what we really didnt know about sweet potatoe (ipoeoma batatas)

Naturally most foods abundant to man mostly in their raw form as plants and meat, it therefore became a duty of man in order to survive to process these raw materials abundant by nature using various processes such size reduction heat processing etc. sweet potato, a tuber crop which is highly nutritious is a popular food in most part of the world today. Sweet potato (Ipomoea batatas), a dicotyledonous plant which belongs to the biological family Convolvulaceae. It is a large, starchy, sweet-tasting, tuberous root. The young leaves and shoots are sometimes eaten as greens.
The plant is a herbaceous perennial vine bearing alternate heart shaped or palmately lobed leaves and medium-sized sympetalous flowers. The edible tuberous root is long and tapered, with a smooth skin whose color ranges between yellow, orange, red, brown, purple, and beige. Its flesh ranges from beige through white, red, pink, violet, yellow, orange, and purple. Sweet potato cultivars with white or pale yellow flesh are less sweet and moist than those with red, pink or orange flesh (Gad et al, 2009). Size reduction is mostly the third process in processing sweet potato after peeling and washing for various products of the tuber crop. Since it is a tuber crop and is hard, much energy is required to overcome the hardness and reduce its size for further processes.
The size reduction technique could be milling, slicing cutting etc. to desired final particle size needed. Ipomoea batatas commonly refers to as sweet potato is a dicotyledonous plant that belongs to the genius ipomoea and of the family convolvulacease originated from the tropical region in America.
Sweet potatoes are a large, starchy, herbaceous perennial vine and tuberous vegetable crops whose young leaves are sometimes edible. It bears an ultimate heart shaped or palmate lobe leaves and medium size sympetalous flower with a long and tempered smooth skin, with either yellow, orange red or brownish coloured tuberous edible roots. it chemical composition includes, 50-81mg/100g moisture content,1.0-2.4mg/100g protein, 1.8-6.4mg/100g fat, 8.0-29mg/100g starch, 0.5-7.5mg/100g non starch, 0.5-7.5mg/100g reducing sugar, and 0.9-1.4mg/100g ash. (Emmanuelle, 2016).
In countries like Nigeria and other tropical region of Africa, sweet potato is use as staple food which provides a certain nutritional values such as the carbohydrate, protein etc. This could be consuming either in tuberous or in chipped form when boiled or fried just like other tuberous crops.

2.1.1CHARACTERISTICS OF SWEET POTATO
Potato plants are herbaceous perennials that grow about 60 cm (24 in) high, depending on variety, the culms dying back after flowering. They bear white, pink, red, blue, or purple flowers with yellow stamens. In general, the tubers of varieties with white flowers have white skins, while those of varieties with colored flowers tend to have pinkish skins (Tony Winch,2006). Potatoes are cross-pollinated mostly by insects, including bumblebees, which carry pollen from other potato plants, but a substantial amount of self-fertilizing occurs as well. Tubers form in response to decreasing day length, although this tendency has been minimized in commercial varieties (Virginia Amador et.al., 2001)
plants are herbaceous perennials that grow about 60 cm (24 in) high, depending on variety, the culms dying back after flowering. They bear white, pink, red, blue, or purple flowers with yellow stamens. In general, the tubers of varieties with white flowers have white skins, while those of varieties with colored flowers tend to have pinkish skins (Tony Winch,2006). Potatoes are cross-pollinated mostly by insects, including bumblebees, which carry pollen from other potato plants, but a substantial amount of self-fertilizing occurs as well. Tubers form in response to decreasing day length, although this tendency has been minimized in commercial varieties (Virginia Amador et.al., 2001).
After potato plants flower, some varieties produce small green fruits that resemble green cherry tomatoes, each containing up to 300 true seeds. Potato fruit contains large amounts of the toxic alkaloid solanine and is therefore unsuitable for consumption. All new potato varieties are grown from seeds, also called "true seed" or "botanical seed" to distinguish it from seed tubers. By finely chopping the fruit and soaking it in water, the seeds separate from the flesh by sinking to the bottom after about a day (the remnants of the fruit float). Any potato variety can also be propagated vegetatively by planting tubers, pieces of tubers, cut to include at least one or two eyes, or also by cuttings, a practice used in greenhouses for the production of healthy seed tubers. Some commercial potato varieties do not produce seeds at all (they bear imperfect flowers) and are propagated only from tuber pieces. Confusingly, these tubers or tuber pieces are called "seed potatoes".

2.1.2 ECONOMIC IMPORTANCE OF SWEET POTATO
Economically, sweet potatoes tend to become one the basic food consumed by people in tropical operations into different final products that serve as food and for other purposes. Some the final food product gotten are deep frozen chips, crisps and mashed product. The by-products of sweet potato could be processed into starch, glucose and dextrose which are used for biscuit and other sweetening products. In the brewing industries and confectionery, some tuber crops are used for the production of distil alcohol and other related products, but in the non-food sector, sweet potato is used as ingredient for cardboard, glue, textile, paint and laundry material production (Roman,2001). So basically sweet potato is of high importance to man as it is basically used as feed for man and animals.
In summary, sweet potato is an important food available by nature to man, it has a good number of final products using different processes involving various unit operations to your desired final food product.
2.2 SLICING PROCESS
Slicing is a form of size reduction that involves the reduction in size by using blades manually or mechanically without change in chemical properties of the material and ensuring a high level of uniformity in size and shape of individual units of the end product. Reducing the size of food raw materials is an important operation to achieve a definite size range (Henderson and Perry, 1980).
Slicing is a post-harvest processing technology utilized on tubers with large mass so that the reduced products can easily be further processed either traditionally or industrially into food for human or other industrial products. In slicing process, certain factors such as moisture content, hardness, the cross sectional area, cutting velocity, shear angle of the cut and the bevel angle of the knife or blade has significant influence over the cutting energy of the slicer and as such a mechanized slicer to be of high efficiency should take into consideration all the about listed mechanical and physical properties mentioned above.

2.3 REVIEW OF ALREADY EXISTING POTATO SLICING MACHINE
Several slicing and chipping machines have been designed and tested in various developing countries especially the Caribbean and South East Asian countries as reported by Clarke (1987). Various types of machines are manufactured from small hand-operated batch-types to large automatic continuous operation models. Some are petrol, diesel or electric motor operated. There are cassava chippers, tomato slicers, okro slicers and other root and vegetable choppers. Ukatu and Aboaba (1996) designed, constructed and evaluated a machine for slicing yam and it was reported that the machine’s thickness of cut can be varied from 2 mm to 20 mm and the slicing efficiency ranged from 82 to 93% and the rate of work is 45 cuts per minute.
Samailaet.al.(2008) design and constructed a manually operated vegetable slicing equipment which consist of a cutting blade with sharp serrated edges to piece and sliced the product effectively. During slicing, a press bar pushes the product against stationary blades and as well pushes the sliced product into the collection chamber. With potato, okro and carrot as the test sample, the equipment was tested and the following test result where obtained.
Aji,et.al,(2013),Development of an electrically operated cassava slicing machine and the performance of the machine were evaluated with cassava of average length and diameter of 253 mm and 60 mm respectively at an average speed of 154 rpm. The machine produced 5.3 kg of chips of 10 mm length and 60 mm diameter in 1 minute. The efficiency of the machine was 95.6% with respect to the quantity of the input cassava. The slices were found to be well sliced to the designed thickness, shape and of generally similar size. Galvanized steel sheets were used in the cutting section to avoid corrosion of components.
The machine is portable and easy to operate which can be adopted for cassava processing in a medium size industry.
Aniyi (2006), design and fabricated an electric motor ginger slicing machine which consist of a cylinder, a piston, blade holder, blade separator, blades, crankshaft and connecting rod. The ginger slicer utilizes the reciprocating principle effect with fixed blade, power by an electric motor. A “TarinGiwa” one of the ginger species was used as sample to evaluate the cutting efficiency which was found to be 77% at 30% moisture content wet basis. Therefore, according to result obtain, the slicing efficiency is higher at moisture content than in the dry basis.
Apart from the above developed chippers and slicers; several chipping machines and slicers are available. They were designed and tested in different part of the world especially in continents such as Asia. Some manufactured from small hand operated batch-type to large automatic continuous operation models (Clarke 1989).
These machines are operated manually and automatically depending on the manufacturers
wish and the required energy and the purpose of utility. They include;
Cassava chippers, tomatoes slicers, okra slicers, and other root and vegetable choppers.
UNIFEM (2006). Reported that Nardi Francesco and Figli of Italy design and constructed a manually operated tuber chipper with a rotating disc fitted with four blades. It also reported that P.T Karta of Indonesia has also constructed a pedal driven cassava chipping machine powered by an electric motor, fitted with multiple chipping blades and claimed to have a chipping throughput of 500 kg/hr.
Ihensonye&Ngoddy (1992) in his research work reported that there had been efforts to mechanize some of the operations involved in the processing of plantain in Nigeria, but mostly the peeling and slicing operations are still being carried out manually using the conventional method of hand knife.
Kachru et al (1996) observed that during cutting, a cutting edge (knife) penetrated into a material, overcoming its strength and thereby separating it. He further stated that during cutting, various deformations occur in the material, depending on the form of the cutting edge and the kinematics of the process. Ukatu and Aboaba (1996) reported a machine for slicing yam tubers working at 45 rpm. Yam or cassava tubers are cut into slices and are fed into the conveyor.
In Nigeria, a manually operated chipper has been developed by “rural agricultural industrial development service” and “international institute of tropical agriculture post-harvest unit” whose length is dependent of the angle of contact of root with the blade. Also a potato chipping machine design and fabricated by international potato centre (CIP) with a capacity of 270 kg/hr. And in Philippine, a root/tuber slicer by department of agricultural chemistry and food science with capacity of 323 kg/hr was design.

CONCLUSION
In conclusion,having shown by research that sweet potato is one of the widely consumed agricultural produce in the Nigeria, its important plays a very crucial role in the food sectors, as well as its great contributions to the nation economy. So much attention has been paid to its preservation and storage to improve high yield. In an effort to improve yield, extend shelf life, and curtail time consumption during processing, the physical an mechanical properties of sweet potato has been measured and calculated and an electronic sweet potato slicing machine has been designed to ease slicing process of sweet potato. Some parts of the machine where made of plastic instead of metal specifications provided, this was due to the effect of cost of metal materials.
The machine cuts potatoes fed into it by a cutting disc and slices efficiently along the breadth of the sweet potato.
From the result, it was observed that the slicing was efficient for the sweet potatoes with the slices having excellent uniformity and thickness.
In nigeria, sweet potatoe cxan be prepared via several methods which may include