Dried Gapal, a staple in Burkina Faso, packs energy and essential minerals, but new research shows its phytic acid levels could be holding back key nutrients like zinc.
Study: Nutritional composition of dried Gapal, a highly nutritious food based on fermented cereal and milk. Image Credit: Vineke
Researchers at the Research Institute for Applied and Technological Sciences, Burkina Faso, recently analyzed the nutritional composition of dried Gapal, a fermented milk-cereal mixture widely consumed in Burkina Faso. The findings are published in the journal Discover Food.
Background
Gapal is a traditional food among the Fulani people in Burkina Faso. It is a mixture of fermented milk and cereals, and is available in dried or yogurt-like form. Millet paste and milk are primarily used for the production of Gapal, with the addition of baobab pulp, spices, and sugar.
Pearl millet, commonly used for Gapal production, contains high amounts of minerals, including calcium, iron, phosphorus, zinc, and potassium. The lactic acid bacteria-based fermentation process enriches gapal nutritionally and improves its flavor, texture, digestibility, and shelf life.
However, some millet components, such as phytates, can reduce the bioavailability of micronutrients by reducing their biodegradability. Food processing methods, including germination, fermentation, and hulling, can remove these components.
Lactic acid bacteria-based fermentation is a highly effective method for degrading phytic acid. During the combined fermentation of milk and millet dough, lactose is converted into lactic acid, which produces volatile molecules, which in turn increase the taste and nutritional value of Gapal.
Despite its high nutritional quality and increasing usage in major cities in Burkina Faso, there is a lack of scientific evidence about the proximate composition and nutritional properties of this indigenous food.
For the first time, researchers at the Research Institute for Applied and Technological Sciences comprehensively analyzed the nutritional composition of Gapal to develop a database for future research.
They purchased Gapal samples from five major cities in Burkina Faso. They assessed the protein, lipid, carbohydrate, free amino acid, mineral, and phytic acid content of these samples using standard methods.
Study findings
The researchers found considerable variations in nutritional composition between Gapal samples collected from five major cities. There was notable variability in nutrient content not only between cities but also among different producers within the same city, reflecting the lack of process standardization.
The analysis revealed that Gapal contains 0.76 to 5.5% of lipids, 5.4 to 9.6% of protein, 84 to 92% of carbohydrates, and 1.1 to 2.1% of ash. Among minerals, the samples contained potassium, calcium, magnesium, zinc, iron, copper, and manganese. The exact measured average values were: potassium (214.18 mg/100 g), calcium (66.74 mg/100 g), magnesium (34.04 mg/100 g), zinc (0.80 mg/100 g), iron (8.14 mg/100 g), copper (0.44 mg/100 g), and manganese (0.85 mg/100 g). These levels varied considerably across the different samples.
Only proline and lysine were consistently detected in all Gapal samples; other free amino acids, including some essential amino acids, were found sporadically and at low levels. However, dried Gapal exhibited a notable amount of phytic acid (365.92 milligrams per 100 grams of dried Gapal).
The tested samples exhibited significant variations in moisture content, pH, and acidity. The moisture content of these samples was higher than that reported for other Gapal-like food products, such as kishk and tarhana, which might impact their storage.
The study also determined the molar ratios of phytate to key minerals, such as zinc, iron, and calcium, in order to estimate bioavailability. The phytate: zinc (Phy :Zn) molar ratio in dried Gapal samples often exceeded 15, a threshold above which zinc bioavailability is considered significantly reduced by the World Health Organization. In contrast, the phytate: iron and phytate: calcium ratios were lower, suggesting that iron and calcium in dried Gapal might be more bioavailable than zinc.
Study significance
The study provides a comprehensive overview of the nutritional composition of the traditional African food Gapal.
According to the study findings, Gapal contains high levels of carbohydrates, which can be attributed to its millet content. The pH and acidity of dried Gapal are similar to those of similar food products such as kishk and tarhana, although Gapal has a slightly lower lactic acid content, which may be due to differences in fermentation and drying time.
The production process of kishk and tarhana includes 5-day fermentation, followed by 3-day drying. In contrast, Gapal production consists of a combined drying and fermentation process lasting 3 to 5 days. A slightly lower lactic acid content observed in dried Gapal might also be attributed to its shorter fermentation and drying duration and the smaller quantity of milk added during production.
Dried Gapal has been detected to have a lower protein and lipid level compared to similar millet-based foods. Proteins in Gapal come from both milk and millet, and the observed reduction in protein content might be due to production-related loss, which can be improved by increasing the fermentation process.
Lipids in dried Gapal mainly come from milk, which is used as fresh milk, fermented milk, or yoghurt during production. Yogurt is obtained from reconstituted milk powder, which is often defatted or fattened with vegetable fats. This variation in the fat content of milk or yogurt, depending on the product, might be responsible for the lower lipid content in Gapal.
Only proline and lysine, free amino acids, have been detected in all Gapal samples; other essential amino acids such as valine, methionine, isoleucine, leucine, and phenylalanine were detected only sporadically and at low levels.
A low milk content in dried Gapal (approximately 20%) might limit the availability of free amino acids. However, as researchers mentioned, the digestion of Gapal could facilitate the release of other, more abundant amino acids.
High levels of vital minerals have been detected in tested samples. However, the bioavailability of these minerals could be compromised by the high phytic acid content of dried Gapal. Millet is the primary source of phytic acid in Gapal, and existing evidence indicates that the phytic acid content of millet can be reduced through hulling (a process of removing the outer husk of millet) and fermentation processes.
The study highlights that, despite the interesting mineral content of dried Gapal, the presence of phytates, particularly in relation to zinc, may limit the actual nutritional benefit for consumers, unless further processing improvements are made.
The authors also note several limitations of their study. They were not able to determine the vitamin content or the total amino acid content of Gapal. Additionally, the study was limited in its geographic scope and sample size, suggesting that further research should include more towns and a greater number of samples. The authors recommend that future studies focus on standardizing manufacturing processes and assessing the sensory and sanitary qualities of Gapal for a more complete nutritional evaluation.
Overall, the study provides valuable information for enhancing the Burkina Faso food composition database.