Effect Of Processing Methods On Dietary Safety Of Water Hyacinth Leaf Protein Products

This work has been carried out to evaluate the effect of different processing methods on the dietary safety of Water Hyacinth leaf protein concentrates.This is able to supply a basal theory and technical data supports for processing and utilizing Water Hyacinth leaf protein products.By fresh Water Hyacinth leaves as studying materials,which contain 23.75%proteins,three different processing methods including water-ethanol,water-ethanol-hydrochloric acid,and water-ethanol-hydrochloric-sodium hydroxide extractions were undertaken.On the basis of the results of pre-evaluation on the dietary safety of these products made by the above described methods,by chemical analysis of toxic components,Water Hyacinth leaf protein concentrate made by ethanol-hydrochloric extraction was selected for further animal feeding for sub-chronic toxicity test.The experimental results are summarized as follows:(1) Efficiency of concentrating proteins in Water Hyacinth leaves by water-ethanol extraction. The results of single factor and orthogonal experiments indicated that the best conditions for concentrating proteins in Water Hyacinth leaves by water-ethanol extraction were water(boiling for 4 minutes),95%ethanol(extracting 8h at 60℃)and a solid-liquid ratio of 1:60.By the above described procedure,the protein in Water Hyacinth leaves was concentrated to 34.88%.(2) Efficiency of concentrating proteins in Water Hyacinth leaves by water-ethanol-hydrochloric acid extraction.The results of single factor and orthogonal experiments indicated that the best conditions to concentrate proteins in Water Hyacinth leaves were water(boiling for 4 min), 95%ethanol(extracting for 8 h at 60℃),4‰hydrochloric acid(extracting for 8 min at 80℃).By the above described procedure,the protein in Water Hyacinth leaves was concentrated to 38.16%.(3) Efficiency of concentrating proteins in Water Hyacinth leaves by water- ethanol-hydrochloric acid-sodium hydroxide extraction.The results of single factor and orthogonal experiments indicated that the best conditions to concentrate proteins in Water Hyacinth leaves were water(boiling for 4 min),95%ethanol(extracting for 8 h at 60℃),4‰hydrochloric acid (extracting for 8 min at 80℃),2‰NaOH(extracting for 5 min at 50℃).Under these conditions, the protein in Water Hyacinth leaves was concentrated to 39.87%.(4) Weight losses of Water Hyacinth leaves caused by three processing procedures and comparison of the main compositions between whole leaf powder and those of three processed products.The weight losses of whole leaf,product number 1,product number 2 and product number 3 were 0,33.5%,37.0%and 37.6%,respectively while their protein contents were 23.75%, 34.88%,38.16%,39.87%,respectively,and their polyphenol contents were 3.62mg/100g, 1.26mg/100g,0.73mg/100g and 0.52mg/100g,respectively.Their alkaloid contents were 19.38mg/100g,4.16mg/100g,2.25mg/100g and 1.87mg/100g,respectively,and their ash contents were 16.13%,11.70%,7.22%and 5.26%,respectively.(5) Results of animal feeding for toxicity tests.Considering weight loss during processing as well as protein concentration and anti-nutrient contents of the products,product number 2 and whole leaf powder were chosen to carry on the animal feeding test for evaluating their acute and sub-chronic toxicities.The result of acute toxic tests indicated that no rats died in four testing groups.The LD(50) of rats oral administration testified by the acute toxicity trial was more than 21.50g/kg.bw.And so,according to the National Food Safety Toxicity Evaluation Criteria,it is suggested that leaf protein concentrate should be innocuous.In the sub-chronic animal feeing test, the rats in blank group are all normal.The rats in whole leaf group were less active than those in blank group and nipped each other 2 months later,but no rats died.After feeding for 3 months,the avoirdupois of all rats was increased.The liver color of the rats in protein concentrate group looked slightly pale,something unclear was occasionally seen.The results of hem analysis,bathing posture tests,pole climbing behavior,general dissection and other internal organic investigation indicated that no abnormity was found.Therefore,it was implied that the Water Hyacinth leaf protein products would not be acutely and sub-chronically poisonous to rats.(6) Effect of Processing Methods on the Safety of Water Hyacinth Leaf Protein Concentrate. Experimental results imply that water-ethanol-hydrochloric acid improved the dietary safety of Water Hyacinth leaf protein concentrate,which seems safer than whole leaf powder.