Exam 2: Milk & Milk Products Flashcards
What are the diff components of milk?
water & milk solids
non-fat MS milk fat
lactose minerals proteins
casein & whey
what fatty acids are found in milk (in general terms)?
what fats do we find in milk: many diff kinds if fats in milk up to 64 diff fats; contribute to milk, milk fat, prodominatly triglycerides
what are the various milk fats?
whole milk
half & half
reduced fat
skim
what are the % milk fat in the variety of milks?
whole milk : 3.25+% half & half: 10.5 - 18% reduced fat: 2% low-fat: 1% skim: 0.1 or less %
what is milk?
1c =11-12 CHOs
It’s an emulsion
mammals - esp cows
predominant carb in milk: lactose
lactose is important in food manu: solubility is low-soluable, they can crystallized if not stored properly (esp in dry milks); browning reaztions: reducing sugar - induce browing in baked products. tend to be browner & less white. maillard reaction browning.
- what’s emulsified: all fats & milk solids are emulsified w/in the water
- butter is the reverse: water is emulsified into a solid complex
how much water is in milk?
water: 87.4%; milk solids : 12.6%
lactose 4.8%
Precipitation of milk proteins: acid vs rennet coagulation
renin: found in the stomach lining of animals
-can precipitate the formation of curds & whey
-how?
ACID: add acid to milk product: changes the pH
-lowers the milk solution below isoelectric -> you induce coagulation.
Milk is slightly charged at isoelectric point they become neutral.
When milk is charged, they can repell & prevent from forming bonds & wont form a curd.
diff milk proteins each have their own isoelectric point. Overall milk has an isoelectric point of 4.6
When coagulated, cannot reverse.
Some cheeses have curds from both acid & rennet
cheddar cheese: add lactic acid starter & add rennin. inc rancidity as cheese ages
rennet: diff types of casing molecules (pericasing: slightly polar)
rennet coag tend to be firmer bc the Ca in the renin cheeses. less Ca w/ coagulation from acid
best pH for next 5.8
when do we coagulate milk proteins?
to make cheese
how can reduced fat cheese be made?
use lower fat milk
may add stabilizers like gums & other things in order to create the textures
how is a processed cheese made?
heating natural cheeses & emulsifying cheese in desired shapes
what is the reason for pasteurization?
process of partial sterilization, especially one involving heat treatment -> making the product safe for consumption and improving its keeping quality
high temp, shorter time
1. To increase SAFETY for the consumer by destroying disease causing microorganisms (pathogens) that may be present in milk.
2. To increase keeping the QUALITY of milk products by destroying spoilage microorganisms and enzymes that contribute to the reduced quality and shelf life of milk.
What are the diff ways to pasteurize milk? (3)
- LTLT: hold method; 145F, hold: 30min; quick cool: 45F
- HTST: temp 161, hold: 15sec, 9c 50F
- UHT: temp: 280F; hold: 2 sec; store in sterile containers
- shelf stable (unopened)
Homogenization
fat removed before homo
process that milk is treated to stay suspended for a longer period of time. It breaks down the fat globules into smaller molecules
CREAMING: milk fat goes to the top; emulsification.
what is homogenization’s affect on milk?
x
how’s ice cream made?
solution of milk, sugar, & flavoring are frozen w/ agitation. agitation is important to incorporate air & keeps crystals smaller. incorporation of air: overrun.
gelato vs ice cream: ice cream has more air incorporated. gelato: slower rate of agitation that has less air which is more dense.
why add salt surrounding the hand cranked ice cream freeze: dec the freezing temp bc of fat & sugar. when add diff items in solu we lower the freezing temp. therefore, we need to create a env below 32 f in order for it to freeze
plain: no flavor particles show
composite: visible flavoring components
frozen custard: + cooked egg yolk
