Foods of Animal Origin Dairy Safety

bovine milk is made of (approx)

90% water, 5%carb, 3% prot, 4%lip

what are the two milk proteins?

casein and whey

what is casein used for

cheese making. precipitating into curds = first step

how does casein make curds

precipitates into curds @ 4.6 PH (isoelectric point)

how much of milk protein is casein?

78%

what is whey

the liquid left after curding. whey proteins are soluble in liquid with lactose and water soluble vitamins

how does casein precipitation occur?

acid (H+) is added to milk, the PH is lowered to 4.6, casein molecules lose their negative charge and clump together

what enzymes can precipitate casein?

rennin

how does rennin precipitate casein?

it splits the hydrophobic and hydrophilic head of casein, allowing the hydrophobic molecules to clump together and form curds

what is whey made of?

lactalbumin, immunoglobulins, serum albumin

what is whey used for?

by product of cheese/curd making, adds viscosity/stability to foods, used in protein powder

what is the most variable component of milk?

lipids, different cow breeds produce milk with different % of lipids

what is the relationship between lipids and $ value

the more lipids, the more $$

what molecule makes up most of the lipids in milk?

triglycerides, specifically, saturated fat, monounsaturated fat, polyunsaturated fat

how many fatty acids are in milk?

64

what part of a glass of milk do lipids make up, if it’s not homogenized?

the cream that sits on top

T/F, milk lipid chain length is more diverse than egg or meat lipid chain length

True

how many carbons in a milk lipid chain?

4-26

what are the most abundant fatty acids in milk?

oleic, steric, palmitic

what is the main carbohydrate in milk?

lactose

what is lactose made of

it’s a disaccharide made of glucose and galactose

what are 4 traits of lactose?

less sweet than glucose, browns during heating, main sugar of milk proteins, lactose crystals = sandy texture in ice cream when off-balance with other sugars.

what are some water soluble vitamins?

riboflavin, thiamin, niacin

what are some water soluble minerals?

calcium, phosphorus

what are some fat soluble vitamins?

A, fortified D

what is milk a poor source of

iron, vitamin C

What pathogens are present in milk?

e coli, staph A, strep A, campylobacter, listeria, cryptosporidium, salmonella, brucella

Non-pathogeneic bacteria in milk

udder commensals

what are udder commensals?

non pathogenic bacteria in raw milk, with low numbers of microorganisms (micrococci and streptococci), that aren’t involved in mastitis and can inhibit pathogens by outcompeting them, and doesn’t affect milk quality or yeild

Microorgs from the environment

from milk equipment (usually psychotropic (cold growing) spoiliage bacteria, or from human workers

what does pasteurization destroy/not destroy

destroys vegetative microbial pathogens, doesn’t destroy endospores, so it’s different from sterilization (canning) which does both

what are the benefits and drawbacks of pasturization

benefits: safety (priority), shelf life lengthening (incidental). Drawbacks: overheating causes browning and poor taste

what are the processes of pasturization?

the hold method (60*/30min, rapid cooling. drawbacks: needs lots of space/time. old school

HTST (High Temp, Short Time.)

72*/15 secs, rapid cool to 50*c, most common. in gal/half gal jugs. still needs refrigeration while in HTST/holding

UHT (ultra high temp)

138*/2sec, while in sterile container, kills all microorgs so it can be stored @ room temp

EU standards for CFUs in milk (least to most)

UHT, Pasturization, 6*/30h, raw

pasturization definition

process minimizing health hazards of pathogenic microorganisms of milk via heat treatment

Raw milk legalities

half states legalized. can be legal for retail, on-farm, herd-share, pet food, illegal

Iowa rules on raw milk

<10 cows at farm, annual vet checks, monthly bacterial count measurement, sold on-farm

oxidative rancidity

oxidative rancidity: oxidation of DBs of fatty acids, metallic flavor.

two kinds of rancidity

oxidative and hydrolytic

hydrolytic rancidity

hydrolytic reaction of free FAs split from glycerol in triglycerides, activated by heat, lipase, agitation. pasturization inactivates endogenous lipases. rancid smell

homogenization

2500psi holes in screen. fat can’t coalesce and separate. protein layers around fat globules. more viscosity, whiter, less stable w’ heat and light sensitive to oxidative rancidity, softer curds, less flavor

homogenization changes size to

from 4-10um to <1.5um diameter

fermentation

adding starter cultures to make specific characteristics. cultures use lactose as energy source, grow @ fermentation/process temperatures, be easily controlled, stop at target PH, and compete with unwanted bacteria

in dairy processing, what becomes what?

lactose (disaccharide) becomes lactic acid (organic acid)

what happens at low PH

precipitation of curds, thicker, higher viscosity, makes yogurt, buttermilk, cheese

cheddaring

before coagulation into curds, chese goop is cut into strips and stacked to drain whey

blue cheese

penicillium roqueforti added to blocks/wheels, needles push it into cheese. Roquefort must be in french caves. Gorganzola = different penicillium. USCFR = Penicillium roqueforte

what’s yogurt?

fermented milk with bacterial cultures

types of yogurt

set type: fruit on the bottom, swiss: fruit blended, greek: strained