*2.1.2 Roasting*

The roasting method is commonly used in preparing "roasted AYB grain," a popular snack consumed in combination with other food in South-East Nigeria [19, 40, 43]. Roasting was effective in increasing the level of phosphorus and in-vitro protein digestibility of grains. An increase in phytic acid was also reported; however, the tannin level was shown to be at the barest minimum [43]. In the preparation of breakfast cereal from AYB grains in combination with maize and coconut fiber, the blends were roasted for 5 minutes at 2800 c temperature. The formulated blends revealed a protein content of 18.26%, moisture content of 4.20%, ash content of 7.36%, and energy content of 339.47% [77]. The roasting approach was likewise used in preparing AYB flour. The grains were subjected to roasting for 45 minutes (**Table 2**) using firewood as the energy source. Then, the roasted grains were dehulled and milled. The analysis of the roasted flour showed a decrease of about 0.27 mg/100 g in the level of the tannin content [78]. In a separate study, AYB grains were roasted in an oven at 1200 c for 300 minutes; and the roasted grains were dehulled and milled. The analysis of the dehulled flour showed a reduction in the emulsifying capacity, foam capacity, and stability of the flour, also the samples presented a high water and oil absorption capacity [79]. In a further experiment, researchers investigated the effect of roasting on the proximate, mineral, and anti-nutrient content of AYB grains. The study preceded the roasting of grains over firewood for 1 hour at 3000 c temperature condition. An increase was reported in the levels of calcium, potassium, copper, iron, manganese, magnesium, phosphorus, and sodium, and a drastic reduction in the percentage level of phytate, oxalate, tannins, hydrogen cyanide, and trypsin inhibitor was reported. On the contrary, there was no significant increase in the nutrient content [47].

## *2.1.3 Steaming*

The steaming approach involves the use of steam as the cooking medium; the steam is mostly generated from vigorously boiling water. Unlike reported in boiling method, the steaming procedure does not require submerging the food directly into the water; in steaming, the target food gets cooked as the result of the steam or vapors generated from the boiling water. Steam is considered a good heat conductor, nevertheless, the temperature release from steam does not exceed that of boiling water except in the pressure system [91]. Steaming was reported to have minimal effects on chlorophyll, soluble protein, sugar, vitamin c, and glucosinolates [92]. The steaming process helped preserve antioxidant properties and maintained the lowest biogenic amine content in bean varieties [93]. In AYB, the steaming approach was reportedly used in preparing a traditional snack

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

called "Moi-Moi". The procedure involved dehulling and wet milling of the grains accompanied by spicing. For the Moi-Moi to get cooked, it was steamed for about 60 minutes [71, 76]. The analysis of the AYB Moi-Moi showed a lower gelation capacity, higher water absorption capacity, lower oil absorption capacity when compared to Moi-Moi made from cowpea. The sensory analysis of AYB Moi-Moi showed no significant difference in color and flavor from Moi-Moi made from cowpea (cowpea is the most common grain for preparing Moi-Moi). Additionally, the acceptance level of the AYB Moi-Moi was similar to Moi-Moi constituted from cowpea [71]. Some researchers utilized the steaming cooking method in making Moi-Moi from AYB and cowpea blends, they reported a total steaming time of about 50 minutes [75].

#### *2.1.4 Frying*

Frying is one of the ancient and well-known cooking methods used for food preparation; the procedure is known for its ease, speed, and unique flavor and taste [94]; in addition, frying gives an attractive color, texture to food. The frying process involves the use of fat or oil which serves as the medium of direct heat transfer with the food [63, 95]. The transfer of heat, oil, and air during the frying process brings about changes like loss of moisture, oil uptake, starch gelatinization, aromatization, denaturation of protein, and changes in the color of the food. The changes in food and oil are largely dependent on the food property, the quality of oil, heating process, length of immersion, the rate at which air mixes with the oil, temperature, and the quality of the frying medium [96]. Frying could lead to the release of toxic products through oxidation, which usually occurs when oil is continuously used under high temperatures and atmospheric air [97]. The frying method of cooking was reportedly used in the preparation of traditional snacks commonly known as "akara" or "beans ball", a snack widely eaten in Nigeria. The grains were soaked overnight and dehulled before wet milling (paste) and spicing. The frying medium (groundnut oil) was heated to 185-1900 c, and the total frying time was about 5 minutes (**Table 2**). The end product (akara) showed an increase in carbohydrate, gross energy, water absorption capacity, oil absorption capacity, bulk density, and gelation capacity. Meanwhile, no significant difference was reported in accepting the AYB akara from the usual cowpea akara [71]. In like manner, the frying method was used in preparing Kokoro a popular snack in South-West Nigeria. The Kokoro process involved deep-frying the paste constituted from the AYB-Maize blend for about 10 minutes. The proximate analysis conducted on the Kokoro showed an increase in protein, sugar, ash, moisture, potassium, and calcium as the proportion of AYB flour increases. On the contrary, a decrease in fat and starch was observed with an increase in AYB flour [72]. Furthermore, the frying process was used to produce AYB cheese, using palm oil as the frying medium. The sensory evaluation indicated a general acceptance of the AYB cheese [73].

#### *2.1.5 Baking*

The baking process is a method whereby the raw dough is transformed into crumb and crust texture, under the influence of heat. During baking, the changes that occur include the crust formation, yeast inactivation, coagulation of protein, volume expansion, starch gelatinization, and moisture loss [98–100]. The baking approach was used in producing cookies from AYB-wheat composite flour. The cookies were baked for 20 minutes using an oven mark of 1800 c. The nutritional analysis of the cookies showed an increase in protein content from 8.59 to 9.35% fat from 3.84 to 4.63%, ash from 4.84 to 5.21%, and crude fiber from 3.84 to 4.22%. An increase in mineral content corresponding to a percentage increase in the level of AYB flour was also observed [74].
