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An Overview of C asein s. Speech: YangJiawei Author: ZhangHong ZhuZhengjiang WuRongde DuanXinyan 2005.5.12. Introduction. When, as a child, that glass of milk was set in front of you at breakfast time, besides it being
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An Overview of Caseins Speech: YangJiawei Author: ZhangHong ZhuZhengjiang WuRongde DuanXinyan 2005.5.12
Introduction When, as a child, that glass of milk was set in front of you at breakfast time, besides it being good for your bones, teeth and health in general, had you any idea how really essential this natural opaque white liquid has been for humans in the past millennia? Why? What composition is the milk?
Protein Composition of Bovine Milk Source: Fennema, O.R. Food Chemistry, Third Edition, pg. 847
The Applied History Of Caseins • The curds were used by the Ancient Egyptians as a fixative thousand years ago • Since the Renaissance, casein has been used as a binder for paints • In the 18th century, was already used in the construction of chalets in Switzerland • Particularly popular for the construction of the wooden frame parts of aircraft during World War I
_ _ PO3 -O O-PO3 Ca2+ Structure of Casein Micelles • Three types of casein proteins • , and casein • Contain distinct hydrophobic and hydrophilic domains • May first cluster to form sub-micelles due to hydrophobic interactions • Surface of submicelle contains charged phosphoserine groups • Complex with Ca2+ to form micelles • -- may have “raspberry structure”
_ Casein Micelles link • Submicelles cluster in presence of Ca2+ to form micelles • Bind calcium • What limits size of • Some submicelles rich in -casein Ca2+ Ca2+ Ca2+ Ca2+ micelles (prevents phase separation)? _ -casein does not bind Ca2+ Polar and charged polar domain is protein is glycosolated (glycoprotein) “hairy raspberries” -casein keeps micelles apart
The stability of the casein micelle: • Role of Ca++ • H Bonding • Disulphide Bonds • Hydrophobic Interactions • Electrostatic Interactions • van der Waals Forces • Steric stabilization
affect the stability of the casein micelle system: • Salt content • pH • Temperature • Heat Treatment
The new application of caseins • Casein glue is used to bond the seam of cigarette paper • One recent discovery was made in the fight against tooth decay • Casein phosphopeptides could actually deliver calcium phosphate on a tray and help build up the tooth again.
cheese • Cheese is a solid food made from the curdledmilk of various animals—most commonly cows but sometimes goats, sheep, reindeer, and water buffalo. ★ There are over 400 types of cheese. http://en.wikipedia.org/wiki/Cheese
The history of cheese • To give you an idea of how old the art of cheese making is, we looked into the history books and discovered that man must have known about making cheese before he invented writing. • A Greek historian named Xenophon, born in 349 B.C., wrote about a goat cheese that had been known for centuries in Peloponnesus.
_ _ _ Acid or enzyme Cheese Formation • Modification of -casein allows micelles to aggregate to form gel strands • Leads to cheese, yogurt formation • Modify protein by lowering pH (e.g. yogurt) • Changes charge on -casein • Modify by cleaving -casein using chymosin (rennet) • Protease enzyme • Cuts off “hairs”
Cheese Manufacture Ripen Aging Note Link Color Air Dry and Coat Rennet Mold and Press Cut the Curd Mill and Salt Cook the Curd Drain http://www.cheesemaking.com
That’s all Thank you
