Currently, no less than 15% of the bananas harvested in the Canary Islands are discarded daily in packaging warehouses because they do not meet the requirements of marketing standards, which are based mainly on external characteristics. At certain times of the year, others retire to avoid falls in the market price. So much so that the problem of managing this organic waste has gained great importance in recent years.
15% of the bananas harvested in the Canary Islands are discarded daily in packaging warehouses.
María Gloria Lobo Rodrigo et al.
For this reason, our Nutrition and Bromatology team at the University of La Laguna, in close collaboration with the Canarian Institute of Agricultural Research (ICIA), proposed to address the valorization of biowaste produced in banana packaging plants in the Canary Islands through its transformation into flour.
Green banana flour is an interesting alternative to take advantage of non-marketable fruits, which are considered waste. Likewise, the skins not used in the process of obtaining flour could be suitable for being ensiled and incorporated into balanced goat diets.
45 kilos of bananas were peeled by hand for this research.
María Gloria Lobo Rodrigo et al.
Researchers get to work
In this jobwe optimize the artisanal process to obtain flour from the pulp of green Cavendish bananas (Musa acuminata, Colla), which came from four banana cooperatives located on the island of Tenerife.
The researchers, in the first phase, cut the bananas into slices and dried them in an air convection oven.
María Gloria Lobo Rodrigo et al.
45 kilos of bananas from each cooperative were peeled by hand with a knife and their pulps were cut crosswise and immersed in tap water at room temperature for 30 minutes. They were then removed from the water, air dried for several minutes on filter paper, placed on perforated trays, and dried at 55–60°C overnight in an air convection oven.
Finally, the dried slices were ground using an electric grinder. Approximately 7 kilos of flour were packaged in polyethylene bags and stored at room temperature.
Healthy properties
Next, the physicochemical and nutritional characteristics of these gluten-free flours were studied.
We found that they had high contents of starch, fiber and ash. Its consumption contributes to the daily intake of resistant starch, fiber, phenolic compounds and other bioactive compounds, of interest for the prevention of degenerative diseases.
In addition, its high potassium and magnesium content prevents hypertension and associated cardiovascular diseases.
The pastry chefs enter the scene
Regarding its use to prepare different foods, in a test carried out with chefs, we observed some advantages compared to other gluten-free flours for baked products. For example, they combined very well with the rest of the ingredients used in the recipes, such as eggs, chocolate, butter and sunflower oil.
Flour mill used in the research.
María Gloria Lobo Rodrigo et al.
However, they did not provide sufficient elasticity to the doughy masses, making it necessary to add other flours in a minimum proportion to improve the physicochemical and viscoelastic characteristics of some products, such as bread.
The sensory acceptance of the processed products was good, both for celiac patients or consumers who followed a gluten-free diet and for those who followed a diet that included gluten. All participants highlighted the good texture and sponginess of the tested food products compared to current gluten-free products, especially in the case of cakes or muffins.
The majority did not perceive a banana flavor. They detected a dark color in the products similar to that of a whole grain product, but they thought it was acceptable. Likewise, all of them assured that they would buy these products made with green plantain flour.
The proof of conservation
When these flours were stored at room temperature without light for ten months, it was observed that there was a slight increase in humidity and acidity, and a decrease in the content of starch, phenolic compounds and pH.
The color analyzed by colorimetry changed after five months, being slightly more acidic and yellowish than at the beginning. However, tasters of the sensory characteristics stated that these were still acceptable after ten months.
The participants valued the sponginess of the muffins made with banana flour, suitable for celiacs.
María Gloria Lobo Rodrigo et al., CC BY
Since the metabolism of bananas continues after harvest, we studied at what refrigeration temperature (6 and 12 °C) they should be stored before making the flour. It was also analyzed how long they could be stored without producing major changes in the physicochemical and organoleptic characteristics of the flours.
Thus, it was concluded that they could be stored at 6 °C for seven weeks. However, when the temperature rose to 12 °C, flours of acceptable quality could only be obtained in the first four weeks of storage.
In conclusion, it has been possible to adjust the process of obtaining banana flour, design an artisanal processing plant and carry out an assessment of its economic cost.
The flour obtained has undergone physical, chemical and sensory analysis to evaluate its composition, properties and evolution. It has been proven to be stable over time and the use of organic acids as antioxidants is not necessary. In addition, the baked goods made with it were well accepted by consumers.
We propose, therefore, a circular approach to take advantage of organic waste produced in abundance in banana cultivation and convert them into food ingredients of high nutritional value.
