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The Biochemistry of Milk Ch. 23
23

The Biochemistry of Milk Ch. 23. How do you milk a cow? How do you milk a cow? Video Video Video %20make .

Dec 14, 2015

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Page 1: The Biochemistry of Milk Ch. 23. How do you milk a cow? How do you milk a cow? Video Video Video  %20make .

The Biochemistry of Milk

Ch. 23

Page 2: The Biochemistry of Milk Ch. 23. How do you milk a cow? How do you milk a cow? Video Video Video  %20make .

How do you milk a cow?How do you milk a cow?

VideoVideo http://www.moomilk.com/http://www.moomilk.com/

faq.htm#To%20makefaq.htm#To%20make

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The Complex Nature of Milk

Milk supplies the calcium for Milk supplies the calcium for building bones and teeth, building bones and teeth, especially during adolescenceespecially during adolescence

Milk is 87% waterMilk is 87% water However that’s a solvent for over 250 However that’s a solvent for over 250

chemical compounds, milk sugar (what is chemical compounds, milk sugar (what is the name for milk sugar_____?____) the name for milk sugar_____?____) water-soluble vitamins and trace water-soluble vitamins and trace minerals and saltsminerals and salts

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Protein

Two main proteins make up milk:Two main proteins make up milk: 80% 80% CaseinCasein = milk protein = milk protein 20% Whey = milk protein20% Whey = milk protein

MicellesMicelles = an aggregation or = an aggregation or cluster, of molecules, often found cluster, of molecules, often found in colloidal dispersionsin colloidal dispersions

The light reflecting from micelles makes milk The light reflecting from micelles makes milk whitewhite

As long as milk keeps its normal As long as milk keeps its normal acidity level, about pH 6.6, casein acidity level, about pH 6.6, casein remains stableremains stable

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Protein Continued

When the pH level decreases the milk When the pH level decreases the milk forms lumps or coagulates.forms lumps or coagulates.

CurdsCurds = The casein clumps that = The casein clumps that separate from the liquid when milk separate from the liquid when milk coagulatescoagulates

When cooking with milk you can prevent curdling When cooking with milk you can prevent curdling by using starch to thicken the milkby using starch to thicken the milk

If you want to coagulate milk, you can use the If you want to coagulate milk, you can use the enzyme rennin or vinegar.enzyme rennin or vinegar.

WheyWhey = protein found in the liquid that = protein found in the liquid that remains after fat and casein have been remains after fat and casein have been removed from milk. removed from milk.

Whey is also called serum proteinWhey is also called serum protein

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Fats

Milk is an emulsion because small globules Milk is an emulsion because small globules of fat (lipid) are dispersed throughout the of fat (lipid) are dispersed throughout the waterwater

CreamingCreaming = process in which some of the = process in which some of the fat droplets come together in larger fat droplets come together in larger clusters that rise and float to the top of the clusters that rise and float to the top of the milkmilk

These clusters rise to the surface because fat is less These clusters rise to the surface because fat is less dense than the watery portion of milkdense than the watery portion of milk

CreamCream = simply milk that is extra rich in = simply milk that is extra rich in emulsified fat dropletsemulsified fat droplets

The fat in cow’s milk are most complex lipids, over The fat in cow’s milk are most complex lipids, over 400 different fatty acids400 different fatty acids

Click For Milk ExperimentClick For Milk Experiment

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Carbohydrate

Lactose or milk sugar is the main Lactose or milk sugar is the main carbohydratecarbohydrate

Lactose provides food energyLactose provides food energy Also adds body to milk as well as a sweet flavorAlso adds body to milk as well as a sweet flavor When milk is heated, lactose reacts with amino When milk is heated, lactose reacts with amino

acids in the protein (giving cooked milk a acids in the protein (giving cooked milk a slightly caramel flavor)slightly caramel flavor)

When you consume milk, lactose becomes When you consume milk, lactose becomes available to the body because of the enzyme available to the body because of the enzyme lactase.lactase.

This enzyme breaks lactose down into This enzyme breaks lactose down into galactose and glucose, which is used in the galactose and glucose, which is used in the body for fermentation during digestion.body for fermentation during digestion.

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Carbohydrate Continued

Do you know someone who cannot Do you know someone who cannot drink milk???drink milk???

People can be People can be lactose intolerancelactose intolerance = = the inability to digest milk due to the the inability to digest milk due to the absence of the enzyme lactase in the absence of the enzyme lactase in the intestinesintestines

People who are lactose intolerant cannot People who are lactose intolerant cannot break down lactose in their body. When they break down lactose in their body. When they drink the milk they can have bloating, drink the milk they can have bloating, stomach cramps and diarrhea.!!! -NOT FUNstomach cramps and diarrhea.!!! -NOT FUN

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Minerals and Vitamins

Milk has salt that occurs naturallyMilk has salt that occurs naturally Salts in milk include chlorides and Salts in milk include chlorides and

phosphates (in very low amounts)phosphates (in very low amounts) Salt in milk helps prevent curdlingSalt in milk helps prevent curdling If an acid is added to milk (what would If an acid is added to milk (what would

be an example of an acid), the pH lowers be an example of an acid), the pH lowers which removes the calcium ions from the which removes the calcium ions from the casein, making the milk curdle – forming casein, making the milk curdle – forming _____and ____________and _______

Four vitamins found naturally in milk, Four vitamins found naturally in milk, riboflavin is found in the largest quantity. riboflavin is found in the largest quantity.

Breaks down when exposed to lightBreaks down when exposed to light

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Pasteurization

Shelf LifeShelf Life = time a food product = time a food product can be stored before deteriorating.can be stored before deteriorating.

When pasteurizing milk, its heated When pasteurizing milk, its heated to high temperatures for a short to high temperatures for a short time to destroy harmful bacteriatime to destroy harmful bacteria

Pasteurization denatures enzymes that Pasteurization denatures enzymes that cause milk to spoilcause milk to spoil

Pasteurization has a small effect on Pasteurization has a small effect on milk’s nutritional value, creating a slight milk’s nutritional value, creating a slight loss of thiamin, vitamin B12, vitamin Closs of thiamin, vitamin B12, vitamin C

DO YOU THIN THAT DRINKING DO YOU THIN THAT DRINKING UNPASTURIZED MILK IS BETTER FOR UNPASTURIZED MILK IS BETTER FOR YOU?YOU?

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Homogenization

Under pressure of 2,000 to 2,500 Under pressure of 2,000 to 2,500 pounds per square inch, milk is pounds per square inch, milk is forced through small openings in a forced through small openings in a machine called a homogenizermachine called a homogenizer

The fat particles break down, an The fat particles break down, an emulsifier surrounds the fat particle, emulsifier surrounds the fat particle, which keeps the particles permanently which keeps the particles permanently separatedseparated

As a result the milk you buy does not have As a result the milk you buy does not have cream on the top.cream on the top.

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Fortification

FortificationFortification = the addition of a = the addition of a nutrient to a foodnutrient to a food

Ex. What nutrient is milk fortified Ex. What nutrient is milk fortified with___?___with___?___

Without vitamin D, your body can’t absorb Without vitamin D, your body can’t absorb calcium and phosphorus very well.calcium and phosphorus very well.

To fortify milk with vitamin D, it may be To fortify milk with vitamin D, it may be exposed to ultraviolet light, which convert exposed to ultraviolet light, which convert some of the milk fat components to some of the milk fat components to vitamin dvitamin d

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Fluid Milk/ Ultrahigh-Temperature Milk (UHT)

Fluid milk is categorized by fat Fluid milk is categorized by fat contentcontent

Whole milk – 8g fatWhole milk – 8g fat Reduce-fat milk (2%) – 5g fat Reduce-fat milk (2%) – 5g fat Low-fat milk (1%) - 2.5g fatLow-fat milk (1%) - 2.5g fat Fat-free milk – trace fatFat-free milk – trace fat

Ultrahigh-Temperature Milk (UHT)Ultrahigh-Temperature Milk (UHT) With special processing milk can be stored With special processing milk can be stored

without refrigeration for three monthswithout refrigeration for three months This is called UHT because it’s prepared by heating This is called UHT because it’s prepared by heating

for a short time at ultrahigh temperatures.for a short time at ultrahigh temperatures. Placed in special sealed packagesPlaced in special sealed packages Flavor improves over timeFlavor improves over time

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Concentrated Milk

Evaporated milk – is whole milk that Evaporated milk – is whole milk that has been heated at low pressures, has been heated at low pressures, causing up to 60% if the water present causing up to 60% if the water present to evaporate at temperatures well to evaporate at temperatures well below milks normal boiling point.below milks normal boiling point.

CarrageeninCarrageenin = a vegetable gum, is = a vegetable gum, is often added to evaporated milk before often added to evaporated milk before processing to stabilize the casein processing to stabilize the casein proteinsproteins

Sweetened condensed milk – canned Sweetened condensed milk – canned product in which 50% of the water has product in which 50% of the water has been removed and sugar added.been removed and sugar added.

Sweetened condensed milk is Sweetened condensed milk is 44% sugar44% sugar

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Cream/Dry Milk

Half-and-half = is 10.5-18% fatHalf-and-half = is 10.5-18% fat Light cream = 18-30% fatLight cream = 18-30% fat Light whipping cream = 30-36% fatLight whipping cream = 30-36% fat Heavy whipping cream = contains at Heavy whipping cream = contains at

least 36% fatleast 36% fat

Dry Milk – water is removed, leaving a Dry Milk – water is removed, leaving a dry solid materialdry solid material Milk SolidsMilk Solids = proteins, carbohydrates, fat, = proteins, carbohydrates, fat,

minerals, and vitamins that were dissolved minerals, and vitamins that were dissolved in the liquid portion of the milkin the liquid portion of the milk

Nonfat milk has a longer shelf life because it has the Nonfat milk has a longer shelf life because it has the least amount of fat (used for baking an enriching least amount of fat (used for baking an enriching products)products)

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Cultured Milk Products

CultureCulture = controlled bacterial population that is = controlled bacterial population that is added to milkadded to milk

The starter bacteria produce acid and flavors that are The starter bacteria produce acid and flavors that are characteristic of each fermented milk product.characteristic of each fermented milk product.

Commercial producers use lactic-acid bacteria to break down Commercial producers use lactic-acid bacteria to break down lactoselactose

InoculationInoculation = adding the starter culture to milk = adding the starter culture to milk during the fermentation process that produces during the fermentation process that produces different cultured milk productsdifferent cultured milk products

Incubation periodIncubation period = time needed for bacteria = time needed for bacteria to grow and ferment the milk during the process to grow and ferment the milk during the process of culturing milk to make various products – of culturing milk to make various products – finally it’s cooled down to stop or slow bacterial finally it’s cooled down to stop or slow bacterial growthgrowth

What are some examples of cultured foods???What are some examples of cultured foods???

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Buttermilk/Sour Cream/Yogurt

ButtermilkButtermilk – used to be the fluid left – used to be the fluid left over from producing butter, today it’s a over from producing butter, today it’s a cultured product prepared from low-fat cultured product prepared from low-fat milkmilk

Sour CreamSour Cream – culture of streptococcus – culture of streptococcus lactis is added to cream.lactis is added to cream.

YogurtYogurt – eastern European food, yogurt – eastern European food, yogurt contains lactose, lactic acid, B vitamins contains lactose, lactic acid, B vitamins and high concentrations of proteinand high concentrations of protein

Yogurt is prepared by adding a bacterial culture Yogurt is prepared by adding a bacterial culture to milk that has been heatedto milk that has been heated

Bacteria used to making yogurt must be incubated Bacteria used to making yogurt must be incubated between 41between 41°C-45°C for around 8 hours°C-45°C for around 8 hours

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Cheese

Cheese is made by coagulating the Cheese is made by coagulating the casein protein in milk.casein protein in milk.

Once the curds have formed, the whey is Once the curds have formed, the whey is drained away. (heating and cutting the whey drained away. (heating and cutting the whey helps this drain)helps this drain)

The curd is then treated and allowed to ripen The curd is then treated and allowed to ripen During ripening, the cheese is hung for at least 60 During ripening, the cheese is hung for at least 60

days, some take monthsdays, some take months Four main categories of cheese are based on Four main categories of cheese are based on

moisture content:moisture content:1.1. Very hard cheese – parmesan and RomanoVery hard cheese – parmesan and Romano2.2. Hard cheese – cheddar, Colby and provoloneHard cheese – cheddar, Colby and provolone3.3. Semi-Soft cheese – Munster, Roquefort, and stiltonSemi-Soft cheese – Munster, Roquefort, and stilton4.4. Soft cheese – brie, camembert, and mozzarellaSoft cheese – brie, camembert, and mozzarellaUnripened Cheese – cottage cheese and cream cheeseUnripened Cheese – cottage cheese and cream cheese

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Storing and Cooking with Milk

How many of you leave milk on your How many of you leave milk on your table when eating dinner??table when eating dinner??

Is that safe?? – Even if it’s for ½ hour?Is that safe?? – Even if it’s for ½ hour?

Milk retains it’s quality for 1-3 weeks Milk retains it’s quality for 1-3 weeks when properly storedwhen properly stored

Extra credit for someone who can tell me the Extra credit for someone who can tell me the correct temperaturecorrect temperature

Remember riboflavin is sensitive to lightRemember riboflavin is sensitive to light Would whole milk or low fat milk spoil Would whole milk or low fat milk spoil

faster or would they spoil at the same faster or would they spoil at the same time?time?

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Making Foams

Several factors affect the ability of Several factors affect the ability of cream to make a foam.cream to make a foam. Fat contentFat content – higher the fat level, the better – higher the fat level, the better

the foam the foam TemperatureTemperature – cold temperature increase – cold temperature increase

the viscosity , including the beaters and the viscosity , including the beaters and bowlbowl

Amount of creamAmount of cream – whipping small amounts – whipping small amounts of cream usually gives better results than of cream usually gives better results than whipping large amountswhipping large amounts

Sugar contentSugar content – adding sugar decreases – adding sugar decreases both the volume and stiffness of the foam, both the volume and stiffness of the foam, its best to add sugar after the cream has its best to add sugar after the cream has reached the desired consistencyreached the desired consistency

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Heating Milk

Milk is sensitive and highly reactive Milk is sensitive and highly reactive to heatto heat Heat denatures and coagulates the Heat denatures and coagulates the

whey proteins of fresh milk, causing whey proteins of fresh milk, causing them to precipitate them to precipitate PrecipitatePrecipitate = to cause a solid substance = to cause a solid substance

to separate from a solutionto separate from a solution To prevent milk from scorching put milk in a To prevent milk from scorching put milk in a

double boiler or heat over VERY LOW double boiler or heat over VERY LOW TEMPERATURETEMPERATURE

What happens to milk when you heat milk in a What happens to milk when you heat milk in a sauce pan that is not stirred?!??sauce pan that is not stirred?!??

Skin develops, if you try to remove the skin it Skin develops, if you try to remove the skin it will regenerate and you lose milk solidswill regenerate and you lose milk solids

What is curdling and how does it happenWhat is curdling and how does it happen

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Questions

1.1. How does casein react to acids?How does casein react to acids?

2.2. How are casein and why alike and How are casein and why alike and different?different?

3.3. What makes milk a solution, a colloidal What makes milk a solution, a colloidal dispersion, and an emulsion?dispersion, and an emulsion?

4.4. Why is lactose a valuable nutrient in Why is lactose a valuable nutrient in milk?milk?

5.5. How do salts prevent milk from curdling?How do salts prevent milk from curdling?

6.6. How is milk processed? What is the How is milk processed? What is the purpose of each type of processing?purpose of each type of processing?

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Questions Continued

7.7. What does the phrase “whole milk” mean? What does the phrase “whole milk” mean? How does whole milk compare to other How does whole milk compare to other classifications of milk?classifications of milk?

8.8. What is the difference between sweetened What is the difference between sweetened condensed milk and evaporated milk?condensed milk and evaporated milk?

9.9. How are cultured milk products made?How are cultured milk products made?10.10. Explain what ripening is and why it’s needed Explain what ripening is and why it’s needed

to make cheese.to make cheese.11.11. To make a cream foam, would you get To make a cream foam, would you get

better results by using light or heavy better results by using light or heavy whipping cream? WHY?whipping cream? WHY?

12.12. What might happen if you leave an open What might happen if you leave an open pan of milk over high heat without stirring?pan of milk over high heat without stirring?