BACKGROUND: The cladodes of Opuntia ficus‐indica (prickly pear cactus) have a low protein content; for use as a balanced feed, supplementation with other protein sources is therefore desirable. We investigated protein enrichment by cultivation of the yeasts Candida utilis and Kluyveromyces marxianus in an enzymatic hydrolysate of the cladode biomass.RESULTS: Dilute acid pretreatment and enzymatic hydrolysis of sun‐dried cladodes resulted in a hydrolysate containing (per litre) 45.5 g glucose, 6.3 g xylose, 9.1 g galactose, 10.8 g arabinose and 9.6 g fructose. Even though K. marxianus had a much higher growth rate and utilized l‐arabinose and d‐galactose more completely than C. utilis, its biomass yield coefficient was lower due to ethanol and ethyl acetate production despite aerobic cultivation. Yeast cultivation more than doubled the protein content of the hydrolysate, with an essential amino acid profile superior to sorghum and millet grains.CONCLUSIONS: This K. marxianus strain was weakly Crabtree positive. Despite its low biomass yield, its performance compared well with C. utilis. This is the first report showing that the protein content and quality of O. ficus‐indica cladode biomass could substantially be improved by yeast cultivation, including a comparative evaluation of C. utilis and K. marxianus. © 2014 The Authors. Journal of the Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Summary: Legumes are vital food sources in global diets, especially in developing nations, offering affordability, nutrition, and sustainability. Legumes are rich bioactive compounds as well as in macro‐ and micro‐nutrients and help combat protein‐energy malnutrition. Fermentation is a food processing technique that enhances nutritional content, digestibility and overall composition, rendering fermented legumes like dawadawa, natto, tempeh, and kinema dietary sources worldwide. This simple process leads to significant perturbations in the numerous metabolites contained in legumes and subsequent fermented products. Such metabolites including bioactive constituents, vitamins, minerals, volatile compounds, lipids, amino acids, among others contribute to the flavour, aroma, nutritional value and health beneficial properties of fermented legume products. Modifications in these complex constituents might be somewhat challenging to investigate and understand thus necessitating a robust technique such as metabolomics. Metabolomics as an analytical approach can elucidate how fermentation alters the composition of fermented legumes revealing compositional changes, nutritional enhancements, and impacts of fermentation conditions and microbial metabolism. This review emphasises fermented legumes' dietary importance, the transformative role of fermentation, and the effectiveness of metabolomics in unravelling complex biochemical changes during legume fermentation, providing insights into nutritional, sensory and safety aspects of fermented legumes.

The reports on the volatile compounds of a dawadawa-type African food condiment produced from the alkaline fermentation of bambara groundnut (Vigna subterranea (L.) Verdc.) using Bacillus starter cultures are limited. Volatile compounds were isolated from dawadawa-type condiments using headspace solid phase microextraction and analysed by comprehensive gas chromatography coupled to time of flight mass spectrometry. Acids, aldehydes and alcohols accounted for over 70% of the volatile compounds produced in the Bacillus fermented samples. B. subtilis subsp. subtilis SFBA3 produced the highest content of acids (4969.60 µg kg⁻¹), while the highest content of aldehydes (2811.90 µg kg⁻¹) and alcohols (1247.60 µg kg⁻¹) was detected with Bacillus cereus PALB7 and Bacillus licheniformis OALB2, respectively. Sulphur-containing compounds concentration (85.80 µg kg⁻¹) was highest for Bacillus amyloliquefaciens SFBA2. Maximum 2-methyl butanoic acid and 3-methyl butanoic acid concentrations, indicative of typical dawadawa aroma, were produced by B. subtilis subsp. subtilis SFBA3.

Summary: Cereal‐based diets supplemented with legumes have proven to be an effective approach to enhancing nutritional value. This study evaluated the consumer acceptability and metabolite profile of fermented sorghum mahewu improved with different proportions (20% and 30%) of Bambara groundnut (BGN). Consumer acceptability, metabolite profile analysis using gas chromatography high‐resolution time‐of‐flight mass spectrometry (GC‐HRTOF‐MS), storage stability and microbial quality of mahewu were determined. Sorghum (100SORG) mahewu without BGN was the most preferred by the consumer panellists followed by 80SORG:20BGN. Metabolites identified in all three mahewu products included esters (21%), alcohols (17%), alkanes (12%), acids and derivatives (9%). Overall, 70SORG:30BGN had an improved metabolite profile but least preferred by consumer. The sorghum‐BGN mahewu maintained their pH, while increases in consistency and TTA were observed with storage time and BGN supplementation. Inclusion of BGN in sorghum mahewu did not alter microbial quality; however, more awareness is required to increase its acceptance among consumers.