TY - BOOK

T1 - Metabolic Profiling of Food Protective Cultures by in vitro NMR Spectroscopy

AU - Ebrahimi, Parvaneh

PY - 2015

Y1 - 2015

N2 - Food spoilage is of major concern to the food industry, because it leads to considerableeconomic losses, a deteriorated environmental food-print, and to possible public healthhazards. In order to limit food spoilage, research on the preservation of food products hasalways received particular attention by the food industry. Traditionally, such efforts havemainly relied on the application of chemical preservatives or drastic physical treatments.However, chemical preservatives are becoming increasingly unpopular by the consumers,and some have even proven to be toxic and linked to cancer and other health problems.Physical treatments of the products, on the other hand, can deteriorate the sensoryproperties of the products, and may even destroy some of the nutrients and vitamins. In thiscontext, biopreservation, which is defined as the use of safe antibacterial/antifungalmicroorganism (so-called protective cultures) has unexploited potential to inhibit thegrowth of pathogenic microorganisms and enhance the shelf life of the final food product.In order to apply biopreservation in food products effectively, detailed knowledge on themetabolism of protective cultures is required. The present PhD project is mainly focused onthe application of in vitro NMR spectroscopy for studying the metabolism of protectivecultures. As an important part of this work, an analytical protocol was developed for realtimein vitro NMR measurements of bacterial fermentation, which includes guidelines fromthe sample preparation to the data processing and the modelling of the metabolic profiles.The protocol is applied in an experimental design with two strains of lactic acid bacteria.The results highlight some of the metabolic differences between the strains, in terms ofnutrients consumption and metabolites kinetics. As a part of this work, an NMR datapreprocessing technique, called ‘Reference Deconvolution’, was employed for the first timeto improve the multivariate analysis of the in vitro real-time metabolomics data and proveda necessary and elegant solution to the inherent inhomogeneity problem of the samples inthe in vitro NMR measurements of cells. A second objective of the project was to developan accurate approach for quantifying mold growth and inhibition. A new method waspresented for quantifying mold growth and measuring different segments of mold colonies,based on multispectral images and k-means clustering. The method was developed into asoftware package called ‘PCLUSTER’, and was demonstrated to be very helpful in two otherbiopreservation related metabolomic studies. In one case, PCLUSTER was used to quantifyhow the concentration of diacetyl affects inhibition of the indicator molds and in the secondcase PCLUSTER served as an efficient tool for quantifying inhibition assays, and findingantifungal metabolites and metabolites that correlated positively/negatively with theinhibition. The developed analytical tools are expected to be very beneficial in the studiesrelated to the biopreservation, and will be used in the future investigations of the protectivecultures.

AB - Food spoilage is of major concern to the food industry, because it leads to considerableeconomic losses, a deteriorated environmental food-print, and to possible public healthhazards. In order to limit food spoilage, research on the preservation of food products hasalways received particular attention by the food industry. Traditionally, such efforts havemainly relied on the application of chemical preservatives or drastic physical treatments.However, chemical preservatives are becoming increasingly unpopular by the consumers,and some have even proven to be toxic and linked to cancer and other health problems.Physical treatments of the products, on the other hand, can deteriorate the sensoryproperties of the products, and may even destroy some of the nutrients and vitamins. In thiscontext, biopreservation, which is defined as the use of safe antibacterial/antifungalmicroorganism (so-called protective cultures) has unexploited potential to inhibit thegrowth of pathogenic microorganisms and enhance the shelf life of the final food product.In order to apply biopreservation in food products effectively, detailed knowledge on themetabolism of protective cultures is required. The present PhD project is mainly focused onthe application of in vitro NMR spectroscopy for studying the metabolism of protectivecultures. As an important part of this work, an analytical protocol was developed for realtimein vitro NMR measurements of bacterial fermentation, which includes guidelines fromthe sample preparation to the data processing and the modelling of the metabolic profiles.The protocol is applied in an experimental design with two strains of lactic acid bacteria.The results highlight some of the metabolic differences between the strains, in terms ofnutrients consumption and metabolites kinetics. As a part of this work, an NMR datapreprocessing technique, called ‘Reference Deconvolution’, was employed for the first timeto improve the multivariate analysis of the in vitro real-time metabolomics data and proveda necessary and elegant solution to the inherent inhomogeneity problem of the samples inthe in vitro NMR measurements of cells. A second objective of the project was to developan accurate approach for quantifying mold growth and inhibition. A new method waspresented for quantifying mold growth and measuring different segments of mold colonies,based on multispectral images and k-means clustering. The method was developed into asoftware package called ‘PCLUSTER’, and was demonstrated to be very helpful in two otherbiopreservation related metabolomic studies. In one case, PCLUSTER was used to quantifyhow the concentration of diacetyl affects inhibition of the indicator molds and in the secondcase PCLUSTER served as an efficient tool for quantifying inhibition assays, and findingantifungal metabolites and metabolites that correlated positively/negatively with theinhibition. The developed analytical tools are expected to be very beneficial in the studiesrelated to the biopreservation, and will be used in the future investigations of the protectivecultures.

UR - https://soeg.kb.dk/permalink/45KBDK_KGL/fbp0ps/alma99122138663005763

M3 - Ph.D. thesis

BT - Metabolic Profiling of Food Protective Cultures by in vitro NMR Spectroscopy

PB - Department of Food Science, University of Copenhagen

ER -