Clinical Studies

Camel milk plays an important role in the nutrition of the population of arid zones. The camel produces more milk and for a longer period of time than any other milk-producing animal held under the same harsh conditions. Daily yields of 3–10 kg in a lactation period of 12–18 months are common.

The main difference between cow’s and camel’s milk lies in the different physicochemical characteristics of the individual components. The average casein content and the whey protein content of camel milk vary between 1.9 and 2.3%, and 0.7 and 1.0%, respectively. Camel milk shows pronounced differences in the quantitative distribution of casein and whey proteins compared with bovine milk.

The fat content of camel milk varies between 2.9 and 5.4%. Camel milkfat contains less short-chain fatty acids and the mean melting point of camel milk butter is around 41.5 °C. The lactose content of camel milk ranges from 4.8 to 5.8% and is slightly higher than the lactose content of cow milk.

Traditionally, the most common forms of consumption are either fresh or fermented form. Due to increasing demand, there is growing interest in processing camel milk for the urban market.

This article outlines the chemical characteristics and technologically relevant properties of camel milk.

Milk Products

Camel milk is one of the most valuable food resources for the people living in arid and semiarid zones. Most of the camel milk is consumed as fresh milk. However, surplus milk is fermented naturally at 25–30 °C until it turns sour. A naturally fermented product called ‘susa,’ which has a long shelf life and is pleasant to drink, is produced in Kenya and Somalia. Susa is made by incubation of camel milk in smoked wooden buckets for 1–3 days. Kenyan researchers have shown that the quality of susa could be improved using selected mesophilic starter cultures rather than spontaneous fermentation; the resulting fermented milk has a uniform taste and a longer shelf life. Similar technology is used in Sudan for preparing ‘gariss’. This beverage is sometimes enriched with spices or garlic. Another fermented camel milk product is ‘shubat’ in Kazakhstan, named also ‘khoormog’ in Mongolia. It is of snow-white color and its fat content reaches 8%. It can be preserved for some time without losing its properties. Some researchers have claimed that shubat can be used to cure tuberculosis and some gastric and intestinal diseases. In Turkmenistan, fermented camel milk is diluted in water (80% water, 20% fermented milk) for drinking it as refreshment in summer. It is called ‘chal.’

Milk Products: Fermented Milk

Camel milk is one of the most valuable food resources for the people living in arid and semiarid zones. Most of the camel milk is consumed as fresh milk. One of the oldest ways of consumption of surplus of camel milk is its fermented form. The diversity of fermented camel milk products in the world is extraordinarily rich. Each camel milk producer region had his own varieties of fermented camel milk with their specific taste, texture and flavor. Nowadays each camel country describes their traditional fermented milk by microbiological, physico-chemical, chemical properties. Most known fermented beverages issued from camel milk are shubat in Kazakhstan (Akhmetsadykova et al., 2014), garris in Sudan (Ahmed et al., 2014), suusac in Kenya (Jans et al., 2012), laben (lben) in Arabic countries Algruin and Konuspayeva, 2015), ititu in Ethiopia (Seifu et al., 2012), chal in Iran (Soleymanzadeh et al., 2016) and Turkmenistan, etc.

Some researchers claimed that fermented camel milk as shubat can be used to cure tuberculosis and some gastric and intestinal diseases (Chuvakova et al., 2000).

Antimicrobial and Antiviral Properties of Camel Milk

Camel milk has been reported to have a higher antimicrobial activity compared to bovine milk (Yagil et al., 1994). Antibacterial activity of camel milk is due to the presence of antimicrobial substances such as lysozyme, hydrogen peroxide, lactoferrin, lactoperoxidase, and immunoglobulins. These antimicrobial agents were reported to completely lose their activity in camel milk if heated at 100°C for 30 min (El-Agamy, 2000a).

Camel milk was reported to have an antimicrobial effect against gram-positive and gram-negative bacteria, including E. coli, Listeria monocytogenes, S. aureus, and Salmonella typhimurium (Benkerroum et al., 2004; El-Agamy et al., 1992). The inhibitory action of camel milk against L. monocytogenes, S. aureus, and E. coli might be attributed to the presence of lactoperoxidase, hydrogen peroxide, and lysozyme, respectively (Benkerroum et al., 2004). The growth of S. typhimurium was inhibited by lactoferrin in camel milk through binding iron and making it unavailable for its growth (El-Agamy et al., 1992; Ochoa and Cleary, 2009).

The stronger antirotavirus activity was reported in camel milk and colostrum (El-Agamy et al., 1992; El-Agamy, 2000b). This indicates that raw camel milk is considered a strong viral inhibitor to human rotavirus. The ability of camel milk proteins to inhibit and/or block the hepatitis C virus entry and replication inside the cell system has been explored (El-Fakharany et al., 2008; Redwan and Tabill, 2007).

Abstract

Camel milk is known for its medicinal properties, which have been widely exploited for human health since ancient times. Many studies have reported that camel milk has potential therapeutic properties such as antidiabetic, wound healing in diabetic patients, hepatitis C infection curing, treatment of autism, hypoallergenic effect, and antihypertensive. It has also been proven as a good alternative for people with cow milk allergy and as a therapeutic agent to reduce the harmful effects of exposure to toxins. Most of these properties are attributed to the unique characteristics of camel milk proteins, especially whey protein. Therefore in this chapter, the health-promoting activities of camel milk and their protein hydrolysates as well as their potential as an alternative for people with cow milk allergy was discussed.

Camel and Dromedary Milk and Dairy Product

Camel milk has an important role in human nutrition, especially in hot regions and arid countries such as Saudi Arabia where it is used fresh or fermented. Also, in countries such as India, Russia, and the Sudan, camel milk is recognized as a treatment for a series of diseases such as dropsy, jaundice, tuberculosis, asthma, and leishmaniasis or kala-azar. Camel milk contains all the essential nutrients found in cow milk (Al haj and Al Kanhal, 2010) and recently was also reported to exert therapeutic properties such as anticarcinogenic (Magjeed, 2005), antidiabetic (Agrawal et al., 2007), and antihypertensive (Quan et al., 2008). It is also useful in infant nutrition as an alternative to cow milk in case of allergy (El-Agamy et al., 2009) (Al haj and Al Kanhal, 2010). Although some authors indicate that camel milk is only suitable for drinking (Yagil et al., 1984), different dairy products have been produced from dromedary/camel milk including soft cheese, fermented milk, yogurt, ice cream, and butter (Al haj and Al Kanhal, 2010). Another interesting characteristic of this milk emerged when Abushelaibi et al. (2017) isolated and identified 9 LAB from camel milk with potential probiotic characteristics. Among these, L. lactis KX881782 was found to be the most promising probiotic. In light of these findings Ayyash et al. (2018) investigated the anticancer, antihypertensive, antidiabetic, and antioxidant in vitro activities of camel milk fermented with extracted autochthonous probiotics, then compared these with cow milk fermented with the same probiotics. Interestingly, the health-promoting benefits, particularly the antioxidant, ACE-inhibition, and antiproliferative activities, in fermented camel milk were markedly higher than those in fermented cow milk. The greater proteolysis observed in camel milk than in bovine milk fermented by Lc.K782 may be attributed to the major susceptibility of camel milk caseins to proteolytic enzymes yielded by the probiotic strain; this could be associated with the higher accumulation of bioactive peptides. Indeed, proteolytic activity promotes the formation of small peptides that could confer health-promoting benefits to the fermented product. Further strains isolated from spontaneous fermented dromedary milk, Enterococcus faecium and Streptococcus macedonicus, were tested in fermented dromedary milk. The sensory features of the dairy product from dromedary milk scored lower overall acceptability than the same product made using cow milk, with the most penalizing scores associated with taste and consistency (El Hatmi et al., 2018).

Akawi cheese is a well-known Middle Eastern cheese that is extensively consumed in North Africa, the Middle East, and states in the Gulf Cooperation Council (Ayyash et al., 2012). Among LAB isolated and identified from camel milk, L. plantarum KX881772 and L. plantarum KX881779 were found to have probiotic characteristics and EPS (exopolysaccharide) production capabilities. They were used by Al-Dhaheri et al. (2017) to produce probiotic low-fat akawi cheese made from cow milk.

Maurad and Meriem (2008), tested the probiotic potential different strains of L. plantarum isolated from traditional butter made from camel milk. Four strains (L. plantarum SH5, SH12, SH24, and SH32) were sufficiently resistant to pH 2.0 for 2–6 h incubation periods, indicating they are able to survive to the gastric phase of digestion. In particular, the L. plantarum SH12 and SH24 strains showed rapid acidification activity, good proteolytic activity, and a high survival percentage after freeze drying. Furthermore, when the same probiotic strains were used as starter cultures in the production of novel probiotic dairy products from camel milk (such as fermented milk, butter, or cheese), the consumer panel highlighted the favorable flavor and sensory qualities.

The role of lactose is essential in the definition of textural properties of ice cream due to the involvement of disaccharide in lowering the freezing point and enhancing the sandiness of the ice cream mixture. Indeed, beyond flavor, the consumer acceptance of ice cream depends largely on the perceived textural quality. Accordingly, in frozen yogurt, a portion of lactose ferments to lactic acid, which can alter its physical properties. Al-Saleh et al. (2011) compared the physicochemical properties of probiotic frozen yogurt made from camel and cow milks enhanced with L. delbrueckii ssp. bulgaricus and S. thermophilus bacteria. They concluded that camel milk is suitable for the production of probiotic frozen yogurt.

9.3 Future perceptions

Camel milk protein–derived peptides have shown a range of bioactive properties both in vitro and in vivo conditions. However, extent of in vivo studies is still limited before any substantial claims into health-promoting effects of these peptides can be made. Overall, it was noticed that selection of enzyme and hydrolysis conditions have a significant effect in controlling the biological functionality of these peptides. Moreover, further studies using clinical interventions are needed to validate the findings of in vitro studies and provide evidence toward the pharmacological and therapeutical values of camel milk–derived peptides. Further studies using synthetic peptides are also warranted to understand their safety, mechanism, and exact biological actions. Moreover, studies such as antiinflammatory, anticancerous, and hepatoprotective effects are scarce and require further explorations. Although some evaluation of antiinflammatory, renin inhibitory properties of peptides identified has been done using in silico tools, direct evidence using pure peptides or using molecular docking tools are still lacking. Therefore this should be considered as the next approach and further investigations through in vivo and cell line model should be undertaken. Also, enzymatic hydrolysate remains the dominant method for peptide generation while use of fermentation as a tool for producing cost-effective peptides remains underexplored, therefore more studies should be conducted in this direction.

Furthermore, most of the studies from camel milk revolve around the use of dromedary camel milk with limited reports from Bactrian camel milk that could also be proven to be an important source of bioactive peptides.

Camels

Camel milk composition and characteristics in different production systems have been reported and components of camel milk are considerably different from those of other ruminants (Elamin and Wilox, 1992; Schwartz, 1992; Dell’Orto et al., 2001). The composition of camel milk generally varies with a range of 3.5%–4.5% protein, 3.4%–5.6% lactose, 3.07%–5.50% fat, 0.7%–0.95% ash, and 12.1%–15% total solids (Gnan and Sheriha, 1986).

Camels are well known for maintaining milk production during drought conditions. They produce more milk for longer periods during drought than any other domestic animal adapted to arid habitats, and this is of great importance to pastoralists as camel milk may contribute up to 50% of their food (Chabeda, 2002). Field (2005) estimated that the volume of milk produced by camels is six times that produced by indigenous cattle found in the dry lands. In recent years, some pastoral communities that did not previously keep camels have started rearing some to supplement their cattle production, especially during the dry seasons (Kagunyu and Wanjohi, 2014). Reducing trends on camel milk production during heat stress conditions, however, have been observed. Severe water deprivation during heat stress was found to reduce the milk yield in camels, and the reduction was generally proportional to the severity of dehydration (Al Jassim and Sejian, 2015).

Shuiep et al. (2008) reported negative impact of summer heat stress on milk composition in camels with high water content in summer samples negatively affecting camel milk components compared to winter samples. The water content of camel milk may fluctuate from 84% to 90%. When animals have free access to water the content of water in milk is 86%, but when water is restricted the water content of milk increases to 91%. Thus, it would appear that the lactating camel loses water to the milk in times of drought. This could be a natural adaptation to provide not only nutrients but necessary fluid to the dehydrated calf (Yagil and Etzion, 1980). Adaptation to warm environment also causes secretion of a profuse watery sweat caused by secretion of endogenous antidiuretic hormone that allows the loss of water into the milk. Water availability and water content of fodder also affect fat content of camel milk. When water milk content increases in thirsty camels, fat content decreases, from 4.3% to 1.1% (Bernabucci et al., 2013). Musaad et al. (2013) also reported seasonal variation for milk components in camels. Maximum level of fat was observed in January (3.46%) and minimum at summer time (2.29% in July). Protein content was maximum in February (3.32%) and minimum in October (2.76%). For lactose, the maximum mean value was 4.38% in February and the minimum in September (3.83%).

4.2.4 Alkaline phosphatase activity in nonbovine milk

Camel milk contains low basal levels of ALP with higher heat stability. Average ALP activities in raw camel milk varies between 15.9 and 24.93 U/L, while 5.8 and 10.2 U/L in pasteurized camel milk (Yadav et al., 2015; Yoganandi et al., 2014). ALP test is not suitable for verifying effectiveness of pasteurization of camel milk (Clawin-Rädecker et al., 2021; Merin et al., 2005; Wernery et al., 2008, 2006).

The concentration of ALP in goat milk is about five to ten times lower than bovine milk (Banks & Muir, 2004; Clawin-Rädecker et al., 2021; Mathur, 1975) and is affected by various factors such as breeds, season, stage of lactation, fat content, and udder health. The significant relationship is observed between the concentration of the ALP in the goat milk and the somatic cell count (Banks & Muir, 2004). Heat stability of goat milk ALP when studied in the temperature range of 54°C–69°C is lower in comparison to bovine milk (Wilińska et al., 2007). There is significant reduction in the ALP activity in goat milk upon heat treatment at both 63°C and 95°C (Banks & Muir, 2004). Based on the available evidence from milk samples after pasteurization, there is 95%–99% probability (extremely likely) that pasteurized goat milk and pasteurized sheep milk would have an ALP activity below a limit of 300 and 500 mU/L, respectively (Clawin-Rädecker et al., 2021).

Human milk has 40 times lower ALP activity as compared to bovine milk (Heyndrickx, 1962). ALP activity, like the activity of most other enzymes, is greater in human colostrum than in ordinary milk (Heyndrickx, 1962; Sharma & Ganguli, 1971).