Quercetin and quercetin glucosides are the major flavonols present in onion (Allium cepa L.) and are predominantly present as quercetin, quercetin-3,4'-diglucoside and quercetin-4'-glucoside. Effect of different light wavelengths on onion after harvest and storage, with fluorescent, blue, red and ultra violet light influenced the quercetin and quercetin glucosides profile. In a peeled onion, all the light treatments elevated quercetin content in bulb. Among them, particularly fluorescent light effect was more eminent which stimulates the maximum synthesis of quercetin in onion. In case of whole onion bulb, skin and pulp showed different responses to light treatment, respectively. The pulp had the highest quercetin glucosides under blue light, whereas the lowest under fluorescent light. Onion skin showed nearly opposite pattern as compared to the pulp. In particular, light treatment proved to be a better way to increase the level of quercetin content in onions which might be utilized for industrial production of bioactive compounds from onion and onion waste products.

In this study, we investigated the volatile flavor compounds and sensory perceptions of Yanbian-style sauced beef prepared from raw meats subjected to different treatments (hot fresh, chilled, and frozen beef). The results indicated that the treatment of raw beef significantly impacted the quality and flavor of sauced beef. Sauced chilled beef (CRSB) exhibited the highest content of fatty acids and total amino acids. A total of 48 volatile compounds were identified. Moreover, a relative odor activity value analysis identified hexanal, nonanal, heptanal, 1-octen-3-ol, and 2,3-octanedione as the characteristic flavor compounds in Yanbian-style sauced beef. The sensory evaluation demonstrated that CRSB was the most palatable and flavorful. Additionally, correlation loading plot analysis indicated strong correlations between sensory evaluation, fatty acids, amino acids, and volatile flavor compounds. These results suggest that chilled beef meat is the best raw material for the production of Yanbian-style sauced beef.

The development of new techniques to rapidly and accurately detect bacteria has drawn continuous attention due to the potential threats posed by bacteria to human health and safety. Recently, a novel strategy based on fluorescent probes has drawn considerable interest for the detection of bacteria due to its high selectivity, fast response, and simple operation. In this review, we summarize the recent progress on fluorescent probes for the specific recognition and discrimination of Gram-negative and Gram-positive bacteria. In particular, we outline current design strategies, such as targeting of the differences in surface components, cell wall components, endogenous enzymes, surface charge, and hydrophobicity of various kinds of bacteria to develop various fluorescent sensors (organic small-molecule fluorescent probes, nanoprobes, and metal ion probes). We also emphasize the application of organic molecules in probe recognition elements. We hope that this review can stimulate this research area in bacterial detection and imaging in the future.