Fresh milk testing

There are many methods for testing fresh milk, aiming to ensure the quality, safety, and nutritional value of fresh milk. Here are some common methods for testing fresh milk:

1. Sensory testing
Sensory testing is one of the most direct and simple testing methods. It mainly judges the freshness and quality of fresh milk by observing the appearance of fresh milk, smelling its odor, and tasting its taste.

Appearance inspection: Fresh milk (sterilized milk) should be milky white or slightly yellowish, without precipitation, coagulation, impurities, foreign matter, and viscosity.
Odor detection: Fresh milk should have an inherent fragrance and no odor.
Taste: The sweetness and taste of fresh milk can be felt by tasting, but it is usually not recommended to taste untreated fresh milk directly to prevent food safety problems.

2. Physical and chemical testing methods
Physical and chemical testing methods are to determine the nutritional components and harmful substances in fresh milk by chemical or physical means to evaluate the quality of fresh milk.

Protein and fat content detection: According to GB25190 and other standards, the protein content of pure milk should be ≥2.9g/100g, and the fat content should be ≥3.1g/100g. Chemical methods such as the Kjeldahl nitrogen determination method and the Rhodes-Gottli method can be used to determine the protein and fat content.
Lactose and acidity detection: Lactose is an important component in fresh milk, and its content and acidity can reflect the freshness and microbial contamination of fresh milk. The content of lactose and acidity can be determined by titration and other methods.
Density and viscosity detection: The density of fresh milk can be determined using a densitometer, while the viscosity can be evaluated by stirring or flow tests. These indicators can reflect the adulteration of fresh milk or quality changes.
3. Rapid test strips and kits method
The rapid test strips and kits method is a convenient and rapid fresh milk detection method suitable for on-site detection and preliminary screening.

Rapid detection of alkali in fresh milk: Use commercially available rapid test paper for alkali in fresh milk to detect whether fresh milk contains alkaline substances to determine whether the fresh milk has been adulterated or rancid.
Rapid detection of melamine in fresh milk: Use melamine rapid test paper cards to detect whether fresh milk contains melamine, which is a common abuse of food additives.
Rapid detection of fresh milk freshness: Use a fresh milk freshness test kit to determine the acidity in fresh milk and thus determine the freshness of fresh milk.
IV. Other detection methods
Boiling test method: Take a certain amount of fresh milk sample and place it in a test tube or transparent glass cup, heat it to boiling, and observe whether coagulation or floccules are produced. If there is coagulation or floccules, it means that the fresh milk is not fresh or has deteriorated.
Hanging cup test method: Pour uncooked or unheated fresh milk quickly into a clean transparent glass cup, and then slowly tilt the glass cup. Observe whether there is a thin milk film left on the inner wall of the cup and whether it is easy to wash it off with water. If the milk film is uniform and does not stick to the cup, it may be fresh milk.
Adulteration detection: For fresh milk that may be mixed with electrolyte solution, sugar, urea, and other substances, specific chemical reagents can be used for detection. For example, fresh milk mixed with sugar can be preliminarily judged by tasting its sweetness; fresh milk mixed with urea can be tested using a urea detection kit.
5. Microbial detection
Microbial detection is one of the important indicators for evaluating the hygienic quality of fresh milk. The total number of bacteria, mold, yeast, and other microorganisms in fresh milk can be detected by technical means such as the culture method. The contamination of these microorganisms may affect the edible safety and nutritional value of fresh milk.

In summary, there are many methods for fresh milk detection, including the sensory detection method, physical and chemical detection method, rapid detection paper and kit method, and other detection methods. In practical applications, appropriate detection methods should be selected according to specific needs and conditions, or a combination of multiple methods should be used for comprehensive evaluation. At the same time, in order to ensure the quality and safety of fresh milk, fresh milk should be tested regularly and produced and managed in strict accordance with relevant standards.