Milk is one of the oldest natural beverages, often referred to as "white blood," highlighting its vital importance to human health. As the name suggests, milk is obtained by milking female cows. Different countries classify milk into various grades. The most common types available today are whole milk, low-fat milk, and skim milk. Many milk products on the market also contain added ingredients, such as high-calcium low-fat milk, which has calcium fortified.
Milk boasts high nutritional value and is rich in diverse minerals. Beyond the well-known calcium, it contains significant amounts of phosphorus, iron, zinc, copper, manganese, and molybdenum.Most notably, milk is the optimal source of calcium for the human body, with an ideal calcium-to-phosphorus ratio that enhances calcium absorption. Its composition is complex, containing at least 100 components, primarily water, fat, phospholipids, protein, lactose, and inorganic salts.
The typical chemical composition of milk is as follows:
Water: 87.5%
Fat: 3.5–4.2%
Protein: 2.8–3.4%
Lactose: 4.6–4.8%
Inorganic salts: Approximately 0.7%
For middle-aged and elderly individuals, milk offers another significant advantage: compared to many animal proteins with higher cholesterol levels, milk contains relatively low cholesterol (milk: 13 mg/100g; lean meat: 77 mg/100g). Notably, certain components in milk can inhibit the liver's production of cholesterol, giving milk a cholesterol-lowering effect.
The chemical composition of cow's milk varies depending on the breed of cow, age, feeding methods, time of milking, living and health conditions, temperature, and other factors.Per 100g of milk: Water: approx. 87g Protein: 3.1g Fat: 3.5g Carbohydrates: 6g Ash: 0.7g Calcium: 120mg Phosphorus: 90mg Iron: 0.1mg Thiamine: 0.04mg Riboflavin: 0.13mg Niacin: 0.2mg Ascorbic acid: 1mg Vitamin A: 140IUThe proteins in milk are primarily phosphoproteins, along with albumin and globulin. All three types contain all essential amino acids. Milk fat consists mainly of glycerides of palmitic and stearic acids, with small amounts of lower fatty acids such as butyric, caproic, and caprylic acids. Additionally, it contains trace amounts of lecithin, cholesterol, pigments, and other substances.Milk contains cations such as Ca²⁺, Mg²⁺, K⁺, and Fe³⁺, along with anions like PO₄³⁻, SO₄²⁻, and Cl⁻. It also contains trace elements including I, Cu, Zn, and Mn. Calcium in nature exists in compound forms; only after being absorbed by plants and animals to form biologically active calcium can it be better absorbed and utilized by the human body. Milk is rich in active calcium, making it one of the best calcium sources for humans.One liter of fresh milk contains approximately 1,250 milligrams of bioavailable calcium, ranking highest among foods—roughly 101 times that of rice, 75 times that of lean beef, and 110 times that of lean pork. Not only is its content high, but the lactose in milk promotes calcium absorption through the intestinal wall, achieving an absorption rate as high as 98%. This regulates calcium metabolism within the body, maintains serum calcium levels, and enhances bone mineralization.Effective absorption is particularly crucial for calcium supplementation. Therefore, the claim that "milk supplements calcium" is scientifically sound.
"Homogenization" refers to a new processing technique where milk fat globules are broken down, allowing fats to fully dissolve into proteins. This prevents fat clumping and coagulation, making it easier for the body to absorb.Their shelf life is typically within 48 hours. Their nutritional value differs little from fresh milk, with only about 10% loss of B vitamins, though some bioactive substances may become inactive. Room-temperature milk—using ultra-high-temperature (UHT) sterilization, it eliminates all harmful bacteria, extending shelf life to 6–12 months without refrigeration. However, nutrients suffer significant loss.
Reconstituted Milk—Powdered milk cannot be used in pasteurized milk, but it is permissible in UHT milk, yogurt, and other dairy products. However, the ingredient must be labeled as "reconstituted milk" or "water and powdered milk."
Raw Milk—In many developed countries, unpasteurized raw milk is the most popular choice among consumers, though it commands the highest price. Freshly milked raw milk contains antibacterial substances like lysozyme, allowing it to be stored at 4°C for 24 to 36 hours.This milk requires no heating, is rich in nutrients, and retains certain physiologically active trace components beneficial for children's growth. Sterilized Milk — To meet the needs of working professionals, many manufacturers produce long-life milk in Tetra Pak packaging. This extended-shelf-life milk undergoes complete sterilization during processing, eliminating virtually all beneficial bacteria along with the milk's nutrients.resulting in the destruction of milk's nutritional components. This milk's packaging closely resembles fresh milk, with most shelf lives spanning 30 days or longer; some sterilized milk products maintain freshness for over six months. Sterilized milk typically possesses a richer flavor, though it experiences some nutrient loss, including a 20%–30% reduction in B vitamins.
Antibiotic-Free Milk—This term is widely recognized, though it won't appear on milk packaging because it's one of the factory-release standards. Reputable manufacturers should meet this benchmark. Buffalo Milk— Though buffalo milk yields are lower, its protein, amino acids, milk fat, vitamins, and trace elements surpass those in Holstein milk.According to national research institutions, buffalo milk is exceptionally high-quality, considered the finest among milks. Its value is twice that of Holstein milk. It is particularly rich in zinc, iron, and calcium—essential for children's growth and development and anti-aging—and abundant in amino acids and vitamins, making it a nutritious food suitable for all ages.
Precautions
Avoid adding sugar while heating milk.
Many people enjoy adding sugar to milk for taste enhancement. However, caution is needed: adding sugar to hot milk causes lysine to react with fructose, forming toxic fructosyllysine that harms health. If sugar must be added, do so only after the milk has cooled completely to avoid health risks.
Milk should not be consumed with chocolate.
The protein and calcium in milk combine with oxalic acid in chocolate to form insoluble calcium oxalate, which impairs calcium absorption. Severe cases may lead to diarrhea, stunted growth, and dry hair.
Milk should not be consumed with acidic fruits or juices.
Avoid eating citrus fruits like oranges or drinking acidic juices while drinking milk or immediately afterward. The proteins in milk react readily with the fruit acids in acidic foods, causing coagulation that impairs digestion and absorption. Wait at least one hour after drinking milk before consuming citrus fruits or acidic juices.
Freshly milked milk should not be consumed immediately.
While raw milk is a natural, additive-free nutritional product, it must be handled hygienically to prevent bacterial contamination, such as Brucella or tuberculosis bacteria. Therefore, raw milk should undergo appropriate heating sterilization.Avoid boiling during heating. The optimal method is to turn off the heat just before the milk reaches boiling point, then reheat it. Repeat this process three times. This approach effectively kills bacteria while preserving the milk's biological activity.
Milk should not be consumed with cola.
Cola is a carbonated beverage, while milk primarily contains protein. Under the influence of phosphoric acid, protein undergoes a chemical reaction known as denaturation, forming phosphoric acid clumps. Overall, protein denaturation does not affect its safety or nutritional value, but it does impact absorption. Therefore, it is advisable not to consume milk and cola together.