Geographical Traceability Of Wheat And Its Products Using Different Analytical Techniques

For agro-product authenticity and traceability,analytical techniques such as mass spectrometry,separation,and spectroscopic techniques have been widely used.However,due to the effect of different processing methods,the authenticity and traceability of processed products is very challenging,and it is still unclear whether these analytical techniques are equally effective to trace the geographical origin.The primary objective of this dissertation was to investigate the influence of industrial processing,regions,grown year and genotypes,on the isotopic composition,NIR fingerprints and volatile profile of Chinese winter wheat,which could provide a theoretical basis for the practical application of identifying the geographical origin of processed agro-products.Three experimental regions namely Huixian（Henan province）,Yangling（Shanxi province）,and Zhaoxian（Hebei province）were selected to conduct five years（2012-2016）field experiment with ten wheat cultivars.The wheat samples were harvested and further threshed,and finally,the wheat kernel was transferred to Key Laboratory of Agro Product Processing of CAAS for subsequent analysis.A Buhler laboratory mill（MLU 220,Uzvil,Switzerland）was used to obtain the break,reduction,bran,and fine bran（shorts）fractions following the approved method of AACC 26-21A（AACC,2000）.Different types of wheat flour（break and reduction）were further used to prepare Chinese dried noodles.The Chinese dried noodles were further cooked and subsequently freeze-dried and grounded to fine powder before further analysis.Isotope ratio mass spectrometry coupled with an elemental analyzer（EA-IRMS）was used to determine the light stable isotopes(δ¹³C,δ¹⁵N,δ¹⁸O,andδ²H)of the whole wheat kernel and different processed fractions.In addition,near-infrared spectroscopy was used to obtain spectral information of wheat whole kernel and processed flour.Moreover,gas chromatography coupled with mass spectrometry was used to investigate the volatile composition of Chinese winter wheat.Combined with multivaraiate analysis,the stable isotopes(δ¹³C,δ¹⁵N,δ¹⁸O,andδ²H)were analyzed to check whether there existed significant difference between wholemeal and different processed fraction.The influence of region,grown year,genotype,and interaction on the isotopic composition of all wheat fractions was assessed.The relation between whoemeal and different milling fractions forδ¹³C andδ¹⁵N were analyzed.The influence of wheat processing along with regions,grown year and their interaction were analyzed forδ¹³C,δ¹⁵N,δ¹⁸O,andδ²H.The effect of region,grown year,and genotype,on the NIR fingerprints of wheat whole kernel and processed flour was also examined.The potential of volatile compounds for classifying the geographical origin of Chinese winter wheat was also investigated.This study suggests the potential of spectroscopic techniques as an alternative to chromatographic or spectrometry techniques for food authenticity studies.Spectroscopic techniques coupled with appropriate chemometrics are a promising tool for food traceability and authenticity.The key findings are as follows:（1）Isotope fingerprints can be successfully used to trace the geographical origin of wheat and its products.Regions,genotypes,production year,and their interaction showed significant influence onδ¹³C andδ¹⁵N of wheat whole kernel and milling fractions.Region executed the largest variation for bothδ¹³C andδ¹⁵N isotopes among all fractions.Carbon isotopes were significantly different for some of the fractions whereas,nitrogen isotopes were more stable and there was no statistically significant difference among wheat kernel and different milling fractions.Nitrogen can be an effective tool for tracing the geographical origin of wheat and milling fractions.Wheat kernels along with milling fractions considerably improve the geographical classification indicating the reliability of fractions fingerprints in geographical traceability.Variation ofδ¹³C‰,δ¹⁵N‰,andδ¹⁸O‰between wheat whole kernel and its products（break,reduction,noodles,and cooked noodles）were?0.7‰,and no significant difference was observed,suggesting the reliability of these isotope fingerprints in geographical traceability of wheat‐processed fractions and foods.The great variation ofδ²H‰along the noodle processing chain shows that it is not suitable for processed wheat traceability.（2）NIR spectroscopy fingerprints showed best classification percentages for flour matrix both for geographical origin and grown years with the correct percentages of 100%and 73%,respectively.For genotypes discrimination,wheat whole kernel showed better classification percentage（98.2%）as compared to processed flour.（3）Volatile compound fingerprints showed significant differences for wheat from varied regions and genotypes.Multivariate ANOVA showed a significant influence of regions,wheat genotypes,and their interaction on the volatile composition of wheat.Region was the main factor which showed highest contribution as compared to cultivars and interaction.A classification model based on the linear discriminant analysis successfully constructs a robust model using the volatile compound for the discrimination of regions and cultivars with the correct classification percentages of 99 and 100%,respectively.