UGEB2380 The Chemistry of Life 2024-25 PDF

UGEB2380 The Chemistry of Life Academic Year 2024-25 Dr. Sam CK HAU (Department of Chemistry) Micronutrients, Food Additives, and Food Safety Micronutrients & Food Additives Components of foods NOT provide directly with bodily substances or energy Vital to our well being (vitamins & min...

UGEB2380 The Chemistry of Life Academic Year 2024-25 Dr. Sam CK HAU (Department of Chemistry) Micronutrients, Food Additives, and Food Safety Micronutrients & Food Additives Components of foods NOT provide directly with bodily substances or energy Vital to our well being (vitamins & minerals) Contribute to the taste, texture, or stability of foods (food additives) May offer additional health benefits 3 Micronutrients Dietary substances needed in trace amount for proper health i.e. Vitamins and Minerals, essential for good health Vitamins are organic compounds that form in small amount within the plants and animals that we eat as foods Divided into water-soluble and fat-soluble vitamins Water-soluble Vitamins Dietary Sources Functions Meat, animal organs, whole Vital for cellular function, support and promote skin, hair, brain Vitamins B1, B2 and B3 grains, green vegetables health and nervous system Improve cardiovascular health, as well as support nervous Vitamin B5 Avocado, Broccoli, Salmon system, hormones Vitamin B6 Carrot, Sweet Potato, Tuna Support cardiovascular health by lowering homocysteine levels Helps in the metabolism of fatty acids, is essential for healthy Vitamin B7 Avocado, Cauliflowers, Carrots bones and hairs Broccoli, Beets, Sardines, Eggs, Vital for cell repair and maintenance, essential for blood cell Vitamin B9 and B12 Chicken formation, helps cardiovascular health Important for immune system health, essential element in Fruits, especially citrus, Vitamin C collagen formation, antioxidant, boosting of resistance to Vegetables infections 4 Vitamins Vitamin C (water-soluble vitamin) HO O Ascorbic acid HO O “Ascorbic” - protect against the disease scurvy (Latin hydroxyl group HO OH ‘scorbutus’) Ascorbic Acid Require for the formation of bonds holding together strands of the collagens of our tissues Tough fibres are important component for our skin, muscles, blood vessels, scar tissues Weakened by the deterioration of the gum’s collagen - cause bleeding 6 Vitamins Vitamin A β-carotene (fat-soluble vitamin) Retinol Maintains the health of eyes, skin Chemical reactions within the body and mucous membranes; important for good vision in dim OH Retinol light Deficiency - night blindness Retinol OH Accumulates in body’s fat cells, particularly in liver Large excess, overwhelming body storage capacity, can cause toxic effect Carrots contain no retinol but lots of β-carotene Consumes excess is safe but imparting the colour to the skin and eyes but reversible 7 Vitamins Vitamin D (fat-soluble vitamin) CH3 group Promotes the absorption of food-borne calcium and H 3C 7-Dehydrocholesterol, a phosphorus for forming and precursor to Vitamin D3, which occurs in the skin maintaining new bones HO Can form cholecalciferol Solar Radiation (Vitamin D3) by our skins through the action of the sun’s UV rays Without vitamin D, bones Cholecalciferaol, Vitamin D3 develop poorly and result in Become this CH2 group the severely bowed legs and CH2 other skeleton deformations HO (i.e. Rickets) 8 Minerals Refers to all nutritionally important chemical elements of our foods, except for C, H, O and N Two significant features distinguish from vitamins Consist of atoms or ions of individual elements Must be absorbed by plants from the soil; then be ingested and absorbed by the animals Minerals cannot be created by living thing but absorbed from the earth in which they exist 9 Major Minerals Minerals required in the diet in amounts greater than 100 mg (100 x 10-6 g) per day or present in the body in amounts greater than 0.01% of the body mass Calcium Between 1.5 to 2.0% of our weight, in the form of Ca2+ ion Among them, 99% of this lies in our bones and teeth For example, 70 kg (154 lb) person, about 1.0 ~ 1.5 kg (roughly 2-3 lb) of calcium in the skeleton and teeth 10 Major Minerals Minerals required in the diet in amounts greater than 100 mg (100 x 10-6 g) per day or present in the body in amounts greater than 0.01% of the body mass Phosphorus 0.5 g for packing 1 g of calcium firmly into the lattices of our bones and teeth Small amount in our soft tissue For example, 70 kg (154 lb) person, about ~1.0 kg (roughly 2 lb) 11 Major Minerals Minerals required in the diet in amounts greater than 100 mg (100 x 10-6 g) per day or present in the body in amounts greater than 0.01% of the body mass Potassium (K+) & Sodium (Na+) Form the major ions of the fluids in and around cells (i.e. intracellular and extracellular fluids) Governs the activities of enzymes in the cells Maintain proper fluid levels by regulating the distribution of hydrogen ions Transmission of nerve signals 12 Major Minerals Minerals required in the diet in amounts greater than 100 mg (100 x 10-6 g) per day or present in the body in amounts greater than 0.01% of the body mass Chlorine (Cl ¯ ) Regulate fluid balances In combination with protons (H+) to provide the hydrochloric acid (gastric juice) Serve to balance the electrical charges of the various bodily cations 13 Major Minerals Minerals required in the diet in amounts greater than 100 mg (100 x 10-6 g) per day or present in the body in amounts greater than 0.01% of the body mass Magnesium (Mg2+) Plays several secondary roles Hard mineral of bones and teeth Regulating biochemical activities within the cells Helps control the formation of proteins inside the cells Transmission of electrical signals within cells 14 Food Additives Chemical added to foods to help preserve them and to make them more nutritious and more appealing A more practical definition: ‘anything intentionally added to a food to produce a specific, beneficial result, regardless of its legal status’ 15 Food Additives Functions of Additives ✓ Improve or maintain the quality of foods, like adding salt, sweeteners to improve the taste ✓ Food colouring, enhance the appearance of foods, like the decorations of a birthday cake ✓ Increase the nutritional values, like adding vitamin D to milk ✓ Preserve freshness, like ascorbic acid protects foods from oxidation 16 Food Additives Sequestrant When added to foods, EDTA molecules wrap around and bond to extraneous metal ions Prevent these ions from catalysing the oxidation of fats and other components of foods Help prevent rancidity and preserve food quality O O OH C C OH N N HO C C HO O O Ethylenediaminetetraacetic acid 17 (EDTA) Food Additives Humectant Compounds that can help attract or retain moisture Propylene glycol - help retain moisture through hydrogen bonding to water molecules The coconut flakes contains propylene glycol to keep them moist H H O hydrogen bonds H O O H H CH O H 3C C H H2 18 Food Additives Emulsifiers Monoglyceride non-polar tail Mono- and diglycerides O O Contain both polar and non- H 2C O C R H 2C O C R polar groups enabling two HO CH HC O C R liquids do not mix together, HO CH2 HO CH2 O but to form a stable mixture or emulsion Diglyceride polar head Peanut butter - emulsifiers R: –(CH2)14CH3 help prevent the peanut solids and oils from separating, and maintain a creamy smoothness during storage 19 Food Safety A poison can be a natural component of foods e.g. caffeine of coffee, tannins of tea, oxalic acid of spinach, table salt … … 20 Poisons & Toxins Poison Any chemical substances that can cause illness or death when it enters the body by eating, drinking, inhalation, or injection Toxin A poison of biological origin, produced by a plant or an animal It might enter the body by eating a spoiled food, stung or bitten by an insect or a snake 21 LD50 Measure the virulence of a poison or toxin is determine the amount needed to kill a living thing - lethal dose Individuals show different responses to identical stress or poisons The amount of a chemical that kills exactly half of a large population of animals within a week - LD50 (Lethal Dose for 50% of the group) 22 LD50 Example LD50 for aspirin fed orally to mice and rats is 1.5 g/kg ✓ Means that feeding orally to a large group of mice or rats at the level of 1.5 g of aspirin per kg of animals will kill half of the population ✓ OR there is a 50% chance that 1.5 g/kg aspirin will kill any particular mouse or rat that eats it 23 LD50 More examples LD50 for aspirin fed orally to mice and rats is 1.5 g/kg LD50 for sodium cyanide (NaCN) fed orally to mice and rats is 15 mg/kg NaCN is 100x more lethal than Aspirin Different animals often respond differently to a particular chemical and the method of introducing: LD50 for nicotine to mice - 230 mg/kg (oral); 9.5 mg/kg (inject to abdominal cavity); 0.3 mg/ kg (inject to bloodstream) 24 Safety As defined by William Lowrance - the acceptability of risk; the risks we find acceptable, are the one defined as safe However, which are considered as safe or acceptable or not, depends on our every individuals, the government, the corresponding agency 25 Natural Foods = Safe? With the variety of chemicals be added to the processed foods, seems that eating the natural foods expose us far fewer hazardous chemicals Mango - tasty tropical fruit; it is considered as a safe food based on the masses of people without ill effect after consume BUT, some individuals may be allergic to mangos 26 Natural Toxins in Foods Compounds in plants are very effective insect poisons O Some plant chemicals are not only toxins but are carcinogenic O Safrole (⿈樟油精), comes Safrole, a major component from the barks around the of oil of sassafras roots of sassafras tree, also can be found less in cocoa, black pepper, spices and herbs Used to produce the taste of sassafras tea (檫⽊茶), and as the principal flavouring ingredient in the manufacture of root beer 27