lemon)
• Terpenoids: Important components of citrus oils and contribute to scents/aromatic properties of fruits (e.g., limonene).
• Sulphur Compounds: Produce aromas in foods (e.g., garlic, onion)
• Other volatile compounds: Contribute scents to foods
• Maltol: Has ability to enhance sweetness in chocolate, candies, ice-cream.

9. Anti-nutritional factors (ANF)

• Substances that hinder nutrient absorption
• Phytates: Found in grains, legumes, nuts, reduce absorption of minerals.
• Oxalates: Found in spinach, reduce calcium absorption.
• Tannins: Found in tea, coffee, reduce iron absorption.
• Lectins: Found in various legumes, bind to protein, impacting its digestion
• Cyanogenic glycosides: Found in some foods, release HCN upon hydrolysis.