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Palm oil is an edible oil from the fruit of oil palm trees (Elaeis guineensis). Oil palm trees only grow in tropical regions. They are native to Africa but were brought to southeast Asia just over a century ago. Now, oil palm plantations in Indonesia and Malaysia supply over 85% of palm oil used all over the world [1].
High-quality crude palm kernel oil and crude red palm oil are processed and used in a wide variety of products. Screening and quality control are critical to ensure that certain specifications are met for palm oil use in several industries. One simple way to do so is with near-infrared (NIR) spectroscopy.
What is palm oil used for?
Palm oil is found in more than 50% of prepackaged consumer goods—from pizza, instant noodles, and sweets like ice cream, to personal care and cosmetic products including deodorant, shampoo, toothpaste, and lipstick [2]. Even cleaning products like soap and detergent are not exempt. This ubiquitous oil is also used in animal feed and as a biofuel in many parts of the world (Figure 1).
Two types of oil can be produced from oil palms. Crude palm oil (or crude red palm oil) comes from pressing the flesh, and crude palm kernel oil comes from crushing the kernel (also known as the stone) in the center of the fruit (Figure 2).
Processing palm oil: milling and refining
Figure 3 illustrates the milling and refining process of palm oil. After milling the fruit, the resulting crude palm oil (CPO) is naturally red in color. This is because of its high beta-carotene content. Crude red palm oil that has been refined, bleached, and deodorized (i.e., RBD palm oil) is light yellow or even colorless since it no longer contains carotenoids.
After milling, the crude palm oil goes through fractionation. This covers both crystallization and separation processes where solid (palm stearin) and liquid (olein) fractions of CPO are obtained. Impurities are removed from these fractions by melting and degumming processes.
The oil is refined further. It is filtered and bleached to remove scents and coloration, ultimately producing RBD palm oil and free fatty acids. RBD palm oil can be fractionated even more to either produce cooking oil or use it as an ingredient in other products.
Quality control of palm oil
There are many stages during its production where palm oil can be monitored for quality control (QC) purposes. Near-infrared spectroscopy is a method that can be used not only for QC during palm oil production, but – very importantly – also for companies that procure palm oil and need to assess its quality before using it in other products.
The use of NIR spectroscopy makes QC more efficient and cost-effective as shown in this article. In the remainder, a short overview of NIRS is presented, followed by NIRS application examples for the palm oil industry. These illustrate how palm oil producers can benefit from implementing NIRS in the QC workflow.
How does NIR spectroscopy work?
Light and matter interact in all kinds of ways. However, the light used in spectroscopic methods (e.g., NIRS) is typically described by the wavelength or wavenumbers rather than the applied energy. A NIR spectrometer (e.g., the Metrohm DS2500 Liquid Analyzer) measures this interaction to generate spectra from a sample (Figure 4).
This analytical technique is quite sensitive to the presence of certain functional groups (i.e., -CH, -NH, -OH, and -SH) in samples. As such, NIRS is ideal to quantify chemical parameters in palm oil like water (moisture) content, free fatty acids (FFA), iodine value (IV), and deterioration of bleachability index (DOBI), among others. The light-matter interaction is also dependent upon the sample. This allows the measurement of physical and rheological parameters (e.g., density and viscosity). This wealth of information is contained in just a single NIR spectrum, making this method suitable for quick multiparameter analysis.
Measuring mode
NIRS measuring modes are dependent on the sample type. The transmission mode is most appropriate for analyzing liquid samples like palm oil (Figure 5). In this case, NIR light travels through the sample while being absorbed. Any unabsorbed NIR light is then detected.
Advantages of using NIR spectroscopy
It is clear that simplicity regarding sample measurement and speed are two major advantages of using NIR spectroscopy for quality control:
- Fast technique – results are obtained in <1 minute.
- No sample preparation – measure the sample as-is.
- Low cost per sample – no reagents needed for analysis.
- Environmentally friendly – no waste is generated.
- Non-destructive measurement – samples can be reused after analysis.
- Easy operation – inexperienced users are immediately successful.
Learn more about NIRS as a secondary technique in our previous blog posts.
Benefits of NIR spectroscopy: Part 1
Benefits of NIR spectroscopy: Part 2
ASTM compliance of NIRS for quality control
ASTM E1655: Standard Practices for Infrared Multivariate Quantitative Analysis
«These practices cover a guide for the multivariate calibration of infrared spectrometers used in determining the physical or chemical characteristics of materials. These practices are applicable to analyses conducted in the near infrared (NIR) spectral region (roughly 780 to 2500 nm) through the mid infrared (MIR) spectral region (roughly 4000 to 400 cm-1).»
Typical applications and parameters for NIRS analysis
Palm oil products are subjected to many standardized test methods to determine their chemical and physical properties. Laboratory testing is an indispensable part of research and development and quality control. Table 1 lists the most relevant test parameters for QC of various forms of palm oil (e.g., crude palm oil (CPO), crude palm kernel oil (CPKO), and refined, bleached, and deodorized (RBD) palm oil).
Table 1. Many QC parameters for palm oil products are measured by conventional laboratory techniques which require chemical reagents, skilled technicians, and sample preparation. NIRS is a suitable alternative technique that can determine all these parameters in less than a minute.
| Parameter | Conventional (primary) method |
|---|---|
| Moisture | Karl Fischer titration |
| Free Fatty Acids (FFA) | Titration |
| Iodine Value (IV) | Titration |
| Deterioration of Bleachability Index (DOBI) | Photometry |
| Carotene | Photometry |
NIRS: a turnkey solution for palm oil analysis
Metrohm offers NIRS as a turnkey solution for palm oil analysis with ready-to-use pre-calibration models for the determination of the iodine value (IV), moisture (water %), and free fatty acids (FFA) content (Table 2). Different, specific pre-calibrations are dedicated for the analysis of products like crude palm oil (CPO), crude palm kernel oil (CPKO), or refined, bleached, and deodorized (RBD) crude palm stearin or olein. These pre-calibration models allow this turnkey solution to be used immediately without any method development.
Table 2. Available Metrohm NIRS pre-calibration models for selected palm oil products shown with measuring range and standard error of cross-validation (SECV).
| Parameter | CPKO | CPO | RBD | |
|---|---|---|---|---|
| FFA (%) | Range | 0–4 | 2.5–6 | 0–0.25 |
| SECV | 0.11 | 0.26 | 0.03 | |
| Moisture (%) | Range | 0–0.3 | 0–0.3 | 0–0.1 |
| SECV | 0.03 | 0.05 | 0.01 | |
| IV | Range | 7–19 | 49–53 | 21–63 |
| SECV | 0.27 | 0.22 | 0.56 |
The results of crude palm oil analysis with the Metrohm DS2500 Liquid Analyzer are shown in Table 3. All constituents measured by NIRS exhibit robust correlation values. Additionally, the standard error of cross-validation (SECV) is close in value to the standard error of calibration (SEC) for all models.
Table 3. Example of multi-component analysis in crude palm oil (CPO) by NIRS.
| Figures of merit | FFA | IV | Moisture content | DOBI | Carotene content |
|---|---|---|---|---|---|
| R2 | 0.835 | 0.911 | 0.638 | 0.842 | 0.677 |
| SEC | 0.266% | 184 mg/100g | 0.046% | 0.17 | 22.9 µg/g (ppm) |
| SECV | 0.270% | 210 mg/100g | 0.047% | 0.19 | 23.4 µg/g (ppm) |
Summary
Near-infrared spectroscopy is an excellent fit for the analysis of several key quality parameters in CPO, CPKO, and RBD palm oil. Just one NIRS instrument can measure multiple QC parameters in a fraction of the time of other analytical techniques.
Analysis of palm oil samples with primary methods (i.e., titration, Karl Fischer titration, and photometry) can take up to 30 minutes. Conventional wet chemistry determination requires chemical reagents, sample preparation, multiple instruments, and skilled laboratory staff. On the contrary, multiparameter analysis of palm oil with NIRS takes less than one minute. Higher sample throughput is possible because of the fast time to result and the fact that sample preparation is not required. This also results in lower costs per sample, not only because of the time savings, but also because no chemicals are needed.
References
[1] WikiCorporates. Palm Oil Industry. https://www.wikicorporates.org/wiki/Palm_Oil_Industry (accessed 2023-09-07).
[2] World Wildlife Fund. Which Everyday Products Contain Palm Oil?. Palm Oil. https://www.worldwildlife.org/pages/which-everyday-products-contain-palm-oil (accessed 2023-09-07).
Your knowledge take-aways
Pre-calibration for crude palm oil analysis
Boost efficiency in the QC laboratory: How NIRS helps reduce costs up to 90%
Underestimating QC processes is one of the major factors leading to internal and external product failure, which have been reported to cause a loss of turnover between 10–30%. As a result, many different norms are put in place to support manufacturers with this. However, time to result and the associated costs for chemicals can be quite excessive, leading many companies to implement near-infrared spectroscopy in their QC process. This White Paper illustrates the potential of NIRS and displays cost saving potentials up to 90%.
