Discrimination of aflatoxin contamination level in nutmeg by fluorescence fingerprint measurement

A fluorescence fingerprint (FF), also known as an excitation–emission matrix, was used to develop a new method of classifying nutmeg contaminated with aflatoxins. The experimental samples were collected from nutmeg with a wide range of fungal contamination levels. After grinding the samples, FF measurement and high–performance liquid chromatography (HPLC) analysis were carried out. The total concentration of aflatoxins (AFB1 + AFB2 + AFG1 + AFG2; total AF concentration) in the samples was determined using HPLC, which varied from 0.0 to 1781.8 ppb. The FFs of the same samples were measured with a fluorescence spectrophotometer. Although the FF patterns changed with increasing total AF concentration, the trend was unclear at lower concentrations. Threfore, models for predicting or classifying AF contamination in nutmeg from FF patterns were developed using partial least–squares regression (PLSR). The total AF concentrations predicted by the PLSR model showed a positive correlation to the actual concentration with a coefficient of determination of 0.69. Moreover, the variable importance in projection plot indicated that fluorescence from AFs as well as from kojic acid derivatives was important for the prediction of total AF concentration. Finally, it was indicated that samples with a total AF concentration of 10 ppb or higher could be reliably discriminated by setting the threshold to 2.2 ppb in the partial least–squares discriminant analysis (PLSDA). While no false negative was observed in the discrimination, the false positive rate was 13.3%. Future studies on nutmeg samples with different origins are necessary to confirm feasibility of FF as a rapid and simple method of predicting aflatoxin contamination of nutmeg

Simultaneous estimation of scavenging capacities of peach extract for multiple reactive oxygen species by fluorescence fingerprint method

In this study, the potential of using fluorescence fingerprint, also known as fluorescence excitation–emission matrix, for estimating the scavenging capacity of peach extract on reactive oxygen species (ROS) was investigated. Samples from each of the five cultivars (Asama Hakuto, Hakuho, Kawanakajima Hakuto, Natsukko and Ougonto) were freeze-dried and crushed. The scavenging capacities of peach extracts for the target ROS (hydroxyl, superoxide, alkoxyl radicals and singlet oxygen) were measured by electron paramagnetic resonance spin trapping method. Fluorescence fingerprints of the same samples were obtained. Partial least squares regression analysis was carried out to develop prediction models for ROS scavenging capacity. The models were assessed by external validation. Fluorescence fingerprint was found to accurately estimate the scavenging capacity for the alkoxyl and superoxide radicals with the prediction error of 0.06 mmol trolox eq./mL and 0.31 mmol α-lipoic acid eq./mL with a coefficient of determination of prediction (R2P) of 0.78 and 0.91, respectively