Novel application of confocal Raman microscopy to determine the microstructure of fermented dairy products including the spatial distribution of proteins, lipids and carbohydrates

Abstract

BACKGROUND: The distribution of components in fermented dairy products forms the microstructure which influences final product texture and taste. Confocal Raman microscopy may provide new molecular information on product structure not possible with other advanced microscopy techniques. OBJECTIVE: Dairy products including non-fat and full fat yoghurt, Camembert and Cheddar cheese samples were surveyed and the product microstructure observed using confocal Raman microscopy in order to determine the applicability of the technique to dairy product analysis. METHODS: Confocal Raman microscopy provided spatially resolved chemical information on the components of fermented dairy products. In conjunction with component analysis and exploratory data analysis, spatially resolved chemical information on the components of fermented dairy products was obtained and compared. RESULTS: Yoghurts with differing fat levels displayed different microstructures, consistent with other techniques. The influence of different molecular structures on the Camembert cheese centre and surface was revealed and Raman microscopy also gave new insights on the chemical structures within Cheddar cheese. CONCLUSIONS:The method provides a new technique for observing the contribution of different components to the product microstructure that may be used to monitor product quality and guide product development.

Single droplet drying of dairy‐based systems at spray drying like temperature–time trajectories

“…2023). For fat, only one specific peak could be identified, at 1750 cm −1 which again is in line with values reported in the literature (Pax and Sheehan 2020, Khan et al . 2023).…”

“…Based on these raw spectra, component characteristic peaks could be identified. For lactose, these peaks are at 355 and 468 cm −1 , in line with values reported in the literature (Pax and Sheehan 2020; Khan et al . 2023).…”

Raman spectroscopy in the quality analysis of dairy products: A literature review

“…Thus, the microstructure of the components is an important analysis for the quality control of yogurt. A recently published study by Pax and Sheehan [ 39 ] showed the application of Raman confocal microscopy to determine the microstructure of fermented milk products such as yogurt. Raman microscopy measurements were performed with a 532‐nm laser, and data analysis was performed by PCA.…”

“…(a) Spectra of the components identified in the microscopy of the whole yogurt samples; (b) spectra of the components identified under microscopy of the skimmed yogurt samples [ 39 ] …”

“…Raman microscopy images of the two types of yogurts with different fat contents were obtained and compared. Both types of yogurts had the characteristic bands of the pyranose ring of carbohydrates at 476 cm À1 , proteins at 1456 cm À1 , bands assigned to carotenoids in the 1520-1530 cm À1 region, and the band at 2432 cm À1 was attributed to F I G U R E 2 4 (a) Spectra of the components identified in the microscopy of the whole yogurt samples; (b) spectra of the components identified under microscopy of the skimmed yogurt samples [39] atmospheric CO 2 . The whole yogurt samples showed bands that were not seen in the skimmed yogurt samples: for example, bands at 1660 cm À1 assigned to lipids and the amide I mode, at approximately 1750 and 2856 cm À1 that were related to lipids, and at 2887 cm À1 associated with lipids and proteins.…”