Most abundant molecule in cells making up 50 or more of their dry weight Every protein has a unique structure or shape Allows it to perform a specific function Enzymes are proteins that function as catalysts for many reactions in foods ID: 784119
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Slide1
Proteins
Milk and Dairy
Slide2Proteins
Most abundant molecule in cells making up 50% or more of their dry weight
Every protein has a unique structure, or shape
Allows it to perform a specific function
Enzymes are proteins that function as catalysts for many reactions in foods
Contains oxygen, hydrogen, carbon, nitrogen
Most also contain sulfur
May also contain: phosphorus, iron, copper, zinc
Very important nutritionally and functionally in foods
Slide3Proteins
https://
www.youtube.com/watch?v=qBRFIMcxZNM
Polymers of amino acids (set of 20)
Some water soluble, some notSome charged, some notSequence programmed by DNA for a purpose
Alanine
Glutamic acid
Phenylalanine
Slide4The hydrophobic groups are concealed in the protein core by spontaneous, natural folding
Water hating (hydrophobic) amino acids
Peptide chain
Protein Folding
Slide5Proteins
Primary
sequence of amino acids
Secondary
- local folding
Tertiary - large scale foldingQuaternary - association structures
Computer model of b-
lactoglobulin, an important milk serum protein
Slide6Lysozyme
KVFGRCELAAAMKRHGLDNYRGYSLGNWVCAAKFESNFNTQATNRNTDGSTDYGILQIN
“
Lysozyme reaction is hydrolysis of the beta (1-4) glycosidic bond between N-acetylglucosamine sugar (NAG) and N-acetylmuramic acid sugar (NAM).
”
www.lysozyme.co.uk
Slide7Protein Denaturation
Abrupt change in protein structure on being moved from non-native conditions (heat, acid, intense mixing, solvents)
Sometimes (rarely) reversible
Enzymes no longer work
Texture may change
https://
www.youtube.com/watch?v=3IL_Df5ouUc
Image: Flickr user ClickFlashPhotos / Nicki
Varkevisser
Slide8Enzymes
http
://
www.youtube.com/watch?v=XTUm-75-PL4
Enzymes are proteins but catalyze reactions with protein and non-protein substances
Each enzyme has a unique structure which enables it to attach to specific substrates and catalyze reactionsWhen the reaction is complete the enzyme is released an able to act as a catalyst againHow might enzymes help in food processing? How might they be a problem in food processing?
Slide9Isoelectric Point
The pH at which a protein is electrically neutral
Does not mean there are no charged groups
It means the number of positive charges is equal to the number of negative charges
The point at which the protein molecules
precipitateMolecule that carry a like charge repel each otherRemoval of the charge allows them to interact with each other
Slide10General composition of milk
Component
COW
GOAT
SHEEP
Water
87.3
87.6
60.7
Lactose
4.8
4.5
4.8
Fat
3.7
3.6
7.4
Protein (casein + whey)
3.4
3.5
4.5
Salts (minerals)
0.7
0.8
1.0
Slide11Slide12Slide13Slide14Slide15Slide16Slide17Slide18Slide19Slide20Slide21Slide22Slide23Slide24Slide25Slide26Slide27Slide28Slide29Slide30Slide31Slide32Slide33Slide34Slide35Slide36Slide37Slide38Slide39Slide40Slide41Slide42Slide43Slide44Slide45Mozzarella Heaven!
Slide46Slide47Slide48Slide49Slide50Slide51Slide52Slide53Slide54Slide55Slide56Slide57Cheese in the Sous Vide
https://
www.youtube.com/watch?v=3mSNJfl9kBE
NATURAL VS. PROCESSED CHEESE
...know what you're buying.
Natural
vs.
Processed
Swiss
Natural cheeses
are made by the traditional methods.
Processed
cheese
is natural cheese that has been ground, mixed, and pasteurized. The heat applied during this process halts the “aging” of the cheese, extending the shelf life and stabilizing flavor changes. Emulsifiers have been added to prevent the separation of fat, producing desirable slicing and melting qualities in the final product. The processed cheese has a slightly different taste and appearance than the natural cheese. For example, natural Swiss cheese has holes in it... processed Swiss cheese doesn’t. Natural cheese is usually more expensive than processed cheese.