Tea polyphenols: prevention of cancer and optimizing health. Discussion 4.

Background Meat is a perishable product and during storage, the actions of microorganisms and endogenous enzymes result in chemical compositional changes. Total volatile basic nitrogen (TVB-N) is often used as a biomarker of protein and amine degradation. The broad adoption of TVB-N to interpret meat freshness is somewhat restricted. This is the result of limited or inconsistent knowledge pertaining to the association between TVB-N and other freshness parameters, for beef, sheep/goat meat, pork, chicken and other types of meat, especially when compared to fish. Current meat studies have failed to address the mechanisms between TVB-N generation and production, processing and preservation strategies. Scope and approach Etiology of spoilage and freshness indicators in fresh meat are discussed and various mechanisms contributing to meat spoilage are highlighted. Further, the use and application of TVB-N for understanding the freshness of different meat types has been comprehensively reviewed with the aim of establishing its usefulness as a freshness marker. Key Findings and Conclusions TVB-N increases with meat storage and is aligned with other biomarkers of spoilage (i.e. function of duration, temperature, packaging, etc.). But these increases are not always consistent. There are different recommendations of TVB-N limits for meat freshness. These are primarily for fish and seafood products and therefore inappropriate for other meat types, are species specific, arbitrary, or have an element of ambiguity (e.g. an intermediary ‘stale’ classification between fresh and spoilt states). The selection of TVB-N limits can therefore introduce inaccuracy and subjectivity into the appraisal of meat freshness. Several destructive and non-destructive methods have been used to determine TVB-N, however, their capacity is limited to the differential between spoilt and non-spoilt samples through chemometric classification systems based on predefined TVB-N guidelines. Further reference populations and investigations of red meat types are required.

Total volatile basic nitrogen (TVB-N) and its role in meat spoilage: A review

The chemical composition and taste quality of tea fluctuate seasonally. However, the compounds responsible for the seasonal variation of metabolic pattern and taste quality are far from clear. This study compared the metabolite profiles of green teas of nine varieties that were plucked in spring, summer, and autumn by using ultraperformance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF/MS) on a reversed phase column. A multivariate analysis indicated distinct differences among the metabolite phenotypes of teas harvested in different seasons. Heat-map analysis and metabolic pathway analysis demonstrated that flavan-3-ols, theasinensins, procyanidins, quercetin-O-glycosides, apigenin-C-glycosides, and amino acids exhibited sharp seasonal fluctuations. An equivalent quantification of tea tastes showed that in summer and autumn teas, the bitterness and astringency were significantly elevated, whereas umami declined. Metabolite content comparisons and partial least-squares analysis suggested that several flavonoids and amino acids are mainly responsible for the seasonal variations in taste quality.

Nontargeted Analysis Using Ultraperformance Liquid Chromatography-Quadrupole Time-of-Flight Mass Spectrometry Uncovers the Effects of Harvest Season on the Metabolites and Taste Quality of Tea (Camellia sinensis L.).

In this study, a turn-on nanosensor for detecting Hg2+ was developed based on the fluorescence resonance energy transfer (FRET) between long-strand aptamers-functionalized upconversion nanoparticles (UCNPs) and short-strand aptamers-functionalized gold nanoparticles (GNPs). In the absence of Hg2+, FRET between UCNPs and GNPs occurred because of the specific matching between two aptamers, resulting in the fluorescence quenching of UCNPs. In the presence of Hg2+, long-stranded aptamers fold back into a hairpin structure due to the stable binding interactions between Hg2+ and thymine, leading to the release of GNPs from UCNPs, resulting in the quenched fluorescence restoration. Under the optimized conditions, the nanosensor achieved a linear detection range of 0.2–20 μM and a low detection limit (LOD) of 60 nM. Meanwhile, it showed good selectivity and has been applied to detecting Hg2+ in tap water and milk samples with good precision.

Turn-On Fluoresence Sensor for Hg2+ in Food Based on FRET between Aptamers-Functionalized Upconversion Nanoparticles and Gold Nanoparticles.

Near infrared system coupled chemometric algorithms for enumeration of total fungi count in cocoa beans neat solution

Public attention in tea quality and nutrition has increased significantly in recent decades, due in part to changes in consumer behavior and the gradually increasing consumption of tea. Demand for high quality tea products obviously requires high standards of quality assurance and process control; satisfying this demand in turn requires appropriate analytical tools for analysis of tea quality and nutrition. Green analytical tool, as an alternative to conventional analysis methods, has the desirable features in terms of operating speed, ease-of-use, minimal or no sample preparation, and avoidance of sample destruction. This paper reviews recent developed technologies, such as near infrared (NIR) spectroscopy, electronic tongue (E-tongue), electronic nose (E-nose), computer vision, integration of multiple sensors, and latest research efforts to assess tea quality and nutrition. Particularly, we have reviewed some relevant data processing algorithms involved in each green analytical tool. Finally, we provided the technical challenges and outlook for the application of these green analytical technologies in analysis of tea quality and nutrition.

Recent developments of green analytical techniques in analysis of tea's quality and nutrition

Rare earth-doped upconversion nanoparticles (UCNPs) have promising potential in the field of food safety because of their unique frequency upconverting capability and high detection sensitivity. Here, we report a rapid and sensitive UCNP-based bacterium-sensing strategy using Escherichia coli. Highly fluorescent and water-soluble UCNPs were fabricated and conjugated with antibodies against E. coli for use as fluorescent probes. The E. coli were successively captured by the fluorescent probes. After the captured cell samples were pelleted, the differences in the fluorescence intensities between sample supernatants and the control were observed to increase linearly with E. coli concentration from 42 to 42 × 10(6) colony-forming units (cfu)/mL (R(2) = 0.9802), resulting in a relatively low limit of detection of 10 cfu/mL. Furthermore, the ability of the bioassay to detect E. coli was also confirmed in adulterated meat and milk samples.

Fabricating Upconversion Fluorescent Probes for Rapidly Sensing Foodborne Pathogens

Real-time monitoring of process parameters in rice wine fermentation by a portable spectral analytical system combined with multivariate analysis

Rare earth-doped upconversion nanoparticles (UCNPs) have promising potential in biodetection due to their peculiar frequency upconverting capabilities and high detection sensitivity. Here, we report a novel dual-color UCNP-based bacterium-sensing biosensor for simultaneously Escherichia coli and Staphylococcus aureus detection using UCNP as a fluorescence marker and conjugated with antibodies as the specific molecular recognition probe. Dual-color UCNPs were fabricated via varying lanthanide dopants to acquire the well-separated emission peaks. When E. coli and S. aureus were added into the reaction system, the recognition probes would capture the target bacteria through the specific binding of antibody. Then, the fluorescence intensities decreased (∆I = I
 o
 -I) were observed to increase linearly with the rising concentration of the E. coli (664 nm) and S. aureus (806 nm) from 47 to 47 × 106 cfu mL−1 (R
 2 = 0.98) and 64 to 64 × 106 cfu mL−1 (R
 2 = 0.97), respectively, resulting in the relatively low limit of 13 and 15 cfu mL−1 for E. coli and S. aureus. Furthermore, this UCNP-based bacterium-sensing biosensor could also be successfully applied to simultaneously detect E. coli and S. aureus in adulterated meat and milk samples.

Dual-Color Upconversion Nanoparticles (UCNPs)-Based Fluorescent Immunoassay Probes for Sensitive Sensing Foodborne Pathogens

This study assessed the feasibility on simultaneous and rapid measurement of total polyphenol and caffeine contents in black tea infusion using a developed spectroscopy system. First, a portable visible/near infrared (VIS-NIR) spectroscopy system was developed for data acquisition, and then synergy interval partial least squares (Si-PLS), backpropagation artificial neural network (BP-ANN), and adaptive boosting (AdaBoost) combined with BP-ANN, namely BP-AdaBoost, were used comparatively for modeling. The performances of these models were evaluated according to the correlation coefficient (R
 p) in the prediction set. Experimental results showed that the performances of nonlinear BP-ANN and BP-AdaBoost models were superior to those of linear Si-PLS models. In particular, BP-AdaBoost models have made a great progress in contrast to BP-ANN models, with R
 p = 0.9382 for total polyphenol content and R
 p = 0.9471 for caffeine content. The overall results indicated that this developed spectroscopy system combined with a suitable multivariate calibration tool could be used for the simultaneous and rapid measurement of the main compositions in black tea infusion.

Simultaneous and Rapid Measurement of Main Compositions in Black Tea Infusion Using a Developed Spectroscopy System Combined with Multivariate Calibration

Wenxiu Pan

Papers

Recent developments of green analytical techniques in analysis of tea's quality and nutrition

Fabricating Upconversion Fluorescent Probes for Rapidly Sensing Foodborne Pathogens

Real-time monitoring of process parameters in rice wine fermentation by a portable spectral analytical system combined with multivariate analysis

Dual-Color Upconversion Nanoparticles (UCNPs)-Based Fluorescent Immunoassay Probes for Sensitive Sensing Foodborne Pathogens

Simultaneous and Rapid Measurement of Main Compositions in Black Tea Infusion Using a Developed Spectroscopy System Combined with Multivariate Calibration