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蓝乳酪

蓝乳酪又称蓝纹干酪、蓝芝士、蓝起司，是干酪的一种，特点是以青霉菌发酵而成，使其表面有一些蓝色的斑纹。蓝干酪可以用牛奶或羊奶制成。较著名的蓝干酪种类包括法国出产的布勒·德·奥福格芝士以及罗克福干酪，还有义大利出产的古冈左拉芝士。

蓝干酪因为青霉菌发酵的作用，味道偏咸，除了单独食用外，也常用于烹饪，为酱汁等的佐料。

蓝干酪据说是意外被发现，当储藏于洞穴中的干酪因潮湿，而长出霉菌。

布勒·德·吉克斯芝士, a creamy, semi-soft blue cheese made in the 汝拉省 region of 法国

Gorgonzola, a veined cow's milk blue cheese from 伦巴第大区 意大利

Blue cheese is a general classification of 干酪s that have had cultures of the 霉菌 青霉菌 added so that the final product is spotted or veined throughout with 蓝色, or blue-grey mold and carries a distinct smell, either from that or various specially cultivated bacteria. Some blue cheeses are injected with 孢子s before the 凝乳 form, and others have spores mixed in with the curds after they form. Blue cheeses are typically aged in a temperature-controlled environment such as a 洞穴. Blue cheese can be eaten by itself or can be spread, crumbled or melted into or over foods.

The characteristic flavor of blue cheeses tends to be sharp and salty. The smell of this food is due both to the mold and to types of bacteria encouraged to grow on the cheese: for example, the bacterium Brevibacterium linens is responsible for the smell of many blue cheeses, as well as foot 气味 and other human body odors.

历史

Blue cheese is believed to have been discovered by accident when cheeses were stored in natural temperatures and moisture-controlled caves, which happen to be favorable environments for many varieties of harmless mold. It was moist in the cave so the mold would form. According to legend, Roquefort was discovered when a youth, eating a lunch of bread and 羊乳 cheese, abandoned his meal in a nearby cave after seeing a beautiful girl in the distance. When he returned months later, the mold (Penicillium roqueforti) had transformed his cheese into Roquefort.

古冈左拉芝士 is one of the oldest known blue cheeses, having been created around 879 AD, though it is said that it did not actually contain blue veins until around the 11th century. 斯蒂尔顿芝士 is a relatively new addition becoming popular sometime in the early 1700s. Many varieties of blue cheese that originated subsequently, such as the 20th century 丹麦蓝芝士 and Cambozola, were an attempt to fill the demand for Roquefort-style cheeses that were prohibitive due to either cost or politics.

Nutritional information

In the 美国, 100 g of generic blue cheese contains the following nutritional values according to the 美国农业部 :

• Calories: 353
• Fat: 28.74 grams
• Carbohydrates: 2.34 grams
• Fiber: 0 grams
• Protein: 21.40 grams
• Vitamin B12: 1.15 mg (50% of recommended daily intake)

Production

Creation

Cambozola, a German variety of blue cheese

Similarly to other varieties of cheese, the process of making blue cheese consists of six standard steps, as well as further additions that give this blue-veined cheese its unique properties. The first step is acidification where a 麹 is added to milk in order to change 乳糖 to 乳酸, thus changing the acidity of the milk and turning it from liquid to solid. The next step is 凝血, where 凝乳酶, a mixture of Chymosin and other material found in the stomach lining of a calf is added to solidify the milk further. Following this, thick curds are cut typically with a knife to encourage the release of liquid or 乳清. The smaller the curds are cut, the thicker and harder the resulting cheese will become. Salt is then added to provide flavor as well as to act as a preservative so the cheese does not spoil. Next, the cheese is given its form and further pressed with weights if necessary to expel any excess liquid. The final step is ripening the cheese by aging it. The temperature and the level of humidity in the room where the cheese is aging is monitored to ensure the cheese does not spoil or lose its optimal flavor and texture.

Blue cheese undergoes the aforementioned steps with an added twist that gives it its unique look of blue streaks found all throughout. The blue veins are a result of adding the molds Penicillium roqueforti and Penicillium glaucum to the cheesemaking process, often introduced after the curds have been ladled into containers in order to be drained and formed into a full wheel of cheese. Although Penicillium roqueforti and Penicillium glaucum are found naturally, cheese producers nowadays use commercially manufactured Penicillium roqueforti culture that have been 冷冻干燥, a form of dehydration where water is evaporated from the frozen state without the transition through the liquid state, to retain their value and are activated with the addition of water. After the addition of the molds to the cheese, the next significant step is needling, which is when the wheels of blue cheese are pierced to create small openings to allow the air to enter and feed the mold cultures, thus encouraging the formation of blue veins.

The distinctive flavor and aroma of blue cheese arises from methyl 酮 (including 2-戊酮, 2-heptanone, and 2-nonanone) which are a metabolic product of Penicillium roqueforti. These compounds are not formed in other types of cheese fermented by bacterial acidification alone.

European Union

In the 欧洲联盟, many blue cheeses, such as 卡伯瑞勒斯芝士, Danablu, Gorgonzola, 罗克福干酪 and 斯蒂尔顿芝士, carry a 欧盟农产品地理标示和传统特产标识, meaning they can bear the name only if they have been made in a particular region. Similarly, individual countries have protections of their own such as France's 原产地命名控制 and Italy's Denominazione di Origine Protetta. Blue cheeses with no protected origin name are designated simply "blue cheese".

Physical-chemical Properties

Structure

The main structure of the blue cheese comes from the aggregation of the casein. In milk, casein does not aggregate because of the outer layer of the particle, called the “hairy layer.” The hairy layer consists of κ-casein, which are strings of 肽s that extend outward from the center of the casein micelle. The entanglement of the hairy layer between casein micelles decreases the 熵 of the system because it constrains the micelles, preventing them from spreading out. Curds form, however, due to the function that the 酶, rennet, plays in removing the hairy layer in the casein micelle. Rennet is an enzyme that cleaves the κ-casein off the casein micelle, thus removing the strain that occurs when the hairy layer entangles. The casein micelles are then able to aggregate together when they collide with each other, forming the curds that can then be made into blue cheese.

Mold growth

Penicillium roqueforti and Penicillium glaucum are both molds that require the presence of oxygen to grow. Therefore, initial fermentation of the cheese is done by lactic acid bacteria. The lactic acid bacteria, however, are killed by the low PH值 and the secondary fermenters, Penicillium roqueforti, take over and break the lactic acid down, maintaining a pH in the aged cheese above 6.0. As the pH rises again from the loss of 乳酸, the enzymes in the molds responsible for lipolysis and 蛋白酶解 are more active and can continue to ferment the cheese because they are optimal at a pH of 6.0.

Penicillium roqueforti creates the characteristic blue veins in blue cheese after the aged curds have been pierced, forming air tunnels in the cheese. When given oxygen, the mold is able to grow along the surface of the curd-air interface. In pressing the cheese, the curds are not tightly packed in order to allow for air gaps between them. After piercing, the mold can also grow in between the curds.

参见

• List of blue cheeses

外部链接

• How to make blue cheese at home
• What makes blue cheese blue? from The Straight Dope