DETERMINATION OF OPTIMUM HARVESTING TIME AND DEVELOPMENT OF CASSAVA ROOT- LEAF FLAKES WITH IMPROVED PROTEIN, MINERALS AND VITAMINS

The current study intended to bridge a gap where coastal Kenya contributes up to 27% of the cassava produced nationally, yet remains highly insecure in terms of food and nutrition. This is at an interface of scientific efforts that led to development of improved cassava varieties suitable for the region. The improved varieties were developed by Kenya Agricultural and Agricultural Research Institute (KARI currently known as KALRO). This study targeted to develop flakes from cassava roots and leaves. Two improved varieties- Karembo and Tajirika against one local variety - Kibanda Meno were evaluated for suitability. Cassava roots were harvested at crop age 3, 6, 9 and 12 months, while leaves for nutrients profiling, were harvested at 3, 6 and 9 months after planting. A total of 18 blends of flakes were formulated from a varied cassava leaf combinedwith root material. Blend 20% fresh leaf material combined with fermented root that emerged thebest preferred by panelists was further evaluated for its nutritional value, shelf life, and suitable packaging material. The results on roots showed significant (p < 0.05) interaction effect of varieties and crop age on nutrients. Karembo and Tajirika had peak dry matter of 43.42% and 41.42% respectively at 12 months while the peak for Kibanda Meno was 44.99 % at 9 months. Mean starch content on dry weight varied with variety; Karembo (91.3%), Kibanda Meno (93.4%) and Tajirika (85.5%). Karembo and Tajirika had peak carbohydrates at 12 months while the peak for Kibanda Meno was at 9 months. Vitamin C was highest at 6 months for Karembo (6.4 mg /100 g) and Kibanda Meno (6.6 mg / 100g). Tajirika had highest vitamin C (7.0 mg / 100 g) at 9 months. Iron was peak at 3 months for Karembo (3.63 mg / 100 g) and Tajirika (5.33 mg / 100 g) but at 9 months for Kibanda Meno (7.12 mg / 100 g). Peak Zinc was 2.1 mg /100 g for Karembo at 6 months while for Kibanda Meno (1.94 mg / 100 g) and Tajirika was (1.75 mg / 100 g) at 12 months. Hydrogen cyanide increased from 8.6 to 9.3 mg / kg in Karembo between 9 and 12 months, it decreased from 7.8 to 5.2 mg / kg and from 5.1 to 4.5 mg / kg in Tajirika and Kibanda Meno, respectively. Leaves profiling showed significant (p < 0.05) effect of crop age on leaf nutrients content. Nutrients peaks were; moisture content (74%) at 3 months in Karembo and Tajirika, 75% at 9 months for Kibanda Meno; dry matter (50%), at 6 months, across varieties; fat (1.0 g / 100 g), was highest in Kibanda Meno at 3 months; protein (36 g/100 g), was highest in Kibanda Meno at 9 months. Vitamin C was highest in Karembo (1236 mg / 100 g) at 9 months. Vitamin A was 190 to 638 mg /100 g, at 6 months across the varieties. Iron and Zinc were 10 mg / 100 g, peak at different crop ages. Cyanide was 7.4 mg / kg, peak at 9 months. Formulation of cassava root - leaf flakes was best accepted at 20% leaf component added on to fermented root. Nutritional value analysis showed that the blend had vitamins A and C improved by 353% and 53%, minerals- iron and zinc by 5.6% and 85% respectively and protein by 430% compared to flakes processed from 100% root. Results on storage and packaging, showed moisture content to be significantly influenced by packaging material as it increased during storage, across the blends, with highest levels (10.75%) registered in kraft material on day 3. Paper insulated polythene had highest nutrients’ levels;- protein at 27.68 g / 100g vitamins A (576.85 mg / 100 kg), Zinc (1.17 mg /100 g), iron 3.69 mg /100 g), fibre 6.12 g /100 g by day 5. Fat was highest at 9.71 g /100 g in the plastic material. Acid and peroxide values gradually increased in all the packages from 0 to 3.6 mg KOH / g and 0 to 6.3 mg / kg respectively. Microbial counts showed paper insulated polythene to be efficient in microbial growth in both spread plate and pour plate methods. The study concluded that roots of varieties - Karembo and Tajirika can be harvested as from 9 months while Kibanda Meno - can be harvested as from 6 months after planting. Levels of leaves micro nutrients are higher over the tender age. Cassava root - flakes is preferred at 20% fresh leaf blended with fermented root material that has improved levels of vitamins, minerals and protein, compared to pure cassava root products. It is recommended that harvesting of both roots and leaves be staggered.

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ASAL - Arid and Semi-Arid Lands AV - Acid Value

AOAC - Association of Official Analytical Chemists DM - Dry matter content

Dwb - dry weight basis

FAO - Food and Agriculture Organization HCN - Hydrogen Cyanide

IFDIC - International Fertilizer Development Center KARI - Kenya Agricultural Research Institute

KALRO - Kenya Agricultural and Livestock Research Organization SAS - Statistical Analysis System

PV- Peroxide Value PDA - spread plate Agar PCA - pour plate agar

SIFOR - Smallholder Innovation for Resilience WHO - World Health organization

 

 

 

 

Agriculture is the backbone of Kenya’s economy, employing over 80% of rural communities. It is the major source of food and / or a sole source of livelihood for Kenya’s coastal communities (Mwamachi et al., 2005). The coast region, experiences harsh climatic conditions and registers high poverty levels. Fortunately, cassava (Manihot esculenta Crantz) grows in sub-optimal agricultural conditions and hence grows in diverse agro - ecological zones in the region. Cassava not only serves as a food but also doubles up as a cash crop with potential for industrial uses (KARI, 2009; FAO 2005) and is of great economic importance worldwide (FAO, 2011). According to a report by Kariuki et al., (2002), cassava is increasingly becoming an important food and cash crop in Kenya. In Western and coastal Kenya, cassava is second to maize in importance as a food crop (Kiura, 2006). It is a crop that has the potential of reducing poverty, categorically in Kenya since it does well in diverse agro-ecological zones.

The coastal region of Kenya majorly covers Kwale and Kilifi counties that according to government report, implies 71% of its communities are people living below poverty line. Prevalence of malnutrition is also high, with most affected being children and antenatal women. (Rao et al., 2011). The two counties lie in the Arid and Semi-Arid (ASAL) with a common phenomenon of erratic and unreliable. Cassava is the most popular as it is drought tolerant and less costly in terms of inputs requirements making the region to contribute up to 27% national cassava production. It is a food crop that is grown for its roots witch are rich in carbohydrates, thus supplying much needed household calories to over 500 million households in the tropical countries (FAO, 2005). Cassava roots are, however, of low nutritional value compared to cereal staples, apart from being an energy source. Cassava roots have approximately 30% starch, 1.4% proteins, 3.8% soluble dietary fiber and 0.6 % ash (Infante et al., 2012; Dischen et al., 2013) that are low as compared to staples like maize, sorghum and millet. Maize has higher nutrient contents, averagely; 73% starch, 5.8% protein, 0.8 fiber and 1.2% ash (FAO, 2003; Jocelyne et al., 2020) while millets and sorghums constituents are approximated 60.3% starch, 7% protein, 4.13% dietary fiber and 2.8% ash (Singh et al., 2012; Elshazali et al., 2011; Saleh et al., 2013). Low nutritional value in cassava roots makes households that continuously use it as staple food to be exposed to nutrient malnourishment especially protein deficiency (Kevin et al., 2010). Vitamin content and other nutrients such as iron are also low in the roots (Lancaster and Brooks, 1983) compared to leaves that have 26.8% protein, 24% starch, 6.4% ash and 10.0% dietary fiber (Montagnac, 2009; Fasae, 2009) and can be used to fortify the cassava root based diets. The leaves are good sources of protein, calcium, iron and vitamins which can provide valuable supplements to predominantly starchy diets. Cassava leaves compare favorably with other green leafy vegetables generally regarded as good protein sources (Montagnac, 2009). The amino acid composition of cassava leaves shows that, except for methionine, the essential amino acid values exceed those of the FAO protein reference and RDA (Montagnac, 2009; Lancaster and Brooks, 1983). Studies have shown that the proteins embedded in cassava leaves are equal in quality to the protein in egg (Montagnac, 2009; Lancaster and Brooks, 1983). Cassava leaves and roots therefore, if properly processed and developed into end products for human consumption, can provide a balanced diet that could protect millions of African children against malnutrition (FAO, 2001; Babaleye, 1996; Montagnac et al., 2009). The current study undertook to develop cassava root - leaf flakes with improved nutrients, shelf stable and high potential for commercial production. The development of the product targeted school going children and pregnant women to easily access nutrients, for better health.

 

World Health Organization (WHO) recognizes three main deficiencies with global significance that include deficiencies of vitamin A, Iron and Iodine, and protein (WHO, 2014). Other deficiencies are those that can have serious health implications if they are localized: vitamin D (rickets); vitamin B1 (beri beri); zinc (stunting) and niacin (pellagra). The world population at risk is estimated at 190 million of which 40 million are already deficient, including 14 million with eye lesions (WHO, 2014 Rivera et al., 2003). Iron deficiency, the cause of anemia is the most common and widespread nutritional disorder in the world affecting over 30% of the world population (WHO, 2014). Protein deficiency is widespread and serious nutritional disorder, present in adults as well as in children (Henley et al., 2010; FAO, 2015; Carvalho, 2001). Critical protein deficiency in children occurs in form of kwashiorkor, while protein - calorie deficiency occurs in form of marasmus. In Kenya, under-nutrition is high in young children particularly in north Eastern and coastal regions (MI, 2009; CBS, 2014). Prevalence of deficiencies is approximated at 84% for vitamin A 36.8% for Iodine; 69% anemia among children of age 5 to 6-year-old and 5.5% (anemia) for women across the regions (Klaver and Mwadime 1998; MI, 2009). Prevalence of underweight, stunting and wasting was noted to have persisted for over a decade and women were seen to be affected by persistent chronic energy deficiency and under-nutrition in 2005 (FAO, 2005).

The coast region contributes up to 27% of the national cassava production and cassava remains an important food crop with roots commonly consumed in pure form as boiled, roasted, fried chunks and crisps (Kiura, 2006). Locals limitedly consume leaves that are a rich source of proteins, minerals and vitamins (Montagnac, 2009). Formulations involving both the roots and the leaves for human consumption are lacking though they could improve the nutrient density of cassava products for both the rural and urban populations. 

Efforts to develop new cassava varieties by Kenya Agricultural Research Institute (KARI) led to release of new varieties among them Karembo and Tajirika in 2008 (KARI, 2009; Gethi, 2008). The varieties were, however, developed for high yields and pests and disease resistance especially cassava mosaic and cassava brown streak diseases. The new varieties along with the local varieties have not been evaluated for suitability for product development (KARI, 2009). Nutrients development over maturity stages and nutrients status in both roots and leaves in these varieties have limitedly been determined.

The presence of unsafe levels of cyanide in the roots and leaves of some varieties of cassava is a major problem as cyanide is known to be toxic to humans. The level of cyanide in the roots and leaves across maturity stages of popular varieties of cassava grown in the coastal region of Kenya has hardly been addressed that prompted breeders (Gethi, 2008) to place a recommendation for the same. There is limited or no data on cyanide content in relation to maturity stages of the improved and local cassava varieties’ roots and leaves grown in the coast region of Kenya. This information is important in the selection of suitable varieties and optimum harvesting time with regard to manufacturing of value added products.

There has been increased promotion of high yielding cassava varieties for production as a means towards food security; but cassava is highly perishable (IFDC, 2010; Kiura et al., 2006; Abong’ et al., 2016) and postharvest loss reduction has remained a challenge to actors along the value chain (IFDC, 2010). Perishability coupled with bulkiness exacerbate transport costs, thereby reducing profit margins (IFDC, 2010). High perishability state of roots has made raising cassava to a market competitive crop not possible and postharvest loses have remained high. Selling of fresh roots - the common practice of most cassava famers has limited cassava to fresh markets. Currently, there is limited diversity of shelf stable cassava based products that are rich in nutrients, and have potential to improve the nutritional status of the coast region with a potential for commercial production as well.

Efforts to achieve food and nutrition security require increased production and utilization of the available food crops where cassava and maize remain the most important food crops in Africa (Eke et al. 2012). Increased production alone without reducing postharvest losses still makes food and nutrient security far from being achieved (Brimer et al., 2013). Postharvest loses remain high for most agricultural commodities but processing technologies have proved effective for reduction (Brimer et al., 2013). For the case of cassava, processing is important both for postharvest loss reduction and reduction of hydrogen cyanide to safe levels (Brimer et al., 2013). The current study undertook to develop cassava root - leaf flakes that is shelf - stable, rich in nutrients with potential for commercial production, targeted for income generation if adopted for processing by the cassava processing producer groups in the coast region of Kenya, a region known to have high poverty levels. The product with improved nutrients was primarily targeted to allow for school going children and pregnant women to easily access the imbedded nutrients. Where also, with improved incomes, food and nutrition insecurity may be reduced to some extent. Utility of cassava cannot be over emphasized and increased utilization has potential to trigger demand and consequently influence commercial cassava processing (Eke et al., 2012). Utilization can be increased when there is a wide diversity of products in the market.

Cassava roots are recommended to be harvested at 12 months after planting (Muli et al., 2008; Nhassico, 2008) but this only applies under ideal food security situations. Under food shortage, farmers start harvesting cassava as early as three or six months after planting when they notice cracks on the ground (FAO, 2005). The study undertook to determine the trend of nutrient development across the growing period (cassava field period) in order to highlight the effect of the early harvesting of cassava roots as well as identify the nutrients peaks suitable for harvesting. The work was carried out in the coast region of Kenya.

Most cassava products are processed from pure form of cassava roots processed into dried chips, flour, starch, crisps and animal feeds (Kariuki et al., 2006). Literature however shows that protein and fat content in roots is low at about 1- 2 % and 0.3%, respectively, but the leaves are, rich with crude protein surpassing that of legumes and leafy legumes. The crude protein content in cassava leaves also compares well to that of fresh eggs. The leaves are also rich in minerals at the rate of 2 to 5 times higher than that of the roots. The leaves have a greater concentration of calcium - 100 times higher than in roots and the phosphorus content is 2 to 3 times higher in roots than in the leaves (Montagnac, 2009). Vitamins and minerals are also high though with some variations in cassava leaf meal (CLM) on dry matter basis. Indeed, thiamin and niacin contents are 4 to 5 times higher in leaves than in roots, and riboflavin and vitamin C are 10 to 12 times higher in the leaves. Vitamin A in the form of pro-vitamin A carotenoid is of high quantity. The leaves from cassava varieties grown in the coast region were profiled in order to determine nutrients levels that can be documented to entice cassava leaves utilization in a region that is nutrient insecure.

Dry processed food products are prone to moisture absorbance that leads to spoilage over period of storage time (Chang et al., 2000). Storage temperatures together with type of packaging materials used help preserve processed products for prolonged shelf life. Cold temperatures are known to preserve commodities better however dry processed products have relatively long shelf life even when stored under room temperatures. It is also expensive and almost un-affordable for communities and or firms to establish and maintain cold rooms, as well as it is un-economical to store dry products under cold temperatures. The suitable packaging material, shelf-life of cassava roots - leaf flakes were therefore determined under room temperatures.

To determine the optimum harvesting time and to develop flakes from cassava roots and leaves with improved protein, minerals and vitamins contents for improved food and nutrition security.