Analysis of Plant-Based Milk
Introduction
Plant-based milks are becoming increasingly popular with consumers as they seek healthier, non-animal based options of milk protein. Unlike animal sourced milk, in plant-based milk production there are frequent changes between crop years and in crop sources. For example, the same plant grown in different climates, different weather patterns or different cultivars can give modest to noticeable differences in the constituent concentrations. The efficient production of high caliber plant-based milk products therefore requires full control over intermediate and final product quality. Producers want to hit their target formulas on cost, quality, and labeling concerns.
Fourier Transform Infrared (FTIR) transmission technology is highly suitable for making proximate constituent measurements in liquid plant-based milks. Unlike traditional wet chemistry methods which can be time consuming and labor intensive, FTIR multiple component analysis is done in under a minute. FTIR sample preparation is minimal, which means that the products can be analyzed as is without drying or making extracts.
Overview
Unlike animal sourced milk, various plant-based milks are generally made up of suspensions of solids. This can be seen by centrifuging a plant-based milk sample. Figure 1 shows a photo of the plant based milk as it looks, and Figure 2 shows the solid residue left in the centrifuge tube. The different components are quite visible.
In Figure 2 it is clear that there are multiple separate ingredients suspended in the product from dark flecks to whiter materials. Those are the suspended particles. When measuring plant based milk, we must ensure that the product is shaken first to unsettle any suspended particles that may have occurred before doing any measurement.
LactoScope 500
The LactoScope 500 is a state-of-the art instrument for compositional analysis of liquid products. With modern FTIR optics, it is simple to use with powerful software for rigorous analysis. It is AOAC and IDF compliant for the analysis of fat, protein, lactose, and total solids in milk.
Figure 1: Liquid plant milk
Figure 2: Plant milk centrifuged
The intuitive Results Plus software provides rapid implementation of testing methods with minimal training. It is designed to make analysis as quick and secure as possible and is compatible with LIMS systems. The instrument maintains its own Microsoft® SQL database of its internal measurements and warnings, operator actions or changes, spectra and results.
Method
Measurements were carried out using a LactoScope 500 according to standard protocol. More than 150 plant-based milk samples were analyzed and spectral data collected. The samples analysed spanned plant-based milks and creamers. The list of plant-based milk types is shown in the table on the right. Each plant-based milk sample was purchased at a commercial retail store and either refrigerated or kept on the shelf as indicated on the packaging.
Table 1: Plant source of milks analyzed
The samples were shaken for 10 complete 180-degree rotations and then poured out for analysis. The pour started into the 50 ml container used to feed the LactoScope sample tube. About halfway full the pour was then moved to the reference sample container that was sent out for reference chemistry. Once the reference sample was filled, the pour continued into the LactoScope sample container so that the average value for the FTIR and reference lab splits were close to one another even if there was some separation in the product. Some of the products clearly separate a bit before they are stocked and sold. Shaking helped considerably.
Reference analysis for protein, fat, total solids, and sugars were carried out using AOAC or ISO standard methods.
The Dumas method for protein measures the nitrogen content which is then recalculated to protein using a conversion factor. This factor differs by type of plant. For example, for soybeans it is 5.71 and 5.18 for almonds. For beverages with multiple ingredients, we used the factor 6.25 as a reasonable average. Calibration models were developed to demonstrate the relationships between the collected FT-IR spectra and reference chemistry results using Partial Least squares regression (PLS). A few samples with unusual spectral or concentration deviations were left out of the calibrations.
Table 2: Reference methods used for analysis
Results and Discussion
The table (right) summarizes the calibration statistics of the developed calibrations:
The large product variability built into the calibrations allow them to be robust and accurate for all kinds of raw and processed plant-based milks. Individual calibrations for individual products will most likely have lower errors because they will have more consistent reference chemistry results and because they won’t span as many variables in composition. For example, there were samples with many different types of sugars. Here the total sugars were added to come up with one number, but their spectra are a bit different from each other. The Predicted vs. Reference calibration lines for these 4 constituents are shown in the following graphs:
Table 3: Calibration statistics
Conclusion
Even though plant-based milks are quite different than dairy milks and creams the basic constituents of protein, fat, sugar, and solids can be measured with the same FTIR instrument, the LactoScope 500. This study showed that a single uniformed calibration can measure the constituent values in many different mixtures.
This article was originally published by PerkinElmer.
30/9/24