Emulsion cosmetics, such as lotions, creams, and butter, due to the process of formula, production, packaging, and storage, may cause the below quality issues.
Poor stability
When emulsion with poor stability is observed under the microscope, the particles in the inner phase are clumpy oil droplets with insufficient dispersity. This is caused by improper formula.
The solution is to properly increase the amount of emulsifier, to enhance the strength of the interface and improve the dispersion of particles.
The other reason for the poor stability may be the low viscosity and the large density difference between the two phases. To fix this issue, you need to increase the viscosity of the continuous phase, but maintain the proper fluidity; Adjust the relative density of the oil-water phase to make it close.
Coarse texture
This is caused by insufficient emulsification, second emulsification will improve the situation. The reasons for roughness include:
- Insufficient mixing
- Premature cooling
- Fast cooling
- Not enough emulsifier
- Extracts or other raw materials bring in high levels of electrolytes
- Insufficient oil phase compatibility
Dehydration and shrinkage
This issue is mainly caused by the packaging and storage environment. The sealing of the packaging is not good, and prolonged exposure to high temperatures can easily cause cosmetics to lose water and shrinkage.
Leakage testing is crucial, whether in development or production stage.
Sweat
Sweat is a serious issue of emulsion destruction, mostly due to insufficient alkali content in the formula or improper emulsifiers, as well as too much salt in the solution.
Salt is an electrolyte that can precipitate potassium stearate from water, known as salting out. If the emulsifier is salted out, the emulsion is inevitably destroyed. After severe freezing or containing a large amount of paraffin, mineral oil, neutral fats, etc., sweat can also be caused.
Mildew and swelling
The presence of microorganisms is the main factor causing this issue. On the one hand, if the water quality is poor, the reaction container, material container, and bottling container are not clean, the raw materials are contaminated, and the packaging is placed in a damp and dusty environment.
On the other hand, without disinfection and sterilization by UV lamps, a large number of microorganisms accumulate in the product and are stored at room temperature (30-50 ℃) for a long time.
The microorganisms multiply in large quantities, producing CO ₂, causing the paste to swell and overflow outside the bottle.
Discoloration and odor change
It is mainly because the unstable ingredients such as aldehydes and phenols in fragrance are too much, and the color turns yellow after a long time or sunlight.
Another reason is that the iodine value of oily raw materials is too high, and the unsaturated bonds are oxidized, resulting in a darker color and a rancid odor.
Quality standard
In order to better control product quality and avoid the occurrence of the above issues, a quality standard should be established.
It should be noted that each region/country has a different limit on this standard.
| Test Item | Limit |
| appearance | delicate and uniform |
| odor | same with the check sample |
| pH | 4.0-8.5 |
| heat-resisting | after 24 hours at 40℃, no oil-water separation |
| cold-resistant | after 24 hours at 40℃, no significant difference in state |
| Mould and Yeast Count+Total Aerobic Microbial Count(per g) | ≤1,000 CFU ^2 |
| Staphylococcus aureus (per g) | Absence |
| Pseudomonas aeruginosa (per g) | Absence |
| Salmonella sp. (per 10g) | Absence |
| Escherichia coli (per g) | Absence |
| Bile-Tolerant Gram-Negative Bacteria (per g) | Absence |
| Clostridia sp. (per g) | Absence |
| Candida albicans (per g) | Absence |
| Mercury/(mg/kg) | ≤1 |
| Arsenic/(mg/kg) | ≤10 |
| Lead/(mg/kg) | ≤40 |
