Milk: From Cow to Cappuccino


A typical Australian coffee order is simply 10% coffee; the remaining 90% is milk. As a coffee roasting firm, we naturally spend a variety of time speaking about coffee origins, roasting and brewing, however now it’s time to give some love to coffee’s biggest pal – milk.

So, what’s milk? Milk is a nutrient wealthy liquid produced by mammals which is used as the first supply of vitamin for his or her infants. However, thanks to the magic of evolution, many people can nonetheless take pleasure in milk as adults. However, once we say ‘milk’ we often imply cow’s milk.

In the 24-48 hours it takes to get milk from a cow to a café, it goes by means of many modifications which have an effect on its flavour, texture and longevity. The key elements are the breed of cow, weight loss plan, pasteurisation, homogenisation and skimming.

Cow breeds

Since the domestication of cattle started roughly 10,500 years in the past, 5 species have been domesticated into over 800 recognised breeds. The breed of a cow influences many issues from the dimensions of the cow to the form of the horn. It additionally has a big impact on the manufacturing of each fat and proteins of their milk. Jersey cows have been proven to produce the very best ranges of milk fats amongst dairy cows. The highest ranges of protein manufacturing are shared between Jersey and Guernsey cows.

Diet

Cows primarily eat grass, however they’re additionally fed silage and cake. Silage is fermented grass which supplies additional nutritional vitamins and helps digestion. Cake is a protein wealthy complement which cows get given on their birthday – or once they want to bump up the protein of their food regimen! The particular grass, silage and cake that a cow consumes will end in a really totally different milk manufacturing.

Pasteurisation

Raw milk is milk which hasn’t been pasteurised. Australian regulation forbids the sale of milk for consumption which hasn’t undergone some type of pasteurisation. Pasteurisation was developed by Louis Pasteur within the 1880s as a approach of inactivating dangerous micro organism in wine. However, it has since been utilized many meals merchandise together with beer, fruit juice and milk. The pasteurisation course of includes heating milk to a selected temperature for a selected time, thus eliminating pathogens and increasing the shelf lifetime of dairy merchandise. There are a number of methods to pasteurise milk, nevertheless the tactic that you’re in all probability most acquainted with is High Temperature Short Time or HTST. Another technique you could have heard of is Ultra-High Temperature or UHT which is used for lengthy life milks.

The larger the temperature, the longer the shelf lifetime of milk is prolonged. Pasteurisation may even take away the necessity for refrigeration within the case of UHT. However, decrease temperatures will sometimes end in a more true illustration of the uncooked milk’s flavour. A typical HTST remedy would maintain the milk at 72°C for 15 seconds, whereas a typical UHT remedy would maintain the milk at 138°C for 3 seconds or much less.

Homogenisation

After a milk has been pasteurised, it is going to sometimes bear a homogenisation course of. The fats in milk is comprised of various sizes of fats clusters and particular person globules. The clusters are much less dense and can rise to the highest, forming a cream layer. Homogenisation is the method throughout which milk is pumped at excessive strain by way of small tubes, breaking apart fats globules into smaller sizes and distributing them evenly all through the milk. Homogenised milk sometimes has a richer texture however tastes extra bland. Homogenisation additionally has the additional advantage of serving to to create a extra secure foam construction in steamed milk.

Skimming

The quantity of fats that results in milk depends on quite a lot of elements from the genetics of a cow to the meals it eats. This may end up in inconsistent fats ranges within the remaining product. To obtain a extra constant product, producers will typically take away some fats – even in full cream milks. Skimming is the method of eradicating the fats from a milk to attain a desired fats degree.

CLSM 3D picture of milk fats globules from uncooked cream stained with Rd-DOPE. Scale bar=5µm. SOURCE: National Center for Biotechnology Information

Milk beneath the microscope

A typical pattern of uncooked milk from a cow will include 5% lactose, four% fats, three.5% protein and 1% ash (amongst water and a bundle of different issues). Let’s take a second to look at what every of those elements are and their significance in a glass of milk or a flat white.

Lactose

Lactose is the sugar in milk. It is a disaccharide comprised of galactose and glucose. It has a light sweetness when chilly. However, heating milk can break down a number of the lactose again into galactose and glucose – leading to greater sweetness. Humans have an enzyme referred to as ‘lactase’ which breaks lactose down into glucose and galactose. Lactose illiberal individuals have much less of this enzyme and subsequently have problem breaking lactose down.

Fats

Fat globules are essential to the feel and style of milk. However, fats has a detrimental impact on each the creation and consistency of milk foam. Higher fats content material has been proven to trigger the liquid in foam to seep out, leading to decrease foam volumes. This destabilisation impact is decreased by homogenisation due to the smaller fats globule measurement and additional decreased by elevated milk temperatures. Many of the fat in milk are strong at colder temperatures and can solely soften as soon as the milk reaches a temperature of 40°C. In foamed milk, this helps create a extra secure foam construction.

Proteins

There are two major proteins in milk – casein and whey. These proteins have a big impression on coffee flavour. Casein has been proven to scale back bitterness in coffee and contributes to the milky flavour. Only a small quantity of protein is required to create milk foam. However, the proteins are essential for foam stability, stopping the drainage of the liquid which is contained within the foam layer.

Alternative milks

Alternative milks have exploded onto the Australian café scene in recent times to the delight of vegans and to the annoyance of many baristas. Many cafes supply soy milk, together with the whole lot from coconut to oat milk. While a coffee order comprising an alternate milk is nice information for the setting, it may be a supply of frustration for baristas utilizing acidic coffees. Baristas and soy drinkers are fairly accustomed to seeing a latte glass full of a curdled, coffee colored tofu. The curdling is brought on by a chemical response which happens once you add an acid to sure proteins at excessive temperatures. The cause it typically occurs to soy and different various milks and never to dairy milks is due to the delicate nature of their proteins. Proteins are often negatively charged, inflicting them to repel one another. Once you add an acid, this unfavorable cost is eliminated, permitting the proteins to clump collectively which pulls them right into a separate strong protein layer with a definite liquid layer beneath. Many various milk corporations try to overcome this by including an acidity regulator. If you’re keen on acidic coffees and don’t need to surrender your various milk, you’ll be able to scale back the acidity of your espresso by including a pinch (zero.2g) of bicarb soda to your espresso and stirring it in earlier than including your milk. You ought to even have the ability to obtain some good latte artwork.

Now that you’ve slightly extra context concerning the 90% of liquid that goes into your cup, take a second to recognize the lengthy and sophisticated journey it took from the cow (or coconut) to the cappuccino.


This article was initially written in a part of a curated cupping which was put collectively in September 2018.





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