Milk Facts - Cow, Goat, Sheep

Source:WorkSmartLiveSmart.com

Not all milk is the same, we all know that, but besides the obvious like the animal and which breed, what is the real difference?  

All milk is made up of water, fat, protein, lactose and minerals but it is the composition of these constituents that makes the difference between them.  The fat and protein vary greatly.  The higher the solids content, the stronger the affect on the acidification and coagulation properties for cheese but also how the human body deals with it in milk form.  The fat and protein content in cow's and goat's milk are fairly similar compared to sheep' milk; however the structure of the fat and protein is what's important.


Fat Content

98% of the fat in milk consists of triglycerides and are made up of fatty acid chains that vary in length. This issue is the size of the fat globules and the type of protein chain.  Sheep and goat’s milk have short to medium chains producing smaller globules, cow’s milk has longer structures. The longer the chain length, the more easily it separates from the water but the more difficult for the human body to breakdown.

While sheep are notoriously difficult to milk, mostly because they have very small teats, the milk is naturally homogenized. This means the cream does not separate out of it but it also makes the milk easier to digest. Sheep produce less milk than their confrere.  The upside is it has a very high fat content with the finest fat globules of the lot.  Goat’s milk come second to sheep’s milk; with cow’s milk a distant third, having the largest fat globules and the longer fatty acid chains. Goat's milk is the closest to human milk and the least fatty of the three. It is the easiest on the human digestive system. It generally requires more milk to make cheese but because of the milks’ fat structure, the cheeses are less suited to aging.

Cow’s milk is the highest in water content of the three, which of course helps produce more quantity-wise.  The typical breeds used for ‘industrial’ milk produce milk that is less well rounded in terms of character.  For drinking, this is not an issue and the fact that due to its' structure, the cream rises and allows for making different percentages of fat content milk.  For cheese production, the regional breeds in most countries produce milk with more complexity and a higher fat content which makes for better cheeses.


Milk Protein

Milk protein differs between milk types.  There are two major types: caseins and whey proteins.  Casein being the major of the two is what transforms when making cheese.  In sheep’s milk 82% of the proteins are casein while it is 80% cow’s milk and 75% in goat’s milk, the rest being whey based. Casein protein has four different types and the proportions differ between the milk types – goat contains more of the beta caseins while cows’ has more alpha caseins with a particular one being the protein responsible for cows’ milk allergies. 

What is important for cheese is that casein coagulates to form the structural backbone of cheese curd. Sheep’s milk coagulates more rapidly and forms much firmer curd thus sheep’s milk produces twice the amount of cheese per unit compared to cow’s or goat’s milk. The richness and cheese yield of sheep's milk makes up for the lower quantity of milk per animal.  Goat’s milk with its lower amount of alpha casein and its beta casein has a lower yield (10 to 15 percent less) and is less adaptable to different cheese type.

It’s the sugar stupid!

Somebody who cannot digest lactose is said to be lactose intolerant. But it is the major sugar – not protein – found in animal milk that causes the problem here.  The intolerance comes when the body’s ability to synthesizing the lactase is compromised.  Lactase is the enzyme responsible for lactose metabolism and in the cheese making process, it is the energy source for our friendly bacteria.

All three of the milk types contain similar levels of lactose; therefore, one is not better than another for those with lactose intolerance when it comes to drinking or using milk.  The good news is that during the process of making and aging cheese, most lactose is lost when the whey drains off and the little that is left begins to convert to lactase.  The older the cheese, the less lactose!  So long aged cheeses like Comté, Beaufort or the Pyrenees sheep’s milk cheeses all have practically no lactose left in them.

Just a fun note:  Milks vary in colour. Cow’s milk tends to be yellow and varies by season because of the level of beta-carotene found in green forages.  Some breeds process this pigment differently or more efficiently and produce very yellow milk – Jersey cows being a good example.  Sheep and goat milks lack beta-carotene because they convert it into vitamin A which is not pigmented so these milks are whiter than cow’s milk.

Side by sidecomparison

Component	Unit	Cow Whole (3.25% fat)	Goat	Sheep
		--- Amount per 100 g ---
Overall Composition
Water	g	88.32	87.03	80.7
Energy	kcal	60	69	108
Carbohydrate2	g	4.52	4.45	5.36
Fat	g	3.25	4.14	7
Protein	g	3.22	3.56	5.98
Minerals (Ash)	g	0.69	0.82	0.96
Vitamins
Vitamin A	µg	28	57	44
Riboflavin (Vitamin B2)	mg	0.183	0.138	0.355
Niacin (Vitamin B3)	mg	0.107	0.277	0.417
Pantothenic Acid (Vitamin B5)	mg	0.362	0.31	0.407
Vitamin C	mg	0	1.3	4.2
Vitamin D	IU	40	12	ND3
Minerals (Ash)
Calcium	mg	113	134	193
Magnesium	mg	10	14	18
Potassium	mg	143	204	137
Sodium	mg	40	50	44
Zinc	mg	0.4	0.3	0.54
Carbohydrate Detail
Lactose4	g	5.26	ND	ND
Fat Detail
Cholesterol	mg	10	11	27
Fatty acids, total saturated	g	1.865	2.677	4.603
Fatty acids, total monounsaturated	g	0.812	1.109	1.724
Fatty acids, total polyunsaturated	g	0.195	0.149	0.308
Source:
http://www.milkfacts.info/Nutrition%20Facts/Nutrient%20Content.htm#Tab2