Determination of Optimum Harvesting Time and Development of Cassava Root- Leaf Flakes With Improved Protein, Minerals and Vitamins

Abstract

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 combined with root material. Blend 20% fresh leaf material combined with fermented root that emerged the best 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 17

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.