The Research And Comparision Of Insect Detection Technology In Flour

The insect fragments, insect eggs or larvae in wheat flour influence seriously the qualityof flour and its products, which affects our flour export trade. To find out a rapid detectionmethod of insects in wheat flour which improving flour quality and the quality of export tradehas very important practical significance. This paper compared and studied the FDA standardflotation, Phosphotungstic reduction measured egg uric acid method, chitin assay method,staining technique and DNA fingerprinting technique. The main results were as follows:（1）The flotation method, chitin method and DNA fingerprinting analysis technologywere applied in detection of insect fragments in flour, the detection result about insectfragments of flotation method was positively correlated with the number of fragments placedin the flour, the detection rate is up to85%of the flotation method. The chitin method candetect whether the flour contain insect fragments or not.However, it can only be qualitative,not quantitative, it is not suitable for the detection of insect fragments in flour, the methodneeds for further research; DNA fingerprint analysis technique can detect insect fragmentsaccounted for2%of the flour samples, and this method is accurate, specificity buttime-consuming and high cost.（2）The flotation method, chitin method, phosphotungstic acid reduction method tomeasure egg uric acid, staining method and DNA fingerprinting technique were applied inflour to detect the eggs. The flotation method detection rate is low (<15%) and no obviousregularity, the flotation method detection process damaged the eggs easily, which was notsuitable for the detection of egg. Chitin detection method which based on the color reactionof chitosan could determine whether the flour containing egg or not. This method is onlyqualitative, not quantitative. It was not suitable for detecting egg. Egg uric acid concentrationwas related to the number of eggs. Uric acid detection method can detect the limit of0.1egg/g flour, The detection method could be applied in flour. but there are still many problemsneed to be further studied.0.1%bromocresol green,1:1bromocresol green and orange Gmixed solution,0.05%of acid fuchsin and0.05mol/L iodine solution were applied in staining method. The eggs and flour were stained different colours respectively and could berecognized easily. The staining method detection rate was about80%. Eggs were dyed yelloworange by0.1%bromocresol green, flour was dyed yellow green, Eggs and flour were dyedpurple by acid fuchsin, but flour was dyed darker. Iodine solution dyed eggs brown, flour wasdyed dark brown. But the two color contrastion was not too obvious. Eggs were dyed yelloworange by1:1bromocresol green and orange G, flour was dyed brownish green. The colour ofeggs and flour was very easy to recognized than other three kinds of stains.The stainingmethod can be preliminary used for detection of eggs in flour. DNA fingerprinting technologywas applied to the detection of eggs in flour.It could be detected eggs accounted for1%of theflour samples.（3）DNAfingerprinting technique was applied to the detection of flour in larvae whichwas precise and specific. It is able to detect insect larva accounted for1%of the floursamples, but But the preparation work was complicated and high cost.