FOODFLUOR - FOOD FLUORESCENCE LIBARY

 

A food fluorescence library by Jakob Christensen, 2005

Background
The present site contains a food fluorescence library (FOODFLUOR) in the form of steady-state fluorescence landscapes from a variety of intact food samples, plus a list of some food relevant fluorophores in pure solutions. The listed fluorescence measurements are intended to serve as a work of reference, a library, which can hopefully inspire and help scientists that are interested in or want to start exploring the intrinsic fluorescence of food and food systems.

Fluorescence database
Fluorescence landscapes of eleven fluorophores and a broad variety of intact food samples is included in this database. Measurements of the fluorophores were performed on two different instruments, yielding three separate lists:

The fluorescence properties of the selected samples can be viewed at this site or the data from the experiments can be downloaded in MS-Excel format. Please note that the presented fluorescence landscapes are not corrected.

Reference
If you want to use the data or refer to the results, please refer to:

Food Fluorescence Library, Quality & Technology, Department of Food Science, Faculty of Science, University of Copenhagen, Denmark, www.models.life.ku.dk

 


LS50 FLUOROPHORE RESULTS OVERVIEW

Pure solutions of fluorophores are measured. Appropriate concentration levels were chosen for each fluorophore in order to avoid concentration quenching. Fluorescence landscapes were measured on PerkinElmer LS50B spectrofluorometer in a cuvette with the traditional right-angle sampling geometry. Water was used as solvent, iso-octan when the fluorophore is not soluble in water. The landscapes were measured in different spectral ranges, using an obey-file in the FLDM instrument controlling software. Common measurement parameters:

  •  Slit width: 5 nm for both excitation and emission light

  • Step size: 2 nm for excitation

  • Step size: 1 nm for emission

  • Fluorescence emission was only recorded between the 1st and 2nd order Rayleigh scatter. No emission above 700 nm was recorded.

  • Picture of the instrument

If any minor Rayleigh scatter appeared in the recorded fluorescence data, it was removed in the preliminary signal processing, before further data analysis.

List of measured compounds
Fluorophore   Conc. (M) EX λmax (nm) EM λmax (nm) Imax * Measuring range
(EX, nm)
Solvent
Phenyl alanine   10-3 M 258 284 32 250-320 Water
Tyrosine   10-5 M

276

302 28 250-320 Water
Tryptophan   10-5 M 280 357 100 250-320 Water
Vitamin A
(Retinol)
  10-5 M 346 480 16 250-380 Iso-octane
Vitamin B2
(Riboflavin)
  10-5 M 270
(382,448)
518 167 250-510 Water
Vitamin B6
(Pyridoxin)
  10-5 M 328 393 51 250-360 Water
Vitamin E
(
α-Tocopherol)
  10-4 M 298 326 167 250-320 Iso-octane
NADH   10-4 M 344 465 16 260-470 Water
ATP   10-3 M 292 388 33 260-320 Water
Chlorophyll A   10-6 M 428 663 56 340-650 Iso-octane
Hematoporphyrin   10-5 M 396 614 27 300-550 Iso-octane

*normalized according to tryptophan (= 100)

 

 


VARIAN CARY ECLIPSE FLUOROPHORE OVERVIEW

Pure solutions of fluorophores are measured. Appropriate concentration levels were chosen for each fluorophore in order to avoid concentration quenching. Fluorescence landscapes were measured on Cary Varian Eclipse spectrofluorometer in a cuvette with the traditional right-angle sampling geometry. Water was used as solvent, iso-octan when the fluorophore is not soluble in water. The landscapes were measured in different spectral ranges, using a measuring routine programmed in ADL in the instrument controlling software. Common measurement parameters:

  • Slit width: 5 nm for both excitation and emission light
  • Step size: 2 nm for excitation
  • Step size: 1 nm for emission
  • Fluorescence emission was by maximum recorded between 1st and 2nd order Rayleigh scatter.
  • Picture of the instrument

Rayleigh scatter appearing in the recorded fluorescence data was removed in the preliminary signal processing, before further data analysis.

List of measured compounds
Fluorophore   Conc. (M) EX λmax (nm) EM λmax (nm) Imax * Measuring range
(EX, nm)
Solvent
Phenyl alanine   10-3 M 262 281 38 230-310/ 230-450 Water
Tyrosine   10-5 M 278 302 96 230-310/ 230-450 Water
Tryptophan   10-5 M (230) 276 355 100 230-310/ 230-450 Water
Vitamin A
(Retinol)
  10-5 M 328 484 8 260-380/ 400-620 Iso-octane
Vitamin B2
(Riboflavin)
  10-5 M 268
(372+444)
528 58 250-500/ 480-590 Water
Vitamin B6
(Pyridoxin)
  10-5 M 326 396 18 220-360/ 350-470 Water
Vitamin E
(
α-Tocopherol)
  10-4 M 298 323 70 220-320/ 290-380 Iso-octane
NADH   10-4 M 338 465 16 260-460/ 380-590 Water
ATP   10-3 M 292 392 20 260-320/ 320-500 Water
Chlorophyll A   10-6 M 428 663 16 350-650/ 640-690 Iso-octane
Hematoporphyrin   10-5 M 394 613 12 300-550/ 590-690 Iso-octane

*normalized according to tryptophan (= 100)

 

 


LS50 FOOD SAMPLES OVERVIEW

Fluorescence landscapes of a variety of intact food samples – liquid as well as solid -  were measured on Perkin Elmer LS50B spectrofluorometer using a front-face solid sample accessory with 60o sampling geometry. Liquid samples were measured in quartz cuvettes and solid samples in sample cups. The landscapes were recorded using an obey-file in the FLDM instrument controlling software with following measurement parameters:

  • Slit width, excitation: 5 nm

  • Slit width, emission: 10 nm

  • Step size: 5 nm for excitation

  • Step size: 1 nm for emission

  • Excitation range: 250-650 nm

  • Picture of the instrument

All fluorescence emission was only recorded between the 1st and 2nd order Rayleigh scatter. No emission above 700 nm was recorded. An emission 1% attenuation filter was used for samples yielding too high fluorescence intensity. If any minor Rayleigh scatter appeared in the recorded fluorescence  data, it was removed in the preliminary signal processing, before further data analysis.

List of measured food samples
Sample   pH Filter EX λmax (nm) EM λmax (nm) Imax
Milk (1.5 % fat)   6.69 285 340 6900*
Yoghurt, plain (3.5 %)   3.98 285 341 6200*
Rape seed oil       360 444 812
Olive oil       610 681 643
Orange juice   3.62   510 530 53
Apple juice   4.02   390 461 57
Soy sauce   4.66   640 685 8
Beer, Carlsberg   4.32   390 465 242
Beer, Elephant   4.29   400 489 221
White wine   3.21   385 456 199
Rice       410 488 584
Wheat flour       285 338 185
Cane sugar       345 462 56
Oatmeal       285 338 18
Emmenthaler     295 354 4500*
Gorgonzola     290 346 4300*
Butter       325 407 923
Beef       285 326 135
Pork       296 334 888
Olive, green       420 677 170
Marzipan       460 517 488
Chocolate       285 338 20
Carrot       285 360 101
Potato       290 377 218
Pear       290 371 100
Tomato       635 655 46
Apple       510 530 60

*calculated value; recorded with 1% attenuation, so Ix100 is listed.

 

 


Matlab users

All the Fluorescence landscapes (both fluorophores for both instruments and intact food samples in one big file) are available in Matlab, version 5/6 compatible.


Also available: the DOMFluor database (Dissolved Organic Matter)