Nutritional Evaluation of Seaweeds for Potential Development of Value-added Biscuits

Abstract

Over the years, the Government of Kenya (GOK) has strived to achieve national, household and individual food security throughout the country. The National Food Security and Nutrition Policy (NFNP) highlights the nutitional effects on a population primarily fed on maize and advocates diversification of eating habits. Seaweeds have been consumed in most Asian countries for their valuable macronutrients such as fibre, protein, lipids, carbohydrates and micronutrients such as vitamins and minerals. In the African continent, seaweeds utilization is limited presumably due to limited knowledge of their nutritional potential. This study adopted a complete random design in sampling and nutritional evaluation of seaweeds. A random complete block design was adopted in the preparation of biscuit and assessment of physical properties and sensory attributes of the baked seaweed biscuits. The aim of the research was to collect selected seaweeds in Kenya and assess their nutritional composition for potential utilization in biscuit development. The seaweed samples were collected and identified from three coastal sites in Kenya (Mkomani, Kibuyuni and Mtwapa) in March, July and October 2013. The sites were selected because they had a wide diversity of seaweed species. The analytical methods by the Association of Official Analytical Chemists (AOAC) were used for proximate analysis whereas mineral composition was determined using atomic absorption spectrophotometry (AAS). The chemical analyses were performed on each species of the seaweed in triplicates. The major proximate component was the nitrogen free extract (NFE) with a mean value of 42.09 ± 0.83% dry weight (dw) whereas the lowest component was crude fat (1.81 ± 0.04% dw). The major mineral element was magnesium with a mean value of 1523.45 ± 66.93 mg/100g dw whereas the lowest component was lead (0.20 ± 0.01 mg/100g dw). The chlorophytes (green algae) had the highest magnesium and calcium contents compared to the phaeophytes (brown algae) and rhodophytes (red algae). The chemical composition of the seaweeds varied significantly among the species, algal divisions, months and sites (p<0.05). The levels of cadmium and lead in the seaweeds collected were higher than the recommended limits in food set by World Health Organisation (WHO) due to pollution of seawater as a result of human activities. Considering the daily recommended intake of 4g/day, little seaweed amount could be incorporated in food products such as biscuits. From the study, the seaweed, Dictyota sp. 2 had the highest iron (314.25 ± 3.87 mg/100g dw) and zinc (50.69 ± 1.40 mg/100g dw) contents, but the lowest cadmium 0.20 ± 0.04 mg/100g dw) and lead (0.02 ± 0.00 mg/100g dw) contents (p<0.05) and therefore could be incorporated in biscuits. Sensory evaluation of seaweed biscuits showed that the scores for the seaweed biscuits (1–5% seaweed) were only slightly lower than the control (0% seaweed). All the seaweed biscuits were of acceptable sensory properties suggesting potential incorporation of seaweeds in biscuits. Howeer, biscuits with more than 3% seaweed content exceeded the permissible limits for cadmium in foods according to Codex Alimentarius Commission (CAC), thus were not recommended due to the risk of toxicity to consumers. Biscuits with 1–3% seaweed content provided recommended daily intake (RDI) levels of 30.58–63.67% for iron and 20.13–25.73% for zinc. However, there was the concern of cadmium accumulation in human beings over time that could result in adverse effects. The findings of this study indicate that seaweeds are rich in nutrients such as protein and minerals, and when incorporated in small amounts in common food vehicles are potential resources for seaweed-based products for improved human nutrition. Further, the Government of Kenya could engage stakeholders in developing a guide in creating awareness of seaweeds in order to develop seaweed-based functional foods for improved health and nutrition.