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][4].
2.5. Xygalo Siteias Production-Procedures
Xygalo Siteias is produced from goat milk or sheep milk, or a mixture of both
[8][4]. Concerning the mixing of goat and sheep milk, in regions where small ruminants are important to the economy, the development of products that include different proportions of sheep and goats milk attracts more consumers and additionally improves the nutritional value of the product, mainly with respect to the variety of fatty acid and mineral contents
[16][12]. Goat milk has a white-matte colour, does not contain β-carotene and has a sweet and pleasant distinctive “freshly milked taste”; however, it can sometimes, at the end of lactation or after a period of storage in a cold environment, acquire a certain flavor one can describe as “animalic”; called “katsikila” in the Cretan idiom. The goat milk has a density ranging between 1.026 and 1.042, with a pH ranging from 6.3 to 6.7; the distinct flavor of goat milk is possibly due to the release of short-chain fatty acids during the handling of milk. Sheep milk exhibits a more marked white opacity and has a characteristic “sheepy” smell
[16][12]. This feature is relatively less-evident in milk that is stored in a good hygienic condition, i.e., put in refrigerated tanks after suction
[16][12]. The milk processed to produce Xygalo should be the product of milking at least ten days after the animal has given birth; either the farmer transports the milk to the cheese production-plant or it is refrigerated in milk chillers and collected frequently (usually under the cheese-plant responsibility), in a suitable vehicle or a refrigerated tank
[8][4].
The cheese Xygalo Siteias is a product of milk acidification. The milk mixture is pasteurized (optionally) and then cooled to 25 °C. Salt (NaCl) is added to a maximum of 2% weight by weight (
w/
w), as are common (mainly traditional yogurt) acidic bacterial cultures, and small amounts of natural rennet from animals’ stomachs (mainly if the milk has been pasteurized)
[3,8][3][4]. Different cheese varieties need different salt contents, from 0.4% for Emmental cheese, up to 4%, or even 5% for blue cheeses. It is considered that through its influence on the growth of curd microorganisms, and the activity of enzymes such as rennet and microbial enzymes, salt modulates cheese ripening. Starter bacteria are more sensitive to salt than non-starter lactic-acid bacteria (NSLAB). Most Lactococci are inhibited from 4% salt-in-moisture, while
Streptococcus thermophilus is inhibited at 2.3%
[17][13]. Overall, salt slows-down proteolysis; while in moisture-concentrations of 2–6%, salt increases the swelling and the solubility of casein, thus promoting the fusion of the cheese curd, especially for cheeses with a low pH. Salt also prevents an unwelcome extensive separation of serum during the ripening process
[17][13].
The production of Xygalo in the “traditional” way does not include the use of lactic acid culture, which is usually similar to that of yogurt (
Streptococcus thermophilus—Lactobacillus bulgaricus), as well as the use of rennet (preparations of the milk-clotting enzyme chymosin or renin), but is based on the gradual coagulation of milk due to the native milk-flora (lactic-acid bacteria), which lasts a little longer than the industrial method. The process duration depends to a large extent on the ambient temperature, and for this reason, this method is usually carried out in the summer months. Initially, Xygalo was produced only during the summer, when goat and sheep milk was scarcer, and there was not enough milk to make hard cheeses, while the temperatures favored the natural acidification of the curd. Housewives, or traditional cheesemakers, used special clay pots (called “kouroupi” in the Cretan idiom), which when gently put upside down, helped to remove the serum without breaking the cheese gel. In addition, according to this “traditional” method, the raw milk is not pasteurized so that there is a sufficient amount of lactic-acid culture, which will cause its gradual coagulation (Lapidakis N., personal communications with local artisanal-Xygalo producers).
The industrial production process of Xygalo PDO Sitia (permitted by the PDO regulation) is: the milk is pasteurized (71.8 °C for 18 sec or at 65 °C for 30 min, or with any other combination of temperatures/time that will bring the desired result). It is then cooled to 30–35 °C, where the lactic-acid culture, based on local traditional-yogurt, is added. The amount of culture is 2–5% per 100 kg of milk. After 15–20 min, a minimum amount of liquid rennet (3–4 g per ton) is added, and at the end, the product is transferred to containers not tightly closed for a month at temperatures of 18–20 °C where it matures (Lapidakis N., personal communications with Xygalo producers). Authentic Greek yogurt with “tsipa” (the solid top-layer of semi-solid yogurt, in the Cretan idiom), a dairy product where the active bacteria
S. thermophilus and
L. bulgaricus are predominant, is usually also produced from sheep and goat milk, by exactly the same factories that produce Xygalo Siteias. Yoghurt may be considered a cheap source of starter cultures that contains adequate types of microorganism of which most are thermophilic and can be utilized in the production of cheese. The yogurt culture/starter can be used at concentrations of 0.5–2.5%. Increasing the culture concentration is considered to be associated with the development of higher acidity, creating unfavorable conditions for the microbes and enzymes to work efficiently and releasing more whey
[18][14].
Following the above, the product is left to ferment naturally in metal or appropriate plastic food-grade containers that are kept stationary and covered, but not hermetically sealed, for seven to ten days at a temperature of 15–20 °C. The excess fat and butter are removed from the surface of the curd. Ripening continues in these containers for approximately one month at a temperature of 10–15 °C, with no stirring of the curds for the entire duration of the acidification-ripening process. Finally, the product is separated from the whey that is concentrated at the bottom of the containers; it is placed in food-grade casks and is refrigerated/kept at a temperature of under 4 °C.