This cheese is identified with an ancient name indicating milk acidification ‘Oξύγαλα’ (Oxygala or acid milk), or simpler ‘Ξύγαλο’ (Xygalo), whose production method goes back to the Hellenistic and Roman times. It remained an artisanal product for centuries. As an industrial product, it was first marketed at the beginning of the 1990s. Ever since, it has been largely accepted by the broader consumers’ population of Crete (especially in eastern Crete) and Greece (especially in Athens and Thessaloniki). Gastronomy initiatives which certify restaurants offering dishes in-line with the Cretan diet, recommend Xygalo as an excellent “hors d’oeuvre”, by the name “Xygalo Steiako” [8,9,10,11]. In the market of Crete in 2021, one can find at least three brands of xygalo, with the factories of two of them being very near the town of Siteia, one of them, the bigger, in the village of Hamezi. The third one lies in the broader Lasithi area, at Neapolis. Furthermore, numerous (we estimate in a few decades level) artisanal producers exist in the Siteia area, producing for local taverns and restaurants since there is a thriving local hospitality industry, as well as for families living in the area. The overall yield of cheeses produced in the area of Siteia, Lasithi Crete, is approximately 1300 tons per year. Of those, we estimate that Xygalo Siteias comprises roughly 60–100 tons per year; with processing of 150–200 tons of milk per year to supply this demand (Nikolaos Lapidakis MSc, personal communications with local producers and relevant authorities).

Processing of the milk, and production of Xygalo Siteias, must take place within the Siteia region, which is within the former Municipalities of Siteia, Makry Yialos, Itanos, Lefki, and all their municipal districts [3]. This is essentially a peninsula comprising the whole of the eastern end of Crete. It comprises mostly middle-mountain terrain (altitude of 300–1000 m, with small plateau), with less than 20% of lowland (under 300 m) and few upland areas (1000–1500 m). The Siteia region has lower rainfall, stronger winds, and higher temperatures than elsewhere in Crete at the same altitude. The number of hours of sunshine is particularly high, ranging from 2700 h per annum in the north, to over 3000 h in the south (highest in Greece). Sheep and goats are reared in many places, mainly in the middle-mountain areas and to a lesser extent in the lowlands [8,9,12].

Studies in the 1960s [13,14] describe varieties of the Greek Zackel on the island of Crete—the Siteia, the Psiloriti (the name Psiloris also used), and the Sfakia. Mature rams of the Psiloriti and the Sfakia variety are estimated to be about 64–66 cm at the withers, compared to about 57 cm for the Sitia; ewes of the three varieties are about the same height, in the range of 52–55 cm. Owners and animal merchants who are knowledgeable of small ruminants on the Crete island, attribute the divergence in the size of the varieties to qualitative differences in the forage available in the respective areas they used to live, with the poorest grazing being in the eastern part of Crete (Lasithi), where the smallest of the three varieties, the Sitia variety, is found. It was noted that the muzzle of Psiloriti (or Psiloris) rams and ewes is straight; Sitia ewes have a straight profile also, but rams have a convex muzzle. Rams of the three varieties have laterally spiraled horns, and most ewes are polled. The fleece measurements of the Cretan Zackel are shown in Table 1 [15]. Since the 1970s, the Sfakia and Psiloriti (or Psiloris) varieties (or breeds) were not considered as threatened and constituted, with crossbreds, the majority of the 385,000 Cretan Zackel (as estimated in 1977) [15]. The Siteia breed, on the other hand, has been endangered ever since the late 70s. It was estimated, at the time of a relevant survey (January 1975), that crossbreeding, with transferred, from other parts of Crete, Sfakia and Psiloriti rams had reduced the number of the Sitia to less than 1000. There is no reason or information to believe that the decline has abated since then [15], so we better refer to “Siteia crossbreeds” with Psiloriti and Sfakia breeds.

The raw material used to prepare Xygalo Siteias is fresh milk from healthy sheep and goats that are reared in the traditional manner within the Siteia region, entirely suited to the particular climate and flora; they stem from goat breeds indigenous to Greece and local sheep breeds (Siteia breeds, Psiloriti and Sfakia breeds, and mainly cross-breeds thereof). The ‘Siteia sheep’ is a subphylum of the Aegean Islands’ small mountain-breed sheep. It is suited to areas with limited vegetation and rainfall, such as the climate in Siteia, and is not reared for milk alone but also for meat and wool. Over the past 30 years, an increasing number of the Psiloriti and Sfakia breeds have also been reared; since they are also adequately suited to middle–high mountain conditions. These Cretan breeds are also cross-bred by shepherds with Siteia sheep to increase the latter’s milk yield. An overall population of 28,000–30,000 animals is estimated [8]. Studies suggest that the Siteia-breed sheep yields a relatively smaller quantity of milk per animal, i.e., 106–115 kg per annum per ewe on semi-intensive farms, and 72–80 kg on extensive farms, in Siteia; whereas, in comparison, the average yield for the whole of the island of Crete is 110–150 kg and 78–98 kg per annum per ewe, respectively [8]. The goats in the Siteia region (estimated as 18,000–20,000 animals) are breeds indigenous to Greece adapted to inaccessible areas with limited shrub-like vegetation. The sheep and goats in the Siteia area are reared in the traditional manner on extensive or, at most, semi-intensive farms, less on lowlands and more in middle–mountain areas (altitude of 300–1000 m), on grasslands with a multitude of indigenous and aromatic plants that give the milk particularly tasty characteristics. In the past 30 years, many farmers have built housing/milking installations near villages, moving towards semi-intensive farming, combining positive elements of extensive and intensive farming methods [8].

The sheep and goats are reared extensively or, at most, semi-intensively in the traditional manner, in the lowlands and middle–mountain areas not exceeding 1000 m. In October and November (when the newborns are suckled), due to the sparsity of natural vegetation and the animals’ increased feeding needs, olive leaves and dried fodder (e.g., clover, hay, maize) are used at a rate of 30–40% depending on the year. From December to around April (higher milk production, after the newborns have been weaned), they feed on the local wild flora (grasses and bushes, mostly aromatic and indigenous), which is more abundant during winter and spring rainfall (sage, Salvia fruticosa and Salvia pomifera), rock-rose (‘aladania’—Cistus creticus), heather (Erica manipuliflora), Jerusalem sage (Phlomis lanata), spiny broom (Calycotome villosa), oak (Quercus coccifera), and others). Right up to the beginning of March, these are supplemented by branches and leaves leftover from the annual pruning and cleaning-up of olive trees. During the winter period, dried fodder is also supplied in quantities usually not exceeding 30% in total so that the animals’ needs are covered during the days of heavy rainfall, snow and frost. From May onwards and throughout the summer (reduced milk production), most flocks feed on various dried cereals originating in the area’s fields, sown specifically for this purpose by the farmers, and graze on grasslands covered with local flora. Depending on the year, dried fodder from other areas of Crete and Greece (e.g., hay, clover, and maize) may be given by way of supplement, at a rate of 30–40% [8].

2.5. Xygalo Siteias Production-Procedures