咖啡里的牛奶有什麼作用——好的和壞的（譯文）

01-27

原文地址：http://www.coffeescience.org/impact-milk-in-coffee-good-bad/

The Impact of Milk in Your Coffee – The Good and the Bad

咖啡里的牛奶有什麼作用——好的和壞的

Pour Milk into Espresso

在意式濃縮咖啡里加奶。

The coffee world is familiar with the use of milk in preparing coffee drinks. Milk』s ability to create perfectly stable foams makes it a favourite among barista coffee makers and customers alike.

咖啡師在調製咖啡飲料時很熟悉牛奶的使用。牛奶能夠製造出完全穩定的泡沫，這使它成為咖啡師和顧客們的最愛。

There are several components found in milk that largely contribute to this ability, and it is these same products that enable the creation of many other daily products found in the market like yoghurt, ice cream, cheese and dairy drinks.

在牛奶中發現的一些成分主要是對這種能力的貢獻，正是這些相同的產品使得在市場上發現的許多其他日常產品，如酸奶、冰激凌、乳酪和奶製品。

Milk proteins and milk fat have crucial importance when creating stable milk foams of stability and attractive texture. However, milk foam creation is not as easy as it sounds. It is an intricate interplay that you have to juggle between harmonising milk proteins – that stabilise air bubbles – with milk fat (which is loved for adding flavour, but an agent of destabilising milk foam)

The Contents of a Cup of Milk

But before we get into the details of how to best merge your milk with coffee, let』s consider briefly what a cup of milk entails.

1. Milk Fat，牛奶脂肪

According to lab analysis 4 – 5% of cow』s milk is made up of fat. And not just fat but a complex combination of various types of fats.

Milk-fat-globules, which range from ~0.1 to 10 micrometres, provide a membrane that gives protection to the milk fat from degradation or oxidation by enzymes that generate an off-flavour in milk.

Triglycerides are surrounded by a membrane that consists of phospholipids, protein and glycerides, and together they form the milk fat globule.

2. Milk Proteins，牛奶蛋白質

There are two classes of proteins that can be found in milk, the whey and casein proteins. These proteins are found on the top surface of milk fat globules after homogenization of milk. The caseins represent ~80 percent of total protein of the 3 – 4% of the protein in cow milk.

The remaining percentage is composed of the whey proteins and small aggregates also referred to as individual proteins. However, extended aggregation of both whey and caseins proteins through heating using sterilisation (e.g., 10 min at 115 degrees Celsius) and UHT treatment (e.g., 140 degrees for 5 sec) can cause extra viscosity.

But such effects can be limited through commercial pasteurisation (e.g., 72 degrees for 15 sec).

Scientifically, it is the milk proteins that merge with the coffee globules to give rise to the signature taste that characterises lattes and cappuccinos. And the flavour gets better if the coffee was hot in the first place.

3. Homogenised milk，（該詞含義有點專業，知道的人指導一下？）

Homogenization is used to reduce the level milk fat globules from forming a cream layer on top of milk which normally occurs during storage. Milk creaming occurs due to lower concentration of fat contained in the milk. Slowing the creaming process is achieved through reduction of milk fat globules sizes. Homogenisation involves passing of milk through a small valve at great pressure.

The process disrupts the fat globules. The science applied here is the creation of more space for the surface area of the flat globules, which makes it possible for proteins to get absorbed by the surface occupied by fat globules.

In short, the moral of the story is that no two cartons of milk are the same – the same way no two coffee companies churn out the exact similar quality of coffee. In the same spectrum, there isn』t a universal metric measure for how much milk you should add to your black coffee. It all comes down to personal preference, whether you like your coffee 『Italian』, 『French』 or American』 or the style you grew up taking. They are good recipes that outline that, nonetheless.

The Effects of Milk in Coffee – Good or Bad?

Now that you already know what is really in every cup of milk you pull out your fridge, it is only fair if we delved a little of the impact of adding dairy to your daily cuppa. (See what I did there?)

And far from the analogy – that milk only enhances the flavour and colour of your coffee – it turns out that there』s actually more to it that what meets your eye and nose every morning. It』s not just a matter of mere preference anymore.

But before we get started it is good to acknowledge that regular consumption of coffee is, in fact, healthy. Some of the major benefits associated with coffee include enhancing your memory and lowering risks of developing liver cancer. Nevertheless, depending on how you take your coffee, there are unique benefits that you stand to enjoy.

Current Research on the Effects of Milk in Coffee

Researchers at Nestle』s Research Centre, located in Switzerland, recently discovered the lasting release of beneficial polyphenols after coffee intake.

These scientists then moved on to examine how non-dairy creamer and milk are affecting the availability of these important nutrients. Their research is helping people get a better understanding of whether there is a big difference in consuming black coffee or coffee with milk.

What are Polyphenols?

Polyphenols is the name of the antioxidants found in coffee. These antioxidants are quite important as they are linked with various health-promoting benefits. Nevertheless, their availability in humans is an area that is yet to be thoroughly studied.