**3.3 Other processing methods in AYB**

#### *3.3.1 Fermentation*

Fermentation increases the bioaccessibility and bioavailability of nutrients and sensory quality in addition to shelf life [126, 127]. The process involves the biochemical modification of food by microorganisms and their enzymes [128]; the process is capable of disrupting the activities of pathogens [126, 129]. The fermentation process was explored for the preparation of "tempeh" from AYB grains; tempeh is a traditional food usually made from fermented soybean or soybean already broken down by microorganisms. The procedures for making AYB tempeh included: cooking presoaked grains for 45 minutes at 1000 c and inoculating the cooked grains with spore suspension to initiate fermentation. The inoculated grains were allowed to ferment over 42 hours. The final product showed significant changes in crude protein and carbohydrate. An increase in protein and amino nitrogen content was reported

#### *A Review on the Cooking Attributes of African Yam Bean (*Sphenostylis stenocarpa*) DOI: http://dx.doi.org/10.5772/intechopen.99674*

whereas a decrease in carbohydrates was observed. The quality of the AYB tempeh was acceptable to a large number of sensory panelists [130]. Meanwhile, some authors reported the minimal effect of fermentation on calcium, iron, magnesium, and zinc contents. However, they reported about a 34% reduction in phytate level and only tannin traces were detected [43]. Further research investigated the solid (3 days) and liquid (62 days) state fermentation approaches in making sauce from AYB grains. The prepared sauce revealed an increase of 11.94%, 4.85%, and 16.75% in ash, protein, and carbohydrate contents respectively. The sensory evaluation showed the acceptability of the AYB sauce was not significantly different from the level of acceptance of the commercial soy sauce in terms of color, aroma, and flavor [131].

Other studies used the fermentation process to formulate a yogurt-like product from dehulled and whole AYB grains. The process involved: the extraction of milk from grains which was followed by inoculation with a starter culture. For fermentation to occur, the inoculated milk was kept undisturbed over a time frame of 12 hours. The analysis of the formulated AYB yogurt presented a high total viable and *Lactobacilli* counts. As storage time increases, a decrease in the microbial load of the yogurt was observed [132]. In a similar experiment, raw AYB grains fermented for 48 hours showed an increase in protein and oil content [70]. "Dawa-Dawa" a traditional condiment was reportedly prepared through fermentation. The grains were boiled in water laced with "potash", the boiled grains were later dehulled and allowed to ferment at room temperature for 72 hours. The proximate analysis of the "Dawa-Dawa" showed an increase in crude protein from 22.00 to 32.80% and crude fibers from 5.70 to 7.77%, ash content increased from 3.20 to 4.60%, and lipid from 1.20 to 1.38%. Nevertheless, a decrease in carbohydrates from 74.20 to 57.21% was observed in the product [133].

#### *3.3.2 Germination*

Germination is a complex process that involves a mature seed to make an immediate change from maturation to the germination-driven stage and prepare for seedling growth [134]. The stages of germination include uptake of water by the seeds (imbibition) and the second phase is the reinitiating of metabolic processes followed by the emergence of the radicle through the seed envelopes. The germination process was used to prepare flour from AYB grains. The grains were soaked in water at room temperature for 48 hours. After soaking, the grains were allowed to sprout for 96 hours and subjected to oven drying. The dried grains were further dehulled and milled into flour. The germinated AYB-wheat composite flour showed an increase in protein; for every increase in the percentage of AYB flour [74].
