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Milk Is a Natural

Milk Is a Natural. Lab – October 6, 2010. Milk Basics. Milk has essential biological molecules Carbohydrates Protein Lipids (fats). Proteins. Needed for cell structure and function Composed of amino acids Tremendous number and variety of proteins

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Milk Is a Natural

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  1. Milk Is a Natural Lab – October 6, 2010

  2. Milk Basics • Milk has essential biological molecules • Carbohydrates • Protein • Lipids (fats)

  3. Proteins • Needed for cell structure and function • Composed of amino acids • Tremendous number and variety of proteins • Biuret Test – will show the presence of proteins • 3 main proteins • Casein • Lactalbumin • lactoglobulins

  4. Casein • Chief nutritional protein • 80% of total protein content • Responsible for high amount of calcium in milk • Insoluble in water, so easily precipitated from milk • 40°C • Add small amount of acid

  5. Lactalbumin and Lactoglobulin • More soluble in water • Smaller proteins • Lactalbumin – enzyme that synthesizes lactose • Lactose (Principal carbohydrate in milk) • Lactoglobulins are proteins that give milk it’s immunological properties (help build immune system) • Remain in milk as casein is precipitated out, but can be separated by heating milk to higher temps (80°-90°C)

  6. Carbohydrates • Monosaccharides (simple sugars – glucose, frustose) • 2 monosaccharides together form a disaccharide (table sugar, maltose, lactose-milk sugar) • Polysaccharides-complex carbohydrates (starch and cellulose) • Glucose (monosaccharide) – energy for metabolism • Starch (polysaccharide) – stores energy in plants

  7. Lactose • Principal carbohydrate in milk • Glucose + Galactose (disaccharide) • Can be separated through crystallization – long time heating (removes water) • Isolated as a white powder • Identified by Benedict’s test • (+ is seen by orange-red precipitate develops)

  8. Lipids (Fats) • Water-insoluble (cholesterol, steroid hormones, vitamin A and D) • In plants and animals • Separate using non-polar organic solvents (hexane) • Store chemical energy • Skim milk – fat layer (top) has been “skimmed” off the top (denser portion remains b/c fat is less dense than water – so top layer)

  9. Lab Process • 20 mL of Skim Milk • Add a bit acid (pH < 5) and heat 40°C • Produces Casein (precipitate-solid): prove this is a protein by Biuret test being positive and Benedict test showing negative • Produces Filtrate – heat to 80°C-90°C to separate Lactalbumin/lactoblobulin (precipitate): Biuret Test should be positive, Benedict’s negative • This will also produce Milk (whey) filtrate – heat to dryness (or slightly damp) to get solid residue (lactose) which should be positive for Benedict’s and negative for Biuret test

  10. Lab Write-Up • Title Page (name, date, title, period, group members) • Purpose Statement (why are we doing the lab?) • Hypothesis • Procedure • Observations • Data (this must include a graph/chart) • Conclusions (include any error that may have altered results – all of our labs have error!)

  11. Lab Write-Up Expectations • All sections of the lab are to be CLEARLY labeled. • This is individual………although you work with others on performing the lab, the write up is INDIVIDUAL • Grammar and punctuation will also affect your grade….write in complete sentences • Never use the words “I” or “We” or “You” instead say “The group”

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