Mango and pineapple snacks: dehydration processes to take advantage of fruit by-products

Juan José Villada Alvarado y Elisabet Lugo Salazar, students from the Food Engineering Program, Tuluá. Credit: students courtesy.

In the food industry, there are products that, due to their characteristics, are not used 100%. Known as by-products, they end up being discarded, which has consequences for the environment. A study proposes a method for the use of these products, using mango and pineapple as a base, with the purpose of converting them into raw material for the manufacture of a snack. Its bet could contribute to new entrepreneurial processes in the region, while helping to take full advantage of what is planted in the region. 

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All the fruit counts: the commitment to full utilization of produce 

The use given to products from agricultural areas by food industries often involves the specific use of some of their components, leaving aside other ones, which are known as by-products. Studies have shown, in the case of fruits, the high nutritional value of these by-products, given the degree of nutrients found in them.  

Seeking to offer the market a product which would take advantage of these nutrients, both at a nutritional and sensory level, students Juan José Villada Alvarado and Elisabet Lugo Salazar, from the Food Engineering Program of the Universidad del Valle, Tuluá, under the direction of researcher and professor Anna María Polanía Rivera, from the same academic unit, undertook the task of evaluating the behavior of the components in two fruits, pineapple and Tommy mango, with a view to creating a snack, based on a dehydration process that would allow preserving their properties and taking advantage of industry waste in a product that could serve as a first step towards the creation of enterprises that would boost the economy of small producers in the region. 

Research: refractance window dehydration process 

The research conducted by the students Villada and Lugo began by determining the fruit matrices that would be used for the analysis. For the main fruit, pineapple was chosen, in its "honey gold" variety, accompanied by the secondary fruit, mango, which in this case began as a variant originating from the Atlantic Coast; however, due to harvesting times, it was necessary to replace it with the Tommy  Aktins , which, despite not having the same concentration in its sweetness, is available during any season of the year.  

Once the products were chosen, samples were processed and prepared to analyze the nutrients contained in the peel of the mangoes and pineapples, in order to verify that the fruit complied with certain requirements. Some of these requirements were the degree of ripeness, brix degrees (measure used to determine the sugar content in the fruit), titratable acidity, existence of fungus or damage inside the fruit. This was accompanied by a disinfection procedure to ensure compliance with quality standards, for which students from the Food Engineering program used sodium hypochlorite (100 ppm) for 8 minutes. Subsequently, the fruit was pulped, separating the peel, pulp and seed from the fruit.  

The drying method of the products was carried out by means of a process called window drying of refractance. This process seeks to eliminate the water contained in the fruit by using hot water, which, as in any body at high temperature, emits infrared radiation. This radiation, as it passes through the plastic sheet arranged in the system, contributes, together with the heat transfer, to accelerate the dehydration process of the food: the infrared radiation penetrates the food, causing the water molecules to vibrate and, as their energy increases, they pass from a liquid to a gaseous state, promoting the drying of the product. Since mango and pineapple have water concentrations close to 85%, this process was chosen to accelerate the dehydration process. "This refraction process allows the molecules of both the fruit and the water to vibrate in the same way, and the vibration process generates faster evaporation, which makes the drying process a little shorter," explains Juan José Villada. 

Treatment of products through the refractive window dehydration process. Credit: courtesy of students.

Bearing in mind that the objective of their research was the production of a snack, the students also evaluated the sensory characteristics produced by this mixture, to arrive at an optimal result: "When we decided on the fruits, we also decided to make a mixture to see how it would taste. People liked it. However, we noticed that the pineapple flavor was lost a lot, because the mango flavor was very strong. So, based on that, we also determined the mix design and left the pineapple at a specific amount so that it could still be felt," says Elisabet Lugo Salazar. 

In this sense, the qualities of the snack to be produced had to ensure high levels of nutritional quality, which made it necessary to evaluate additional characteristics for the selected fruits. The aim was to determine the added value that these foods could provide to the final consumer. Some of the values were ascorbic acid, antioxidant compounds, phenolic compounds, and the shelf life of the product to be developed. It was also necessary to take into account the texture of the snack.  

"Based on that, multiple analyses were made. The first one was of vitamin C, which was done through a titration with the Indophenol Method, where we sought to look at the turning (the color change that is generated in a liquid solution). As our product was not a solution but a solid, what we did was a grinding process, where the samples are converted into powder, with the aim of dissolving them better in water", explains Juan José Villada Alvarado. 

A similar process was used for the measurement of phenolic compounds using a spectrophotometer, which by means of a light measurement establishes the amount of phenolic compounds in the samples. This was also the case for the measurement of antioxidant capacity and for the actual percentage of water contained in the samples, the results of which were favorable: "it is generally recommended that it be less than 0.6%. We obtained one equal to 0.4%", says the student Villada.  

The lower the percentage, the less chance there is for microorganisms to grow inside the samples, thus extending their shelf life for a longer period of time.    

Result after the dehydration process by refraction window. Credit: courtesy of students.

Experimental results 

The objective of the research conducted by students Juan José Villada and Elisabet Lugo Salazar was to determine if, by varying the components of the fruits used in aspects such as percentage and volume, significant differences were obtained at a nutritional level for the aforementioned parameters. From this, with the help of a results optimization method called Minitab (whose purpose was to help them establish an optimal mix to follow for the creation of the snack), they sought to know if the product complied with the required quality standards, and if it was to the taste of potential consumers.   

The result was positive. "By varying the components, the nutritional capacity of the product was increased or decreased, and it was also possible to demonstrate that pineapple and mango peels increased this nutritional value. Even the optimized value showed higher percentages in both pineapple and mango peel and mango pulp, because even though they are not very attractive sensorially, they do have bioactive and nutritional components of very high value, and that are normally being lost," explains the student Villada. 

The final product was presented to a representative group, and more than 80% gave their approval. "We took into account an age range that went up to 67 years old, and that they were regulars at the Universidad del Valle, because it was easier for them to try it in the same place," says student Elisabet Lugo. 

What's next 

Having developed the snack, as a result of their research, the students hope that this bet can be scaled, through companies interested in the development of the prototype at a commercial level.  

Similarly, this development also aims to open up a market for product derivatives, so that they can be put to similar uses. "For example, companies that manufacture juices. They generally use the pulp and the peels are discarded and treated as waste. These go to certain places where, when degraded by bacteria, greenhouse gases are produced, which affect the environment," says student Juan José Villada. 

For both students, this research seeks to have an impact on the way in which the use of natural resources is conceived. "We hope that, in some way or another, this idea will lay a foundation, in which certain components of fruits and vegetables, such as the peels, the core and even the stem, which are not usually consumed, can begin to maximize what nature is offering us. We contribute a small grain of sand. Our goal is to expand what we already have to feed and prevent malnutrition in different people," concludes the student Villada Alvarado.

If interested in being in touch with the students or any further information about the investigation, please write the Faculty of Engineering Communications Office: comunicaingenieria@correounivalle.edu.co.