Characterization of Quinoa Fibre-Rich Fractions Isolated via Wet-Milling and Their Application in Food ^†

Abstract

Dietary fibre intake has beneficial effects on immunonutritional health and prevents the development of chronic non-communicable diseases such as obesity and diabetes, cardiovascular disease, and cancer. Currently, dietary fibre consumption worldwide is below the WHO recommended daily intake of 25 g. An excellent source of dietary fibre is the fibre-rich fractions of quinoa, which have a high technological potential, nutritional value, and biological activity. This fraction can be isolated via wet-milling, which offers a higher yield and recovery of the main chemical components of cereals/pseudocereals with a higher purity than those obtained via dry-milling. The objective of this work was the isolation of fibre-rich fractions of Royal Bolivian quinoa (white, red, and black) obtained via wet-milling and their characterization as technofunctional ingredients in the formulation of cereal-based food products. The extraction yield of the fibre fraction and its proximal chemical composition were determined, in addition to phytic acid content; minerals such as calcium, iron, and zinc; and technofunctional properties (particle size distribution, water and oil holding capacity, and swelling capacity). All fibre fractions isolated via wet-milling could be used as food ingredients. In particular, the fibre-rich fraction of black quinoa contains the highest amount of insoluble fibre. However, from a technological point of view, red quinoa fibre could be the most suitable for inclusion in the formulation of food matrices due to its high water and oil retention capacity, as well as its swelling capacity. The incorporation of a low proportion of quinoa dietary fibre (5–10%) allows increasing the nutritional profile of cereal-based food products.

1. Introduction

The consumption of dietary fibre has shown notable health benefits in terms of immunonutritional well-being and in the prevention of chronic conditions including obesity, type 2 diabetes, cardiovascular ailments, and cancer [1,2]. However, the current global intake of dietary fibre falls below the recommended daily amount of 25 g set by the WHO/FAO [3].

A remarkable reservoir of dietary fibre resides within the fibre-rich fractions of quinoa, which not only possesses high technological potential but also boasts considerable nutritional value and biological activity. These fibre-rich fractions can be efficiently extracted through the wet-milling process of quinoa. This method yields greater quantities and enhanced recovery of vital chemical components found in cereals and pseudocereals (as depicted in Figure 1), while maintaining a higher level of purity compared to dry-milling techniques.

The primary aim of our study was to isolate fibre-rich fractions from different varieties of Bolivian quinoa—white, red, and black—utilizing wet-milling techniques. A comprehensive characterization was subsequently carried out, evaluating their potential as technofunctional ingredients in the development of cereal-based food products, including applications such as fresh pasta.

2. Materials and Methods

2.1. Materials

Royal quinoa grains (white, red, and black) produced in Bolivia were obtained from Organic Quinoa Real^® (Figure 2).

2.2. Methods

Wet-Milling

Quinoa seeds were steeped in a sodium bisulfite solution adjusted with lactic acid at pH 5.0, in a Biostat^® B plus fermenter from Sartorius BBI Systems. Wet-milling was performed according to the methodology recommended by Ballester-Sánchez et al. [5], with some modifications (Figure 3).

2.3. Chemical Composition

Moisture was determined via gravimetry, starch via the enzymatic/spectrophotometric micromethod [6], protein via combustion Dumas (conversion factor N 5.7) [7], lipids via Randall [8], ash via ignition [9,10], and soluble dietary fibre (SDF) and insoluble dietary fibre (IDF) via the enzymatic/gravimetric method [11,12]. Minerals such as calcium, iron, and zinc and total phosphorous were determined via atomic absorption spectrophotometry [13].

2.4. Fresh Pasta Production

Laboratory-scale tagliatelle were made using the Nina electric pasta machine from Springlane^® (Düsseldorf, Germany). All formulations included wheat flour mixed with water and egg yolk. However, four different formulations were prepared: a control made with 100% wheat flour, and three types in which 6% of the wheat flour was replaced by the fibre fractions isolated via wet-milling of white, red, and black quinoa.

3. Results

Extraction yield of the quinoa fibre fraction obtained via wet-milling was between 14 and 21% in dry matter. The proximate composition (protein, lipid, starch, ash, and total dietary fibre (TDF) content) is shown in Figure 4. The fibre fractions show significant differences (p < 0.05) with respect to the TDF, with black quinoa having the highest proportion, followed by red quinoa. However, no significant differences were observed in the percentages of SDF between the different fractions (Figure 5). In terms of their technofunctional properties, the red quinoa fibre presented between 40 and 60% more water and oil retention capacity, as well as more swelling power than the rest of the fibres studied.

In general, the quinoa fibre showed high concentrations of minerals Ca, Fe, Zn, and P (Figure 6). No significant differences were found in the phosphorus of the different dietary fibre fractions of the differently coloured quinoas. However, the high phosphorous could indicate a high phytate content, meaning mineral absorption may be compromised due to the formation of insoluble compounds with phytates.

The intake of 100 g of pasta fortified with a 5–10% fraction of dietary fibre sourced from white, red, or black quinoa fibre can contribute approximately 35% of an adult’s daily fibre requirement (Figure 7 and Figure 8).

4. Conclusions

All fibre fractions obtained through the wet-milling process have the potential to serve as valuable food ingredients. Notably, the fibre-rich fraction extracted from black quinoa boasts the highest content of insoluble fibre. However, considering technological aspects, the fibre derived from red quinoa emerges as an optimal candidate for incorporation into food formulations. This is attributed to its capacity for water and oil retention, alongside its ability to swell.

Incorporating a modest proportion of dietary fibre sourced from quinoa can significantly enhance the nutritional value of cereal-based food products.