Milk is considered one of the most abundant foodstuffs in our foods, due to its nutritional value, and milk as a liquid is easy to digest, which makes it the ideal and closest to perfection food, so it is called a complete lunch. It is for adults only, but a basic food for newborn babies, and milk consists mainly of vitamins, including (thiamin, riboflavin, pantothenic acid (and vitamins A, D, K,). Milk is known chemically as a complex slime system, containing key elements that play an important role in growth The human body and its health in general, such as proteins, fats, lactose, salts, mineral elements, and vitamins [1]. Milk and its products are the most diverse of natural foodstuffs in terms of composition, as they contain some necessary and important rare mineral elements such as copper, zinc, magnesium, and iron, and these minerals They are common factors in many physiological functions and the absence of these minerals causes disturbances and pathological conditions, and the solid components of milk are spread in a dissolved or suspended form, and the percentage of water in milk ranges between 80-90, and it is the middle of the spread of its many components, which are known as total solids and fats (fats), and non-fat solids include proteins, nitrogenous compounds, carbohydrates (lactose), minerals, and enzymes. The contents of milk and the proportions of its components differ from one type to another. Condensed milk is produced by evaporating water from natural milk or modified milk. By the end, it means milk in which one of its components has been removed and replaced with another, such as removing fat from milk to produce skim milk, or adding vegetable fat instead of animal fat, or adding a new substance such as sweeteners. There are two types of condensed milk, sweetened condensed milk and unsweetened condensed milk. Previously, 17 types of condensed milk sold in the local markets in the city of Benghazi were studied, where the German content of ash, fat, protein, lactose, non-fat solids, acidity and pH were estimated, and the results of the obtained analysis were compared with the numbers recorded by the factory, and it was found It is close to it as it was found close to the Libyan and international specifications [2].    

The study aimed to study the chemical composition of several types of milk and compare them with infant formula and a study of the mineral elements in the types of milk and comparing them with those in infant formula.

Determination of the Heavy Metal Content of Milk

The milk content of heavy elements was estimated using the American-made Atomic absorption Salam Spectrophotometer at Tikrit University / College of Engineering / Department of Chemical Engineering and according to the method used by:

• Take 100 ml of different milk samples and place them in the drying oven

• Dry the samples at a temperature of less than 72°C

• Weight of 3 grams of powdered milk in ceramic lids

• Putting concentrated nitric acid at a concentration of (5%) on the samples

• Placing the samples in the incineration oven at different temperatures until reaching 550 C for a period of 4 hours

• When the samples reach the ash stage (gray to white color)

• Washing the samples with nitric acid, filtering the suspension with filter paper, and completing the volume of the filtrate to 25 milliliters in a beaker

• Placing samples in an Atomic absorption Salam Spectrophotometer and taking readings

Determination of Moisture

The moisture percentage in milk samples was estimated by heating the sample at a temperature of 105 degrees until the weight stabilized according to what was stated in (A.0.A.C, 2004). It is a method in which a sample of a substance is weighed, then heated in an oven at a certain temperature for a specified period until a constant weight is obtained. The weight loss is then calculated and used to determine the moisture content The moisture percentage was calculated according to the following equation:

Moisture percentage = (Wet weight - Dry weight) / Dry weight x 100

Determination of Oil

The percentage of fat in milk samples was estimated according to using the Soxhlet device.

Oil percentage = (Weight of extracted oil / Weight of the sample) x 100

Determination of Protein Content

The percentage of protein in milk samples was estimated according to what was stated in A.O.A.C using the microcalcification device. The percentage of protein was calculated by multiplying the percentage of nitrogen by the protein coefficient of 4.7, which represents the protein digestion coefficient.

Determination of as

The percentage of ash in the milk samples was estimated using the incineration oven, where the weighed sample is transferred to the oven and heated to a specific temperature, usually ranging from 500 to 600 degrees Celsius. The sample is burned in the oven for a specific period of time, usually ranging from one to five hours, to allow complete combustion of the organic materials until white ash is obtained according to what was stated in. The percentage of ash was estimated as follows:

Ash percentage (%) = (weight of residual ash ÷ original sample weight) x 100

Determination of the Percentage of Carbohydrates

The percentage of carbohydrates was extracted according to the equation as mentioned in.

Determine the other components in the sample apart from carbohydrates. Typically, this includes fats, proteins, ash, and water.

After determining the content of the other ingredients, the percentage of carbohydrates can be calculated simply using the following equation:

Carbohydrates percentage (%) = 100 - (proteins percentage + fat percentage + ash percentage + water percentage)

The percentages in the mentioned equation must be in the form of a percentage or a fractional percentage in order to get the percentage of carbohydrates.

Determination of the Heavy Metal Content of Milk

The milk content of heavy elements was estimated using the American-made Atomic absorption Salam Spectrophotometer at Tikrit University / College of Engineering / Department of Chemical Engineering and according to the method used by:

• Take 100 ml of different milk samples and place them in the drying oven

• Dry the samples at a temperature of less than 72°C

• Weight of 3 grams of powdered milk in ceramic lids

• Putting concentrated nitric acid at a concentration of (5%) on the samples

• Placing the samples in the incineration oven at different temperatures until reaching 550 C for a period of 4 hours

• When the samples reach the ash stage (gray to white color)

• Washing the samples with nitric acid, filtering the suspension with filter paper, and completing the volume of the filtrate to 25 milliliters in a beaker

• Placing samples in an Atomic absorption Salam Spectrophotometer and taking readings

Determination of Moisture

The moisture percentage in milk samples was estimated by heating the sample at a temperature of 105 degrees until the weight stabilized according to what was stated in (A.0.A.C, 2004). It is a method in which a sample of a substance is weighed, then heated in an oven at a certain temperature for a specified period until a constant weight is obtained. The weight loss is then calculated and used to determine the moisture content The moisture percentage was calculated according to the following equation:

• Moisture percentage = (Wet weight - Dry weight) / Dry weight x 100

Determination of Oil

The percentage of fat in milk samples was estimated according to using the Soxhlet device.

Oil percentage = (Weight of extracted oil / Weight of the sample) x 100

Determination of Protein Content

The percentage of protein in milk samples was estimated according to what was stated in A.O.A.C using the microcalcification device. The percentage of protein was calculated by multiplying the percentage of nitrogen by the protein coefficient of 4.7, which represents the protein digestion coefficient.

Determination of As

The percentage of ash in the milk samples was estimated using the incineration oven, where the weighed sample is transferred to the oven and heated to a specific temperature, usually ranging from 500 to 600 degrees Celsius. The sample is burned in the oven for a specific period of time, usually ranging from one to five hours, to allow complete combustion of the organic materials until white ash is obtained according to what was stated in. The percentage of ash was estimated as follows:

• Ash percentage (%) = (weight of residual ash ÷ original sample weight) x 100

Determination of the Percentage of Carbohydrates

The percentage of carbohydrates was extracted according to the equation as mentioned in.

Determine the other components in the sample apart from carbohydrates. Typically, this includes fats, proteins, ash, and water.

After determining the content of the other ingredients, the percentage of carbohydrates can be calculated simply using the following equation:

Carbohydrates percentage (%) = 100 - (proteins percentage + fat percentage + ash percentage + water percentage)

The percentages in the mentioned equation must be in the form of a percentage or a fractional percentage in order to get the percentage of carbohydrates.

Determination of Acidity

The acidity percentage was estimated according to:

• 17.6 ml of milk sample is taken with a pipette and placed in a clean and dry glass beaker

• Add - drops of phenophthalene index to the milk in the beaker and mix well

• Sodium hydroxide solution 1.1 N, which is present in the burette, is added to the beaker gradually with stirring until it obtains a light pink color, and this is an indication of the neutralization of the added base of the acid present in the milk sample

• Calculate the amount of base added

Calculate the amount of acidity (the percentage of acidity estimated as lactic acid) using the following equation in

Acidity percentage = ((number of milliliters of sodium hydroxide x 0.009) ÷ weight of the milk sample) x 100

Concentrations of Heavy Metals in Milk Samples

Table 1 shows the mineral elements in the milk samples that were examined. The results indicate that the cadmium element had the lowest percentage in infant formula 0.016, the highest percentage in buffalo milk 0.241, and the closest percentage to infant formula in sheep milk 0.021. The results of the nickel element were the lowest in buffalo milk 0.12, and the highest percentage was recorded in sheep’s milk 0.127, and the percentage was in infant formula 0.38, and the closest to it was in cow’s milk 0.41. The results of the zinc element recorded the lowest value in infant formula 0.015, and the highest value was recorded in goat's milk, which was 0.237, and the closest to infant's milk was found in sheep's milk 0.049.

The results of the cobalt element were similar, as the lowest value was recorded in sheep’s milk 0.046 and the highest value was recorded in cow’s milk 0.132, and the closest ratios were for infant’s milk 0.095 in goat’s milk 0.064. Cadmium in infant formula in Britain amounted to 0.020, and it was close to the percentage of cadmium in the results, except for buffalo and goat milk, which was high, and the reason is due to the food ingested by the animal. Mentioned that the percentage of zinc in Polish infant formula0.164), which is relatively higher than the results found

Table 1: Concentrations of Heavy Metals in Milk Samples

The Chemical Composition of Milk

• Moisture Content: It is the largest content in milk, ranging between 80% and 90% of the components of fresh milk. It shows the moisture content in the studied milk samples, which ranged between (80-8.89), which was within the required limit

• Protein: Milk contains 5.0% of its weight nitrogen, most of it in the form of proteins, and the rest in the form of non-protein nitrogenous materials. The results in Table 2 show that the amount of protein in sheep’s milk 5.9 is higher than the other amounts of protein, and it was the lowest value for protein in infant formula 3.06. The protein concentration in cow’s milk agreed with what was found (Imran et al., 2008). As for sheep's milk, the ratio was consistent with what was found [3] and goat's milk, it was consistent with what was stated by [4]

Table 2: The Chemical Composition of Milk

• Fat: Fat-rich milk is considered to have more nutritional value than low-fat milk, and the Food and Drug Administration (FDA) recommended that the percentage of fat in whole milk should not be less than 3.25% [5]. The results are shown in Table 2-3. The amount of fat in sheep's milk is higher than the amounts of fat in other milk samples, and the percentage of fat in infant formula was less than the required limit 3.25, and the percentage of fat in cow's milk was consistent with what was found [6] and in sheep's milk it was consistent with what Mentioned by [7] and in goat's milk, it is consistent with what was stated by

• Ash: We note in Table 2 the ash content of infant formula, cows, sheep, goats and buffaloes. The study revealed that the highest percentage of ash was in infant formula compared to the rest of the samples, while the lowest was in cow's milk. The concentration of ash in cow's and goat's milk corresponds to what It was brought by [8] and in sheep's milk, in agreement with the study of [9]

• Carbohydrates: We notice in Table 2 that the percentage of carbohydrates was high 13.46, which is the highest among milk percentages, and the lowest percentage was in goat’s milk, whose percentage was 2.51

Properties, Physio-Chemical of Milk

Ph: The results in Table 3 refer to the pH values, which were between (6.65-6.38), which was the highest value in cow's milk and the lowest in infant formula. The results were consistent with what was mentioned [10].

Table 3: Physio-chemical Composition of Milk

Aidity

The acidity of milk expresses the activity of bacteria in the milk and how fresh it is, and it is an indicator of quality. Milk of high quality must have an acidity of less than 0.14%, and the acidity of milk affects the taste of milk. When the acidity ratio exceeds 0.3%, the taste of milk becomes unacceptable, while when it exceeds The ratio is 0.4%, the milk becomes acidic, and when it exceeds 0.6%, the milk precipitates at the normal temperature. The results in Table 3 indicate that the highest value of acidity was recorded in sheep’s milk 0.22 and the lowest value was recorded in sheep’s milk 0.22. Goat 0.14 as the acidity value in cow's milk is consistent with what was mentioned by Wendorff and Haenlein (and in sheep's milk it is consistent with what was mentioned by and in goat's milk it was consistent with what was indicated by [11].

Specific Weight (Density) 

Milk contains substances that increase the specific weight, and therefore the specific weight of milk is greater than the specific weight of water, just as the fat reduces the specific weight, so the higher the amount of fat in milk, the more this leads to a decrease in the specific weight, while the effect of non-fat solids is the opposite. The specific weight of fresh cow's milk ranged between 1.029 - 1.035 [8]. Table 3 shows the specific weight of milk samples, and the density of sheep milk samples was greater than all other results. These results are consistent with what was mentioned by [12]. (As for cow's milk, and in sheep's milk, it agrees with what he mentioned) Haenlein [13].

1. Meurant, G. Handbook of Milk Composition. Academic Press, 1995.

2. Faiza, N. et al. “Comparison of the nutritive values of different types of evaporated milk available in local markets of Benghazi City, Libya.” Scholars Journal of Applied Medical Sciences (SJAMS), vol. 5, no. 6B, 2017, pp. 2188–2197.

3. Park, Y. W. et al. “Physico-chemical characteristics of goat and sheep milk.” Small Ruminant Research, vol. 68, 2007, pp. 88–113.

4. Maher, J. “Nano-bio-technology and bioavailability.” BioPharma Science, 2007, www.biopharmasci.com.

5. Bangladesh Standards and Testing Institution. Specification for Pasteurized Milk. BSTI, 2002, pp. 2–3.

6. Kanwal, R., T. Ahmed and B. Mirza. “Comparative analysis of the quality of milk collected from buffalo, cow, goat and sheep of the Rawalpindi–Islamabad region of Pakistan.” Asian Journal of Plant Sciences, vol. 3, 2004, pp. 300–503.

7. Pavic, V. et al. “Influence of stage of lactation on the chemical composition and physical properties of sheep milk.” Czech Journal of Animal Science, vol. 47, 2002, pp. 80–148.

8. Imran, M. et al. “Physicochemical characteristics of various milk samples available in Pakistan.” Small Ruminant Research, vol. 68, 2008, pp. 88–113.

9. Bylund, G. Dairy Processing Handbook. Tetra Pak Processing Systems AB, 1995, pp. 436.

10. Enb, A. et al. “Chemical composition and nutritional quality of milk.” Global Veterinaria, vol. 3, no. 3, 2009, pp. 268–275.

11. Sawaya, W. N. et al. “Chemical composition and nutritional quality of camel milk.” Journal of Food Science, vol. 49, 1984, pp. 744–747.

12. Jenness, R. et al. “Milk chemistry.” Fundamentals of Dairy Chemistry, edited by B. H. Webb, A. H. Johnson and J. A. Alford, AVI Publishing, 1974, pp. 402.

13. Haenlein, G. F. W. and W. L. Wendorff. “Sheep milk production and utilization.” Handbook of Milk of Non-Bovine Mammals, edited by Y. W. Park and G. F. W. Haenlein, Blackwell Publishing, 2006, pp. 137–491.