Salted Egg Testing

The methods of salted egg testing usually cover multiple aspects to ensure its quality and safety. Here are some of the main salted egg testing methods:

1. Sensory inspection
Sensory inspection is the first step in salted egg testing and is also the most intuitive method. Inspectors check the appearance, smell, texture, etc. of salted eggs by vision, smell, touch, etc.

Appearance inspection: Observe whether the eggshell is intact and without cracks, whether the surface is clean and smooth, and whether the color is bright. At the same time, check whether the yolk and egg white are evenly distributed and there is no excessive slag.
Odor inspection: Smell the smell of the salted egg to determine whether it has a fragrant salty aroma and no peculiar smell or odor.
2. Physical and chemical index detection
Physical and chemical index detection is an important means to evaluate the quality of salted eggs, including indicators such as salinity, moisture content, protein content, fat content, ash content, and pH value.

Salinity detection: The salt content of salted eggs is determined by potentiometric titration or ion chromatography. Usually, the salt content of high-quality salted duck eggs should be between 2.5% and 3.5%.
Moisture content detection: The moisture content of salted eggs is determined by the drying method, which should usually be controlled between 65% and 70%.
Nutrient component detection: The content of nutrients such as protein, fat, and vitamins in salted eggs is detected by chemical analysis.
pH value detection: The pH value of salted eggs is determined using a pH meter or precision pH test paper to reflect their freshness. The pH value of fresh salted duck eggs is usually between 7.0 and 7.5.
III. Microbial index detection
Microbial index detection is crucial to ensure the hygienic safety of salted eggs. The main test items include total colony count, coliform group, Salmonella, and Staphylococcus aureus. These tests are usually carried out by the plate count method or the maximum possible number method. Qualified salted eggs should control the total colony count below 10^5 CFU/g, and no pathogenic bacteria should be detected.

IV. Heavy metal and pesticide residue detection
Heavy metal and pesticide residue detection is an important link to ensure the safety of salted eggs. Common heavy metal detection items include lead, cadmium, mercury, and arsenic, which can be detected by atomic absorption spectrophotometry or inductively coupled plasma mass spectrometry. Pesticide residue detection mainly targets organochlorine, organophosphorus, and carbamate pesticides, and is usually analyzed by gas chromatography-mass spectrometry or liquid chromatography-mass spectrometry.

V. Specific quality detection
Egg yolk oil quality detection: The egg yolk oil content can be determined by Soxhlet extraction. The egg yolk oil content of high-quality salted eggs should be between 30% and 35%. In addition, the acid value, peroxide value, and iodine value of the egg yolk oil need to be tested to evaluate its freshness and degree of oxidation.
Packaging and labeling detection: Check whether the packaging of salted eggs is complete and clean and whether the label information meets the general standards for food labels, including product name, production date, shelf life, storage conditions, producer information, etc.
Eggshell strength and egg yolk coagulation detection: Eggshell strength can be measured by a pressure tester, while egg yolk coagulation can be evaluated by measuring the yolk diameter.
VI. Other testing methods
Light-transparent testing: Use light to see through the salted egg on the egg-lighting device to observe whether the inside of the egg is clear and translucent, whether the egg white is as clear as water, and whether the egg yolk is bright red and close to the eggshell. At the same time, turn the egg and observe whether the egg yolk rotates with it.
Shaking test: Hold the egg in your hand and gently shake it next to your ear to feel whether the egg white flows and whether there is a sound of splashing water.
Shelling test: After opening the eggshell, observe whether the yellow and white are clear, whether the egg white is watery, colorless, and transparent, and whether the egg yolk is firm and vermilion.
Cooking and dissection: After the salted egg is cooked, cut it open to observe whether the egg white is fresh and white, whether the egg yolk is firm and vermilion, and whether there are dew-like oil droplets. At the same time, taste the saltiness and taste of the salted egg.
In summary, the testing methods of salted eggs include sensory testing, physical and chemical index testing, microbial index testing, heavy metal and pesticide residue testing, specific quality testing, and other testing methods. These testing methods can comprehensively evaluate the quality and safety of salted eggs and provide consumers with safe and high-quality salted egg products.