Development of a Nutritional Drink Based on Kurugua Wholemeal Flour as a Source of Minerals and Amino Acids ^†

Abstract

Adequate intake of mineral nutrients and amino acids is essential for nutrition in the Western diet, where deficiencies of minerals such as Zn, Fe, and good quality proteins are highly prevalent in vulnerable populations in Latin America and the Caribbean (LAC). The aim of the present study was to evaluate the mineral and amino acid content of Kurugua (KWF) wholemeal flour and a derived product (9% K w/v, 0.8% chia oil (w/v), and 1% sweetener v/v). Proteins were analyzed by Microkjeldhal, minerals Na, K, P, Ca, Mg, Zn, Cu, Mn, and Fe by AOAC, and amino acid profile by HPLC-DAD methods. KWF presented a high content of Mg and Zn (207.63 ± 5.27 and 15.76 ± 0.04 mg/100 g, respectively). A KWF-based drink provides 5.05 mg Zn/100 g, equivalent to 46% of the recommended daily intake (RDI) in a 200 mL serving of the beverage. Amino acids (glutamic acid + glutamine) and (aspartic acid + asparagine) were the most abundant in KWF (112.2 and 245 mg of aa/g protein, respectively), with 18.0% of total protein. A serving of KWF-based drink contains about 3.02 g of protein and the essential amino acids Hys, Val, Met, Phe, Ile, Leu, and Lys (31.6, 213, 198, 89.3, 186, 3.7, and 194.3 mg AA/200 mL, respectively). The ready-to-drink Kurugua drink takes full advantage of the wholemeal flour of an indigenous fruit such as Kurugua, providing a source of zinc and an adequate amount of essential amino acids and expanding the supply of healthy products within the framework of food safety.

1. Introduction

The accelerated destruction of natural habitats due to land use changes, particularly for agriculture and urbanization, leads to the loss of genetic diversity in ecosystems and the displacement of traditional and ancestral crops such as chia and Kurugua [1]. These crops, though undervalued, have the potential to enhance dietary diversity and people’s quality of life. However, their nutritional properties and value chains are not well understood. This scenario underscores the need to recognize the nutritional potential of these crops to improve food security [2].

Adequate intake of mineral nutrients and amino acids is essential for nutrition in the Western diet, where deficiencies of minerals such as Zn, Fe, and good quality proteins are highly prevalent in vulnerable populations in Latin America and the Caribbean (LAC) [3]. The objective of the present study was to evaluate the mineral and amino acid content of Kurugua (KWF) wholemeal flour and a derived product. This assessment aims to determine its nutritional value and potentially propose an alternative nutritious beverage.

2. Materials and Methods

2.1. Sample

The whole flour of Kurugua (KWF) was obtained from nine whole fruits of Sicana odorifera, as described previously [4]. From this flour, a derived product was created, which was a plant-based beverage with a formulation of 9% KWF w/v, 0.8% chia oil (w/v), and 1% sweetener v/v in water. The beverage mixture was prepared using a colloid mill.

2.2. Minerals

For mineral analysis such as Na, K, Ca, Mg, Fe, Cu, Zn, and Mn, the atomic absorption AOAC method 975.03 was used by triplicate [5]. An AA 6300 Shimadzu (Kyoto, Japan) spectrophotometer was employed. The phosphorus content was determined using the colorimetric AOAC method 935.45. For each mineral, a calibration curve was made using standard solutions (Merck, Darmstadt, Alemania).

2.3. Proteins and Amino Acids Profile

The protein analysis was determined by AOAC Method 920.152 [5], employing the conversion factor of 6.25 from N2 to proteins. For amino acid (AA) analysis, defatted samples (500 mg) were hydrolysed following the standard AOCS procedure [6]. Hydrolysed samples were filtered using a 0.45 μm membrane filter and then submitted to pre-column derivatization as described previously [7]. Amino acid derivatives were analyzed by reversed-phase HPLC (PerkinElmer, Shelton, CT, USA) under conditions used previously [7]. Identification was carried out by means of authentic AA standards (Sigma-Aldrich, St. Louis, MO, USA). Quantification was performed by the external standard method. The linearity of the response was verified by fitting the line results of each one of the AA individuals (five standard solutions with known concentrations), covering the concentration range from 10 to 100 ppm. Calibration curves from the tested AA standards showed linearity regression coefficients (R2) ranging between 0.96 and 0.99.

2.4. Statistical Analyses

The data were recorded in an Excel spreadsheet and analyzed in the statistical program GraphPad prism 5.0 (GraphPad Software Inc., CA, USA). Student’s t (p ≤ 0.05) was used to determine the significant differences.

3. Results

Table 1. Minerals in Whole Kurugua Flour (KWF) and Its Derived Product.

Mineral	Kurugua Wholemeal Flour (mg/100 g)	Derived Product Dry Basis (mg/100 g)	Derived Product in 200 mL (mg/200 mL)	% of RDI per 200 mL
Na	13.09 ± 0.30 a	41.49 ± 13.96 b	8.59	0.4
K	1734 ±124 a	2638 ± 78.6 b	441.22
Fe	6.85 ± 0.32 a	6.65 ± 0.41 a	1.11	6.2
Ca	58.99 ± 0.91 a	122.77 ± 8.06 b	20.52	1.6
Mg	207.63 ± 5.27 a	222.94 ± 17.30 a	37.27	8.9
Cu	2.68 ± 0.15 a	1.73 ± 0.05 b	3.56	395
Zn	15.76 ± 0.04 a	30.20 ± 2.28 b	5.05	46
Mn	1.11 ± 0.06 a	0.46 ± 0.06 b	0.08	3.4
P	559.24 ± 11.46 a	532.41 ± 12.82 a	43.71	3.5

Values are expressed as mean ± standard deviation (n = 3). Different lowercase letters in each row indicate a significant difference between the means, Student’s t-test (p ≤ 0.05).

displays the mineral results for both KWF and the derived product, as well as in a 200 mL portion of the beverage. Notably, Mg and Zn stand out in both samples, with Mg and Zn values of 207.63 and 15.76 mg/100 g in KWF and 222.94 and 30.20 mg/100 g in the product on a dry basis; contributing 37.27 and 5.05 mg of the respective minerals in a 200 mL serving of the beverage. The protein content in KWF was 18.00 ± 0.29 g/100 g, in the beverage on a dry basis, there was 16.23 ± 0.18 g/100 g, and in a 200 mL portion of the beverage, there was 2.71 g of protein.

Table 2. Amino Acid Profile in Whole Kurugua Flour (KWF) and Its Derived Product.

Amino Acids	Kurugua Wholemeal Flour (mg AA/g Protein)	Derived Product on a Dry Basis (mg AA/g Protein)	Derived Product in 200 mL (mg AA/Portion Serving)	Reference Composition (mg AA/g Protein) a
Ac. Asp+ Asn	112	112	304
Ac. Glu + Gln	248	248	671
Ser	21.1	21.9	57.6
Hys	10.6	10.5	29.2	15
Gly	13.3	13.5	36.7
Thr	35.0	35.1	95.2
Pro	13.3	13.6	36.7
Arg	20.6	20.3	55.9
Ala	108	108	292
Val	71.1	70.9	192	39
Met	65.6	65.6	178	22 *
Phe + Tyr	37.7	37.6	103	38 **
Ile	61.7	61.6	167	30
Leu	1.1	1.2	3.3	59
Lys	64.4	64.4	174	45

^a Reference: Adapted with permission from Joint WHO/FAO/UNU Expert Consultation FAO/WHO/UNU [2007] [8]. * Corresponds to the protein composition reference value of Met + Cys (not determined) and ** to that of Phe + tyrosine.

contains the results of the amino acid profile. The derived product contained 16.23 g/100 g protein on a dry basis and 1.51 g/200 mL serving in the reconstituted drink, which would provide eight essential amino acids with the exception of tryptophan.

4. Discussion

Significant differences in mineral content were found between Kurugua whole fruit flour and the plant-based beverage, except for Fe, Mg, and P. This is probably due to the contribution of these minerals from the Kurugua flour, which does not vary its content in the derived drink. Particularly noteworthy is the high content of Zn in both samples, contributing up to 46% of the Recommended Daily Intake (RDI) for Zn. Previous reports indicated Zn values of 42 mg/100 g and 2 mg/100 g in Kurugua pulp and seeds, respectively [9]. The values obtained in this study fall within this range.

The plant-based proteins in the samples were analyzed for their amino acid profiles, to evaluate their potential contribution as quality proteins. Based on the results and in accordance with the nutritional claims, a 200 mL serving of the vegetable drink would provide seven essential amino acids (histidine, threonine, arginine, valine, methionine, phenylalanine, isoleucine, leucine, and lysine), exceeding the amino acid levels of the reference food for good quality proteins [8]. However, for a food to be considered a source of protein, it must provide at least 6 g of protein per serving. This indicates the need to continue adjusting the formulation based on the functional properties of the product to obtain a protein drink; however, the profile of essential amino acids is interesting for this nutritional purpose. Pérez Venegas et al. [10] examined the amino acid profiles of commonly used plant-based beverage raw materials and reported lower amino acid values compared to those found in this study.

5. Conclusions

In this work, the mineral, protein, and amino acid content of Kurugua whole fruit flour and a derived plant-based beverage were analyzed. The beverage stands out for its zinc content and amino acid profile, positioning it as a valuable option for enriching the diet with essential nutrients. The utilization of the entire fruit, including the typically inedible skin, contributes nutrients to these products.