You have most likely eaten, and perhaps even crave for, cheese with ‘a crunch’. Cheeses such as Goudas, Parmesan, and Cheddars have perceptible crystals, either inside their body or on their outside surface. This blog entry is all about these crystals: what, how and why.
The Magic Crystal
First, what is a crystal? We see crystals every day, perhaps without thinking much about them. Sugar and salt are common household crystals.
Salt, for example, is made up of sodium and chloride ions, Na+Cl-. The physical form of the crystal consists of a regularly repeating geometric lattice of sodium (Na+) and chloride (Cl-), with their positive and negative charges forming an attraction, or electrostatic bond, which keeps the whole thing together in a solid form.
If they are big enough, we can see crystals with our naked eye, like sugar and salt, but we can also visualize the crystals at an atomic and molecular level, using high energy X-rays. When a focussed stream of X rays are aimed at a regularly repeating unit (like a crystal), the X-rays bounce through it in a specific way depending on the components of the crystal. The pattern in which the X rays leave the other side of the crystal can then be back-converted (using some very fancy mathematics) into the internal repeating structure of the crystal. This method is called X-ray diffraction, and a method using powdered crystal as the target is commonly used to examine cheese crystals (powder x-ray diffractometry or PXRD).
Salt, NaCl, is an inorganic crystal — meaning that it can be formed from non-living processes (think of rock or sea salt). Sugars (e.g. glucose, fructose) are organic crystals. These crystals contain the element carbon, and are generally derived from living processes and organisms.
Cheese is an entire environment formed from a product from a living organism (milk from an animal) and is full of living organisms (microbes), therefore crystals in cheese are organic crystals, formed from microbial action on complex building blocks of cheese, and inorganic, formed from the various salts which become concentrated through the cheese.
All crystals ultimately form by the same physical mechanism. Components of the crystal (say Na+ and Cl-, or Ca2+ and lactate CH3CH(OH)CO2-) begin by being dissolved in water. Once the salt reaches a level of maximum saturation in the water — where no more can be held in solution — then solid crystals of salt spontaneously start to form or nucleate.
This saturation can be caused by adding more components, e.g. Na+ and Cl-, until that level is reached, or by removing the water (such as by evaporation) until that level is reached, or by altering the acidity of the solution (which affects the ions themselves).
This is how cheese crystals form – components that are dissolved in the water content of the cheese hit that saturation level, e.g. by loss of water or acidity (pH) changes, and nucleate in situ.
Now you are armed with the basics about crystals, let's see how that applies to cheese.
Crunch on the Outside
One of the most common crystals that you might see on cheese is calcium lactate. Milk and cheese is rich in the sugar, lactose. Lactate is produced from the breakdown of lactose in cheese by microbes, such as the aptly named, lactococci and lactobacilli. Lactate is the negatively charged (-) form of lactic acid. The positively charged calcium (Ca2+) is naturally present in abundance in milk and cheese. On reaching saturation, Ca2+ forms an electrostatic, attractive bond with this lactate(-), forming crystals.
Calcium lactate is easy to see on the surface of aged cheeses, in particular block cheddars, where the method of packaging (wrinkly vacuum packed plastic) leaves enough oxygen and water present to encourage the lactic acid to concentrate there. Ultimately this allows the calcium to join with the lactate as it hits the saturation level, and form a long smear of small crystals (see images 2 & 3 below). Calcium lactate can also be seen in some other aged sheep cheeses, such as pecorino, where they appear as stellate dots inside the main body (see first image).
Due to their small individual size, these crystals don’t provide much crunchiness, and therefore are often mistaken for surface mould and are scraped off.
Crunch on the inside
Perhaps the most obvious, and desired, crystals found in cheese, are those found in aged Goudas, Parmigiano Reggiano, some Swiss-styles and some aged Cheddars. These crystals are within the cheese body, and can be found in ‘holes’ in the cheese (see picture) or as punctate clusters in the body. These organic crystals are remnants of the cheese’s solid protein structure (interested in learning more about the contents of cheese come to a cheese class!).
Cheese is made of a solid matrix of protein, which are themselves made of building blocks called amino acids. Crystals such as these are made of individual amino acids, mostly tyrosine and sometimes leucine. How they are deposited in cheese involves chemistry of the cheese and the biology of the microbes, and is fascinating.
The process of ageing to release flavours relies on the microbes present in the cheese and milk, breaking down the proteins and fats within the cheese. These breakdown products are one of the main drivers of flavor: the longer the ageing, the more breakdown, often the stronger the flavor.
The microbe Lactobacillus helveticus, is a favourite for many cheesemakers, as it is responsible for producing some sweet flavors – such as found in many aged goudas. L. helveticus is not able to synthesise all the amino acids (e.g. tyrosine, leucine) it needs for its own proteins – it has to scavenge them by actively breaking down proteins from other sources – such as cheese. And this is what happens.
In the image above, the white crystals in the large hole are formed by the work of L. helveticus and its cellular machinery on cheese proteins. This action produces significant amounts of tyrosine (and/or leucine). As the microbes live in the cheese, they also release carbon dioxide gas, which if the texture of the cheese is right, can expand to form a hole in the cheese.
At some point, the L. helveticus, die, but their protein breakdown machinery continues to function, and increases the amount of these amino acids present. These two amino acids happen to have a low solubility in water, and so even a small increase in the amount will result in reaching the saturation level, and crystals will start to form.
The hole and the crystals in the cheese are therefore echoes of the microbes which once lived and worked in that very spot.
Blue cheeses can have crystals inside them, which are also found within their 'holes' or caves. These holes, however, are slightly different to the holes found in swiss cheeses. Swiss cheese holes are formed by the gas released from microbes, which gives them a smooth surface. Blue cheese holes, are formed at the beginning of cheesemaking by pieces of curd, and so are really small areas which act like cheese rinds, and at the rinds, crystals can form through different methods...
The Crunchy Rind
There are some cheeses which have crystals within their rinds — although these tend to be hard to sense.
Some soft white rind cheeses, like Brie, and soft washed rind cheeses, like French Munster or Oma from the Cellars at Jasper Hill, can have crystals form within their rinds. The crystals found in Brie-style cheeses are generally below the threshold for us feeling them within our mouth (66 uM in length, if you’re interested), but the crystals within washed rind cheeses can be large enough for us to sense them — normally as a grittiness in the rind.
The rinds of both bloomy white rind cheeses, and washed rind cheeses are a rich, dynamic, active and diverse mix of microbes, forming a ‘living microbiome’ (read more about Microbiomes in another blog entry). This microbiome is in flux — the make-up of its microbial population changes over time as the rind develops. It has been shown that different microbes grow in a particular order, as the conditions at the rind change – a process called ‘microbial succession’. The conditions at the initial rind are created by the cheesemaker (for example salt washing), but then the subsequent activity of the waves of microbes changes the conditions on the rind as it ages. (This reinforces the idea that cheesemaking, and the cheesemaker can help set a cheese for a particular direction e.g. through moisture level and texture, but ultimately, it will be the microbes which define how and what the final cheese produced.)
On soft washed-rind cheeses, it has been shown that the acid and salt-tolerant yeasts are the first microbes to populate the rind. The yeasts metabolise lactic acid producing carbon dioxide and ammonia, and this begins to shift the acidity of the rind towards neutral (from pH 5.0 - 5.5 to pH 6.0 - 6.5 to pH 7). Once this level of acidity is reached bacteria are able to thrive, and as their populations grow the pH continues towards neutral, as they metabolize the lactic acid and produce substantial amounts of ammonia. In the holes of blue cheese, the fungus dominates the 'rind', and acts to drive the pH towards neutral mainly by its own activity.
This significant trend towards neutral pH at the rind results starts to affect the whole cheese. Firstly, the solubility of various ions in the rind, such as calcium (Ca2+) and phosphate (PO4-), decreases significantly, and this allows simple crystals to form, such as Brushite (small punctate crystals of calcium phosphate Ca2(PO4-)2) and Calcite (calcium carbonate, CaCO3) — these are pictured in the cave-like hole of the blue cheese above. Because of the loss of these ions into the solid crystal phase, other calcium, phosphate etc. ions begin to move down the ion gradient (via osmosis) from the centre of the cheese to the rind. This replenishes the ion supply, allowing further and greater crystal development.
The continuous metabolic production and osmotic influx of ammonia (NH4+), carbon dioxide (CO2/H2CO3), phosphate (PO4-) and other ions, at the rind allows more unusual and elaborate crystals to grow in complex with water molecules.
Recent work has observed two types of crystal outside of their ‘normal habitats’ growing within cheese rinds. Ikaite (CaCO3•6H2O), which is a highly unstable crystal that is rarely seen outside of freezing sea or lake environments, the cold being necessary in holding the crystal together. Another Struvite (NH4MgPO4•6H2O), which is often linked to bacterial activity, and found in warmer situations – in particular in urinary tract infections.
Even more curious, like the microbial succession, it was observed that these crystals existed in phases or waves. The Brushite being the first to appear, followed by Calcite, then Ikaite and finally Struvite – which seems to follow the level of complexity for each of these crystals, and may suggest the simpler crystals take less time to form than the more complex ones, and that the complex crystals use the simpler crystals as building material or nucleation sites.
So there you have it. Cheese crystals are a rich combination of physical chemistry, and microbiology, and I hope that now, when you eat a piece of cheese and hit that satisfying texture, you will pause for amount and be able to reflect on the wonders which brought you that fleeting moment of pleasure.
One of the hot health-related topics in the past couple of years or so, is the microbiome and how it affects human health.
We thought it was time, that we broke down the microbiome, what it does, how we affect it, and how the microbiome has been shown to positively – or negtivaley – affect our health. And, of course how eating cheese, and other dairy products will help your microbiome maintain its healthy diversity, which in turn can contribute in a positive way to asthma, allergies, and even response to some types of cancer therapy.
right? Well, read on!
A microbiome is a complex community of micro-organisms (microbes), including bacteria, fungi, archaea and viruses, which exist on and in, higher multicellular organisms – like us! This means that on our body, on different surfaces inside and outside, exists a layer of a community of microbes, each community composed differently depending on its location.
The microbiome is responsive and dynamic: as conditions inside and outside our body change, so does the microbial content of the microbiome, reflecting that the changed conditions may be more favorable for growth of one type of microbe, than another.
For example, if we eat a well-balanced diet, then our gut microbes exist in a healthy, co-operative state. If we change our diet, for example, to fatty fast foods, the changes are rapid (within 2 weeks!) and dramatic. Not only is there an overall loss in microbial diversity, but helpful microbes are reduced in number, and microbes linked to cancer and gastric ulcers increase in number. For more information, this is a good place to start.
Incredibly, under normal conditions, our microbiomes do not cause an immune reaction from us. Unlike dangerous microbes, which are immediately targeted by our immune system, they are deemed safe.
Our microbiomes co-exist and are tolerated by our bodies – more on that later.
We have microbiomes on our skin, in our nose, mouth, throat, lungs and gut. Each of the different areas will have a different microbiome content, caused by the different conditions of those different areas: for example, the skin microbiome in between our toes (warm and salty), will be different from the microbiome on our head (dry and agitated), and in our guts (moist, warm and slightly acidic). We have our microbiomes from birth – microbiomes are easily picked up from the environment, but our gut microbiome relies heavily on a natural birth - as our open screaming mouths grasp more than air on the way out of the birth canal.
The role of the microbiome.
A significant amount of research is underway to understand what our microbiomes do, but we already somewhat understand these complex communities.
1) A Microbial Wall. The microbiome provides protection against invasion by harmful microbes, by outcompeting invaders, through their established presence on our body surfaces. When we undergo a course of antibiotics, in addition to pathogenic microbes, our microbiomes are also eliminated, which can cause issues post-treatment (since this 'home-turf' competitive-advantage no longer exists)!
2) Chemical recyclers & messengers.
Microbes are able to metabolise chemicals in their environments, such as salts (skin), toxins (gut) and complex carbohydrates (gut), which may have unwanted side-effects for our bodies, protecting us from their effects. They also produce molecules which have effects in our bodies either at a local site, or at a distant one.
3) Trainers of the Immune System. The microbes act as continuous trainers and tuners of our immune system, it is this which allows tolerance to their presence, and helps reduce excess immune activation.
Let’s have a look at the first two roles of the microbiome, as it involves an active participation by the microbiome.
Communicating with Me, Myself and I
For at least 10 years, it has been known that there is a line of communication between the gut microbiome and the central nervous system (including the brain). However, it hasn’t been clear how this actually exists.
A recent paper in Nature from the Quintana lab in Boston (Nature, 557, 724-728), demonstrated one method where the gut and the brain communicate. Using a mouse model of multiple sclerosis, they showed that particular molecules produced by the gut microbiome travelled to the brain, and inhibited the inflammatory behavior of specific brain immune cells. This directly limited the inflammation and neurodegeneration created by these cells in multiple sclerosis. By examining the brains of MS patients, they saw fingerprints of this activity, suggesting that this method is also at work in humans.
Evidence showing that a healthy gut, means a healthy mind.
Hello, It's Me
How about the other active role of the microbiome - tuning our immune system?
Our immune system is a complex system which is able to recognize self- from non-self. Inside our thymus glands and bone marrow, we develop certain types of immune cells called T and B cells. During their development, these cells come into contact with ‘pieces of self’. Each B or T cell is genetically programmed to recognize different ‘pieces’, and if any of these cells recognize ‘self’ too strongly, then they die. If the cells don’t recognize ‘self’ during this period, they mature, develop further recognition machinery and leave, to become active in our immune system.
This is not the end to the cell’s ‘Immune Education’. The gut lining is an area of intimate contact between our cells and the microbiome. A cell called Type 3 Innate Lymphoid (ILC3) cell, actively engages the microbiome and presents ‘pieces’ of the microbiome to the mature T and B cells. The extra recognition machinery of T & B cells developed when they matured is not engaged by ILC3 cells, therefore T and B cells which recognize the microbiome pieces, die without engaging a full immune response, creating a tolerance for the microbiome. (For a good book on Immunolgy, try this one, from Roslindale-resident Geoffrey Sunshine).
Immune education, such as this occurs in other microbiome environments in the throat and airways as well.
So, why is this important?
In both humans and mice there is overwhelming evidence that disrupting this close interaction/education between our microbiomes and immune system is a cause of health issues. This continuous training keeps our immune system focused on dealing with harmful bacteria, rather than over-reacting to harmless stimuli. The best training for our immune system is provided by a diverse selection of microbes (which may differ between the gut, lungs etc.).
Studies in mice and children show that lessened exposure to environmental microbes during development (for example from farm or house dust), shows a correlation with airway hypersensititvity (asthma) and, at least with mice, reintroduction of particular microbes found in these dusts, relieves this hypersensitivity. There has been extensive comparative work on the children from Hutterite (clean mechanized farms) and Mennonite (old style, manual, dusty farms), showing the latter benefit from the exposure to microbes. Try this review for an in-depth survey of current literature.
The process of fecal microbiota transplantation (FMT) was a brief case report and is now the basis of major innovations in the treatment of Clostridium difficile infection (CDI) and, potentially, inflammatory bowel disease (IBD). A pill of frozen poop (from a healthy donor!) is provided to a patient, and this increases the diversity of the microbiome and alters the metabolic pathways active in the intestinal flora, causing C.difficile to be eliminated – without resorting to antibiotics.
How does this all relate to cheese?
All cheese is a fermented food – certain microbes breakdown the lactose to lactic acid and CO2, which is one of the first steps of cheesemaking. Microbes (from the milk) then start to work on the other components of the cheese to provide flavors and aromas, and to affect the texture. If the milk is pasteurized, which eliminates all the microbes present, then the cheesemaker has to introduce their own selection of microbes to produce the desired flavor profile. If the milk is unpasteurized, then the cheesemaker just rolls with what the environment has provided!
There is therefore a vast number of microbes in both pasteurized and unpasteurized cheese – although there is likely to be a much higher diversity of microbes found in unpasteurized cheeses.
As we have seen above, a broad microbial diversity is beneficial to our health, which all points to this:
Eat cheese, and if you can, eat unpasteurized, raw milk cheese. This will maintain a natural gut microbiome, and provide the broadest selection of microbes possible.
Other dairy products work too, such as yoghurt, as do other fermented foods to some extent (eg Kombucha, rather than beer!), as long as they have microbes within them, but these tend have a producer, who makes a selection of desired microbes, therefore will not have the microbial diversity of unpasteurized, raw milk cheese.
Currently it is unclear is there are specific microbes which have specific benefits. For example, a recent study on response to a cancer therapy (anti-PDL1) identified one specific microbe as being important, although two other similar studies did not find the same connection (seea summary here). Our microbiomes are so complex, that it will likely take a long time to figure out — if at all — any direct, causative link between one microbe and one solution.
A cheese designed purely to boost cancer therapy is therefore some way off!
Way out in northwest Massachusetts, you will find Cricket Creek Farm. It's at the end of long dirt road, which itself is at the end of a long, seemingly endless river of tarmac spewing out from the city of Boston. It may be a long drive, but the beauty of the countryside, and the final destination make it all worthwhile.
Cricket Creek Farm has been through a number of iterations, from being a large dairy farm only which produced liquid milk for market, to its current form of a small artisanal farmstead cheese producer. It is one of a small collection of farms in Massachusetts which make raw milk cheeses, and also sell their raw milk (on the farm only, of course). The farm and operation is owned and run by Beth Lewand - who made the jump from owning a cheese shop in Brooklyn, to owning and running Cricket Creek Farm in September 2017.
We were lucky enough to see Cricket Creek on a stunning Spring day in April. Most of the mud had dried up, the grass was starting to green, and the cows were itching to be turned out into the pastures — Beth assured us it would be within the next week or so that they would get their wish.
The herd owned by the farm is about 70 strong, which includes a few bulls, with the cows being a mix of Brown Swiss, Jersey, and Devon Red - all known for their high quality milk. Of course, good quality milk means good quality cheese. There are about 30 - 40 cows giving milk for cheese at one time.
Our day started with a tour of the farm. It's really quite small, yet running at full capacity, even with a complete staff of 8 or so (including interns etc.). With it being Spring, we were lucky to see some new calves from the herd, as well as some heavily pregnant mothers - and also the farm pigs with their new litter of piglets. Because the pigs are fed on whey (the byproduct of cheese making) and waste cheese, their existence is completely farm-contained.
All the cows are field grass fed, which helps them to make their rich milk. The farm also has a complex rotational system in place to help them juggle the grazing with the harvesting of hay for the winter - which will maintain the quality feed the cows get throughout the year.
The milking parlour is now quite small, since the farm has reduced it's size significantly from the days when the farm produced only liquid milk. It's now the right size for the amount of cheese that is made, and the amount of raw milk which is bottled. Anymore milk and one can tell that things would get quite out of hand. The milk from the parlour is piped directly to a chilled storage tank, and from there either to the bottling system, the pasteuriser or the cheese vat.
Not only did our trip get lucky with great weather, but we also timed it perfectly to make some cheese. In the make for the day was Maggie's Round, and Maggie's Reserve.
The milk was set, had just been cut in the stainless steel vat, and was currently being cooked at 100 F, to help shrink the curd and give it the right solidity. It was now hooping time - essentially gathering up the curds into the Maggie's moulds and starting the draining process. The amount of whey produced from cheese making is always impressively large, and the speed at which the curd start to naturally take to, and hold, their shape is likewise something that needs to be seen to be appreciated.
Where does the cheese go after the draining and flipping? Well, the ageing caves of course. The caves are rarely caves nowadays, normally just a temperature and humidity controlled room. Cricket Creek has two small rooms. One is used for the harder cheeses, like the Maggie's Round, and is kept around 55 F and 85% humidity. The other is used for the softer cheeses, like Tobasi, Sophelise, and Berkshire Bloom, which is also 55 , but nearer 95% humidity.
Ageing cheese - or affinage - is not a set-it-and-forget-it kind of flavour!thing. Each cheese has it's own requirements, like Maggie's Round, which needs to be flipped or brushed to make the rind brown and tight, rather than fluffy and grey (from the natural moulds). The soft cheeses, not only need to be flipped, but also the entire stock needs to be rotated around their room, since the temperature and humidity is not evenly distributed, and this will affect the ageing, and therefore the final cheese.
At every stage in dairying and cheesemaking, small changes can make a large difference in the final cheese.
From the care of the herd, to the rotation of the grazing, to the seasonal milk variations, to the changes in temperature and humidity within an enclosed room. The amount of variables to mind, and to keep within paramteres is overwhelming, and nothing short of impressive.
As always, trips to farms and cheesemakers are humbling, and this trip was no different.