A method for quality control of a blood product comprising an erythrocyte concentrate, a platelet concentrate, a granulocyte concentrate, a leukocyte concentrate, whole blood or blood plasma, the method comprising: providing a computer having one or more processors or controllers, storing, in a database in a memory of the computer, reference spectra, wherein the stored reference spectra includes one or more of the following: position of Raman peaks and/or wavenumber ranges of fresh cells of one or more cell types of said blood products; position of Raman peaks and/or wavenumber ranges of functionally modified cells of one or more cell types of said blood products; and information regarding ranges of a multi-dimensional space of a cluster analysis in which the reference spectra are respectively arranged; trapping at least one cell of a sample of said blood products, said sample containing blood cells that are in solution, in an optical trap; recording a Raman spectrum (40; 71, 72) by Raman spectroscopy of the at least one cell of the sample of the blood product, comparing the recorded Raman spectrum of the at least one cell of the sample with reference spectra stored in the database, evaluating cell death, sterility, contaminants, or functional modifications of a cell type of the sample based on the results of the comparison, and determining whether the blood product is usable for transfusion based on the evaluation of the Raman spectrum (40; 71, 72). providing a computer having one or more processors or controllers, storing, in a database in a memory of the computer, reference spectra, wherein the stored reference spectra includes one or more of the following: position of Raman peaks and/or wavenumber ranges of fresh cells of one or more cell types of said blood products; position of Raman peaks and/or wavenumber ranges of functionally modified cells of one or more cell types of said blood products; and information regarding ranges of a multi-dimensional space of a cluster analysis in which the reference spectra are respectively arranged; trapping at least one cell of a sample of said blood products, said sample containing blood cells that are in solution, in an optical trap; recording a Raman spectrum (40; 71, 72) by Raman spectroscopy of the at least one cell of the sample of the blood product, comparing the recorded Raman spectrum of the at least one cell of the sample with reference spectra stored in the database, evaluating cell death, sterility, contaminants, or functional modifications of a cell type of the sample based on the results of the comparison, and determining whether the blood product is usable for transfusion based on the evaluation of the Raman spectrum (40; 71, 72). position of Raman peaks and/or wavenumber ranges of fresh cells of one or more cell types of said blood products; position of Raman peaks and/or wavenumber ranges of functionally modified cells of one or more cell types of said blood products; and information regarding ranges of a multi-dimensional space of a cluster analysis in which the reference spectra are respectively arranged; trapping at least one cell of a sample of said blood products, said sample containing blood cells that are in solution, in an optical trap; recording a Raman spectrum (40; 71, 72) by Raman spectroscopy of the at least one cell of the sample of the blood product, comparing the recorded Raman spectrum of the at least one cell of the sample with reference spectra stored in the database, evaluating cell death, sterility, contaminants, or functional modifications of a cell type of the sample based on the results of the comparison, and determining whether the blood product is usable for transfusion based on the evaluation of the Raman spectrum (40; 71, 72).