Consumption Patterns, Protein Quality and Hazards of “NULs” Utilization
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Date
NOVEMBER, 2017
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Abstract
Many people consume large quantities of plant-based products, including neglected and underutilized legumes (NULs), because of their availability or affordability. This makes NULs a critical food security resource. However, NULs are known to contain toxins such as lectins (glycoproteins) which persistently resist heat inactivation, making them a potentially serious health hazard. In order to promote their continuous and sustainable utilization, consumption profile, safety and nutritional quality by way of essential amino acids need to be investigated. Furthermore, suitable ways of attenuating the possible risks of lectins in NULs need to be investigated. A survey was carried out aimed at finding the processing and consumption patterns of five selected NULs; Vigna subterranea, Cajanus cajan, Mucuna pruriens, Phaseolus lunatus and Canavalia ensiformis focusing on consumer characteristics such as: age, house hold numbers, educational levels, marital status and occupation. Also considered were, the familiarity of NULs, perception of hazards and the risks, in terms of exposure assessment and exposure frequency of dishes consumed per body weight of consumers. Time-heat inactivation of the lectins in NULs flours, as well as their NULs’ model dishes were studied, from which risk was evaluated, using the hazard-based approach. Five different NULs protein extracts were profiled to ascertain the essential amino acids, and the quality evaluated by matching them against the standard FAO/WHO dietary indispensable amino acids for three age groups; infants, children and adults. −Radiated starches prepared using radiation doses from 3 to 42 kGy were composited at 10% composition with defatted NULs flours, with respect to quantities of native starches present in NULs. The composites were agitated in an extruder which operated within intrinsic temperature ranging from 2 to 12 oC. Residual lectins from the extrudates were quantified by ELISA analysis. The statistical analysis of the collected survey data involved the use of Palisade @Risk software to fit each measured parameter to the most adequate probabilistic distribution, based on its Akaike information criterion. Subsequently, the central tendency characteristics of the measured parameters, together with their variations, uncertainties and distribution functions were recorded. In the survey of the consumption of NULs, it was observed that, majority of the respondents who were over 40 years (67.6%) were familiar (59.4%) with NULs and consumed NULs dishes. The most popular dishes were prepared from Vigna subterranea (15.9%) and Phaseolus lunatus (14.95%). The majority of consumers (66%), perceived the presence of hazards in NULs, citing pesticide residues (58.7%), but no intrinsic hazards as threat. However, a few (16.6%)
considered the interaction between pesticide residues and food additives as dangerous. Majority (66.1%) regarded NULs dishes as safe, while at the same time complained of stomach discomfort (97.2%) after consumption. In spite of these observations, they would still recommend their use to others. Through the ELISA analysis, significantly high quantities of lectins still remained in Vigna subterranea flours even after cooking for 1 h. Risk analysis of the modelled foods revealed that the hazard quotient (HQ) of all the NULs dishes were above 1, meaning consumers are at risk of systemic toxicity. Assessment of essential amino acids revealed that, out of the five NULs studied, Vigna subterranea had adequate quantities of histidine (26.2 mg/g) that met the dietary requirements of all the three age groups. However, the levels of isoleucine (35.9 mg/g) and the aromatic amino acids phenylalanine and tyrosine (94 mg/g) were adequate for only children and adults. In the case of Phaseolus lunatus, lysine (53.6 mg/g) and threonine (44 mg/g) were relatively high. However, this could only meet the adults’ requirement. In spite of these contributions of amino acids, protein quality of Vigna subterranea and Phaseolus lunatus proteins, based on digested indispensable amino acid scores (DIAAS) presented a different outlook. Thus, the DIAAS of Vigna subterranea (3.6) and Phaseolus lunatus (2.5), show low quality, relative to international standards. In the studies involving the attenuation of lectins in NULs, Mamdani type fuzzy logic inference system was used to model the two input variables of the NULs flour treatment to predict the optimal lectin inactivation at 100% accuracy. While lectins from Canavalia ensiformis recorded 83% inactivation, lectins from Vigna subterranea rather potentiated up to 44%. Thus, -radiated starches incorporation into NULs flours during low temperature extrusion treatment, inactivated NULs lectins at varying degrees and these were adequately predicted by the model.
Description
A thesis submitted to the Department of Food Science and Technology, College of Science, in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Science and Technology,