Strained yogurt is older than the word for it.
The process of allowing fermented milk to drain through cloth until it reaches the consistency that the Greek table calls straggisto, strained, is a process that the pastoral communities of the eastern Mediterranean and the Aegean islands were practicing long before the product acquired its contemporary international designation. The chemistry of the transformation does not require knowledge of the chemistry to produce the transformation: a clay vessel of milk, left in the warmth of a summer afternoon in the proximity of the naturally occurring lactic acid bacteria that the environment provides, undergoes spontaneous fermentation. The acidified milk, placed in a cloth and suspended in the shade, drips whey for several hours and thickens to the consistency that the shepherd or the island householder recognized as the preserved and concentrated form of the milk that would keep through the heat of the day and provide the protein and fat that the pastoral diet required.
This is the origin of what the international market now calls Greek yogurt, and the designation is accurate in the sense that Greece has been producing and consuming strained yogurt from sheep and goat milk as a staple of the ordinary diet for longer than most of the world has known dairy fermentation existed. The contemporary commercial product, typically made from cow’s milk, strained mechanically in industrial facilities, and packaged with a protein content and texture calibrated to the international wellness market, is the industrial version of a preparation that the Greek pastoral tradition developed from the materials at hand in the ecological conditions of the Greek landscape.
Understanding what the original was is understanding why the contemporary version has the properties that have made it internationally significant.
The Fermentation and What It Produces
Yogurt is the product of the metabolic activity of lactic acid bacteria, primarily Lactobacillus bulgaricus and Streptococcus thermophilus in the standard commercial cultures, acting on the lactose in fresh milk. The bacteria consume the lactose, the primary sugar in milk, and produce lactic acid as their metabolic byproduct. The lactic acid causes the milk proteins, primarily casein, to coagulate, producing the gel structure that gives yogurt its characteristic texture. The fermentation also produces the aromatic compounds, acetaldehyde, diacetyl, and others, that give yogurt its flavor profile: the tanginess that distinguishes fermented milk from fresh.
The straining process that transforms ordinary yogurt into the strained form removes the whey, the liquid fraction of the milk that the fermentation has separated from the casein network. Whey contains water, lactose, whey proteins, and various minerals. Removing it concentrates what remains: the fat, the casein proteins, and the flavor compounds of the fermentation in a reduced volume of material.
The nutritional consequences of straining are and significant. A 100-gram serving of plain strained Greek yogurt contains approximately twice the protein of the same weight of unstrained yogurt, because the protein that was present in the original volume of milk is now concentrated in half the volume of product. The lactose content is reduced, because much of the lactose that the bacteria did not consume is removed with the whey: strained yogurt is generally better tolerated by people with mild lactose sensitivity than unstrained yogurt or fresh milk. The calcium content per serving is comparable to unstrained yogurt despite the reduced lactose, because calcium binds to the casein network rather than being primarily present in the whey.
The probiotic dimension of strained yogurt is the dimension that the contemporary wellness literature has most extensively discussed, and the discussion is accurate in its general claims: the live cultures present in genuine strained yogurt, when consumed in sufficient quantity, do contribute to the microbial diversity of the gut microbiome. The health outcomes associated with a diverse and well-populated gut microbiome, from the immune function modulation to the gut-brain axis effects that the research has consistently identified, are outcomes that the regular consumption of live-culture strained yogurt can contribute to.
The qualification live-culture is important. Commercial strained yogurt that has been heat-treated after straining to extend its shelf life does not contain live bacterial cultures, because the heat treatment kills them. The strained yogurt that provides the probiotic benefit is the strained yogurt made with live cultures and not heat-treated after production: the traditionally made straggisto, drained from the cloth still carrying its active microbial community, is the probiotic food. The heat-treated commercial product is a concentrated protein source without the probiotic dimension.
The Pastoral Tradition and Its Milks
The Greek strained yogurt tradition developed primarily around sheep and goat milk rather than cow’s milk, and this origin explains a set of characteristics that the contemporary cow’s milk product approximates but does not exactly replicate.
Sheep’s milk contains approximately twice the fat content of cow’s milk, a higher protein content, and a profile of short and medium chain fatty acids that give it the distinct flavor that separates sheep’s milk dairy from cow’s milk dairy in any blind tasting. The casein structure of sheep’s milk produces a yogurt with a different texture than cow’s milk yogurt: denser, creamier, and with a mouth feel that the fat content and protein structure of the milk determine. Strained sheep’s milk yogurt from the small dairy operations that the Greek mountain communities still maintain in the spring and early summer, when the sheep are producing the richest milk of the year after the birth of the lambs, is the product that the Greek culinary tradition built its yogurt applications around, and it is the product that the contemporary cow’s milk commercial version is a technically competent but sensorially different approximation of.
Goat’s milk yogurt has a different character again: less fat than sheep’s milk but with the flavor compounds, caproic acid, caprylic acid, capric acid, that give goat’s milk its pungency and that make goat’s milk yogurt more intensely flavored than cow’s milk yogurt at the same fat content. The island communities that maintained goat herds as their primary dairy animals developed yogurt applications that worked with the assertiveness of the goat’s milk product rather than against it.
The contemporary Greek market still sells strained yogurt made from sheep’s and goat’s milk alongside the more widely distributed cow’s milk version. The price differential, which is substantially higher for the traditional milks, reflects both the lower productivity of sheep and goats compared to cows and the persistent consumer recognition that the heritage product possesses a quality the commercial cow’s milk version does not achieve.
What the Greek Kitchen Does with Yogurt
The Greek kitchen uses strained yogurt in a wider range of applications than the international wellness context typically acknowledges, and the range reflects a culinary tradition that developed the ingredient as a functional component of preparations rather than as a standalone health food.
Tzatziki is the preparation that most completely expresses what strained yogurt does when combined with the ingredients it was developed alongside in the Greek agricultural landscape. The preparation is not a dip that happens to contain yogurt: it is the combination of the yogurt’s acidity and fat, the cucumber’s moisture and freshness, the garlic’s aromatic sharpness, the olive oil’s complementary fat, and the dill or mint’s herbal brightness, each ingredient in a relationship with the others that the Greek kitchen developed across centuries of eating these components together in the same landscape. The salt that the grated cucumber must be allowed to drain under reduces the cucumber’s water content before it enters the yogurt, preventing the dilution that would make the tzatziki thin and watery. The yogurt that receives the drained cucumber is the full-fat strained yogurt, not the reduced-fat version: the fat carries the flavors that the leaner product cannot.
The marinade use is the application that most directly reflects the yogurt’s original functional role in the pastoral kitchen: meat marinated overnight in strained yogurt becomes measurably more tender than the same meat marinated in any other acidic medium, because the lactic acid of the yogurt denatures the surface proteins of the meat more gently than the acetic acid of vinegar or the citric acid of lemon juice, and the fat of the yogurt penetrates the meat surface and carries the aromatics, garlic, oregano, thyme, into the outer layers of the flesh where they flavor the cooked meat from within rather than only from the surface. Chicken pieces, lamb chops, and the pork shoulder preparations of the Greek summer grill all benefit from this overnight yogurt marinade in ways that the leaner, sharper acidic marinades do not produce.
The sauce use of strained yogurt in the Greek kitchen is less internationally visible but equally embedded in the tradition: the cold yogurt sauce that accompanies the fried zucchini of the summer table, the yogurt that the Greek kitchen uses in place of béchamel in certain versions of the pastitsio and the moussaka, and the yogurt that the winter kitchen stirs into bean soups and legume stews to add creaminess and acidity to preparations whose long cooking time has developed deep savory flavors that the yogurt’s brightness clarifies and lifts.
The sweet applications are simpler and more direct: strained yogurt with honey is the preparation that appears on the Greek table at the end of a meal or at the beginning of the day in its most fundamental form, the two ingredients that the beehive and the dairy provided simultaneously in the landscape where both were present, combined in proportions that each person determines for themselves from the jar of honey and the bowl of yogurt on the table. The thyme honey of the Greek mountain, whose aromatic character the wild thyme that the bees worked gives to the honey, is the honey that the Greek tradition pairs with strained yogurt in the combination that centuries of eating the two together have made into one of the most complete simple pleasures that the Greek table provides.
Making Strained Yogurt at Home
The home preparation of strained yogurt requires no specialized equipment and produces a result that the commercial product cannot exactly replicate, because the home preparation can use the milk the cook chooses and can strain to the thickness the application requires.
Heat one liter of full-fat milk, sheep’s milk if available, to 43 degrees Celsius, the temperature at which the lactic acid bacteria are most active without being damaged by excess heat. The temperature can be verified with a cooking thermometer or estimated by touch: the milk should feel hot but not uncomfortable to hold a clean finger in for three seconds.
Remove the milk from the heat and stir in two tablespoons of plain live-culture yogurt as the starter culture. The starter introduces the bacterial populations that will perform the fermentation. The better the quality of the starter yogurt, the better the quality of the fermentation it initiates.
Pour the inoculated milk into a bowl or container, cover it tightly with a plate or lid, and place it in a warm location that maintains a temperature of approximately 40 degrees Celsius for eight to twelve hours. The interior of an oven with only the pilot light running, or an oven that has been briefly heated and then turned off, or a location near a radiator in winter are all appropriate. The fermentation should not be disturbed during this period.
After the fermentation period, the yogurt will have set to a gel: it will jiggle as a unit when the container is moved rather than sloshing as a liquid. Transfer it to a colander or sieve lined with a double layer of muslin or cheesecloth set over a bowl to catch the whey, and refrigerate for a minimum of four hours. Six to eight hours produces a consistency comparable to the commercial strained product. Twelve hours produces a consistency closer to labne, the Arabic strained yogurt that has been drained to a semi-solid state. The whey that drains from the yogurt is protein-rich and mildly acidic: it can be used in bread dough, in the cooking water for legumes, or in smoothies.
The finished strained yogurt will keep refrigerated for five to seven days. It will continue to acidify slightly as it sits, becoming more tart with time, in the way that all live-culture fermented products continue to evolve in the refrigerator.
Tzatziki | The Application That Defines the Ingredient
The recipe that most directly demonstrates what strained yogurt is and what it does is tzatziki, and the quality of a tzatziki is among the most reliable indicators of the quality of the yogurt used to make it, because the yogurt is the majority of the preparation and its flavor is not concealed by the other ingredients but revealed by them.
For four as a meze or an accompaniment:
500g full-fat strained yogurt 1 medium cucumber, grated on the coarse side of a box grater 2 garlic cloves, pressed or very finely grated 3 tablespoons extra virgin olive oil 1 tablespoon white wine vinegar or lemon juice 1 tablespoon fresh dill, finely chopped, or 1 teaspoon dried mint Sea salt, to taste
Place the grated cucumber in a clean cloth and wring firmly to remove as much water as possible. The cucumber should be as dry as you can make it: any remaining moisture will loosen the tzatziki and dilute its flavor as it sits.
Combine the drained cucumber with the yogurt, garlic, olive oil, and vinegar or lemon juice. Season with salt and stir until uniform. Fold in the dill or mint.
Refrigerate for at least one hour before serving. The resting time allows the garlic to soften and the flavors to integrate. A tzatziki served immediately after preparation tastes of its components separately. A tzatziki served after an hour in the refrigerator tastes of itself.
Bring to the table in a wide bowl with a further drizzle of olive oil over the surface. Serve with bread, with grilled meat, or with the fried zucchini and eggplant that the Greek summer table produces in the months when the vegetable garden is at its most abundant.
The tzatziki keeps for two days in the refrigerator, though it will release a little more liquid from the cucumber as it sits. Drain this off and stir before serving.
At Olympus Estate, Food and Seasonal Life traces Greek cuisine as a living calendar. Strained yogurt is older than the word for it, made from the milk of the spring lambing season by pastoral communities who did not know they were practicing microbiology. The thyme honey that accompanies it on the Greek table is made from the same mountain landscape that the sheep grazed. These are not coincidences. They are the accumulation of centuries of people eating what was in front of them and discovering that it was exactly right.
