Cassava leaves have the potential to address protein and micronutrients deficiencies but the downside is the presence of cyanogenic glycosides. Consumption of a cyanogenic plant has been implicated in many pathological disorders including goitre. No study had been done in Ghana between cassava leaves consumption and goitre which was reported endemic in the northern belt. The northern belt of Ghana widely consumes cassava leaves, unlike the southern and the middle parts. The main objective of the study was therefore to identify Ghanaian cassava leaves with safe cyanide levels for use as vegetable. The study was conducted in three communities each in the southern, transition, and the northern belts of Ghana, on the basis that an identified agricultural research station closest to those communities in the respective belts, was the most active in the root and tuber improvement and marketing programme in Ghana. Cyanide analysis was done using the standard Chloramine-T/Pyridine barbituric acid colorimetric method, at the Société Générale de Surveillance laboratory in Tema. The cyanide content of Ghanaian cassava leaves from most commonly consumed varieties ranged from 72.79 – 203.50 ppm, dry weight. This is relatively lower than what have been reported by some researchers in other countries. Ghanaians in general, therefore, grow relatively low-cyanide cassavas. Two-factor analysis of variance revealed a significant interactive effect (p=0.024) between type of variety (genotype) and the geographical location (environment), of which the impact was greater in the unimproved varieties. By adequate processing involving pounding followed by boiling, all cassava leaves considered in this study were all safe for consumption. It is recommended that Ghanaian cassava leaves be promoted for use as vegetable, especially in the south. This must however be accompanied with proper education on the potential toxicity and on adequate processing techniques.
Table of Contents
1.0. INTRODUCTION
1.1. Background
1.2. Problem Statement
1.3. Rationale for the Study
1.4. Research Questions/Hypotheses
1.5. Objectives
1.5.1. Main Objective
1.5.2. Specific Objectives
2.0. LITERATURE REVIEW
2.1. Cassava Cultivation in Ghana
2.2. Prevalence of Micronutrient Deficiencies in Ghana
2.2.1. Impacts of Micronutrient Deficiencies
2.3. Nutritional Value of Cassava Leaves
2.3.1. Micronutrient Potential of Cassava Leaves
2.3.1.1. The Effects of Vitamin C on Iron Status
2.3.1.2. The Effects of Carotenoids on Vitamin A Status
2.3.1.3. Dietary Protein as Enhancer of Zinc Absorption
2.3.1.4. Nutrient Requirements: The Case of Vitamin A
2.3.2. Amino Acid Profile of Cassava Leaves
2.3.3. Effects of Processing on the Nutrient Contents of Cassava Leaves
2.4. Cassava as a Cyanogenic Plant
2.4.1. Synthesis, Transport and Contents
2.4.2. Factors Affecting Cyanogenic Glycoside Contents
2.5. Pathological Effects of Cassava Cyanide Exposure
2.5.1. Metabolism/Detoxification of Cyanide in the Body
2.5.2. Pathological Effects of Cassava Cyanide Consumption
2.5.2.1. Evidences of Chronic Cassava Cyanide Intoxication
3.0. METHODOLOGY
3.1. Field Survey
3.1.1. Selection and Description of Study Sites
3.1.2. Sample Size Calculation and Selection of Respondents
3.2. Sample Collection
3.2.1. Sampling Technique
3.2.2. Exclusion/Inclusion Criteria
3.3. Chemical Analysis
3.3.1. Materials
3.3.2. Preparation of analytical Samples
3.3.3. Determination of Cyanide Concentration
3.4. Statistical Analysis
4.0. RESULTS
4.1. Field Survey
4.1.1. Consumption of Cassava Leaves among Ghanaian Farmers
4.2. Chemical Analysis
4.2.1. Cyanide Content of Leaves of Most Commonly Consumed Cassava Varieties
4.2.2. Predictors of Cyanide Concentration
4.2.3. Identifying Safe Varieties by Wet weight Cyanide Content Only
4.2.4. Identifying Safe Varieties by Dry Weight Cyanide Content Only
5.0. DISCUSSION
5.1. Field Survey
5.1.1. Background Characteristics of Respondents
5.1.2. Consumption of Cassava Leaves among Ghanaian Farmers
5.1.3. Commonly Consumed Cassava Varieties
5.2. Chemical Analysis
5.2.1. Cyanide Contents of the Leaves Popular Ghanaian Cassava Varieties
5.2.2. Environmental Impacts on Improved Varieties as Opposed to Unimproved Ones
5.2.3. Identifying Leaves with Safe Cyanide Levels
5.2.4. Reasons for Difference in the Effects of Processing Methods
6.0. CONCLUSIONS AND RECOMMENDATIONS
6.1. Conclusions
6.2. Recommendations
Research Objectives and Focus
The primary objective of this research is to identify Ghanaian cassava varieties that possess safe cyanide levels in their leaves for human consumption. The study seeks to address critical issues regarding the nutritional potential of cassava leaves as a vegetable and to evaluate the safety risks associated with their consumption in various geographical belts of Ghana.
- Nutritional characterization of cassava leaves compared to other vegetables.
- Evaluation of cyanogenic glycoside content in commonly consumed Ghanaian varieties.
- Assessment of the impact of environmental and ecological factors on cyanide levels.
- Comparison of various processing methods and their effectiveness in reducing toxicity.
- Promotion of safe consumption practices based on empirical findings.
Excerpt from the Book
2.4. CASSAVA AS A CYANOGENIC PLANT
The endogenous presence of cyanogenic glycosides in cassava (leaves, petioles, stem, roots, etc.) is well documented (Wobeto et al., 2007; McMahon et al., 1995; Bradbury et al., 1991). In cassava, the cyanogenic glycosides exist predominantly as linamarin (95% of total content of cyanogens) and lotaustralin (methyl linamarin, 5%) (Bradbury et al., 1991). The precursors for their synthesis are L-valine (for linamarin) and L-isoleucine (for lotaustralin). The amino acids are hydroxylated to form L-hydroxyl amino acids, and then converted to aldoxime, and in turn to nitrile (Fig. 2.3). Hydroxylation of the nitrile forms hrodroxynitrile leading to the formation of the corresponding cyanogenic glycoside, following glycosylation.
When cassava tissues are disrupted by any mechanical means such as cutting, grating, bruising, etc., the endogenous enzymes (linamarase) come into contact with their substrates (cyanogenic glycosides) and hydrolyse them into glucose and cyanohydrins (Fig. 2.4). This is because the cyanogens (cyanogenic glycosides) and the cyanogenic enzymes are found in different compartments in the cell (Whyte et al., 1994). This presupposes that cassava (leaves), when intact, cannot generate free hydrocyanic acid (Teles, 2002). At pH > 5 and temperature >30˚C, cyanohydrins break down spontaneously into ketones and hydrocyanic acid (HCN) (Fig. 2.4). In the leaves, cyanohydrins can also be decomposed by a second enzyme hydroxynitrile lyase; hence giving a higher linamarase catalytic efficiency in cassava leaves than in the roots (Whyte et al., 1994). Bokanga (1994) has reported that the enzymatic catalytic activity in cassava leaves is over 200 times greater than in the roots.
Summary of Chapters
1.0. INTRODUCTION: This chapter introduces cassava as a vital staple food and evaluates its nutritional potential, while highlighting the public health concerns regarding cyanide toxicity and the rationale for the study.
2.0. LITERATURE REVIEW: This section details the cultivation and nutritional profile of cassava leaves, discusses cyanogenesis in plants, and reviews the pathological risks associated with chronic cyanide exposure.
3.0. METHODOLOGY: The chapter outlines the field survey design across three agro-ecological belts in Ghana, the selection of study sites, and the standardized chemical analysis protocols used to measure cyanide concentrations.
4.0. RESULTS: This chapter presents data on the socio-demographic characteristics of farmers, the consumption patterns of cassava leaves, and the laboratory findings regarding cyanide levels across different varieties and locations.
5.0. DISCUSSION: This section interprets the study's findings, comparing them with existing literature and analyzing the influence of environmental factors and processing methods on cyanide reduction.
6.0. CONCLUSIONS AND RECOMMENDATIONS: The final chapter summarizes key findings, confirms that cassava leaves can be safely consumed with appropriate processing, and suggests future research directions.
Keywords
Cassava leaves, Cyanogenic glycosides, Food safety, Micronutrient deficiency, Cyanide toxicity, Processing methods, Pounding, Boiling, Linamarin, Linamarase, Ghana, Public health, Nutritional value, Dietary protein, Food security
Frequently Asked Questions
What is the core focus of this scientific research?
This thesis investigates the safety of consuming Ghanaian cassava leaves, specifically focusing on cyanogenic glycoside levels and how they are affected by variety, geographical environment, and traditional processing methods.
What are the central thematic fields?
The research combines nutritional science with food toxicology, focusing on the micronutrient potential of cassava leaves, their cyanide content, and the efficacy of traditional processing techniques in rendering them safe for consumption.
What is the primary research goal?
The main objective is to identify and validate Ghanaian cassava varieties that maintain safe cyanide levels after preparation, aiming to promote these leaves as a viable, nutritious vegetable option for the population.
Which scientific methodology is utilized?
The study employs a field survey to capture consumption habits and data on varieties, combined with chemical analysis using the Chloramine-T/Pyridine barbituric acid colorimetric method to determine cyanide concentrations.
What is discussed in the main part of the thesis?
The main part covers the nutritional composition of the leaves, the biochemical process of cyanogenesis in cassava plants, the pathological risks of cyanide exposure, and the statistical analysis of how ecological factors like temperature influence cyanide concentration.
Which keywords characterize this work?
The key concepts include cassava leaf utilization, cyanogenic glycosides, nutritional biochemistry, food processing, cyanide toxicity, and safe consumption levels.
Why are different processing methods important in this study?
The study highlights that methods like pounding followed by boiling are significantly more effective at reducing cyanide to safe WHO levels compared to chopping and boiling, which leaves residual levels potentially unsafe for consumption.
What role does the geographical location play?
The study found that geographical factors—particularly higher atmospheric temperatures in the northern belt of Ghana—are significant predictors of increased cyanide concentration in cassava leaves.
What is the conclusion regarding safe consumption?
The author concludes that with proper processing—specifically, thorough pounding followed by boiling—Ghanaian cassava leaves are generally safe for human consumption and can serve as a vital source of protein and micronutrients.
- Citar trabajo
- William Opoku-Nkoom (Autor), 2011, Identifying Ghanaian Cassava Leaves with Safe Cyanide Levels for Use as Vegetable, Múnich, GRIN Verlag, https://www.grin.com/document/278572
