Determination Of Royal Jelly Quality And Detection Of Manuka Honey Adulterated Based On Infrared Spectroscopy

Royal jelly is a pale-yellow slurry that is secreted by the hypopharyngeal and mandibular glands of nurse bees.Royal jelly has health benefits and therapeutic effects such as cancer prevention,diabetes treatment,and lowering of blood lipid levels,etc.Royal jelly contains many different types of fatty acids.These fatty acids are intimately associated with biological functions of royal jelly.Among these fatty acids,the most important is 10-hydroxy-2-decenoic acid(10-HDA).Manuka honey is a monofloral honey collected and made from the nectar of Manuka trees by bees.Compared with other types of honey,Manuka honey has excellent antibacterial activity and strong inhibitory effects against staphylococcus aureus.Because the superior antibacterial activity of Manuka honey can be utilized for preventing wound infections and facilitating wound healing,its medicinal value is relatively high.At present,the methods of measuring royal jelly quality and manuka honey adulteration still have the disadvantages of time-consuming inspection,cumbersome procedures,and the need for chemical reagents.Therefore,exploring a fast,simple,and green detection method has important application value and scientific research significance.In this paper,a new method for determinating the quality of royal jelly and detecting adulteration of Manuka honey by infrared spectroscopy has been established.The main contents are as follows:(1)Determination of 10-HDA using NIR spectroscopy combined with wavelength selection.A rapid quantitative analysis model for determining the 10-HDA content of royal jelly based on near-infrared(NIR)spectroscopy combining with PLS has been developed.Firstly,NIR spectra of 232 royal jelly samples with different 10-HDA concentrations(0.35%-2.44%)were be collected.Second-order derivative processing of the spectra was carried out to construct a full-spectrum PLS model.Secondly,GA-PLS,CARS-PLS,and Si-PLS were used to select characteristic wavelengths from the second-order derivative spectrum to construct a PLS calibration model.Finally,58 samples were used to select the best predictive model for 10-HDA content.The result show that the PLS model constructed after wavelength selection was significantly more accurate than the full spectrum model.The Si-PLS algorithm performed best and the corresponding characteristic wavelength range were:980-1038,1220-1278,1340-1398,and 1688-1746 nm.The prediction results were RMSEP=0.1496%and R_P=0.9380.(2)Determination of 10-HDA in royal jelly by ATR-FTMIR and NIR spectral combining with data fusion strategy.The attenuated total reflectance-Fourier transform mid-infrared(ATR-FTMIR)and NIR spectra of royal jelly samples were collected.Low-and mid-level data fusion strategies in combination with the PLS regression algorithm were used for quantitative modeling analysis of10-HDA content in royal jelly samples.In low-level data fusion,each raw spectrum was pre-processed before splicing into a new data matrix for PLS model construction and analysis.In the mid-level data fusion,Si-PLS was used for variable selection and principal component analysis/independent component analysis was used for feature extraction to obtain variables.The extracted variables were spliced before inputting into the PLS model for modeling and analysis.The results showed that the PLS analysis model constructed by mid-level data fusion is better than the PLS models constructed by independent data and low-level data fusion.Among these models,the PLS model that was constructed by the mid-level data fusion after Si-PLS variable selection had the best 10-HDA content prediction accuracy,with RMSEP=0.1118(%)and R_P=0.9585.(3)Manuka honey adulteration detection based on NIR spectroscopy combined with Aquaphotomics.The syrup-blended adulteration of Manuka honey was detected using NIR spectroscopy combined with aquaphotomics.Manuka honey was blended with five different syrups(corn syrup,sucrose syrup,high fructose syrup,beet syrup,and rice syrup)in degrees from 10%to50%(with gradients of 10%)for NIR spectra collection.Spectral variance analysis,PCA analysis,and PLS regression model regression vector analysis were then performed for the spectral region of 1300-1800 nm.Finally,12 characteristic bands(1324,1344,1356,1386,1418,1426,1434,1460,1476,1502,1528,and 1586 nm)were selected according to the analysis results,and the aquagrams constructed on the basis of these wavelengths were used for aquaphotomic evaluation.The results showed that Manuka honey dominated at long-wavelength regions(1476,1502,1528,and 1586 nm),indicating that more water molecules with strong hydrogen bonds and more structured water molecules are present in Manuka honey compared with sugar syrups.On the other hand,sugar syrups dominated at short-wavelength regions(1324,1344,1356,1386,1418,1426,1434,1460 nm),indicating that sugar syrups mainly contain unstructured free water molecules with few or no hydrogen bonds.Furthermore,as the degree of adulteration increased,the number of structured water molecules,which facilitate molecular interactions,in Manuka honey decreased.Therefore,it is feasible to determinate the quality of royal jelly by infrared spectroscopy and detect adulteration of Manuka honey.This method has the advantages of being fast,simple and green.The research results of this paper have positive and practical significance for maintaining the market order of royal jelly and manuka honey and protecting the legitimate rights and interests of consumers.