Comprehensive Food Science Identification Reviewer

Basic Concepts of Food Science

  • Food Science

    • Defined as the study of the chemical, physical, and microbiological nature of foods.

    • Encompasses any transformation food undergoes as reflected in its characteristics and properties.

  • Food Quality

    • A composite of several criteria determined by stimuli from the food itself and attitudes attached by the consumer.

    • Core components include nutritional quality, digestibility, palatability, economy, and sanitary quality.

  • Three Definitions of Food (Perspective-based)

    • Physiological: Provides energy, builds and repairs tissues, and regulates body processes.

    • Biological: Sustains life and nourishes the body.

    • Sociocultural: Satisfies human senses and emotional needs.

  • Five Aspects of Food Quality Evaluation

    • Nutritional quality: Evaluated based on the presence and balance of water, carbohydrates, proteins, fats, vitamins, and minerals.

    • Digestibility: Evaluated by the completeness of digestion and absorption in the body.

    • Palatability: The eating quality as judged by human senses.

    • Economy: Includes the food cost, preparation time, required equipment, and labor involved in cooking or storage.

    • Sanitary quality: The condition of being free from microbiological, biological, chemical, physical, and radiological contamination.

  • Types of Food-borne Illness

    • Food intoxication: Illness caused by toxins (poisons) already present in food before consumption.

    • Food infection: Illness caused by living microorganisms that enter and multiply in the body after eating contaminated food.

Chemical Composition of Food

  • Three Main Groups of Composition

    • Macronutrients: Carbohydrates, proteins, fats, and water.

    • Micronutrients: Vitamins and minerals.

    • Non-nutritional components: Pigments, enzymes, gums, organic acids, tannins, esters, ketones, and flavoring compounds.

  • Forms of Water in Food

    • Water can exist in five distinct forms:

      • Free water.

      • Hydrates.

      • Adsorbed on the surfaces of solids or crystals.

      • Absorbed or imbibed within gels.

      • Bound water.

  • Nutritional Minerals (17 Essential Minerals)

    • The minerals identified include: Calcium, phosphorous, potassium, sulfur, sodium, chlorine, magnesium, iron, zinc, manganese, copper, selenium, iodine, molybdenum, cobalt, chromium, and fluorine.

  • Vitamins Classification

    • Water-soluble Vitamins

      • B vitamins: Found in whole grains, meat, eggs, milk, legumes, and leafy green vegetables.

      • Vitamin C: Found in oranges, lemons, guava, strawberries, kiwi, bell peppers, and broccoli.

    • Fat-soluble Vitamins

      • Classified under the acronym ADEK (AA, DD, EE, and KK).

      • Found in sources like carrots, egg yolk, spinach, and cabbage.

Natural Pigments in Food

  • Plant Pigments

    • Fat-soluble pigments:

      • Chlorophyll: A green pigment that captures sunlight to produce food via photosynthesis. It is essential for plant growth as it converts light energy into chemical energy. Examples include spinach, lettuce, and grass.

      • Carotenoids: Yellow, orange, or red pigments. They help absorb sunlight during photosynthesis and protect chlorophyll from damage caused by excessive sunlight. Found in carrots, pumpkins, sweet potatoes, corn, mangoes, and autumn leaves.

    • Water-soluble pigments:

      • Flavonoids and Tannins

      • Anthocyanins: Give fruits, vegetables, and flowers red and purple colors.

      • Anthoxanthins: Give plants white, cream, or pale yellow colors.

  • Animal Pigments

    • Includes hemoglobin, myoglobin, riboflavin, and sepia.

Water and Proteins

  • Nature of Water in Food

    • The most common dispersing medium and the most abundant compound found in food.

    • Bound Water: Tightly held to food components and not easily removed. It is distinct from free water, which is loosely held and readily available.

  • Nature of Proteins

    • Organic compounds composed of amino acids linked by peptide bonds; notably contains nitrogen.

    • Classifications: Simple, conjugated, or derived.

    • Complete Proteins: Contain all essential amino acids. Primary sources are animal-based: meat, poultry, fish, shellfish, milk, cheese, yogurt, and eggs.

    • Incomplete Proteins: Lack one or more essential amino acids. Primary sources are plant-based, such as grains (legumes are generally an exception).

  • Protein Functions in Food

    • Hydration: The ability to form a gel through gelling or hydrating capacities.

    • Denaturation: A structural change in the protein caused by heat, acid, or other factors (e.g., egg whites turning solid when cooked).

    • Enzymatic reactions: Both useful and undesirable chemical reactions catalyzed by enzymes.

  • Enzyme Applications in Food

    • Useful Applications:

      • Rennin (Chymosin): Used in cheese production to convert milk to curd.

      • Papain, bromelain, and ficin: Used as meat tenderizers.

      • Pectinase, cellulose, and amylase: Used in fruit juice processing.

      • Invertase: Facilitates sucrose inversion in candy and confections.

      • Amylase: Used for starch splitting in bread making.

      • Pectinases: Facilitate fruit ripening (converting protopectin to pectin).

      • Microbial enzymes: Used for fermentation and proteolysis.

    • Undesirable Enzyme Reactions:

      • Enzymatic browning: Occurs when phenolic compounds react with oxygen to produce brown products.

      • Rancidity: Spoilage of fats and oils (e.g., in butter, coconut oil, nuts, and bacon) leading to unpleasant smells, tastes, and odors.

      • Maturation of vegetables.

      • Spoilage: Includes the putrefaction of fish and meat or the decay of fruits and vegetables.

Carbohydrates

  • Definition

    • Hydrates of carbon (CHOCHO) synthesized through photosynthesis.

  • Classification by Structure

    • Monosaccharides: Glucose, fructose, and galactose (found in fruits, honey, grapes).

    • Disaccharides: Sucrose, lactose, and maltose (found in table sugar, milk, malted cereals).

    • Digestible Polysaccharides: Starch, dextrins, and glycogen (found in rice, potatoes, corn, bread, liver).

    • Partially Digestible Polysaccharides: Galactogens, inulin, mannosans, and pentosans (found in garlic, onions, chicory root, asparagus, legumes).

    • Indigestible Polysaccharides: Cellulose, hemicellulose (agar, pectin), and lignin (found in vegetables, fruit peels, whole grains, woody stems, seeds).

  • Dietary Fiber

    • Soluble Fiber: Dissolves in water; helps lower blood cholesterol and glucose. Found in dried beans, peas, lentils, oats, rice bran, barley, and oranges.

    • Insoluble Fiber: Absorbs water, increases stool bulk, and prevents constipation. Found in whole wheat (wheat bran) and rye products.

  • Starch and Sugar Processes

    • Gelatinization: The process where starch is heated with water, increasing its viscosity and making it useful as a thickener or binder.

    • Crystallization: A candy-making process where small sugar crystals form around a nucleus.

Fats and Lipids

  • Definition

    • Organic compounds insoluble in water but soluble in organic solvents (e.g., benzene, chloroform, ether, acetone).

    • Fats are typically animal-sourced; oils are typically plant-sourced.

  • Three Groups of Lipids

    • Triglycerides (Fats & Oils): The most abundant type of lipid in foods and the human body, composed of one glycerol molecule attached to three fatty acids.

    • Phospholipids: Contain both water-attracting (hydrophilic) and fat-attracting (hydrophobic) properties.

    • Sterols: Complex lipids with a ring-shaped chemical structure; they do not contain fatty acids.

  • Fatty Acids

    • Saturated Fatty Acids: Primarily from animal foods (meat, dairy, butter) and specific plant oils (coconut, palm); solid at room temperature.

    • Unsaturated Fatty Acids: Primarily from plant foods like olives, peanuts, and avocado; liquid at room temperature. Exception: Fish oils are liquid/unsaturated at room temperature.

    • Omega-3 Fatty Acid (Linolenic Acid): Essential polyunsaturated fatty acid found in fatty fish, flaxseed, chia seeds, and walnuts; known for anti-inflammatory effects.

    • Omega-6 Fatty Acid (Linoleic Acid): Essential polyunsaturated fatty acid found in vegetable oils (corn, soybean, sunflower, safflower); vital for skin growth.

  • Fat Degradation and Terms

    • Oxidative Rancidity: Degradation via reaction with oxygen, prevented by antioxidants.

    • Hydrolytic Rancidity: Degradation via reaction with water (hydrolysis), producing free fatty acids.

    • Acrolein: A pungent compound formed when fat is heated beyond its smoke point, causing a burnt oil flavor.

Browning Reactions and Prevention

  • Classification of Browning

    • Non-Enzymatic Browning

      • Caramelization: Direct heating of sugar above 160 ∘C160\,^\circ\text{C}. Sucrose melts and turns from white to brown.

      • Maillard Reaction: Reaction between the free aldehyde group of a sugar and the amino group of a protein. Responsible for color in toasted bread, baked goods, and cooked meat.

    • Enzymatic Browning

      • Polyphenol oxidation: Enzymes act on phenolic compounds (anthocyanins, tannins, flavones) in the presence of oxygen. Common in cut fruits and vegetables.

      • Ascorbic acid oxidation: Oxidation of Vitamin C.

  • Preventing Browning

    • Prevent contact with oxygen (using wraps or soaking in water).

    • Use of salt.

    • Use of acid.

    • Blanching: Brief immersion in boiling water or steam followed by rapid cooling in ice water.

    • Refrigeration: Storage at low temperatures.

    • Use of antioxidants.

  • Syneresis

    • The separation or "weeping" of liquid from a gel (e.g., jelly), often occurring when the gel is too acidic.

pH and Dispersion Systems

  • pH Applications in Food

    • Refers to acidity and basicity.

    • Pasteurization is used for acidic foods; sterilization is used for basic foods.

    • Acidic pH inhibits microorganism growth and contributes to sourness.

    • Specific Levels:

      • pH 3.2\text{pH } 3.2: Required for gel formation in jellies.

      • pH 5\text{pH } 5: Optimal for good bread volume and texture.

      • pH 7\text{pH } 7: Results in crispy, cream-colored biscuits.

  • Categories of Dispersion

    • True solution: Homogenous, transparent, high osmotic pressure; particles are invisible under an ultra-microscope.

    • Colloidal dispersion: Two-phased system; particles visible under an ultra-microscope; no osmotic pressure.

    • Suspension: Mixture with large particles that may separate on standing and will not gel.

  • Major Colloidal Systems in Food

    • Sol: Dispersed phase is solid; dispersing medium is liquid (a liquid gel).

    • Gel: A solidified sol (e.g., custards, gelatin, jellies).

    • Emulsion: One liquid dispersed in another immiscible liquid (e.g., oil-in-water).

    • Foam: Gas dispersed in a liquid or solid medium (e.g., beaten egg whites, whipped cream, marshmallows).

  • Flavor Components

    • Taste Substances: Sugars, acids, aldehydes, esters, alcohols, ketones, and sulfuric compounds.

    • Volatile acids: Partly responsible for the aroma of fruits and root crops.

    • Non-volatile acids: Do not change to a vapor state when heated.

Heat and Cooking

  • Key Definitions

    • Heat: Energy resulting from the vibratory or kinetic movement of molecules (∘C^\circ\text{C} or ∘F^\circ\text{F}).

    • Cooking: The process of combining food with heat (or cooling/freezing) to produce an edible, palatable, nutritious, aesthetic, and safe product.

  • Methods of Cooking

    • Moist heat: Uses water or liquid (boiling, stewing, simmering).

    • Dry heat: Uses little or no liquid (frying, broiling, grilling, baking).

  • Modes of Heat Transfer

    • Conduction: Direct transfer via materials; copper has the highest and glass has the poorest conductivity.

    • Convection: Transfer via vapor molecules of air/liquid from fuel sources.

    • Radiation: Transfer from a red-hot coil (griller/toaster) to food.

    • Microwave: Electromagnetic waves from a magnetron; longer wavelengths than infrared.

  • Key Temperatures in Food Preparation

    • 0 ∘C/32 ∘F0\,^\circ\text{C} / 32\,^\circ\text{F}: Freezing point.

    • 5 ∘C/40 ∘F5\,^\circ\text{C} / 40\,^\circ\text{F}: Refrigerator zone.

    • 65 ∘C/150 ∘F65\,^\circ\text{C} / 150\,^\circ\text{F}: Scalding.

    • 82−99 ∘C/180−211 ∘F82-99\,^\circ\text{C} / 180-211\,^\circ\text{F}: Simmering range.

    • 100 ∘C/212 ∘F100\,^\circ\text{C} / 212\,^\circ\text{F}: Boiling water.

    • 112−116 ∘C/234−240 ∘F112-116\,^\circ\text{C} / 234-240\,^\circ\text{F}: Pressure canning.

    • 150−220 ∘C/300−425 ∘F150-220\,^\circ\text{C} / 300-425\,^\circ\text{F}: Baking zone and candy making.

    • 190 ∘C/375 ∘F190\,^\circ\text{C} / 375\,^\circ\text{F}: Deep-fat frying.

  • Effects of Heat, Cold, and Acid

    • Heat on Protein: Causes coagulation and denaturation.

    • Heat on Fats: Fats are removed or absorbed; overheating creates acrolein.

    • Heat on Starch: Causes gelatinization and increased viscosity.

    • Heat on Sugar: Raises the boiling point; causes caramelization above 160 ∘C160\,^\circ\text{C}.

    • Cold: Can make separating egg yolks from whites difficult; improves tenderness and flavor of frozen meat.

    • Acid: Turns chlorophyll olive-green; causes syneresis in jelly; reduces the thickness and firmness of starch pastes.

  • Physical and Mechanical Treatments

    • Agitation and stirring: The basic mixing action.

    • Whipping/beating: Introduces air, aiding tenderness and foam stability.

    • Kneading: A process where dough is repeatedly pressed, stretched, and folded to align the gluten network to trap yeast gas and provide bread volume.