Aquaphotomics & NIR hyperspectral imaging

Transcription

1 Aquaphotomics & NIR hyperspectral imaging tools for understanding the role of water in foods School of Biosystems Engineering, University College Dublin, Ireland.

2 Key Questions What does water look like in the NIR? What can hyperspectral imaging show us? How can we use this to understand the role of water in foods?

3 H 2 O molecule

4 H 2 O molecule Nonlinear molecule: 3N-6 vibrational modes 3 vibrational degrees of freedom ν as 3657 cm nm ν s 3756 cm nm δ s 1595 cm nm Band locations from Chs 1 & 9 in Siesler, Ozaki, Kawata and Heise, 22, Near-Infrared Spectroscopy: Principles, Instruments and Applications, Wiley GIFs from 4

5 NIR spectrum of Water Absorbance (log (1/T)) Absorbance (log (1/T))

6 2 nd derivative NIR spectrum of Water Absorbance (log (1/T)) 3 x λ(nm) Tentative assignment [expected λ] v s [ ] v as [ ] v δs + v s [ ] 1463 v as + 2v δs [ ] 1647 v as + 2v δs [ ] Siesler, Ozaki, Kawata and Heise, 22, Near-Infrared Spectroscopy: Principles, Instruments and Applications, Wiley

7 NIR spectra of Water: temperature Absorbance (log (1/T)) 1.5 Temperature Peak Blue Shift : as T λ

8 Hydrogen Bonding Normal modes are perturbed when the vibrating O-H bond senses another water molecule oriented so that its lone e s face H of the vibrating bond. Proton Donor Proton Acceptor Frequency of v s decreases from 377 cm -1 in the isolated molecule to 3628 cm -1 in liquid water and to 3277 cm -1 in ice. *Adapted from Ch 2 (p. 14) in Franks, 2, Water: A matrix of life 8

9 Suggested Assignments of Water Bands Assignment 2v s 2v as Free OH in free water molecule Free ( Dangling ) OH H bond in dimer H bond in trimer H bond in tetramer Indicates blue shift of bands when less H bonding between H 2 O molecules *Observed in solid N2 matrix. Adapted from Luck, W.A.P. Infrared studies of Hydrogen Bonding in Pure Liquids and Solutions, in Franks, 1973, Water: A comprehensive treatise (Ch 4 p ) 9

10 Water bands in NIR Assignment Min Max 3v s v as +2v s v as +v s v as Assignment Min Max 2 vs V as Free OH v as +v s v as Dangling OH v as v s Free OH v s Dangling OH v as H bond in dimer v as H bond in trimer Assignment Min Max 2v as H bond in tetramer v as H bond in polymer v s H bond in tetramer v s H bond in polymer nm nm nm nm nm λ Assignment Min Max v ds +2v s v as +v ds +v s 111 2v as +v ds Assignment Min Max 2v ds +v s v s H bond in dimer v as +2v ds

11 Aquaphotomics Aims to extract water absorbance patterns to describe biological systems e.g. animals, plants Prof. Roumiana Tsenkova Kobe University, Japan How to extract water absorbance pattern (WAP) from NIR Spectrum? 11

12 Spectra of water over 1 hour at constant temperature of 28 o C Log (1/T)

13 PC1 of water over 1 hour at constant temperature of 28 o C % Explained Variance.1 PC

14 Expt. 1: Salts in Water 4 salts: NaCl, KCl, MgCl 2 or AlCl 3 Concentration range:.2.1 Mol.L -1 Control: Millipore water x 3 Gowen et al, Talanta, 214

15 Experimental Design A. Gowen (Dublin) NIR Systems 65 S. De Luca (Rome) Nicolet 67 FT-NIR Y. Tsuchisaka (Kobe) NIR Systems 65

16 Water spectra

17 PC 1 Water only

18 PC 1 Salts

19 PC 2 Salts

20 Question How to remove effect of temperature in spectra? Extended Multiplicative Signal Correction!

21 EMSC Model X b b X b I b I PC Interference Spectra Corrected spectrum Xˆ X b 1 b b 2 b I 1 1 b 3 b I

22 PC 1 EMSC Salts LOD ~.1 % (mass/mass)

23 How watery is food? 5% 6% 7% 8% 9% % water

24 Hyperspectral Imaging Single wavelength image λ Y X Pixel spectrum 24/35

25 Hyperspectral Imaging Equipment Objective Slit Spectrograph Camera Mirror Wavelength range (nm) Spectral resolution (nm) 7 Detector InGaAs

26 Expt. 2: Mushrooms 5 vibration times => induce surface damage x 24 mushrooms x 3 reps

27 Mushroom Curvature

28 EMSC on Mushrooms Raw Spectra: 1 mushroom EMSC(Reflectance) Reflectance EMSC Spectra: 1 mushroom

29 EMSC on Mushrooms Mean Spectra: 12 mushrooms Mean EMSC Spectra: 12 mushrooms 3.9 2nd derivative (EMSC) nd derivative (EMSC)

30 EMSC Mushrooms: difference spectra s 12s 3s 6s.15.1 Difference EMSC (log(1/r)) PC1 EMSC (log(1/r)) Blue shift indicating more free water as damage proceeds

31 PC1 EMSC Mushrooms PC1 EMSC (log(1/r)) λ (nm) 2D Tentative assignment 155 -I 3v as I 2v as dangling OH or 2v s Free OH in free water molecule I 2v ds +v s or v as in dimer

32 Abs Peaks Mushroom Abs 155 nm Abs 1384 nm Abs 1454 nm Vibration time Vibration time Vibration time 3v as 2v as dangling OH 2v ds +v s or v as in dimer EMSC corrected images at 1384 nm Undamaged Damaged

33 Free v s Bound water Free water: can be extracted easily from foods by squeezing or cutting or pressing Bound water: cannot be extracted easily Bound water molecules can t escape as vapor => Even upon dehydration food contains bound water.

34 Water activity W J Scott (1952) established that it was not water content that correlated with bacterial growth in foods, but Water activity: ratio of the water vapor pressure of the food to the water vapor pressure of pure water under the same conditions

35 Moisture Content Vs Water Activity

36 Expt 3. Aqueous solutions Transflectance Cell 3 μl Aqueous solutions: Salt Aw LiCl.25 LiCl.5 NaCl.76 NaCl.92 KCl.98 W 1

37 Mean Sample Spectrum No pretreatment EMSC Log(1/Reflectance) Log(1/Reflectance)

38 Difference Spectrum (EMSC (Water -)) EMSC(W) - EMSC(AW) EMSC(W) - EMSC(AW)

39 Difference Spectrum EMSC Aw >.5.1 2D λ (nm) Tentative assignment.5 I+ 114 v δs +2v s EMSC(W) - EMSC(AW) v as + v δs v as or 2v s dangling OH M v as in dimer or trimer I v as + 2v δs or 2v as in tetramer

40 Difference Spectrum EMSC Aw<=.5 EMSC(W) - EMSC(AW) D λ (nm) Tentative assignment -I 145 2v as or 2v s dangling OH -I v ds +v s or 2 v s H bond in dimer or v as +2v ds

41 Expt. 4: Water temperature 1ml water pipetted on ceramic tile Glass slide heating wire placed through centre of drop Glass slide placed on top =>thin layer of water Heating wire switched on Images obtained every minute for a total of 15 mins. White tile Heating wire

42 Expt. 2: Water temperature 4.2 EMSC (log(1/r)) PC1 EMSC (log(1/r)) Classic effect of temperature

43 PC 1 EMSC PC1 EMSC (log(1/r)) λ (nm) 2D Tentative assignment 145 I- 2v as dangling OH 1475 I- v as +2v ds Or 2v as in tetramer

44 Absorbance at PC1 peaks Abs 145 nm Abs 1475 nm Abs 1475 nm Time Time (min) (min) 2v as dangling OH Time Time (min) (min) v as +2v ds or 2v as in tetramer

45 PC1 Score images

46 Expt. 5: Hydration of Dry foods Coffee Hydrate to different MC & AW Wafer Soybeans Sample # Sample size Coffee 33 2g Wafer 21.6g Soybeans 42 2 kernels Measure NIR HSI, MC, AW

47 AW/MC Wafer MC AW

48 AW/MC Coffee MC AW

49 Soybean MC AW

50 Correlation between Aw, MC: wafer 1.8 MC Aw Correlation Coefficient

51 Correlation between Aw, MC: coffee 1.8 Correlation Coefficient

52 Correlation between Aw, MC: soybean 1.8 MC Aw Correlation Coefficient

53 PC 1 EMSC Spectra.5.4 Coffee Wafer Soybean.3 PC1 EMSC (log(1/r))

54 Difference EMSC (subtracting T) Wafer Difference Spectrum % 1.1% 11.2% 11.3% 11.8% 11.9%

55 Wafer: PC1 EMSC loading.5 PC1 EMSC (log(1/r))

56 PC1 EMSC Wafer 2D λ (nm) Tentative assignment.5 -M 197 v δs +2v s PC1 EMSC (log(1/r)) I v s -I v s Free OH in free water molecule or 2v s Dangling OH -M v s in dimer or 2v as in dimer -M v δs in tetramer

57 Abs Peaks Wafer Abs 197 nm Abs 1335 nm Abs 1412 nm Abs 1454 nm Abs 1573 nm MC MC MC MC MC Abs 197 nm Abs 1335 nm Abs 1412 nm Abs 1454 nm Abs 1573 nm AW AW v δs +2v s 2v s 2v s Free OH in free water molecule or 2v s Dangling OH AW AW 2v s in dimer or 2v as in dimer AW 2v δs in tetramer

58 Difference EMSC (subtracting T) Coffee Difference Spectrum % 5.6% 5.8% 6.5% 6.6% 7.%

59 Coffee PC1 EMSC loading.5 PC1 EMSC (log(1/r))

60 PC1: EMSC Coffee PC1 EMSC (log(1/r)) D2 λ (nm) Tentative assignment M- 197 v δs +2v s I v s or 2v as Free OH in free water molecule I v s dangling OH or 2v as H bond in dimer

61 Abs Peaks Coffee Abs 197 nm MC Abs 1349 nm MC Abs 1419 nm MC Abs 197 nm AW v δs +2v s Abs 1349 nm AW 2v s or 2v as Free OH in free water molecule Abs 1419 nm AW 2v s dangling OH or 2v as H bond in dimer

62 Difference EMSC (subtracting T) Soybeans Difference Spectrum % 15.3% 14.9% 17.4% 14.6%

63 Soybean: PC1 EMSC loading.5 PC1 EMSC (log(1/r))

64 PC1 EMSC Soybean 2D λ (nm) Tentative assignment PC1 EMSC (log(1/r)) I v s -I v s Free OH in free water molecule or 2v s Dangling OH -M v δs in tetramer

65 Abs Peaks Soybean Abs 1349 nm Abs 145 nm Abs 1587 nm MC MC MC Abs 1349 nm Abs 145 nm Abs 1587 nm AW 2v s AW 2v s Free OH in free water molecule or 2v s Dangling OH AW 2v δs in tetramer

66 Key Questions What does water look like in the NIR? What can hyperspectral imaging show us? How can we use this to understand the role of water in foods?

67 Acknowledgements 67