Abstract
The research interest in underutilised but nutritionally and phytochemically rich whole-grains is vital to promoting diet diversity, nutrition transition and food security. Quinoa is recognised as a superfood of the twenty-first century due to its excellent nutritional and functional food values and a broader range of agronomic adaptability. On the other hand, cowpea is a climate-smart legume that is abundantly produced in Africa (approximately 97% share of the world production) and a good source of complementary phytochemical and functional constituents with quinoa. However, most cowpea produce is not utilised for human consumption in sub-Saharan Africa. At the same time, the continuous prevalence of adverse epidemiological situations around the globe, especially protein–energy undernutrition and related dietary non communicable diseases in Africa, requires practicable interventions. While consumers’ preferences for refined products exist, increased consumption of whole-grain processed foods has been strongly linked to providing functional needs in addition to basic nutrients and reducing the risk of dietary-related diseases. Therefore, holistic approaches to address the highlighted problems can include concerted efforts to systematically re-innovate underutilised edibles in their whole-grain forms for balanced nutrition, wellness and food sustainability.
Minimal processing techniques like fermentation and malting are simple and inexpensive treatments reported to improve food values in nutraceutical potentials and technological characteristics. Temperature and time are critical process conditions determining the desirable quality changes induced by these processes. Short-term temperature and time have been demonstrated to improve the quality of resultant products. In this regard, an investigation was made to use short-term solid-state fermentation and germination (a process step in malting) to ease processability and improve the quality characteristics of whole-grain cowpea and quinoa flours. The fermentation of whole-grain flours and subsequent sourdough production and germination of whole-grains were prepared at 28 ℃ for 48 h. The sourdough and germinated grains were freeze-dried and kilned, respectively, milled and sieved to obtain sourdough and malted whole-grain flour samples. The biochemical, nutritional quality and techno-functional properties of the obtained flours were determined. The macromolecules’ biomodification by microbial metabolism and endogenous enzymes activation influenced quality variations in the biomodified flours. The cowpea
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sourdough flour had lower acidity (pH 4.72), higher total flavonoid (29.63 mg QE/g), total phenolic (8.21 mg GAE/g) and antioxidant activity. The flour also showed high contents of fibre (5.30%), ash (4.42%), calcium (864.49 mg/kg), potassium (12848.64 mg/kg), zinc (33.83 mg/kg), good protein (21.43%) and a moderate fat level (2.65%). Higher oil absorption and water solubility indices were also noted for cowpea sourdough flour. In contrast, malted quinoa flour exhibited higher swelling power, increased dispersibility, low cooking temperature and improved final, peak and trough viscosities. Cowpea sourdough displayed higher redness and browning index, whereas malted quinoa flour had greater lightness. The results suggest that cowpea sourdough and malted quinoa flours had the best complimentary quality attributes. Their formulation as a whole and gluten-free multigrain ingredients may promote healthy choices for individualised growing dietary needs and thus, influences the next study phase.
Complementing the conventional processing means of whole-grain foods with emerging ones such as three-dimensional (3D) food printing has the potential to re-innovate and position the derived products among trendy, sustainable and functional meals. The growing trends in the functional food market necessitated the need to develop a healthy 3D printed whole-grain cowpea sourdough and malted quinoa snack for consumers in the hospitality industry. The processed whole-grain flours: raw, cowpea sourdough, malted quinoa and multigrain flours (comprising substituted cowpea sourdough flour with malted quinoa flour at 20% and 40%) were used as ingredients to prepare 3D printed whole-grain snacks that were compared with traditionally made (manually moulded) snacks. The nutritional quality, biochemical properties and structural analyses of the resulting snacks were examined using standard procedures. The distinct flour characteristics and preparation modes (traditional and 3D printing) caused differences in the examined quality attributes of the produced snacks. The probable void fraction in layers between the printed snacks—as opposed to the traditionally prepared snacks—and exposure degree to the baking process caused varying changes in the quality properties of the snacks. The composite snack formulations had a proportional share of quality attributes of both cowpea sourdough and malted quinoa snacks. Compared with the traditional composite snacks, the 3D printed composite snacks had a similar proximate composition and better compositions of the essential amino acids (histidine, isoleucine, methionine and threonine) and nonessential amino acids (alanine, aspartic acid, glutamic acid, glycine, Ho-proline, proline and serine). Composite 3D printed snacks showed improved concentrations of essential minerals (iron, magnesium, molybdenum, phosphorus, potassium and zinc). The formulated 3D printed snacks exhibited lower and higher total polyphenol contents in the snacks’ free and bound extracts, respectively. Similar observations were noted for their antioxidant activities. Although the traditional and 3D printed snacks presented consistent health-promoting compounds (apigenin, kaempferol, luteolin and quercetin), the complete profile of the quantified eleven phenolic compounds at elevated concentrations was observed in the 3D printed composite snacks’ bound extracts.
Further comparison between the composite 3D printed snacks revealed that the snack containing 80% cowpea sourdough and 20% malted quinoa had higher contents of ash (2.47%), fibre (3.59%), protein (15.11%), amino acids, molybdenum (1.25 mg/kg), potassium (9258.57 mg/kg), zinc (26.65 mg/kg), total polyphenols (free extract), targeted phenolic compounds (free extract) and antioxidant activity (free extract). In contrast, the formulated snacks containing 60% cowpea sourdough and 40% malted quinoa showed improved concentrations of fat (12.29%), carbohydrate (65.29%), energy (427.48 kcal/g), iron (144.23 mg/kg), magnesium (1496.70 mg/kg), phosphorus (3096.77 mg/kg), total polyphenols (bound extract), complete targeted phenolic compounds (bound extract) and antioxidant activity (bound extract). The top and bottom views of the substituted snack with 40% malted quinoa showed higher lightness, redness, yellowness and browning index. The structural characteristics of the composite 3D printed snacks were slightly varied and the 3D printed snack containing 60% cowpea sourdough had less hardness.
From the results obtained, either the 80% cowpea sourdough and 20% malted quinoa, or the 60% cowpea sourdough and 40% malted quinoa 3D printed snacks may be recommended as a healthy snack, depending on their personalised use for the dietary needs of consumers in the hospitality industry.
Keywords: Cowpea, Quinoa, Short-term Processing, Sourdough Fermentation, Malting, Whole and Multigrain Flours, 3D Food Printing.