Food Science and Technology Project Topics

Proximate, Microbial and Sensory Properties of Spiced Chips Produced From Sweet and Irish Potato

Proximate, Microbial and Sensory Properties of Spiced Chips Produced From Sweet and Irish Potato

Proximate, Microbial and Sensory Properties of Spiced Chips Produced From Sweet and Irish Potato

Chapter One

Objective of the Study

Therefore, this project study focus to examine the proximate, microbial and sensory properties of chips spiced with ginger produced from sweet and Irish potato.



Origin of Potato Crop

Sweet Potato (Ipomoea batatas (L) Lam.)

Sweet potato (Ipomoea batatas (L) Lam.) is a member of the Convolvulaceae family (Purseglove, 2002). Approximately 900 different species of Convolvulaceae in 400 genera have been identified around the world. Yen (2004) and Austin (2008) recognized 11 species in the section batatas, which includes sweet potato. The closest relative of the sweet potato appears to be Ipomoea trifida that is found wild in Mexico, and Ipomoea tabascana. Sweet potato has a chromosome number of 2n = 90. Since the basic chromosome number for the genus Ipomoea is 15, sweet potato is considered to be a hexaploid. Most sweet potato cultivars are self-incompatible, which means that when self-pollinated, they cannot produce viable seed. It is accepted that cultivated sweet potato originated in Central America or tropical South America. Nishiyama (2001) and Martin and Jones (2002) suggested Mexico as a centre of diversity of the batatas section of Ipomoea.

 Irish Potato (Solanum tuberosum L.)

Potato is generally considered to have originated from the region between latitude 10°N and 20°S at an altitude of 2000 meters but to be precise in Bolivia (Okonkwo et al., 2001). FAO (2008) identified the centre of origin to be between Mexico and Chile but specifically suspected the Andean highland of Bolivia or peru, where the presence of wild species of the crop serves as clues. The neighborhood of laketitican located at an altitude of 3512 meters above sea level in the peru-Bolivia Plateau area is more definite. Potatoes were introduced outside the Andes region four centuries ago, and have become an integral part of much of the world’s cuisine. It is the world’s fourth-largest food crops, following rice, wheat and maize (Hawkes, 2000). Long term storage of potato requires specialized care in cold warehouse (Lang, 2001).

Wild potato species occur throughout the Americas, from the United States to Southern Chile (Langar, 2005). The potato was originally believed to have been domesticated independently in multiple location (McNeill, 2009), but later genetic testing of the wide variety of cultivars and wild mild species proved a single origin for potatoes in the area of present-day southern and extreme north western Bolivia (from a species in the Solanum berevicaule complex) where they were domesticated 7,000-10,000 years ago (McNeill, 2009). Following centuries of selective breeding, there are now over a thousand different types of potatoes of these sub-species, a variety that at one point grew in the Chile Archipelago (the potato’s south central Chilean sub-center of origin) left its garn plasum on over 99% of the activated potatoes world-wide (Salaman, 2009).

The crop moved out of the south America (center of origin) by deliberate introduction to spain in 1570, to England in 1586, then to Ireland by Spanish explorers from 1663, the crop was grown on a large scale in Ireland and becomes so popular such that it is not too surprising that it acquired the name “Irish Potato” (Randel, 2003) indicated that the English introduce potato into Virginia in 1621 and into Bermuda island in 1913. The years 2007-2008 saw dramatic increase in the world food prices, creating global crises that led to political and economic instability in both the developed and developing nations. The initial causes of the late 2006 price increase were due to draught in grain producing nations and the rising oil prices, the increase in oil prices also cause general escalation in the cost of fertilizers, food transportation, industrial and agricultural products.

This factors coupled with the following world food stock pilled contributed to the global rise in food prices (Global and Mail, 2008) in response to the severity of the food crises and the need for prompt action, the world bank set up the global food crises response program (GFRP) in May 2008 to provide immediate relief to countries hard hit by food high prices. The bank’s response has been articulated in collaboration with united nations “High task force” on food security “HLTF” (World Bank, 2009) highlighted potato’s role in world food production, they cited it’s enormous potentials for boosting food production, being a cheap and abundant crop that grows in a wide variety of climates and locality due to its perish ability however, only about 5% of the world potato production is traded internationally. This contributes to its stable pricing during the 2007-2008 world food crises (FAO, 2008).

It is a source of starch and alcohol, in addition to its food and feed supply value to both human and animals, respectively (Uniferm, 2009). Its production is lopsided to the predominant small scale farmers. This category of farmers suffers from a crippling technical inefficiency in the use of their production inputs (Hamidu, 2000).

History of Potato in Nigeria

Potato crop was brought into Nigeria by the European tin miners in the 19th and 20th centuries. Plateau (Jos plateau) and aria provinces of the northern Nigeria constituted the main centers of production in those early days of potato production. The Jos plateau was favored as a result of the high altitude thus cool climate which favours the development of the crop. The cultivation of potato did not reach significant level until the outbreak of the second world war in 1939, one may regard the earliest effort to  increase potato production in Nigeria as principally  directed to meeting the food need of Europeans in the armed forces and civil service mainly in west Africa sub-region to support expansion of potato production, the colonial government initiated studies as far back as 1940 to test the suitability of some European variety under Jos plateau environment.

These experiences established the superiority of varieties such as grent scot, graig defiance and irish cobbler over the early   pre-war introduction although they did not perform as well as in Europe. It is known that the “local” varieties grown in Jos plateau originated from these early introductions (Akpoko et al., 2008). The period after 1960 shows a phenomenal increase in production. By the early sixties, the area under potato cultivation was about 405ha of which about 75 was reported to be in Jos plateau. By 1975-76 seasons potato production in the Jos plateau alone was estimated to about 48,000 tonnes. In 1976 the total land area and annual total production was 10,000ha and 52,000 tonnes, a thirty fold increase over the early sixty figures. The importance of large quantity of high quality seeds tubers was identified as a major constraint in the period 1939-1961.

As demand for seed potato increased an attempt was to established a local multiplication scheme by the ministry of agriculture and the Jos and pankshin native authorities. 1961 marked the beginning of another period in the development of potato in Nigeria with the establishment of the potato program of the national root crop research institute in vom, as part of general improvement objectives, it was realized that not only was the availability of healthy seeds of proven high yielding varieties necessary, but that efficient disease and pest control measures as well as good husbandry practice were necessary to increase yield per unit area of land. This is responsible for the significant increase in total land area and total annual production from 14,000 ha, and 70,000 tonnes between 1983–1984 to about 50,000 ha and 400,000 tonnes in 2001 respectively (Okonkwo et al., 2001).





Sweet and Irish Potato (Ipomoea batatas and Solanum tuberosum L.) were purchased in Oja-Oba, Owo in Ondo State. Other materials such as vegetable, spice (ginger), salt etc were also purchased in the same market. The chips was processed in Food processing laboratory of Food Science and Technology and the analysis was carried out in chemistry laboratory of Food Science and Technology, Rufus Giwa Polytechnic, Owo, Ondo State.


            The potatoes (Sweet and Irish potatoes) were washed, peeled and cut into slices. Peeled slices were soaked in 0.1 % sodium metabisulphide solution for 15 minutes to prevent enzymatic browning. The wet chips were drained and powder spice (ginger) was added to wet chips after which it was fried in oil till taste. The fried chips were allowed to cool at room temperature (30°C), it was the packaged and sealed in polyethylene nylon for further analysis.




Table 4.1: Proximate analysis of spiced sweet and irish potato chips





Sweet potatoes and Irish potatoes are starchy staple food raw materials that are highly perishable which can be preserved by frying and other preservation methods. The fortification of the samples above is aimed at improving the nutritional value of the products and by so doing it also reduced the rate of microbial growth in the sample. From the results above, it was observed that sweet potatoes had best preservation status due to the low amount of moisture in the sample while Irish potatoes cannot be effectively preserved by frying and cannot be produced for commercial purpose by frying methods.


Therefore, this research work is recommended for continuous evaluation for more results.


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