Validating the preeminence of biochemical properties of camel over cow and goat milk during the Covid‐19

Abstract In the light of the Covid‐19 pandemic outbreak, and the need‐of‐the‐hour to boost immunity to residents, especially those residing in an arid environment, a comparative study was made on the physical and biochemical properties of dairy milk. This novel study in Kuwait revealed the lesser consumed pseudoruminant camel milk as a better potential source of dietary inclusion and an immune booster over true ruminants—cow's and goat's milk. Analysis using a wide array of instruments determining the physical characteristics in camel's milk (pH, conductivity, specific gravity, moisture, and total solids), biochemical constituents (crude protein (CP), nonprotein (NP), and fat), and inorganic constituents (K‐919; Ca‐907; Zn‐4.2 mg/100 mg) revealed conducive properties that validate immunity to consumers when compared to the regularly used cow's milk (K‐841; Ca‐776; Zn‐2.43 mg/100 mg) and goat's milk (K‐914; Ca‐849; Zn‐2.45 mg/100 mg). Log‐transformed results revealed high vitamin C in camel's milk (0.42 mg/100 g), indicating high antioxidant properties compared to those of goat's milk (0.12 mg/100 g) and cow's milk (0.04 mg/100 g). Statistical tests by analysis of variance (ANOVA) revealed significant differences and the correlation coefficient between the three milk samples validating the multiple reasons to use camel's milk over the cow's and goat's milk. Furthermore, this study recommends the consumption of camel's milk due to its low concentrations of contaminants as well, their status below permissible limits in Kuwait, set by global standards over the other sampled milks.


AL-SAFFAR
Covid-19 pandemic outbreak, although the camel milk experiences have created a novel awareness on their use in the Western world, ever since the Food and Agricultural Organization (FAO) promoted the camel's milk business (Mirzaei, 2012).
Globally, the human's favorite choice of the palate is the milk of cow and goats, and hence, the nutritional and economic wellbeing of humans is tremendous from the contribution of cow and goat milk. These milks have several characteristics that are attributed to innumerable nutritional and health benefits (Alcantara et al., ;El-din, 2012;Legesse et al., 2017;Turkmen, 2017;Zenebe et al., 2014). Comparatively, goat's milk has a higher nutritional value than cow's milk. However, the cow's milk is widely used because of people being habituated to drinking milk, voluminous production, lower market price, and organized global apportionment of milk and its dairy products (Statista, 2019).
Globally, the consumption of camel milk is limited, although studies reveal excellent antioxidant and antimicrobial properties, lactoferrin content resulting in low citrate concentrations, and high level of immunoglobulin G (IgG) (1.64 mg/L) compared to the IgG in cow's (0.67 mg/L) and goat's (0.7 mg/L) milk (Tahereh & Hussain, 2021). Nevertheless, the merits of these milks were shown, the adverse effects on human health and a serious threat to food safety were found to have developed into a worldwide significant issue because of inorganic pollutants such as heavy metals in soil and plants (Muhib et al., 2016). The trophic transfer of metals followed the food chain from plants, soil, water, and anthropogenic sources through milking animals to humans (Ali & Khan, 2019;Boudebbouz et al., 2021;Chirinos-Peinado & Castro-Bedriñana, 2020).
Accumulation of metals in ruminants causes toxic effects not only in cattle, but also in humans consuming meat and milk contaminated with toxic metals (Mason et al., 2014;Mohsin et al., 2019;Pilarczyk et al., 2013). Earlier studies (by Ping et al., 2014;Sarsembayeva et al., 2020;Shahbazi et al., 2016)  Among the prevalent three types of milk, the quality of camel's milk from the local supply was suspected of metals bioaccumulation and exceeding the permissible limits, although immunity properties such as the high levels of vitamin C, high immunoglobulins (IgG), and low citrate levels were observed (Faye et al., 2019;Tahereh & Hussain, 2021). Thus, the present study corroborates the impact from the recent Covid-19 pandemic outbreak and the seldom evidence to the physical, chemical, and environmental variables in these milks in Kuwait.

| Collection of samples
Milk samples of camel, cow, and goat (each, 30 numbers) were collected by direct milking in sterile glass bottles to avoid potential contamination due to metallic containers from a major farm outlet in Kuwait. The samples were transferred from the farm in an icebox to the laboratory within six h and stored at 4°C. Samples (250 g) were weighed and frozen in the freeze dryer (Labconco FreeZone 18) at −50°C and vacuum applied at 133 × 10 −3 mbar for 48 h. After the freeze-drying cycle, the containers were sealed and stored at 5°C and analyzed following the method described by Ibrahim and Khalifa (2015). Freeze-drying augmented in longer shelf-life preservation of the solid over the liquid state of milk (Ibrahim & Khalifa, 2015).

| Physical and chemical analyses
The collected fresh milk samples were analyzed for pH and conductivity using Fisher Scientific Accumet Research AR50 meter and titratable (total) acidity by following the standard method (AOAC, 2000). Acidity is measured in percentage of lactic acid (Equation (1)). Because 1 ml of 0.1 N lactic acid contains 0.009 g of lactic acid, multiplying the volume of 0.1 N NaOH required to neutralize the lactic acid in the sample by 0.009 will yield the amount of lactic acid (grams) in the sample. This is divided by the weight of the milk sample and multiplied by 100 to obtain the percentage of lactic acid (AOAC, 2000). The specific gravity of the samples followed the gravimetric method by weighing the known measure of milk. Moisture content (Equation (2)) was determined from the loss of mass freeze-drying in the Labconco-FreeZone18 Freeze Dryer (Ibrahim & Khalifa, 2015, Valentina et al., 2016. The milk samples were subjected to a prefreezing temperature between −15 and −23°C at 1.65 and 0.67 mbar vacuum set point, respectively, in the freeze dryer. The loss of weight was calculated to determine the moisture content of the sample following the laboratory manual of Labconco-Freezone18 and method described earlier (Valentina et al., 2016). The freeze-dried samples were analyzed for ash content (muffle furnace-Carbolite AAF 1100) by the Association of Official Agricultural Chemists (AOAC) (2000) method. Calorific content (1 g sample) was determined by a bomb calorimeter (Ujor et al., 2014).

| Determination of trace metals
Open digestion method was applied for the preparation of the samples (1 g) with the acid mixture (10 ml) of HNO 3 :H 2 SO 4 (3:1) following the method described by Oreste et al. (2016) and the United States Environmental Protection Agency (USEPA) (2014). The digested sample was cooled and allowed to settle before analysis. The essential metals (K, Ca, Na, Mg) and lesser essential trace metals (Ag, Al, As, Ba, Cd, Cu, Fe, Mn, Mo, Se, V, Zn) were determined using inductively coupled plasma-atomic emission spectrometry (ICP-AES -PerkinElmer Optima 7300 DV) and inductively coupled plasma-mass spec-

| Determination of nitrogen and protein
The nitrogen contents of crude protein (CP), true protein (TP: nitrogen-associated protein minus the nonprotein sources), NP nitrogen (NPN) contents were determined following the standard Kjeldahl methods (DeVries et al., 2017;ISO, 2016;ISO, 2016;Lynch & Barbano, 1999). Minor changes to this method to meet accuracy followed the lyophilized milk samples (1 g) digested in the Kjeldahl digester (Gerhardt-Kjeldatherm) in the presence of Kjeldahl digestion tablet (catalyst) with the oxidizing agent namely, conc. H 2 SO 4 (12 ml) and H 2 O 2 (6 ml) for 1 h at 200°C and another 1 h at 380°C. The digested sample was diluted with distilled water (75 ml). Ammonia was steam distilled from the digested sample. To this, 50% NaOH (50 ml) solution was added using the Kjeldahl distillation unit (Gerhardt-Vapodest 300). The distillate was collected in a conical flask containing 4% boric acid (50 ml) with two drops of methyl red indicator. The ammonia trapped in boric acid was determined by titration with 0.1N HCl with endpoint color change from red to yellow. Trichloroacetic acid (TCA) (15%-40 ml) was added to the 10 ml of the reconstituted samples (5-10 g) in warm water at 40°C. The solution was settled (5 min) and the formed precipitate (true protein) was filtered through Whatman No. 1 filter paper. The total nitrogen content of a weighed aliquot (up to 20 ml) of filtrate (nitrogennonprotein (N-NP)) was determined by the Kjeldahl assay (AOAC, 2012). Quality assurance followed the above determination on all reagents (blanks). The total amount of nitrogen (%N) in the respective milks was calculated using the factors of 6.25, and 14.0067 for CP, TP, and NP (Equations (3-4) )), respectively (AOAC, 2012). The nonprotein nitrogen (%NPN) composed of urea, amino acids, uric acid, creatine, creatinine, and ammonia in the milk samples was calculated following the standard method (AOAC, 2012) as indicated (Equation (5)).

| Calculations
Weight of the sample = Volume of milk × specific gravity. 0.1 N lactic acid contains 0.009 g of lactic acid. c. subtracting the "moles of base" added from the "moles of acid" gives "moles of ammonia" from the protein, the number of "moles of ammonia" is the same as the "moles of nitrogen," Thus, grams nitrogen = moles nitrogen × atomic mass (g N = moles N × 14.0067).

| Statistical analysis
All the data were analyzed in triplicate. The data were treated using descriptive statistics (Dhanalakshmi & Gawdaman, 2013;Ibrahim & Khalifa, 2015). The results of the physical parameters were incorporated in Section 3.1, while they were transformed to logarithmic values to display the wide-ranged differential units and reduce the dispersed numerical data values to visualize or respond to skewness toward large values and show the figure in compactness. Additionally, ANOVA was used to test the significant differences between the variables and the samples (Table 1).
The conductivity of the three milk samples ranged from 4 to 5.8 mS/cm, with the cow milk (4.00 mS/cm) having the lowest conductivity, followed by goat milk (4.10 mS/cm and camel milk (5.80 mS/ cm) having the highest conductivity. The varied types and quantities of electrolytes present in these milk samples may account for the differential conductivity (Henningsson et al., 2005). The variant-specific gravity in the milk samples (Figure 1) reflected the presence of water content derived from feed, body constituents, the type of breed, age, and gender of the animals (Ping et al., 2014;Sabahelkhier et al., 2012).
Milk samples had moisture levels that ranged from 85.78% to 88.28%. The low to high moisture content was reported in the sequence of goat > cow > camel milk among the tested milk samples ( Figure 1). Their percentages ranged from 80% to 90%, which was like the previous findings (Mohsin et al., 2019). The other components in milk are suspended in colloidal suspension in water, which serves as a medium for the solution.
Total solids in milk samples ranged from 11.72 to 14.22%, which included fat and nonfat components (Figure 1). In camel, cow, and goat milk, there was a progression of low to high concentrations. The low total solids' contents are attributable to an increase in water content in the milk caused by thirsty camels consuming too much water. This was consistent with previous research (Sabahelkhier et al., 2012). Acidity ranged from 0.14 to 0.20% (Figure 1). This level corresponded to the previous findings (Yang et al., 2013). Although the statistical test of ANOVA revealed significant differences between the different physical parameters and the three milk samples (

| Biochemical constituents
The amount of CP, TP, NP, fat, vitamin C, calorific value, ash, and trace metals in the milk samples was also measured using various chemical F I G U R E 2 Major heavy metals' concentrations in the three milk samples

F I G U R E 3 Minor trace metals'
concentrations in the three milk samples analyses, as shown in Figure 1. Chemical characteristics of samples varied widely, and they excelled in one or more aspects. The logtransformed value of the CP (25.15 g/100 g to 27.65 g/100 g = 1.40 to 1.44), TP (22.68 g/100 g to 25.5277 g/100 g = 1.355 to 1.40), and NP (2.13 g/100 g to 2.92 g/100 g = 0.33 to 0.47) proved that milk contains more protein than other elements. The fat content (logtransformed value) was found to be low in the goat milk (25.77 g/100 g = 1.411), compared to cow's milk (26.57 g/100 g = 1.42) and camel milk (29.76 g/100 g = 1.47). This is due to a dilution effect caused by an increased goat milk volume until lactation peak, as well as a decrease in lipid mobilization, which reduces plasma nonester fatty acid availability (ISO, 2016;Lopez et al., 2019). Camel's milk showed high vitamin C (9.89 g/100 g), followed by goat's milk (7.98 g/100 g) and cow's milk (2.09 g/100 g), demonstrating their impact of nutrition. The total energy calorific values in camels, cows, and goats were 5.38 × 10 −6 kcal/kg, 5.61 × 10 −6 , and 5.76 × 10 −6 , respectively.
Furthermore, despite residents of a particular country's preference for distinct tastes, this study indicated not only the possibility of replacement of camel's milk over other milk, but also attributed in line with earlier studies (El-Agamy et al., 1992;Shamsia, 2009;Tahereh & Hussain, 2021)

| Inorganic constituents
Metals of importance in the milk samples were analyzed in the ICP-MS (Figures 2-3). The concentrations of Na, K, Ca, and Zn were high in camel, compared to their concentrations in goat and cow ( Figure 2).
This indicated the medicinal properties and transfer of minerals from herbs in camel milk and which were found to be in line with the earlier findings (Chirinos-Peinado & Castro-Bedriñana, 2020;Kaskous, 2016;Rasheed, 2017). However, Mg was found to be high in goat's milk compared to cow and camel milk. This validated the superior nutritional characteristics in goat's milk, as described by Zenebe et al. (2014), Dhanalakshmi and Gawdaman (2013). The increase in lead (Pb) and cadmium (Cd) concentrations has drawn the attention of researchers, since Pb is known to disturb the effects on brain development (Mason et al., 2014;Pilarczyk et al., 2013;Sarsembayeva et al., 2020). Furthermore, the concentrations of Pb and Cd in milk showed serious dietary constituent concern to infants and children.
This agreed with the earlier research of Ali and Khan (2019) and Miclean et al. (2019). However, the Cd concentration in the cow's and goat's milk was below detectable limits, except in the camel milk (0.009 ± 0.0009 mg/100g). Few trace metals that were harmful to human health ( Figure 3)  attributed to the variations met within each milk sample (Table 1-

| CON CLUS ION
The exposition on the analysis of less commonly ingested camel milk found distinct characteristics in terms of immune booster for the health of Kuwait's residents. In view of the recent Covid-19 pandemic outbreak, the unparalleled physical, biochemical properties and chemotherapeutic value of camel's milk inherited from antioxidant nutritionally rich desert plants were found to generate a strong immunity in normal healthy residents as well, and to combat the ailment in patients with respiratory ailments. Furthermore, the comparative analyses validated the supreme qualities of camel milk such as the action of high lactoferrin, calorific value, and antimicrobial properties over the cow's and goat's milk. Additionally, this study recommends regular monitoring and analysis of these milks for safe consumption, since the camel milk is consumed raw, unlike the consumption of other milk by the residents.

Acknowledged the Director and staff of Research Sector Projects
Unit for the analysis of our samples in the ICP-MS GS01/05. This TA B L E 2 Correlation coefficient between physical, biochemical, and inorganic constituents in the three milk samples Bold value represents significant difference at 0.01 p-value research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

CO N FLI C T O F I NTE R E S T
The author declares that she has no conflict of interest.

PATI E NT CO N S E NT
Not applicable.

E TH I C S A PPROVA L
All study methods were carried out in accordance with relevant guidelines and regulations. As this study has not involved in any human and animal subjects, the author declares no applicability of ethical standards. Local guidelines followed as per the Kuwait University direction.

PE R M I SS I O N TO R E PRO D U CE
Following as per the guidelines of publisher acceptance.

DATA AVA I L A B I L I T Y S TAT E M E N T
The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy, ethical, and commercial restrictions made in agreement with the farm owners who generously supplied milk for this study.