Achieving Custom Crafted Outcomes with Blue Cheese PDF Print E-mail
Written by Pav   
Sunday, 18 July 2010 18:15
One of the oldest cheeses made (Pliny wrote about it in the first century) is a type containing Penicillium roqueforti fungus that creates a distinctive blue veining, piquant flavor, and strong aroma. Blue cheese is made from many types of milk and has multiple variations in flavor, texture, and appearance. The texture and mouthfeel vary from crumbly and slightly acidic, to smooth, spreadable, and creamy. It is commonly molded into a cylinder shape ranging from 6 to 12 inches in diameter and 6-20 inches in height. The rind may be a natural, blue rind that dies off and turns a brown color, as in the case of Stilton, or without a blue rind, as in the case of Gorgonzola, or even wrapped, as in the case of Valdeon.

The decisions you make in crafting a custom blue cheese work together to contribute to the final sensory and texture profiles. And these are many decisions possible, starting with the milk composition, all the way to the room temperature at which it's served and consumed. Thankfully, there are predictable outcomes you can achieve by making decisions at key points, such as milk acidity at adding rennet and draining whey, and manner of salting. I'll cover major decision points, and their resulting outcomes, as well as minor tweaks you can make to achieve a specific flavor profile. Most of the time, the minor tweaks are variations in the major points, such as salting to a specific salt level to balance out fat content, creaminess and blue taste. This article covers the individual tradeoffs for making blue cheese to give you a solid understanding in the decisions possible.

General Process Flowchart

It is helpful to start right away with how blue cheese is made. Even with all the variations, some aspects are constant for traditional soft blue cheese. If you're after specialty creations, like a gouda cheese with blue mold, then there are, of course, differences. In general, blue cheese is made by heating milk to the temperature conducive to mesophilic bacteria growth, adding the bacteria starter, introducing the blue fungus either to milk or to curds, draining off whey from the curds, and putting them in a cylinder shape. Figure 1 shows a more comprehensive diagram of this process. Please do NOT use the flowchart to make a cheese, it is just for illustration. See the individual howtos for information on making specific blue cheese styles.

Figure 1. Flowchart of blue cheese manufacture

The figure doesn't cover all the various variations out there (this is an overview article after all), and omits some steps for finishing, such as adding yeast culture and yeast maturation, as well as rind washing for gorgonzola. I'll try to cover those specifics in individual make notes for each style. When you look at the figure, don't be intimidated because one of the wonderful aspects of blue cheeses is that if you screw everything else up, but the milk is inoculated with mold spores, and the curds are acidified enough to a pH below 4.8, you should still get an acceptable cheese, assuming maturation and affinage are done right. That approach of saving mistakes shouldn't be practiced commercially, of course, but don't be discouraged if something doesn't go exactly as planned. Take notes, and try to do better next time :)

Now let's go over what the figure does cover. All the labels in the gray boxes, such as Milk Preparation and Coagulation cover categories for the major decision points that influence how your cheese will turn out. And the individual boxes cover common tasks that must be completed while making cheese. The categories represent possibilities for major variations, and the tasks represent possibilities for more minor variations and fine-tuning.

Milk Preparation

Blue cheese texture is determined in good part by the milk quality and composition. This is the first major decision point. The major components in milk you can change are the whey proteins (by adding concentrate), the fat content (by adding or removing cream), and the protein content (by adding dry milk). Changing the fat and protein percentages are fairly common practices commercially to standardize the milk and make consistent cheese. In the artisan world, it is more common to change only fat, either by skimming fat from milk, or adding cream back in. The changing of protein and fat also changes one important indicator that affects the final cheese fat content, and curd moisture, the protein to fat ratio or PF.

Increasing the fat content in milk past its normal range of 3.2-3.8% increases the tendency of the curds to retain whey. That is, milk with more fat makes for a softer curd, which is very slow to release whey. Softer curd that retains more moisture tends to make for a cheese with higher moisture, especially if the curd is not drained well before it is packed into molds. A higher moisture cheese has the potential to age faster, which is not always advantageous. It also tends to be softer and more spreadable. So overall, to make a more spreadable or softer blue cheese, one option is to increase the fat content of the milk by adding cream.

There are other options possible to alter milk before adding rennet. One other one is milk pre-ripening, during which some culture is added to pasteurized milk to introduce additional sources of flavor compounds. This is a fairly common practice for soft mold cheeses, such as brie, blues, and camembert. It is used mostly commercially because of the added cost and expense of pasteurizing twice.

One trick used to help create openings in the cheese to create veining is to use a mesophilic culture that is heterofermentive and produces CO2, such as Leuconostoc mesenteroides.

Coagulation

The acidity level of the milk when you adding rennet and the time from adding rennet to the time you cut the curd are two important decision factors in making blue cheese. The acidity level is important because it coincides with the amount of starter added earlier, and the time spent in ripening the milk to activate the starter. Normal milk has a pH of about 6.6. Most blue cheeses are renneted at a pH of 6.4-6.5. If the pH is too high, the rennet is not as effective and the milk takes longer to set. If it is much lower, then the bacteria are active, or too much starter has been used, or the milk is off, or too much time has gone to ripen the milk. A slightly acidified milk also retains moisture better because the acid degrades calcium, making the casein proteins more likely to retain water.

After adding rennet, the next aspect to consider is the strength of the curd when cutting it. This is crucial to obtain the proper final moisture content of the cheese. A strong curd that sets for a long time after adding rennet retains moisture better than a weak curd that has not set for long. It may seem counterintuitive, but the longer a curd sets, the stronger the coagulum gel becomes, and it is less likely to release moisture from within that coagulum.

A good way to determine when to cut, especially without years of experience, is to use a multiplier method in combination with timing the point when the surface gels. Rennet coagulates milk in two phases. The first phase is when the rennin cleaves about 75% of the k-casein protein, which enables the other caseins to bond together. And the second phase is when those proteins actually initially bond and form a weak gel. The transition point happens very quickly, and that's when a surface gel forms. If you measure the amount of time it takes from when you add rennet to when a surface gel forms, it is possible to use a multiplier to determine when to cut the curd. The time it takes for the surface to gel varies with the milk, which itself varies with the lactation period, time of year, feed, etc. By using a method to time the initial surface gel and a multiplier, you can be fairly sure that the coagulum strength is the same regardless of the milk.

To use a multiplier method with the surface gel point, measure the amount of time it takes from when you add rennet to when the surface gels, and then multiply that time by a multiplier. Blues use a 4x multiplier. A useful method to determine the surface gel point is to float a sanitized bowl that floats on top of the milk and nudge it. When you nudge it and it doesn't move, the surface has gelled. This usually takes 10-15 minutes. To determine the point of cutting the curd, multiply the time to surface gel by the multiplier. For example, if it takes 10 minutes for the surface to gel, with a 4x multiplier, you will wait 40 minutes total from the time you added rennet to the time you cut the curd.

Curd Cutting

After the curd is ready to cut, either by observing the strength visually through experience or by using a surface gel method with multiplier, it may be cut. This is relatively straightforward, with the decision point being how big to cut the curd. Bigger curds retain more moisture. A curd cut to 1" will result in a more moist cheese than curd cut to 1/2". However, this also depends on the protein solids in the milk and the length of time you take to stir the curds. For example, late lactation milk has more solids, and usually may be cut to larger curd size and cooked for less time. Mid-lactation milk, on the other hand has lower solids, and you may need to cut the curd to smaller size and cook longer.

For blue cheese, a 1" curd size is about average. Many blue cheese styles heal the curd for 5-15 minutes, which means letting it sit in the vat to firm up after cutting and before stirring. Healing increases curd strength and tends to increase yield. Commercial vats often use shorter or no heal times because it takes so long to cut the curd that it heals while being cut.

Curd Cooking

Cooking manner, temperature, and duration vary greatly among the blue cheeses. For example, Stilton curds are stirred and left to settle under whey, whereas gorgonzola curds are cut and put on a conveyor belt, where they drain. Generally, the manner of draining should fit with the rest of the choices to fit a specific target moisture content. For example, to get a more moist cheese, you can cut the curds larger and cook shorter or for a dryer cheese, cut them smaller and cook longer. Generally, blue cheesecurd is not heated, or barely heated, and stirred to get to the final moisture target.

Whey Draining

Whey draining is relatively straightforward with blues. There are variations, like for commercial gorgonzola manufacture (moved on conveyor), but overall, the whey is drained completely and the curd left to acidify, or left under the whey to acidify. The important part is that the curds need to be strong enough to not seep out much whey by the time they are packed.

The acidity in the curd at time of whey draining is also very important. A higher acidity (lower pH) when draining whey means the curd has lower calcium levels and has greater water retaining capacity. Both are important to the final texture. Higher calcium levels make for a more solid cheese that is not as soft when cut. This applies to all cheeses. Cheeses with higher calcium levels than blues include most hard cheeses. Blue cheeses vary in their approaches. For stilton and roquefort, the pH is lower, approaching 6.0, or lower. For gorgonzola, it is high, 6.3-6.4. Gorgonzola differs because it uses a thermophilic starter such as L acidophilus that acidifies to lower pH than mesophilic starter.

Curd Knitting

Curd knitting is crucial for blue cheese because this is how the veining is formed. Curds need to be dry enough when they come together to allow for mechanical openings to form. This is usually accomplished by waiting for them to firm up, and sometimes helping by salting the curds lightly with .8% salt. The salt also helps the Penecillium mold to grow.

Molding

Molding for blue cheeses is as simple as putting the curds into molds with a scoop. The size of molds differ, with a general cylindrical shape being the norm. Stilton has a higher height than width, others tend to be more even. French and Italian blues tend to be wider than they are tall.

Pressing

In general, blue cheeses are not pressed with a weight or pneumatic press. They are left to form under their own weight, flipping them repeatedly for even draining.

Salting

Blues have a salt content between 1.5 and 5%. Higher fat cheeses, such as Stilton, tend to have higher salt content. In general, a 2-3% salt target is suitable. The home equivalency is about 2 teaspoons per pound of cheese, or a little less.

It is worthwhile to note that the manner of salting has a lot to do with the final rind approach. One approach to salting is to not salt the curds, but heavily salt the rind, to a point above 10% where P roqueforti mold does not grow. A heavy exterior salting establishes a gradient where the salt slowly works its way into the cheese, and the rind remains moldless. It's useful for creating a clean rind without mold, which can then be covered in foil, such as for gorgonzola.

So in general there are three ways to introduce salt: brining, dry salting the rind, or salting the curd and then packing it. Brining in general is not used for blue cheese. Salting the curd is used for Stilton, and the rest are generally dry salted after forming. The salting schedule of the rind differs among the variants. Some producers salt heavily at first to produce a rindless blue, and some salt over 2-4 days to allow the salt to penetrate and create a basic rind.

Affinage

The maturation process for blues is absolutely crucial to producing a proper cheese. In general, blues are left to acidify for several days in their molds before moving them to the cave. Stiltons are smoothed to create a uniform surface. Gorgonzola undergoes two days of yeast ripening before being moved to the aging room. Other blues are left in the mold at ambient temperature to allow the blue mold to take hold, and are then moved to the aging room. I cover individual affinage approaches for each style in the individual howtos.

The three key aspects for affinage are temperature, humidity, and air exchange. The best conditions are like the ones in natural caves, such as the ones used to make Roquefort. In those caves, the temperature remains 55F, the humidity is generally 90-95%, and the air volume is exchanged about 5x per hour. Imitating as much of these factors as possible is crucial.

One good way to accomplish blue cheese affinage at home is to use a modified refrigerator and a plastic container as an affinage chamber. This creates a micro atmosphere where you can regulate temperature via a thermostat and regulate humidity and air exchange by taking out the container as necessary 6-10 times per week to allow air exchange and maintain humidity below saturation.