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In this study, we addressed the challenge of excessive fluorescence background in bacterial colony Raman detection and aimed to achieve rapid identification of colonies. To overcome this issue, we employed a combination of droplet microcavity and label-free Surface Enhanced Raman Spectroscopy (SERS) technologies for spectroscopic analysis of five species of lactic acid bacteria (LAB) colonies during fermentation. This approach, coupled with Supported Vector Machine (SVM) and K-Nearest Neighbors (KNN) machine learning algorithms, facilitated the identification and analysis of spectral data. Comparing the results with conventional bacterial colony Raman spectra, the SERS spectra exhibited clear peaks, a higher and more stable signal-to-noise ratio, and noticeable spectral differences between various colonies, overcoming the limitations of insufficient fluorescence background. Moreover, the detection speed was notably enhanced, each SERS spectrum requires only 0.5 s, and the acquisition of the 100 spectral data points necessary for one bacterial colony is accomplished in less than 1 min. The SVM algorithm demonstrated a bacterial colony identification rate exceeding 95%, while the KNN algorithm achieved a rate surpassing 90%. These findings highlight the practical importance of using droplet microcavity combined with label-free SERS technology for quick and robust identification of the bacterial colonies. • Droplet optical microcavity combined with label-free SERS technology for direct ultra-fast identification of colonies. • The process does not require additional processing of the colonies and can complete data collection within 1 min. • Excellent results for the identification of lactic acid bacteria colonies for yogurt fermentation. [ABSTRACT FROM AUTHOR]

Large yellow croaker roe phospholipid (LYCRPLs) is a kind of multi-functional marine phospholipids. Advanced insights into its emulsifying properties and stability require a deeper exploring. In this study, the chemical composition of LYCRPLs, egg yolk phospholipids (EYPLs) and soybean phospholipids (SPLs) were determined, and their emulsifying properties were investigated systematically. Results suggested that the contents of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in LYCRPLs were the highest (39.35 ± 1.05%) and LYCRPLs had a different phospholipid composition compared with EYPLs and SPLs, but FTIR analysis shows there was no significant difference in the composition of the main functional groups among LYCRPLs, EYPLs and SPLs. Meanwhile, the initial astaxanthin nanoemulsions showed small particle size (0.23–0.27 μm) and had the lowest surface tension (34.29 ± 0.33 mN/m). Furthermore, LYCRPLs was the best one when they prevented nanoemulsions aggregation and phase separation. Findings indicate that LYCRPLs might be used as a reasonable emulsifier in the future. • The emulsifying properties of marine phospholipids from large yellow croaker roe were evaluated. • Large yellow croaker roe phospholipids are rich in EPA and DHA. • Lysophosphatidic of marine phospholipids may enhance its emulsifying properties. • The astaxanthin nanoemulsions stabilized by Large yellow croaker roe phospholipids has the best stability. [ABSTRACT FROM AUTHOR]