DAIRY TECHNOLOGY: MILK COMPOSITION
Diagram
Goat milk and cow milk side by side
Goat milk
Milk from the goat: smaller fat globules, a goaty flavour, and less of the casein type that curdles firmly.
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Cow milk
Milk from the cow: larger fat globules, mild flavour, and the standard drinking milk.
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The core difference
Goat milk fat stays mixed in smaller droplets and its protein curd is softer, so many people find it easier to digest.
Figure 1: Goat milk compared with cow milk. Drawn in our own style from Young W. Park et al., Handbook of Milk of Non-Bovine Mammals, 2nd ed., Wiley, 2017.
Introduction
Goat milk and cow milk are both common drinking milks, and their fat, protein and lactose are close in amount. The difference is in the structure of the fat and the protein, not in the headline numbers.
The core difference is digestion and flavour. Goat milk has smaller fat globules and a softer protein curd, and it carries a distinct goaty flavour from its short-chain fatty acids. Cow milk is milder and is the milk most people grow up drinking.
Quick comparison
Table 1: Goat Milk compared with Cow Milk
| Aspect | Goat Milk | Cow Milk |
|---|---|---|
| Source animal | Goat | Cow |
| Fat content | About 3.5 to 4.5 percent fat, close to cow milk | About 3 to 4 percent fat |
| Fat globule size | Smaller fat globules, so the fat stays mixed | Larger fat globules, so cream rises faster |
| Flavour | Distinct goaty flavour from short-chain fatty acids | Mild, neutral flavour |
| Main casein type | Low in alpha-s1 casein, so the curd is soft | Higher in alpha-s1 casein, so the curd is firmer |
| Digestibility | Often easier to digest, softer curd in the stomach | Normal digestion for most people, firmer curd |
| Lactose | Contains lactose, about the same amount as cow milk | Contains lactose, about the same amount as goat milk |
| Colour | White, almost no carotene | Slightly yellowish white from carotene |
| Cheese use | Soft cheeses such as chevre, with a tangy flavour | Wide range of cheeses, from soft to hard and ripened |
| Availability | Common in many regions, less common in large supermarkets | The most widely sold drinking milk in the world |
Scientific explanation
Definition
Goat milk is the milk secreted by the goat. It contains water, fat, protein, lactose, minerals and vitamins in proportions close to cow milk.
Cow milk is the milk secreted by the cow, the standard reference milk for drinking and for most dairy products.
Working principle
Fat digestion starts with the fat globules. Smaller globules give digestive enzymes more surface to work on, which is one reason goat milk is often described as easier to digest.
Protein digestion depends on the curd. In the acid of the stomach, casein clots into a curd. Goat milk, low in alpha-s1 casein, forms a softer and looser curd than cow milk, so it breaks down more easily.
Apparatus
No single apparatus defines the difference. Fat globule size is measured under a microscope or with a particle size analyser, and protein types are separated by electrophoresis in a dairy laboratory.
Routine composition is measured the same way for both milks: fat by Gerber or milk analyser, protein by Kjeldahl, and total solids by drying.
Measurement procedure
To compare the two milks, measure fat, protein, lactose and total solids by the standard milk analysis methods, then examine fat globule size under a microscope and compare the firmness of the acid curd.
The books give no single standard procedure that names this pair, so the comparison uses the standard milk analysis methods.
Factors affecting readings
Breed, feed, season and stage of lactation change the composition of both milks.
Feed strongly affects the goaty flavour of goat milk: certain feeds and the presence of male goats near the milking herd can strengthen the flavour. Handling and cooling also matter, because stale or warm milk tastes stronger.
Formulas and calculations
The books give no formula for this pair. The difference is in fat globule size and protein type, which are measured and compared, not calculated.
Total solids can be worked out for either milk the same way: Total solids (percent) = Fat (percent) + Solids-not-fat (percent).
Industrial applications
- Goat milk: drinking milk for people who prefer its flavour or find cow milk heavy.
- Goat milk: soft cheeses such as chevre, feta style cheese and yoghurt, where its tangy flavour suits the product.
- Cow milk: drinking milk, tea, coffee and the base for most dairy products.
- Cow milk: hard and ripened cheeses such as cheddar, where a firm curd and high yield matter.
- Both milks: infant formulas and cultured products, with the milk chosen for flavour and for the product in mind.
Advantages and limitations
- Goat milk advantage: smaller fat globules and a softer curd, so many people find it easier to digest.
- Goat milk limitation: a strong goaty flavour that not everyone likes, and lower availability and higher price in many markets.
- Cow milk advantage: mild flavour, wide availability and low price.
- Cow milk limitation: larger fat globules and a firmer curd, so some people find it heavier to digest.
FAQ
Does goat milk have less lactose than cow milk?
No. The lactose is about the same in both milks, so goat milk is not safe for people with lactose intolerance.
Why does goat milk taste goaty?
Its fat contains more short-chain fatty acids such as caproic, caprylic and capric acid, which give the characteristic goaty flavour.
Is goat milk easier to digest?
Many people find it so, because its fat globules are smaller and its protein curd is softer, but this varies from person to person.
Can I use goat milk in place of cow milk in cooking?
Yes, in most recipes, but the goaty flavour will come through, which suits tangy dishes and soft cheese better than mild ones.
Why is goat milk whiter than cow milk?
Goat milk has almost no carotene, so its fat is white, while cow milk fat carries a yellow tint from carotene.
References and further reading
- Young W. Park et al. (eds.), Handbook of Milk of Non-Bovine Mammals, 2nd ed., Wiley, 2017 (Google Books page read)
- FTN books on disk: Chemistry of Milk, Handbook of Milk Composition, Market Milk (agrimoon dairy series).
