In the food and cosmetics industry, fat gel lotion is becoming a research and development hotspot due to its unique rheological properties and bioavailability advantages. However, small changes in droplet size distribution, interface stability and gel network structure will directly lead to uneven product texture or delamination failure. Traditional methods such as centrifugal settling and microscopic observation often have limitations in being destructive, time-consuming, and difficult to reflect dynamic processes. Therefore, the introduction of low field nuclear magnetic resonance (LF-NMR) technology has become a key path to achieve "nondestructive, rapid and online" quality control of oil gel lotion.

Application background: Why do we need more advanced quality control methods?

With the improvement of consumers' requirements for product sensory experience (such as coating feeling and moisture), it is impossible to comprehensively evaluate the shelf life stability of grease gel lotion solely relying on physical and chemical indicators (such as acid value and peroxide value).

Pain points of traditional detection methods:

Destructive testing: After sampling, the sample needs to be destroyed, making it impossible to track the long-term evolution of the same batch of products.

Lag effect: Many changes in physical properties, such as droplet aggregation, are not visible at the macroscopic level until stratification or metamorphism occurs.

Complicated operation: relying on manual microscope counting, low efficiency and strong subjectivity.

Current industry demand:

Real time monitoring: The production line needs to provide real-time feedback on droplet size and dispersion status.

Multidimensional characterization: simultaneously obtaining information on the interactions between moisture, oil, and solid particles.

Non contact: suitable for testing fully packaged finished or semi-finished products.

Core principle: How does LF-NMR "see through" the microscopic world?

The core of low field nuclear magnetic resonance technology is to infer the physical and chemical properties of substances by utilizing the relaxation behavior of hydrogen nuclei in a magnetic field.

When the sample is placed in a low-intensity magnetic field, the free water and bound water in it exhibit different transverse relaxation times (T2). For grease gel lotion:

Water in the droplet: bound by the boundary facial mask, its T2 value is short.

Water in continuous phase: has good fluidity and a longer T2 value.

Oil phase: usually contains a small amount of hydrogen nuclei, and its signal characteristics are different from water.

By measuring and fitting the T2 spectrum, it is possible to accurately distinguish the proportion of free water, bound water, and oil content, and further invert the droplet size distribution (SANS/NMR combination principle) and interfacial permeability.

Technical application: specific practice in droplet quality control

In the R&D and production process of oil gel lotion, LF-NMR is mainly applied to the following three dimensions of quality control:

A. Analysis of droplet size and dispersion stability

By analyzing the signal attenuation curves of water in different states in the aqueous phase, the average particle size and polydispersity index (PDI) of droplets can be calculated. The research shows that LF-NMR can effectively monitor the coalescence or fracture of lotion droplets during storage, so as to predict the shelf life of the product.

B. Evaluation of strength and permeability of interfacial facial mask

The stability of oil gel lotion is highly dependent on the strength of the interfacial facial mask. LF-NMR can indirectly evaluate the density of the interface facial mask by measuring the diffusion rate of water molecules from the inside of the droplet to the outside environment (that is, the relaxation rate of T2). The denser the membrane, the more difficult it is for water molecules to escape, and the more stable the droplet.

C. Integrity of gel network structure

For systems containing polysaccharide or protein gel matrix, LF-NMR can distinguish the bound water and free water in the gel network. If the gel network collapses, the bound water will be converted into free water, resulting in an increase in the signal of the long relaxation time component in the T2 spectrum, which provides an early warning for judging the failure of gel formation.

The advantages of LF-NMR technology

Non destructive: No sampling is required, and the entire bottle or can of the product can be directly tested, avoiding errors introduced by operation.

Fast and efficient: A single test only takes a few minutes, with a high degree of automation in data processing.

Rich information: Multiple parameters such as moisture content, oil content, and droplet size can be obtained simultaneously with one scan.

In situ monitoring: supports online installation and can monitor quality fluctuations in real-time during the production process.

With its non-invasive and high sensitivity, low field NMR technology is reshaping the quality control standard of oil gel lotion. It can not only provide accurate data on the size and distribution of droplets, but also reveal the micro dynamic behavior of the boundary facial mask in depth. For enterprises, establishing a quality control system based on LF-NMR means that they can shift from "remedial measures" to "preventive measures", significantly reducing research and development costs and improving product quality consistency.