In this study, micro-Raman spectroscopy has been used to investigate the vibrational properties of laterally epitaxial overgrown (LEO) GaN. The LEO GaNfilms were grown by metal organic chemical vapor deposition on a 2 in. sapphire substrate with SiN mask. Photoluminescence and polarized Raman scattering measurements have been performed in the two regions of GaNgrowth (wing and window regions). Raman scattering results are consistent with the lateral growth of GaN in the overgrown region. We have observed second-order Raman scattering in the wing and window regions of GaN. The observations of longitudinal optical phonon plasmon modes in the overgrown region demonstrate that LEO GaN is doped. We have carried out micro-Raman mapping of the local strain and free carrier concentration in the LEO GaN. Anharmonicity due to temperature in LEO GaN has also been investigated. The anharmonicity was found to increase with increasing temperature, and such temperature-induced anharmonicity introduces changes in the linewidth and line center position of the Raman active phonons. The phonon lifetimes in GaN are estimated in the LEO region as well as in the coherently grown region (window region).

Fermentation of meat products refers to a series of physical, biological or chemical changes in raw meat that occurs under the actions of enzymes or via microbial fermentation and results in the formation of meat products with special flavours, colours and textures that have a long history in China. These products have a unique fermented flavour, bright colour and longer shelf life than ordinary meat products, and some have proteins that are more easily absorbed by the body due to the fermentation of beneficial bacteria. Flavour development in meat products is a dynamic process. During the processing and storage of fermented meat products, the breakdown of proteins and fats is accelerated due to the addition of different fermenting agents. Moreover, the physicochemical reactions that occur within the meat products and the actions of microorganisms during the fermentation process result in the production of flavour compounds, which will determine the final flavour characteristics of the fermented meat product. This paper reviews the flavour characteristics of Chinese dry-cured hams, sausages, bacon, cured fish and sour meat and analyses the flavour substance composition of various products. Due to the differences in the raw materials, processes, auxiliary materials and fermentation processes of various types of fermented meat products in China (ham, sausage, bacon, etc.), the flavour substances contained in the various types of fermented meat products in China are different from each other. However, most fermented meat products in China are cured and fermented, and therefore, they share similarities in terms of their flavour substance composition. The flavour substances in fermented meat products mainly include alcohols, ketones, aldehydes, acids, phenols and aromatic hydrocarbons. The study of such flavour characteristics is of great significance in fermented meat product quality, and provides certain theoretical references for the study of domestic fermented meat products.

In this study, the effect of the use of Penicillium nalgiovense (M600) or Penicillium nalgiovense + Geotrichum candidum (M800) on the physicochemical, microbiological, and flavor substances taking place during the manufacture of Mianning ham, a traditional Chinese ham, was studied. Three groups of hams were created and analysed during the manufacturing process (samples were taken and analysed at 30, 90, 150, and 210 days). At the end of fermentation, a total of 178 flavor substances were identified in the three groups of fermented hams, including 30 aldehydes, 29 alcohols, 14 ketones, 23 esters, 14 acids, 53 hydrocarbons, and 15 other substances. Compared with the control group, aldehydes, esters, and hydrocarbons were significantly increased (p < 0.05), acids were significantly decreased (p < 0.05), and ketones were not significantly changed in the M600 and M800 groups. The control group had the greatest bacterial and fungal abundance at the end of fermentation, with a higher degree of uniformity in fungal composition. M800 group had the highest degree of uniformity in bacterial and fungal composition. In this study, the microbial community changes and volatile flavor substances during the fermentation of Mianning ham were investigated, and the key microorganisms in the fermentation process were analysed. The results of this study indicate that the addition of Penicillium nalgiovense and Geotrichum candidum is an effective strategy to improve ham flavor and enhance ham quality. The results of the study provided a basis for the industrial production of Mianning ham.