Effect of centrifugal ultrafiltration on the composition of aqueous extracts of saffron spice (Crocus sativus L.)

Evaluation of storage time effect on saffron chemical profile using gas chromatography and spectrophotometry techniques coupled with chemometrics

Saffron quality is commonly determined by three parameters: color, aroma, and taste. Several factors including harvesting and post-harvesting conditions, affect these parameters. In this study, the effect of storage time on saffron quality was evaluated. At first, the relative concentration of the saffron secondary metabolites in freshly dried and 2 years stored saffron samples prepared with ISO 3632 and UA-DLLME methods and then measured using UV-Vis and GC-FID techniques. In order to find saffron storage time biomarkers, the obtained data were subjected to several data analysis steps including data preprocessing, principal component analysis (PCA), partial least square discriminant analysis (PLS-DA) and variable selection methods. Based on the obtained main biomarkers and proposed molecule mechanism, it can be concluded that during the storage periods, the intensity of saffron color reduces, while its aroma increases, reflecting a negative correlation between them. Freshly dried samples have a higher level of the crocins as coloring agents, β-isophorone, 4-hydroxy-3,5,5-trimethylcyclohex-2-enone and picrocrocin, while the stored samples were more abundant by safranal as the main saffron aroma agent.

Separation of plasmid DNA isoforms using centrifugal ultrafiltration

Centrifugal ultrafiltration is a well-established method for concentrating and purifying DNA. Here, we describe the use of centrifugal ultrafiltration for the separation of plasmid DNA isoforms based on differences in elongational flexibility of the supercoiled, open-circular, and linear plasmids. Transmission of each isoform is minimal below a critical value of the filtration velocity, which is directly related to the magnitude of the centrifugal speed and the system geometry. A discontinuous diafiltration process was used to enrich the desired isoform, as determined by agarose gel electrophoresis. The simplicity and efficacy of this membrane-based separation are attractive for multiple applications requiring the use of separated DNA isoforms.

Picrocrocin kinetics in aqueous saffron spice extracts (Crocus sativus L.) upon thermal treatment

The kinetics of picrocrocin degradation in aqueous extracts of saffron upon thermal treatment from 5 to 70 °C have been studied, together with the degradation of purified picrocrocin in water at 100 °C. The best fits to experimental data were found for a second-order kinetics model. Picrocrocin showed high stability with half-life periods (t(1/2)) ranging from >3400 h at 5 °C in saffron extracts to 9 h in the experiments with purified picrocrocin at 100 °C. In saffron extracts, the evolution of the rate constant (k) with temperature showed maximum values at 35 °C, and filtration of the extracts contributed to picrocrocin stability. In the case of purified picrocrocin, the generation of safranal in the first 5 h (yield up to 7.4%) was confirmed. Spectrometric parameters used in saffron quality control (E(1cm)(1%) 257 nm and ΔΕ(pic)) were not appropriate for documenting the evolution of picrocrocin.