Carob Gum Production Process: Peeling Methods
Locust bean gum (E410) is obtained by grinding the inner tissue of the carob kernel, called endosperm. However, it is not easy to reach this tissue; the hard and durable shell surrounding the seed must be removed without damaging the endosperm and germ. The most critical and most discussed stage of gum production is this debarkation process.
In this article, we discuss how dehulling is done with acid, roasting (thermal) method and hot water, the subsequent germ separation and grinding steps, the effects of the methods on the color, viscosity and purity of the gamut, and research into more sustainable alternatives, based on sources.
The Structure of Carob Seeds: Why Do You Need Peeling?
When processing carob fruit, the first step is to separate the kernel from the flesh. As mentioned in the compilation by Martins-Loução et al. (2024), the first step in evaluating the fruit is the chibbling process, which separates the kernel from the flesh. The separated kernel consists of three main parts: the shell, endosperm, and germ (embryo).
According to Medronho et al. (2025), the shell is a hard and brown covering that makes up about 30–35 percent of the dry weight of the kernel. The germ in the center of the kernel makes up about 15–30 percent of the dry weight and is rich in protein. The endosperm, located between the shell and the germ, makes up about 40–50 percent of the total weight and is the main source of the carob gamut.
In the 2017 reassessment report of the European Food Safety Authority (EFSA), it is stated that carob kernels are difficult to process because the shell is very hard and durable, based on information received from the industry. According to the report, the kernels are peeled with special processes without damaging the endosperm and germ. If the barking fails, the shell fragments become part of the gum; this darkens the color, increases the foreign matter content and decreases the galactomannan ratio, which is the main functional component of the gum.
Acid Peeling (Sulfuric Acid Method)
The most widely used method in the industry is acid peeling. The process described in the EFSA report is as follows:
- The kernels are heated with sulfuric acid and the shell is charred.
- The remaining shell fragments are removed from the clean endosperm "sandwich" by washing and brushing.
- Sandwiches are dried and broken; the germ, which is crispier, crumbles at this time.
- The crumbled germ fragments are separated by sieving them from the endosperm halves that remain unbroken.
Medronho et al. also state that in the acid peeling method, the bark is charred with sulfuric acid at high temperature, the residues are removed by washing and brushing, resulting in a white colored gum. In the same study, it was found that the gum obtained from acid-peeled beans showed higher galactomannan content, better solubility at high temperature, larger molecule size and higher intrinsic viscosity; therefore, it is reported that the thickening feature is superior. The effect of peeling with acid and water on the composition and physicochemical properties of the gum has also been the subject of research such as the study of Dakia et al. (2008).
There is also an important study on this subject from Turkey. In the master's thesis prepared at Süleyman Demirel University (Kıvrak, 2011), the shells of carob seeds were peeled with 60 percent sulfuric acid, 30 percent hydrochloric acid and boiling water; it was determined that the obtained gums showed significant differences in terms of color, moisture, protein, ash, sugar, foreign particle, acid-insoluble ash and viscosity. The gum obtained by the sulfuric acid method had the lowest protein (5.01 percent), the lowest acid-insoluble ash (1.29 percent) and the highest viscosity (533.9 mPa·s) values. The author concluded that the sulfuric acid method is more suitable than other methods for the production of good quality gum. The same research group also published their findings in an international journal (Kıvrak et al., 2015).
Peeling by Roasting (Thermal) Method
The second basic approach is based on heat treatment. According to the EFSA report, in the roasting method, the beans are roasted in a rotary oven and the shell is separated from the seed and falls off. The germ and endosperm halves are then separated in a similar way to the acid method.
The method has two distinct features:
| Feature | Roasting method (according to EFSA 2017 and Medronho et al. 2025) |
|---|---|
| Advantage | Since sulfuric acid is not used, no acidic wastewater comes out of the process. |
| Color | The resulting product is slightly darker in color. |
| Viscosity | High processing temperatures can reduce the gamut's ability to achieve high viscosity. |
| Checkpoint | EFSA noted that knowledge of polycyclic aromatic hydrocarbons may be important for specifications because roasting is used. |
In short, while the thermal method offers environmental advantages, it requires careful process control on the color and viscosity side.
Peeling with Hot Water
The third method is dehulling, which is done with boiling water without the use of chemicals. According to Medronho et al., in this method, the beans are kept in boiling water for about an hour, then washed and the shell is easily broken and separated from the endosperm by hand; the result is a yellowish scale.
In Kıvrak's (2011) thesis, the gum obtained by the water method showed the lowest viscosity (260.9 mPa·s) with the highest ash (1.94 percent) and protein (6.65 percent) values. This result suggests that failure to adequately remove shell and germ residues from the gum may reduce the scale's thickening performance. Although the water method is practical for small-scale experiments and laboratory studies, it is not as common as acid and thermal methods on an industrial scale.
Germ Separation, Grinding and Screening
After the debarkation is completed, the endosperm-germ whole obtained continues to be processed. The definition in EU legislation is also included in the EFSA report: The germ is separated from the peeled kernels, then the endosperm is ground and sieved to obtain the natural (native) carob gum. The gum can be washed with ethanol or isopropanol to control the microbiological load; this product is referred to as "washed carob gum".
The importance of germ separation is directly related to the purity of the product. According to the EFSA report, commercial galactomannan preparations may still contain germ and shell residues rich in protein and fiber; this lowers the galactomannan content. The galactomannan content is therefore an important indicator of quality. The separated germ is not waste: According to the compilation by Martins-Loução et al., germ flour contains about 50 percent of a water-insoluble protein called "carubin", which shows gluten-like rheological properties.
When a purer product is desired, a "clarified" gum is produced. In the EFSA report, with reference to JECFA and Barak and Mudgil (2014), it is stated that the clarified gum is recovered by dissolving it in hot water and precipitating it with ethanol or isopropanol.
Parameters Determining the Quality of the Final Product
The EFSA report states that the carob gum consists of high molecular weight polysaccharides (galactomannans) with approximately 87–88 percent dry matter and mannose and galactose in a ratio of approximately 4:1, while the remaining 12–13 percent consists largely of protein and germ, shell and cell wall residues. In the definition in EU legislation, the molecular weight is given in the range of approximately 50,000–3,000,000. According to industry knowledge, the protein content in the additive is below 7 percent.
The peeling method directly affects these values. When the sources are read together, the main parameters that the producer should follow can be listed as follows:
- Galactomannan content and viscosity
- Protein, ash and acid insoluble ash values
- Foreign particle (shell and germ residue) ratio
- Color
- Microbiological burden and possible contaminants
The EFSA report also states that, according to industry knowledge, residual enzyme activity (amylase, galactosidase, mannosidase) may be present in the gum depending on the production method (sulfuric acid or heat treatment); this is largely assumed to be inactivated during pre-use solubilization and heating. A data for storage stability is also cited: In a 12-month test with six samples from different manufacturers, the drop in viscosity was below 5 percent at 20 °C and 10 percent at 40 °C.
More Sustainable Peeling Quests
Although the sulfuric acid method is effective, it has been criticized in terms of environmental and occupational safety. Medronho et al. state that the traditional sulfuric acid process raises economic and environmental concerns due to its corrosive and oxidizing nature, the possibility of toxic SOₓ gases formation, the necessity of treating wastewater and the risks to workers. They also note that the temperature and concentration values used on an industrial scale are often information specific to companies and are not included in the literature in detail.
The researchers tested methanesulfonic acid, which is less toxic and more easily biodegradable, as an alternative. Under optimized conditions, 24.5 g of beans were treated with a 50 mL mixture of 41 percent methanesulfonic acid and 59 percent sulfuric acid at 90 °C for 10 minutes, then washed with water. It was reported that the processed beans remained morphologically intact and their color characteristics were comparable to commercial samples. Such studies are on a laboratory scale; it is emphasized in the same study that issues such as cost analysis and solvent recovery should be investigated separately for their transfer to industry.
Frequently Asked Questions
From which part of the kernel is carob gum obtained?
It is obtained from the endosperm part of the seed between the shell and the germ.
Is there a difference between acid-peeled scale and roasting scale?
According to sources, the acid method may give a whiter and thickening feature strong gamut, while the roasting method gives a slightly darker product; on the other hand, it does not create acidic wastewater.
What happens to the separated shell and germ?
Germ is rich in protein and can be considered as a separate product. The shell is the subject of different by-product evaluation studies.
What is clarified carob gamut?
It is the purer form of gum, which is obtained by dissolving it in hot water and precipitating it with alcohol.
Carob Seed with Carob Türkiye
The starting point of a quality carob gamut is a clean, dry and correctly sorted kernel. The yield of the dehulling and separation stages is closely related to the cleanliness and homogeneity of the incoming raw material.
At Carob Türkiye, we supply carob fruit, crumbs, flour/powder, kernels, and extracts. Enterprises looking for raw materials for gamut production Carob Seed You can review our product page; where we explain the features of the core. What is Carob Seed? You can read our article. For your wholesale and export requests Contact Now You can contact us on our page.
Domestic resources
Kıvrak, N. E., "Determination of some physical and chemical properties of gum produced from carob seeds using different barking methods", Master's Thesis, Süleyman Demirel University Institute of Natural and Applied Sciences, 2011. I'm hungry.
SDU. edu. en/ handle/ 123456789/ 28782 Kıvrak, E., Aşkın, B., Küçüköner, E., "Comparison of some physicochemical properties of Locust bean seeds gum extracted by acid and water pretreatments", Food and Nutrition Sciences, 6(2), 278–286, 2015. doi.
org/ 10. 4236/ fns. 2015. 62028 Foreign sources
EFSA ANS Panel (Mortensen, A. et al.), "Re-evaluation of locust bean gum (E 410) as a food additive", EFSA Journal, 15(1), e04646, 2017. doi.
org/ 10. 2903/ j. efsa. 2017. 4646 Medronho, B., Boutoub, O., Duarte, H., Aliaño-González, M. J., Guerra, R., Brázio, A., Gonçalves, S., Romano, A., "On the Optimization of Carob Seed Peel Extraction Using Aqueous-Based Acidic Systems", Molecules, 30(7), 1397, 2025. doi.
org/ 10. 3390/ molecules30071397 Dakia, P., Blecker, C., Robert, C., Wathelet, B., Paquot, M., "Composition and physicochemical properties of locust bean gum extracted from whole seeds by acid or water dehulling pre-treatment", Food Hydrocolloids, 22(5), 807–818, 2008. doi.
org/ 10. 1016/ j. foodhyd. 2007. 03. 007 Barak, S., Mudgil, D., "Locust bean gum: processing, properties and food applications—a review", International Journal of Biological Macromolecules, 66, 74–80, 2014. doi.
org/ 10. 1016/ j. ijbiomac. 2014. 02. 017 Martins-Loução, M. A., Correia, P. J., Romano, A., "Carob: A Mediterranean Resource for the Future", Plants, 13(9), 1188, 2024. doi.
Scientific Resourcesorg/ 10. 3390/ plants13091188
