Kamil Perry
When melting cheese, it's common for some of the cheese's fat content to separate and form a pool of oil. This phenomenon is known as oiling off or fat leakage. It is more likely to occur with harder, aged cheeses that have lower moisture content, such as cheddar or parmesan. Younger, higher-moisture cheeses like mozzarella, Gruyère, or Emmental tend to melt more smoothly without excessive oiling off. The melting behaviour of cheese is determined by its ratio of water to fat and the strength of its protein network. When cheese is heated, the bonds that hold together its proteins begin to break down, causing the cheese to melt. If the balance of water and fat is not maintained, the fat molecules can slip away and pool together, creating an oily mess.
Should I remove the oil after melting cheese?
| Characteristics | Values |
|---|---|
| Oil separation | When cheese is melted, it separates into proteins and fat. This phenomenon is called "oiling off" or "fat leakage" and is influenced by cooking temperature and sample dimensions. |
| Melting behaviour | Younger, high-moisture cheeses like mozzarella, Gruyère, and Brie melt more easily than drier, aged cheeses like Parmesan or Pecorino-Romano, which tend to separate into clumps or break into proteins and fat. |
| Emulsifiers | Using an emulsifier like sodium citrate can help improve the melting properties of cheese and reduce oil separation. |
| Cooking applications | Some people use the fat rendered from melted cheese as a cooking oil, adding flavour to dishes like grilled cheese sandwiches and soups. |
| Bland flavour | Oil separation from cheese can result in a bland flavour, which can be improved by mixing aged cheese with a younger, more melty variety or by adding emulsifiers. |
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What You'll Learn
Oiling off property of cheese
The oiling off property of cheese refers to the separation of liquid fat from the melted cheese body into oil pockets, particularly on the cheese surface. This phenomenon is also called free oil formation or fat leakage. It is considered a critical aspect of cheese production due to consumers' concerns about food appearance and health. From an aesthetic standpoint, a moderate amount of free oil release is desirable as it gives the food a shiny look without forming pools of oil. However, excessive oiling off can negatively impact the appearance of dishes like pizza.
Traditionally, the oiling off property of cheese is determined using two main methods: the fat ring test and a quantitative test. The fat ring test involves placing cheese discs on filter paper and heating them at a specific temperature for a set time. The boundary of the fat ring that forms around each disc is then traced, and the area within this periphery is measured as the index of fat leakage. While this method is simple, it may not be sensitive enough to detect slight oiling off, and it can be challenging to obtain representative measurements from large cheese samples.
On the other hand, the quantitative test using centrifuges is more accurate but labour-intensive and time-consuming. To address these limitations, researchers have explored computer vision methods to evaluate the oiling off property of cheese. These methods involve extracting image features such as luminance, histogram-related features, and percentage oil area (POA) from images of cheese before and after cooking. By correlating these image parameters with fat leakage determined by traditional tests, researchers can assess the oiling off property more efficiently and objectively.
The oiling off property of cheese is influenced by various factors, including cooking conditions such as temperature and sample dimensions. For example, Cheddar cheese exhibits obvious oiling off at temperatures ranging from 70 to 200 °C, with the maximum oiling off occurring at 160 °C. In contrast, Mozzarella cheese produces little free oil below 100 °C, with the highest value of POA observed at 130 °C. Additionally, the size of the cheese slices affects the amount of oiling off, with larger slices tending to exhibit increased fat leakage.
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Melting temperature of cheese
When it comes to melting cheese, the temperature plays a crucial role in achieving the desired consistency and texture. The melting point of cheese is influenced by various factors, including its composition, age, and the presence of emulsifiers.
Cheese is primarily made up of milk protein (casein), water, fat, and salt. The fat content in cheese affects its melting behaviour and consistency. Cheeses with higher fat content, such as cheddar (31% fat), tend to become rubbery when melted and do not run. On the other hand, cheeses with slightly lower fat content, like Emmental (28% fat), will retain their shape and not run unless exposed to very high heat.
The melting point of cheese can vary depending on the type. For example, the melting point of cheddar cheese is around 150°F (66°C). At about 90°F (32°C), the fat in cheddar cheese starts to soften and melt. As the temperature increases by about 40-60 degrees, the protein molecules begin to break apart and disperse throughout the fat and water. This dispersion creates the stringy, melty texture associated with perfectly melted cheese.
However, if the cheese is heated beyond its melting point, the proteins will firm up and squeeze out moisture, resulting in rubbery, clumpy bits of cheese protein that separate from the fat. This separation is known as "oiling off" or "fat leakage," where liquid fat separates from the melted cheese body and forms oil pockets, particularly on the surface. The oiling-off property of cheese is influenced by cooking temperature and sample dimensions. For instance, cheddar cheese exhibited obvious oiling off at temperatures ranging from 70 to 200 °C, with maximum oiling off occurring at 160 °C.
To achieve the ideal melted cheese consistency, it is recommended to melt cheese slowly and gently at low temperatures. Shredding the cheese and bringing it to room temperature before heating can also help achieve a smoother melt. Additionally, the use of "melting salts," such as sodium citrate, can improve the emulsifying ability of the proteins, resulting in a smoother and more homogeneous cheese sauce.
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How to stop oil from separating
When hard cheeses are melted without an emulsifier, they break down into proteins and fats. This separation of liquid fat from the cheese body is called "oiling off" or "fat leakage". The amount of oiling off depends on the type of cheese, the cooking temperature, and the sample dimensions. For example, Cheddar cheese exhibits obvious oiling off at temperatures from 70 to 200 °C, with maximum oiling off at 160 °C, while Mozzarella cheese forms little free oil below 100 °C.
To prevent oil from separating when melting cheese, you can use an emulsifier such as mustard powder. Here's a general method for making a cheese sauce that minimizes separation:
- Make a light roux by combining equal parts butter and flour in a saucepan over medium heat. Cook the roux, stirring frequently, until it turns a light brown color.
- Slowly add milk to the roux, whisking continuously, until the mixture thickens.
- Add shredded cheese to the sauce a little at a time, stirring constantly, until the cheese is fully melted and combined.
- Season the sauce with salt, pepper, and any other desired spices or herbs.
- If the sauce does separate, try reheating it over medium-low heat and using a stick blender to emulsify it again.
It's important to note that pre-shredded cheese should be avoided when making cheese sauce, as it often contains dextrose and other additives that can cause the sauce to separate. Instead, shred your own block cheese and toss it with a small amount of cornstarch before adding it to the sauce. This will help to thicken the sauce and prevent separation.
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Using cheese oil for cooking
When hard cheeses are melted without an emulsifier, they separate into proteins and fats. This phenomenon is known as "oiling off" or "fat leakage," and the fat that is released can be used for cooking.
Some people choose to fry cheese in a pan and then use the leftover oil to make grilled cheese sandwiches or cook chicken. Others have mentioned frying an egg in the cheese oil. One user on Reddit mentioned that they add grated Parmesan or Romano to the oil until it forms a cheesy paste that can be eaten with the original melted cheese.
There are also recipes for making oil-cured cheese, which involves curing hard cheeses like Manchego, Parmesan, or aged Gouda in oil. This technique helps preserve the cheese and can be used to restore dried-out cheeses. The oil also acts as a barrier against bacteria, keeping the cheese safe to eat for months or even years without refrigeration.
Additionally, you can make fresh white cheese in oil with herbs. This involves creating cheese curds, which are then covered in olive oil and herbs and left to marinate for a few days. These cheeses can be stored and will keep for a couple of months without refrigeration.
While using cheese oil for cooking may not be a common practice, some people experiment with it and find it tasty. However, others find the idea unappealing, describing it as "permanently melted white yucky stuff." Ultimately, it is a matter of personal preference whether one chooses to use cheese oil for cooking or not.
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Emulsifiers to prevent separation
When cheese is heated, it undergoes a chemical change that causes it to melt. However, as seen in the case of aged farmhouse cheddar, the melted cheese separates into a pool of orangey oil and solids. This phenomenon is known as "oiling off" and occurs due to the breakdown of the protein matrix in the cheese, which results in the fat separating from the protein mass.
To prevent this separation, emulsifiers can be added to the cheese-making process. Emulsifiers are molecules that stabilize mixtures of two immiscible substances, such as oil and water. In cheese, they play a crucial role in preventing separation, enhancing creaminess, and extending shelf life.
There are two types of emulsifiers commonly used in cheese production: natural and synthetic. Natural emulsifiers, derived from plant, animal, or microbial sources, are often used in clean-label products and are considered more consumer-friendly. Examples include lecithin, found in soybeans, sunflower seeds, or egg yolk, which helps create smooth and creamy textures while preventing fat separation.
Synthetic emulsifiers, on the other hand, are widely used in mass-produced cheeses due to their cost-effectiveness and consistency. Distilled monoglyceride is currently the most commonly used synthetic emulsifier globally.
Some specific examples of emulsifiers used in cheese production include:
- Sodium citrate: Primarily used in processed cheeses, it improves meltability, prevents fat separation, and maintains the correct pH balance.
- Sodium phosphate: A synthetic mineral salt used to improve texture, prevent moisture loss, and enhance overall stability.
- Polysorbates (polysorbate 80): Derived from the esterification of sorbitol and fatty acids, it is used to blend oil and water phases in processed and spreadable cheeses, improving texture, stability, and preventing fat separation.
Additionally, when making cheese sauces or dips, cornstarch and evaporated milk can be added to create a stable emulsion and transform semi-solid cheese into a pourable consistency. This combination adds milk proteins and starch, which help stabilize the emulsion by preventing protein tangling and fat separation.
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Frequently asked questions
Milk's most crucial component is casein, a type of protein that clumps together in families called micelles. When milk is heated with rennet, caseins form a gelled network that traps fats and liquids, resulting in curds. Cheese is an emulsion of dairy fat and water, held together by a protein network. When heated, the protein structure loosens, and the fat reaches a liquid state.
Oil separation from melted cheese is influenced by cooking temperature and sample dimensions. Higher temperatures cause more free oil to separate from the cheese matrix. Firm and aged cheeses are more prone to oil separation during melting due to their lower moisture content and tighter protein clumps.
To prevent oil separation, use younger, high-moisture cheeses such as mozzarella, Taleggio, brie, Gruyère, Emmental, or Jack, which are known for their reliable melting properties. You can also add emulsifiers like sodium citrate or use processed cheeses, which already contain emulsifiers.
Yes, the oil that separates from melted hard cheeses can be used for cooking. For example, you can fry cheese curds in the oil or use it as a flavourful addition to dishes like soup or tomato sauce. However, it's important to note that the smoking point of cheese oil is very low.
To improve the meltability of cheese, maintain a balance between water and fat content and ensure a strong protein network. Excessive or long-term heat should be avoided as it can reduce the water content, causing milk proteins to shrink and fat molecules to escape and pool together.
