Citric acid is a versatile organic acid found in many fruits, especially citrus fruits like lemons, oranges, limes, and grapefruits. Its chemical formula is C6H8O7, and it's classified as a weak acid. Citric acid has a wide range of applications, from food and beverage production to household cleaning and skincare. In this comprehensive description, I'll delve into its properties, uses, production methods, health effects, and environmental impact.
*1. Properties of Citric Acid:*
Citric acid appears as a white crystalline powder or granules. It's odorless and has a tart, sour taste. It's highly soluble in water, making it easy to incorporate into various products. Citric acid is stable at room temperature but decomposes at higher temperatures, losing its acidic properties. It's a chelating agent, meaning it can bind to metal ions, making it useful in certain industrial processes and household cleaners.
*2. Sources of Citric Acid:*
While citric acid occurs naturally in citrus fruits, it's also produced commercially through microbial fermentation, primarily using strains of the fungus Aspergillus niger. This method allows for large-scale production of citric acid to meet the demand in various industries. Additionally, it can be synthesized chemically, although this method is less common due to higher production costs and environmental concerns.
*3. Uses of Citric Acid:*
*- Food and Beverage Industry:* Citric acid is widely used as a flavoring agent, acidity regulator, and preservative in the food and beverage industry. It enhances the flavor of many products and provides a tart taste in sodas, candies, jams, and preserves. It also acts as a preservative, extending the shelf life of packaged foods and preventing discoloration in fruits and vegetables.
*- Pharmaceutical Industry:* Citric acid is used in pharmaceuticals as a pH regulator, excipient in tablets and capsules, and as a flavoring agent in syrups and liquid medications.
*- Cleaning Products:* Due to its chelating properties, citric acid is used in household cleaning products such as descalers, bathroom cleaners, and dishwashing detergents. It effectively removes mineral deposits and stains without the need for harsh chemicals.
*- Cosmetics and Personal Care:* Citric acid is found in skincare products like exfoliating scrubs, facial peels, and anti-aging creams. It helps to promote skin renewal by gently removing dead skin cells and promoting collagen production.
*- Industrial Applications:* Citric acid is used in various industrial processes, including water softening, metal cleaning, and the production of detergents and surfactants.
*4. Production Methods:*
*- Microbial Fermentation:* This is the most common method for commercial production of citric acid. It involves fermenting glucose or sucrose-containing substrates with strains of Aspergillus niger in large-scale bioreactors. The fungus produces citric acid as a byproduct of its metabolism, which is then extracted and purified.
*- C
2. Digestion, Mobilization, and Transport of Fats
• three sources: Dietary fats, stored , synthesized in
one to export in other.
• Highly industrialized countries :On average, 40% of
the daily energy requirement of humans is supplied
by dietary triacylglycerols (recommend no more
than 30% ).
• Triacylglycerols provide more than half the energy
requirements of some organs: e.g., liver, heart, and
resting skeletal muscle.
• virtually the sole source of energy in hibernating
animals and migrating birds.
3. Dietary Fats Are Absorbed in the Small
Intestine
• bile salts, such as taurocholic acid
• Lipases….Mono and diacylglycerol and free fatty
acids.
• triacylglycerols and packaged with dietary
cholesterol and specific proteins into lipoprotein
aggregates called chylomicrons.
• Apolipoproteins are lipid-binding proteins in the
blood, responsible for the transport of
triacylglycerols, phospholipids, cholesterol, and
cholesteryl esters between organs.
• Lipoprotein…… VLDL to VHDL
15. ω oxidation of fatty
acids
• In endoplasmic
reticulum of liver and
kidney
• the preferred
substrates are fatty
acids of 10 or 12 carbon
atoms.
16. α oxidation of fatty
acids
• Peroxisome
• Refsum’s disease, resulting
from a genetic defect in
phytanoyl-CoA
hydroxylase, leads to very
high blood levels of
phytanic acid
• A severe neurological
problems, including
blindness and deafness
19. Cholesterol biosynthesis
• Cholesterol, like long-chain fatty acids, is made from
acetyl-CoA
• Synthesis takes place in four stages,
• 1. condensation of three acetate units to form a six-
carbon intermediate, mevalonate;
• 2. conversion of mevalonate to activated isoprene
units;
• 3. polymerization of six 5-carbon isoprene units to
form the 30-carbon linear squalene;
• 4. cyclization of squalene to form the four rings of the
steroid nucleus, with a further series of changes to
produce cholesterol.
