Safety Evaluation Of Water-hyacinth Leaf Protein Products

This work has been carried out to evaluate the dietary safety of Water-hyacinth leaf protein products. This study is able to supply a basal theory and technical data support for processing and utilizing Water-hyacinth leaf protein products.By researching on fresh Water-hyacinth leaves, comparison of the efficiency of different methods for preparing protein products from them has been undertaken. On the basis of this study, two feasible procedures were selected and used for preparing Water-hyacinth leaf protein products. Whole Water-hyacinth leaf powder and Water-hyacinth leaf protein concentrate were prepared by the selected procedures. The dietary safety of these products was evaluated by chemical analysis of toxic components and animal feeding for acute toxicity test. The experimental results are summarized as follows:1,Preparation of Water-hyacinth Leaf Protein ProductsThe experiment put emphasis upon studies on comparison of the efficiency of making protein products from Water-hyacinth leaves using aqueous solvents extraction followed by precipitating the extracted proteins by heating alone or acidification plus heating, and ethanol extraction. The experimental results showed that the extraction rate of Water-hyacinth leaf proteins using an aqueous solvent was 57.3% under operating conditions of 30°C, pH10.0 and 0.3mol/L NaCl concentration, and the precipitation rate of the extracted proteins was 73.61% at 80°C and pH4.0. On the other hand, the extraction and precipitation rates of proteins by ethanol were 87.6% and 91.89%, respectively. Protein contents of the products made by three methods described above were 48.67%, 57.56% and 55.63%, respectively. It was therefore concluded that ethanol extraction was the most efficient method for preparing Water-hyacinth leaf protein concentrate.For practical purpose, whole Water-hyacinth leaf powder and leaf protein concentrated by ethanol extraction were prepared and, their protein contents were 20.3% and 55.63%, respectively.2,Analyses of toxins in Water-hyacinth leaf protein productsFor evaluating the safety of leaf protein products, total alkaloids and polyphenols contents were determined, respectively, as a starter.(1) The experimental results of qualitative analysis by bismuth kalium iodide showed that there were alkaloids in both whole Water-hyacinth leaf powder and leaf protein concentrated by ethanol. The results of quantitative analysis indicated that total content in the whole Water-hyacinth leaf powder was 0.0205% on dry weight basis. However, in the leaf protein concentrate prepared by ethanol, no alkaloids were quantitatively detected.(2) The total polyphenols contents in whole Water-hyacinth leaf powder and leaf protein concentrate prepared by ethanol were 4.57mg/100g on dry weight basis and 0.685mg/100g on dry weight basis, respectively.It was therefore suggested that leaf protein concentrate prepared by ethanol should not be toxic due to the presence of alkaloids and polyphenols. 3,Animal feeding test(1) The result of acute toxic tests indicated that no rats died in four testing groups. The LD50 of rat oral administration testified by the acute toxicity trial was more than 21.5g/(kg·bw). And so, according to the National Food Safety Toxicity Evaluation Criteria, it is suggested that leaf protein concentrate prepared by ethanol should be innocuous.(2) The visual observation result of acute toxic animal feeding test indicated that all of the rats were seemingly well-balanced. After feeding for 7 days, the avoirdupois of all rats was increased. The results of hem analysis, bathing posture tests, general dissection and internal organic investigation indicated that no abnormity was found. Therefore, it was implied that the Water-hyacinth leaf protein products would not be poisonous to rats.On the basis of these studies, the dietary safety of Water-hyacinth leaf protein products was evaluated. The methods developed for preparing Water-hyacinth leaf protein products could be adapted to industrialized production, and they're important to extend biomass production. These offered scientific arguments and data for exploiting Water-hyacinth leaf proteins.