Food Component Part 1

Introduction

• Apologies for technical issues with the projector.

• Last week's topic: Food categories.

• Today's focus: Food chemistry.

• Upcoming topics: Food properties and functionality on Thursday.

• Key food components: Carbohydrates, fats, and proteins. These macronutrients are essential for energy, growth, and various bodily functions.

Assignments and Assessments

• Video Assignment

  • Groups should be in place; contact team members.

  • Find a topic (sodium reduction, nutrient deficiency, obesity, food waste). These topics are critical for addressing current public health challenges.

  • Create a 3-minute video: problem, science, solution. Videos should clearly outline the issue, the scientific principles behind it, and potential solutions.

  • Referencing at the bottom of the video. Proper citation is necessary to give credit to sources and avoid plagiarism.

• Food Science Essay

  • One-pager on the rise in popularity of Ozempic/Wegovy. Essays should explore the reasons behind this trend, and the implications for public health and nutrition.

  • Focus, less is more. Concise and well-argued points are preferred over lengthy, unfocused discussions.

  • Referencing is important. Use credible sources to support arguments.

  • Start early to show drive and interest. Early start helps in thorough research and thoughtful composition.

Definitions

• Chemistry: The science of atoms and molecules. It explains the composition, structure, properties, and reactions of matter.

• Atom: Building block of a molecule; comes from Greek word meaning unsplittable. Atoms are the smallest units of an element that retain its chemical properties.

• Molecule: Multiple atoms linked together through chemical bonds. Molecules can be simple, like water (H_2O), or complex, like proteins.

• Protein: Chain of amino acids linked by peptide bonds. Proteins perform a wide array of functions in living organisms.

• Carbohydrate: Carbon and hydrate (water), C
  H2O. Carbohydrates are a primary source of energy for the body.

• Lipid: Fat. Lipids include fats, oils, and waxes and are essential for energy storage, insulation, and hormone production.

Relevance of Food Chemistry

• Understanding food labels (protein, fat, carbohydrates, sugars, sodium, etc.). Food chemistry helps consumers make informed dietary choices.

• Goal: Clarity on food components and their roles. Understanding how these components affect health and nutrition.

Course Outline

• Food chemistry is a major aspect of food science, providing a foundation for understanding food's properties and behavior.

• Today and Thursday: Proteins, carbs, and lipids. Deep dive into their structures, functions, and interactions.

• Also covering vitamins, minerals, and fibers. Micronutrients and their importance in maintaining health.

• Importance of understanding the chemistry of food. Essential for developing new food products and improving food
  safety.

Atoms and the Periodic Table

• Atoms are elements that can be ordered using the periodic table. The periodic table organizes elements based on their atomic number and chemical properties.

• UNSW has Professor Bryn Hibbert, a guardian of the periodic table. Highlighting expertise and resources available.

• Core components of an atom: electrons, protons, and neutrons. These subatomic particles determine an atom's properties.

• Protons: Positively charged, mass of one. Located in the nucleus.

• Neutrons: No charge, mass of one. Also located in the nucleus.

• Electrons: Negligible mass. Orbit the nucleus in electron shells.

• Periodic table arrangement: By the number of protons, which defines the element.

• Lightest atom: Hydrogen, followed by Helium. Fundamental elements in the universe.

• Atomic number: Number of protons (e.g., Aluminum is 13). Atomic number uniquely identifies an element.

• Atomic weight of aluminum: 27. The average mass of an atom of aluminum.

• Isotopes: Atoms with the same number of protons but different numbers of neutrons. Isotopes have different mass numbers but the same chemical properties.

  • Examples: C14, Uranium 235, Uranium 238. Used in various applications like carbon dating and nuclear energy.

• Ions: Charged entities. Formed when atoms gain or lose electrons.

  • Cations: Positive, formed by losing electrons.

  • Anions: Negative, formed by gaining electrons.

• Important atoms/elements for food and bodies: Carbon, hydrogen, oxygen, nitrogen, sodium, potassium, calcium, iron.

Proteins in Food

• High protein foods: Tuna, beans, chicken breast, tofu, eggs. These foods are excellent sources of protein for a balanced diet.

• Protein sourcing: Animals vs. plants. Understanding the differences in amino acid profiles and digestibility.

• Soy has a high amount of protein per 100g. Soybeans are a complete protein source, containing all essential amino acids.

• Food proteins:

  • Alpha-lactalbumin (milk): A whey protein important for infant nutrition.

  • Ovalbumin (egg): The main protein found in egg white.

  • Gluten (gliadin and glutamin): Proteins found in wheat, responsible for the elasticity of dough.

Amino Acids

• Proteins are made of amino acids. Amino acids are the building blocks of proteins.

• There are 20 common amino acids, plus selenocysteine (21st). These amino acids are encoded by the genetic code.

• Amino acid features: Carboxylic group (COOH) and amino group (NH2). These functional groups are crucial for peptide bond formation.

• Acid: Molecule that can give away a proton (H^+). Acids donate protons in chemical reactions.

• Base: Molecule that can take on protons. Bases accept protons in chemical reactions.

• Zwitterion: An amino acid with both positive and negative charges. This amphoteric nature allows amino acids to act as both acids and bases.

  • Amino acid with \ NH_3^{+} and O- groups.

• C alpha atom: Core feature of an amino acid including R (residue side chain). The R group determines the unique properties of each amino acid.

• Proteins are polymers of amino acids. Long chains of amino acids linked by peptide bonds.

• 20 common amino acids are joined by peptide bonds. Peptide bonds form between the carboxyl group of one amino acid and the amino group of another.

• Stereo center, with L and R hand possibilities (chirality). Amino acids exist as stereoisomers, with L-amino acids being the predominant form in proteins.

Amino Acid Residues

• 21 different amino acids, ordered/arranged based on features. The arrangement of amino acids determines the protein's structure and function.

• Common feature: C \alpha , NH_3^{+},COO^{-} . The basic structure of all amino acids.

• Differing residue (R) gives unique properties. The R group dictates the amino acid's chemical behavioUr.

• Categories:

  • Electrically charged side chains (Arginine, Histidine, Lysine, Aspartic Acid, Glutamic Acid). These amino acids are hydrophilic and often found on the surface of proteins.

  • Polar uncharged side chains (Serine, Threonine, Asparagine, Glutamine). These amino acids can form hydrogen bonds with water and other molecules.

  • Special cases (Cysteine - contains Sulfur, Selenocysteine, Glycine, Proline). These amino acids have unique structural properties that influence protein folding.

  • Hydrophobic side chains (Alanine, Valine, Leucine, Isoleucine, Methionine). These amino acids tend to cluster in the interior of proteins, away from water.

  • Aromatic (Phenylalanine, Tyrosine, Tryptophan). These amino acids absorb UV light and contribute to protein stability.

• Umami taste related to MSG (monosodium glutamate) and glutamate. Glutamate enhances the savory flavor of foods.

• Glutamate: Glutamic acid. A non-essential amino acid that acts as a neurotransmitter.

Peptide Bonds

• Amino acids linked together through peptide bonds.

• One amino acid + another amino acid make a di-amino acid (a dipeptide).

• Eliminate water to form a peptide bond (CONH). Dehydration reaction creates the peptide bond.

• Peptide bonds are planar (form a plane). This planarity restricts the conformation of the protein backbone.

• No free rotation around the C-N bond. Partial double bond character limits rotation.

• Electron pair/double bond smears into C-N, making it a partial double bond. Resonance stabilization of the peptide bond.

• Chain of planes creates 3D structures. The arrangement of peptide bonds influences protein folding.

• Ramachandran plot: Maps rotatability of one angle against the other. Visual representation of allowed phi and psi angles in a peptide chain.

Protein Structure

• Structure determines the function. The three-dimensional arrangement of a protein dictates its biological activity.

• Major component is protein structures.

• Different Hierarchies:

  • Primary: Sequence of amino acids in the chain. The linear order of amino acids determines the protein's identity.

  • Secondary: Alpha helices or beta sheets. Localized folding patterns stabilized by hydrogen bonds.

  • Tertiary: Coiling up into bigger scale. The overall three-dimensional structure of a single protein molecule.

  • Quaternary: Multiple tertiary structures associate i.e. HeAmoglobin. The arrangement of multiple protein subunits in a multi-subunit complex.

Essential and Nonessential Amino Acids

• Essential: Must be obtained through diet (9 of them). The body cannot synthesize these amino acids, so they must be consumed.

• Conditionally Essential: Needed during infancy or illness. These amino acids may become essential under certain physiological conditions.

• Nonessential: Can be produced by the body. The body can synthesize these amino acids from other precursors.

PDCAAS

• Protein Digestibility Corrected Amino Acid Score. A measure of protein quality based on amino acid requirements and digestibility.

• Mapping of essential/nonessential amino acids onto specific foods. Used to evaluate the nutritional value of different protein sources.

• PDCAAS = 1.0 is perfect. Indicates that the protein source meets or exceeds the body's amino acid requirements.

Proteins in Food

• Milk: Casein (cheese proteins), whey (soluble proteins). Milk contains a variety of proteins with different properties and functions.

• Egg: Ovalbumin, lysozyme. Egg proteins are highly nutritious and easily digestible.

• Wheat: Gluten, gliadin, glutinins. Wheat proteins give dough its elasticity and structure.

• Molecular biology of proteins: DNA to mRNA, then using the ribosome. The central dogma of molecular biology describes the flow of genetic information.

• Post-translational modifications (PTMs). Modifications to proteins after they are synthesized, affecting their activity and localization.

  • Phosphorylations. Addition of phosphate groups to amino acid residues.

  • Glycosylation. Addition of sugar molecules to amino acid residues.

  • Ubiquitination. Addition of ubiquitin molecules, often targeting proteins for degradation.

  • Sumoylation. Addition of SUMO (Small Ubiquitin-like Modifier) proteins.

  • Disulfide bonds. Covalent bonds between cysteine residues, stabilizing protein structure.

  • Lipidation. Addition of lipid molecules, targeting proteins to cell membranes.

• Allergenicity varying by source (animal vs. plant). Some proteins are more likely to cause allergic reactions than others.

Denaturation

• Breaking hydrogen bonds and disulfide bonds. Disrupting the non-covalent interactions that maintain protein structure.

• Exposing hydrophobic residues. Hydrophobic amino acids become exposed to the surrounding environment.

• Denaturation Examples: Roasting of meat, cooking of egg, whipping of egg white. These processes alter the protein structure, leading to changes in texture, color, and flavor.

Functionality

• Proteins do impact functionality; color, texture, and flavor. Proteins contribute to the sensory properties of food.

• Maillard Reaction: Browning during cooking (starts on Thursday's lecture). A chemical reaction between amino acids and reducing sugars, producing flavorful compounds.

• Individual amino acids:

  • Bitter (Glycine, Alanine, Threonine, Proline, Serine, Glutamine). Some amino acids have a bitter taste.

  • Sweet. Some amino acids have a sweet taste.

  • Umami (Glutamate: Important, dose dependent). Glutamate enhances the savory taste of food, but its effect depends on concentration.