Sweet potato (Ipomoea batatas
L. Lamarck) is the main tuber root cultivated in Brazil due to high tolerance to drought and offers a wide adaptation to the climate and land [1
]. According to the Food and Agriculture Organization (FAO) statistics, the world’s production of sweet potatoes in 2016 was concentrated in Asia and Africa [2
]. It is considered one of the main sources of food, animal feed and raw material for the industry. In the development of food, sweet potato is widely used in the extraction of starch but is little explored in beverage preparations [3
This tuberous root is rich in starch and other nutrients [4
]. Sweet potato has a composition of high value to the human diet, which is important in meeting human nutritional needs such as carbohydrates, fibers, potassium, vitamins A and C and high-quality protein. Sweet potato is consumed in different ways; it is boiled, baked, fried or mashed. It can also be used for the preparation of breads and starch in the industry [5
Some studies have been carried out to further the development of carbohydrate solutions for athletes, with a view to improving performance during long-term physical activities besides an increase in glycemic levels [7
]. One of the energetic supplements used in this field is maltodextrin, which is a saccharide-based polymer containing D-glucose units linked by glycoside bonds, which is an easily absorbed carbohydrate that is obtained from the partial hydrolysis of starch. It is beneficial to athletes, for example, when running, playing soccer or tennis, as it provides energy during training [11
]. In conformity with the benefits mentioned above, energy drinks are also marketed as an option for people who are not athletes but are looking for a way to decrease tiredness and boost energy, enabling weight loss and enhancing mental alertness [13
Sports drinks can be ingested before, during and after exercise. When ingested before exercise, they can prevent or even delay homeostatic disorders that can accompany physical activities [14
]. In addition, pre-exercise consumption can improve the circulation of blood glucose concentrations through the supply of carbohydrates. When sports drinks are consumed during exercise, the carbohydrates can improve performance, as demonstrated by Carter et al. [15
The consumption of carbohydrate and protein supplements is recommended by the Brazilian Society of Sports Medicine, aiming to favor a maximum resynthesis of muscular and hepatic glycogen [16
]. Ballistreri et al. [17
] performed a study to establish the drinking pattern of energy drinks among physical education students from an institution in Argentina. Most of these drinks contain ingredients such as taurine, caffeine and vitamins. Considering that the potential risks of energy drink consumption can be increased when consuming them concomitantly with, for example, alcohol, the results denote the importance of reducing consumption among young people and also reinforce the importance of adequate eating to achieve good performance in any physical activity.
It is due to these concerns that the shake beverage is presented as an alternative product. It is easy-to-prepare and also aids in gym training by providing energy. It is also a natural food source and a natural product, thus lowering the chances of causing complications in consumers. To further increase the applicability of sweet potato as a major source of carbohydrates, in this study, we tested sweet potato flour as a partial replacement for maltodextrin in a shake beverage.
2.1. Sweet Potato and Sweet Potato Flour
Sweet potatoes (Ipomoea batatas L. Lamarck) were kindly provided by the Department of Agronomy, State University of the Center-West (Parana, Brazil)-CEDETEG Campus (Parana, Brazil).
The tubers were selected, washed, weighted and grated. Thereafter, the samples were dried in a drying oven at 65 °C for 24 h. After drying, the samples were crushed and processed to obtain sweet potato flour [18
2.2. Preparation of Shake Beverage
The shake beverage was elaborated and one batch was made from a formulation that uses maltodextrin as a basis for the determination of the percentages of the other ingredients in the shake (Table 1
). The original shake beverage formulation was modified by the addition of sweet potato flour at different concentrations according to a 22
factorial design with three central points, thus generating 7 formulations (Table 1
The other ingredients used in the shake beverage formulation were, as fixed parts, xanthan gum Aminna® (2.50%), refined sugar União® (35.00%), grape flavoring hydroalcoholic artificial aroma Duas Rodas® (0.05%), purple artificial liquid dye Duas Rodas® (0.10%), whole milk integral powder Sancor® (21.00%); and as variable parts: sweet potato flour (10.00 and 20.00%) and grape flavor commercial maltodextrin Body Action® (5.00 and 25.00%). The ingredients in maltodextrin are maltodextrin, citric acid (acidulant), tricalcium phosphate (acidity regulator), caramel dye, sucralose (sweetener), bordeaux dye and indigotine blue dye.
2.3. Proximate Composition of Sweet Potato Flour
The protein (Kjedahl, N × 6.25 for flour), ash (gravimetric), lipid and fiber brut contents of sweet potato flour were determined using AOAC 2005 methods [19
]. The total carbohydrate content was calculated as the difference between the initial mass of the sample (100 g) and the total mass of the proteins, lipids, fixed mineral residues and fibers.
2.4. Physicochemical Analysis
All analyses were performed for sweet potato flour and the shake beverage. The moisture content analysis was performed through the adaptation of the method in [20
], by drying the samples in a conventional oven at 105 °C for 8 h. The pH was evaluated by direct measurements through a potentiometer (bench thermometer for aqueous solutions Mpa-210, Tecnopon) of the samples prepared in a solution at a 1:10 (w/v) ratio with distilled water before using the potentiometer.
The colorimetric analysis [21
] was performed only for the shake drink, using CIELAB color system L* a* b* and colorimeter (Konic Minolta CR-400) with illuminant C and a 10° angle that was previously calibrated. The parameters analyzed in triplicate were: L* (lightness) where L* = 0 means black and L* = 100 means white, for a* and b* (set as chromaticity) where +a* means red and −a* means green; −b* means blue and +b* means yellow [22
The particle size of the flour was determined with a system consisting of five sieves. The mesh opening diameters of the sieves were: 10 (nominal aperture of 2.00 mm), 12 (nominal aperture of 1.68 mm), 14 (nominal aperture of 1.41 mm), 35 (nominal aperture of 0.500 mm) and 48 (nominal aperture of 0.300 mm).
2.5. Sensory Evaluation
This part of the study was approved by the Ethics Committee in Research of the State University of the Center-West (Parana, Brazil) under the project identification code no. 81426725. The sensory analysis was performed by 50 panelists, comprising students from the CEDETEG Campus of the State University of the Center-West. Two methods were chosen for the sensory evaluation of the formulations. The acceptance test [23
] was conducted to assess whether the panelists liked the appearance, flavor, color and texture of the shake beverage, applying the 9-point hedonic scale categorized as 9 “like extremely”; 8 “liked”; 7 “liked moderately”; 6 “liked slightly”; 5 “neither liked nor disliked”; 4 “dislike somewhat”; 3 “dislike moderately”; 2 “dislike very much”; and 1 “dislike extremely” to express their overall impression. The formulations that obtained higher acceptance levels were submitted to physicochemical analysis. The purchase intent test was measured using a five-point structured scale (from 1 = definitely would not buy to 5 = definitely would buy) adapted from [24
The samples were prepared with 10 g of shake powder added to 100 mL of cold water at 6 °C. Each panelist received seven samples of approximately 50 mL of the shake beverage presented in plastic cups which were previously coded with three-digit random numbers. The panelists evaluated the samples from left to right and cleansed their palate with water between samples.
2.6. Statistical Analysis
Results are expressed as mean and standard error of the mean. Differences between formulations were analyzed using ANOVA, followed by the Tukey test or Student test, with p
< 0.05 considered significant. All analyses were performed using the Assistat Software version 7.7 beta (DEAG-CTRN-UFCG, Pernambuco, Brazil) [26
According to the results of the sensory analysis, shakes containing 10% sweet potato flour and those with 25% maltodextrin obtained higher scores from the panelists, a greater global acceptance and greater purchase intention. For the appearance, aroma, flavor, texture and overall impression, the values obtained were higher than 5, which denotes “good acceptance”.
Sweet potato flour can be used as a raw material in the development of the shake. No statistical differences were found between the formulations in most analyses. For this reason, we consider maltodextrin as a suitable replacement for sweet potato flour, which, in addition to reducing the final value of the product, is also a low-cost raw material. The replacement of maltodextrin for sweet potato flour is a credible alternative for shakes. According to the sensory evaluation, the replacement had good acceptance values from the panelists, showing that the production of this shake is feasible considering the taste and also a good alternative drink for people who practice physical activities.