*2.5.9 Acha*

Acha, which is also referred to as "fonio", "findi", "fundi", "pom, and kabug" "hungry rice" and "petit mil", is a small-grained cereal that is native to West Africa, which is generally classified among the millet [74, 75]. It is cultivated in various parts of Nigeria, Sierra Leone, Ghana, Guinea Bissau and Benin Republic on less fertile sandy soils that could not support the growth of other more demanding cereals. There are two known varieties of acha which are *Digitaria exilis Kippis stapf.* and *Digitaria iburua Kippis Stapf.* It is regarded as one of the lost crops in the West Africa sub region. Its production is important to West African Farmers, though hindered by several factors among which are poor agronomic performance because of unimproved seeds and husbandary practices. Its West Africa annual production is about 250,000 tonnes [17]. The annual yields of 3098 metric tonnes, 112,000 metric tonnes and 126,000 metric tonnes of fonio were reported in Nigeria [76]. The economic returns of acha when compared with other crops like rice, sorghum, and cowpea showed that it was profitable to grow the crop on a commercial scale [77]. Fonio are the most nutritious and testiest of all grains [77] and it contains 7%

crude protein that is high in leucine (19.8%), methionie and cystine (7%) and valine (5.8%) [78]. Fonio grains are mostly consumed wholly, they are also milled into flour and constitute a versatile raw material for preparation varieties of food such as gruels, porridges, couscous, bread, beer, and beverages [79]. Starch extracted from fonio possesses good disintegrant and binding properties [80] and it also has good glidant properties [81].

### **2.6 Food starch properties**

The starch granules sizes obtained from different crops vary in properties, because of their sources, extraction methods and cultivars [82]. The purity as well as the granules size can be determined using scanning electron microscopy [83]. The amylose content of starch is one of the most important factors influencing the cooking and textural qualities of whole storage root, and quality of starch-based foods [84]. *Dioscorea* starch granules possess varying shapes, which are spherical, oval and polygonal, depending on the species with granule size varying from 2 to 50 mm [85]. Also the X-ray diffraction pattern of the *Dioscorea* starch granules range from the B to C-type, depending on the *Dioscorea* specie [18]. *Dioscorea* starches contain18 to 30% amylose contents and their gelatinization temperature vary from 70 to 92°C [84].

Starch particle sizes obtained from white and yellow yam varieties showed similar patterns with a single symmetrical distribution centered at approximately 32 and 35 mm respectively. Sources, varietal differences and growing conditions significantly influence size and shape of starch granules. However, due to better mouth feel, small sized starch granules has been suggested as possible lipid substitute in food systems [86]. They are also used as laundry-stiffening agents because they possess good fabric penetration ability, better glossiness and stiffness, which are required in textile industries [87].

Sweet potato starch granules possess spherical, oval, and polygonal shapes, and they are about 2–46 mm in size. The X-ray diffraction patterns of the sweet potato starch granules are of type A and they also exhibit 38% crystallinity [88]. The starch in sweet potato is made of 16.1–24.4% amylose, having a swelling power of 80% at 90°C and gelatinization temperature of 64.6–84.6°C [84]. Cassava starch possesses small spherical granules, having an average granule size of 14.7 mm. Its amylose content ranges from 13.6 to 23.8% [84, 89] and its crystallinity has been reported to be 38% [84], while the gelatinization temperature varies from 59.6 to 87.2°C [84, 89]. The X-ray diffraction patterns of the cassava starch granules depict type A [90]. The cocoyam granules (Taro) are small rounded and ellipsoidaltruncated, with their sizes varying from 0.5 to 5 mm in diameter, making them to be more easily digestible [84]. Taro starch has been used in the preparation of some baby foods and diets of people who are allergic to cereals [91]. The X-ray diffraction patterns of the taro starch granules exhibit the typical A-type pattern, while the starch contains 14.0–19% amylose with the pasting temperatures varying from 81 to 85°C [92]. Interestingly, starch from Tannia (*Xanthosoma sagittifolium*) comprises of small rounded and large truncated ellipsoidal-shaped granules, which possesses granular diameters which range from 2 to 50 mm [91]. The amylose contents of different cultivars range from 21.3 to 25.4% [93]. Tannia starch possesses a type A X-ray diffraction pattern, higher pasting temperatures and lower paste viscosity than those of other starches, such as potato starch [89]. Also, it has higher swelling power and solubility at relatively high temperatures than sweet potato starch granule [84]. The maize starch granules exhibit polyhedral granule shapes and differences in their mean granule size range from 2.3 to 19.5 μm. The starch samples show A-type diffraction pattern with strong reflection at 15.25, 18.11,

**205**

*Utilization of Starch in Food and Allied Industries in Africa: Challenges and Prospects*

depending on both genetic and environmental factors [98].

order to meet the requirements of specific industrial processes [13].

and 23.33° [94]. The gelatinization temperatures of maize starch range from 69.16 to 76.98°C [95] and the amylose content varies from 24.74 to 30.32% [94]. Fonio starch granules are polygonal in shape with diameter ranging from 2.0–14.3 mm. Their X-ray diffraction patterns are of the type-A crystalline form [96], with the amylose contents ranging from 18.7% to 19.6%. The millet starch granules are small, spherical to polygonal in shape, but may vary from specie to another. The granular sizes range from 0.8 to 10 mm. The gelatinization temperatures of millet starch ranged from 75.8 to 84.9°C and the amylose content vary from 16.0 to 27.1% [84]. The starch granules obtained from sorghum are typically 3–27 mm and the gelatinization temperature range 61.1–81.2°C [97]. The starch showed the A-type crystalline diffraction pattern and its amylase content varies from 11.2–28.5%,

Native starches are crude starches that are extracted directly from their sources and they are mainly used as food, but irrespective of their sources they are undesirable for many applications because of their inability to withstand processing conditions. Each starch has unique functional properties, and much of the starch used industrially is modified before use, giving a wider range of useful products [99]. Starch can be readily converted chemically and biologically into many useful and diverse products such as paper, textiles, adhesives, beverages, confectionery, pharmaceuticals, and plastics, so as to improve desirable functional properties in

Starch granules' settling is often prevented by presence of various components like mucilage and latex, which may lead not only to loss of starch, but also reducing the quality of extracted starch. However, microbial growth can also be promoted if the extraction residence time is prolonged than necessary, which may also result into breakdown of starch and resultant loss of starch quality. It also affects the color of the starch limiting its utilization in food and industrial applications. Therefore, optimum recovery of starch having physicochemical and functional qualities coupled with economical extraction of starches from cereals and tubers is important. Extraction of starch with water is the most common form of starch extraction, but this has been improved upon over time. The Central Tuber Crops Research Institute, Trivandrum, India research on various chemicals that could improve the yield of starch from various tubers [100, 101]. It was discovered that ammoniacal solutions gave the best results. However, when aqueous ammonia (0.03 M) was used for starch extraction, the yield, paste viscosity and swelling capacity of the extracted starch improved. Ammonia formed a complex with the mucilagenous material in the slurry, thereby releasing the starch granules and promoting faster settling of starch in less viscous slurry, which prevents microbiological damage of the starch due to short residence time. Moorthy [101] observed that lactic and citric acids improved the yield and color of starch from sweet potato tubers. Interestingly, an enzymatic method for enhancing the recovery (26% increase) of starch from cassava tubers using pectinase and cellulase enzymes [101]. The aforementioned enzymes work by altering the integrity of the pectin-cellulosic matrix of cell membranes and thereby promoting the release of the starch granules. The same technique was used to promote starch recovery from sweet potatoes by 20% without affecting starch properties [101].

*DOI: http://dx.doi.org/10.5772/intechopen.95020*

**2.7 Forms of starch**

*2.7.2 Extraction techniques*

*2.7.1 Native starch*

*Utilization of Starch in Food and Allied Industries in Africa: Challenges and Prospects DOI: http://dx.doi.org/10.5772/intechopen.95020*

and 23.33° [94]. The gelatinization temperatures of maize starch range from 69.16 to 76.98°C [95] and the amylose content varies from 24.74 to 30.32% [94]. Fonio starch granules are polygonal in shape with diameter ranging from 2.0–14.3 mm. Their X-ray diffraction patterns are of the type-A crystalline form [96], with the amylose contents ranging from 18.7% to 19.6%. The millet starch granules are small, spherical to polygonal in shape, but may vary from specie to another. The granular sizes range from 0.8 to 10 mm. The gelatinization temperatures of millet starch ranged from 75.8 to 84.9°C and the amylose content vary from 16.0 to 27.1% [84]. The starch granules obtained from sorghum are typically 3–27 mm and the gelatinization temperature range 61.1–81.2°C [97]. The starch showed the A-type crystalline diffraction pattern and its amylase content varies from 11.2–28.5%, depending on both genetic and environmental factors [98].
