In the food industry, butter, as a complex water in oil emulsion, directly determines the taste, shelf life, and shelf stability of the final product based on its quality. Traditional physical and chemical detection methods often have limitations such as destructive, time-consuming, or only providing a single indicator. Low field nuclear magnetic resonance (LF-NMR), with its advantages of nondestructive, rapid and multi parameter detection, is gradually becoming the "gold standard" for quality control of butter lotion.

Technical Background: Quality from a Micro Perspective

Butter is essentially an emulsion system containing approximately 16% -18% moisture. During the processing and storage, the change in moisture state (such as from free water to bound water) and the distribution of droplet size directly determine the melting characteristics, spreading sensation, and whether there will be layering or water separation of butter. Traditional detection methods, such as microscopic observation and centrifugation to determine moisture content, often require complex pretreatment of the sample, which is not only time-consuming and laborious, but also difficult to capture the dynamic changes in microstructure over time. Therefore, it is particularly urgent to introduce a technology that can monitor the internal microenvironment of butter in real time and without damage.

Core principle: Fingerprint recognition of hydrogen protons

The core of low field nuclear magnetic resonance technology is to use magnetic fields and radio frequency pulses to excite hydrogen nuclei in the sample, and record the signal attenuation process of their released energy.

1. Relaxation mechanism of hydrogen proton

Butter contains a large number of hydrogen atoms (mainly present in water molecules and fat molecules). When these hydrogen nuclei are placed in a magnetic field and excited by radio frequency pulses, they absorb energy and resonate. Once the excitation is stopped, the hydrogen nucleus will release energy back to the surrounding environment at a specific time constant (relaxation time T2).

2. Differentiated signal characteristics

Hydrogen protons in different states have different relaxation characteristics:

Free water: Strong fluidity, short relaxation time (small T2), and fast signal attenuation.

Combined with water: bound by protein or fat matrix, with longer relaxation time (larger T2) and slower signal attenuation.

Oil: Hydrogen protons are in a free state and have unique relaxation spectrum characteristics.

By analyzing the T2 relaxation time spectrum, we can completely separate the moisture signal in butter from the oil signal, and further distinguish water molecule populations with different binding strengths. This "fingerprint" recognition ability enables LF-NMR to accurately quantify the total moisture content, dry matter content, and moisture binding state in butter.

In the quality control research of butter lotion, LF-NMR mainly plays a role through the following three dimensions:

Analysis of droplet size distribution

The stability of butter is highly dependent on the size of the fat globules. LF-NMR can use gradient field sequence (such as D-Var method) to determine the average particle size and distribution range of dispersed phase (fat globule) in lotion without damage. The more uniform the particle size, the better the stability of butter; If large particle aggregation occurs, it indicates potential stratification risk.

Monitoring of moisture status and binding strength

LF-NMR can distinguish between "free water" and "bound water" in butter. Combined water usually binds tightly to proteins or fatty acids and is not easily lost. By monitoring the proportion of bound water, the stability of butter during heating or freezing, as well as its water holding capacity during baking or application, can be evaluated.

Non destructive online testing

Compared with traditional methods, LF-NMR can complete detection without damaging the sample. This makes it very suitable for online quality control on production lines, real-time monitoring of the uniformity of butter filling process, timely removal of non-conforming batches, and ensuring the consistency of factory products.

Compared with traditional detection methods, low field NMR technology has shown overwhelming advantages in quality control of butter lotion:

Traditional chemical/physical methods

Destructive: Unable to retest after sampling, making continuous monitoring difficult.

Time consumption: Oil extraction or centrifugal separation often takes several hours.

Single indicator: Usually only a single parameter can be measured (such as oil content only).

Low field nuclear magnetic resonance (LF-NMR)

Non destructive: Fully enclosed testing, samples can be directly used for subsequent sales or research.

Fast response: A single measurement only takes a few minutes, suitable for online real-time monitoring.

Multidimensional information: simultaneously obtaining data on moisture status, oil content, and microstructure.

For butter lotion, low field NMR technology is not only a detection tool, but also a bridge connecting microstructure and macro quality. It can help manufacturers accurately control the binding state of moisture, optimize emulsification processes, prevent delamination and water separation, and ensure the optimal sensory experience of the final product.