Chemistry of Milk and Qualitative Analysis

Flashcards for reviewing key vocabulary terms and definitions from lecture notes on the chemistry of milk, enzymes, digestion, carbohydrates, lipids, and proteins.

Milk

A good example of emulsion, colloid, molecular and ionic solution

Lactose

The sugar naturally found in milk that requires the enzyme lactase to digest.

Lipids (Milk fat)

Gives milk its creamy texture and energy content.

Casein

Protein in milk for slow, steady nutrition and bone support (80%).

Whey

Protein in milk for fast muscle recovery and immune support (20%).

Lacto-albumin

Supports lactose synthesis

Lacto-globulin

Fat transport and immune system benefits

Test for Lacto-albumin and Lacto-globulin

Indicates the presence of protein in a milk sample (purple color).

Test for Lactose

Indicates the presence of sugar (brown color).

Benedicts reagent

Tests for sugar- Presence of sugar indicated by brown color

Test for Calcium

Indicates the presence of calcium (white precipitate). Reagent: 0.1M sodium oxalate (Na2C2O4)

Test for Phosphate

Indicates the presence of phosphate (white precipitate). Reagent: Ammonium molybdate solution

Saliva

Contains enzymes that chemically act on food during mastication; lubricating food for swallowing, facilitating the taste process, initiating the breakdown of carbohydrates (starch) and fats (lipids).

Salivary amylase (Ptyalin)

Breaks down starch into maltose. Reagent: Fehling’s solution

Saponification Principle

Hydrolysis of ester bond (fats or oils)

Triglycerides

Fats or oils

Sodium hydroxide (NaOH)

Sodium salts of fatty acids are formed, which are the characteristic hard soaps (bar soap) High melting point

Potassium hydroxide (KOH)

Potassium salts of fatty acids are formed, which are the characteristic soft soaps (liquid soaps, shampoos). Low melting point

Enzymes

Protein molecules that speed up the chemical reactions in the body; must bind with substrate to activate a specific protein.

Natural Enzymes

Harvested from natural sources (plants, animals, microorganisms) by fermentation or extraction.

Synthetic Enzymes

Manufactured artificially or engineered through genetic modification.

Papain and bromelain

Protease enzymes (enzymes that break down proteins) that have important applications in the detergent industry

Papain

An enzyme derived from the papaya fruit

Bromelain

A group of enzymes found in the pineapple

Proteases

Break down proteins and help to remove protein-based stains (eggs, sweat, blood)

Amylases

Break down starches and help to remove food stains that contain starch (potatoes, sauces, rice).

Lipases

Break down fats and oils and are used to remove greasy and oily stains from fabrics (butter, cooking oil).

Cellulases

Break down cellulose and help soften fabrics, reduce pilling, and improve the brightness of clothes.

Pectinases

Break down pectin, a polysaccharide found in fruits, and help remove stains from fruit-related sources (berries or jam).

Pepsin

Protease enzymes used by the stomach to further breakdown food.

Hydrogen Peroxide (H202)

A strong oxidizing agent that decomposes into water (H₂O) and oxygen (O₂). Bubbles.

Antacid

Widely used to relieve heartburn and indigestion; they work by neutralizing excess stomach acid, providing quick relief; pH ranging from 7.1 – 14.

Heartburn

Occurs when stomach acid irritates the esophagus; antacids help by neutralizing this excess acid, reducing the burning sensation in the chest or throat.

GERD (Gastroesophageal Reflux Disease)

A chronic form of acid reflux, where acid frequently leaks into the esophagus, leading to discomfort and potential damage to the esophageal lining.

Peptic Ulcers

Are sores that form on the inner lining of the stomach or the upper part of the small intestine (duodenum), often due to excess stomach acid.

Sodium bicarbonate

Can cause metabolic alkalosis

Sodium alginate

High sodium intake may occur. Lead to water retention, swelling, and increased blood pressure, particularly in individuals who are sodium-sensitive

Calcium carbonate

Contribute to kidney stone formation

Magnesium hydroxide

May lead to diarrhea

Aluminum hydroxide

Can cause constipation

Carbohydrates

A group of organic compounds that contains carbon, hydrogen and oxygen; sugars, starches, celluloses, and gums contain these elements and serve as a major source; main source of energy of the muscles.

Molisch Test

Chemical test which is used to check for the presence of carbohydrates in a given analyte; concentrated sulfuric acid (H2SO4) is added to the analyte; an appearance of reddish violet or violet ring indicates a positive reaction of Molisch’s reagent.

Iodine Test

Is a simple chemical test used to detect the presence of starch in a sample; it gives a characteristic blue-black color, indicating the presence of starch; starch reacts with iodine solution forms complex colour solution.

Tollen’s Test

To detect reducing sugars, specifically aldoses (sugars with an aldehyde group); Carbohydrates react with Tollens reagent and forms a silver mirror on the inner walls of the test tube; this confirms the presence of reducing sugars.

Fehling’s Test

This test is given by reducing sugars; Fehling’s solution is added and heated in water bath; the formation of red precipitate confirms the presence of reducing sugars.

Benedict’s Test

Used to identify reducing sugars (monosaccharides and some disaccharides); red precipitate of cuprous oxide is formed.

Barfoed’s Test

Is used to distinguish between monosaccharides and disaccharides based on their ability; any slight change in coloration is an indication of positive results.

Lipids

Are the organic biomolecules soluble in non-polar solvents; the qualitative analysis of lipids helps us determine the presence or absence of lipid.

Hydrophobic molecules

Non-polar substances that do not mix with water

Grease Spot Test

A simple qualitative test used to detect the presence of lipids (fats and oils) in a sample; Lipids do not evaporate, they leave a permanent translucent stain on paper.

Soluble

A substance that dissolves in a solvent to form a homogeneous solution.

Insoluble

A substance that does not dissolve in a solvent, remaining separate or forming a suspension.

Sudan Red Test

Is a qualitative test used to detect the presence of lipids; Sudan Red is a lipid soluble dye. When it is added to a mixture of lipids and water, the dye will move into the lipid layer coloring it red

Test for the Presence of Cholesterol in Food

Cholesterol reacts with acetic anhydride and concentrated sulfuric acid, producing a green or blue-green color, confirming the presence of cholesterol; greenish color indicates the presence of cholesterol.

Bromine Water Test

This test will validate the presence of unsaturated fatty acids

Ammonium Molybdate Test

Is a qualitative test used to detect the presence of phospholipids; The test is specific to phospholipids

Protein

Large organic compounds composed of amino acids; vital components of cells used by organisms for all biological processes; speeds up biochemical reactions to regulate body metabolism

Urine Protein

Is a rapid, qualitative or semi-quantitative test used to detect proteinuria (the presence of abnormal levels of protein in the urine)

Biuret test

Qualitative test used to detect the presence of proteins and peptides in a solution

Xanthoproteic Acid Test

Is a qualitative test used to detect aromatic amino acids (such as tyrosine, tryptophan, and phenylalanine) in proteins

Cystine

Is used to detect the presence of cystine, a sulfur-containing amino acid found in some proteins.

Ninhydrin Test

Is a qualitative test used to detect free amino acids and proteins with free amino groups.

Millon’s Test

Is a qualitative test used to detect the presence of tyrosine, an aromatic amino acid found in proteins

Denaturation of Protein

Is a process in which protein or nucleic acids lose their secondary structure by application of some external stress or compound.