Method and apparatus for detecting hydrocarbon oxidation

• US 5,712,165 A
• Filed: 08/22/1994
• Issued: 01/27/1998
• Est. Priority Date: 08/22/1994
• Status: Expired due to Fees

• Current Assignee: BETH Israel Medical Center (Mount Sinai Beth Israel)
• Original Assignee: Beth Israel Hospital Adminstration
• Inventors: Alvarez, Juan G., Modell, Mark
• Primary Examiner(s): Warden, Robert J.
• Assistant Examiner(s): CARRILLO, BIBI SHARIDAN
• Application Number:
  US08/294,173
• Time in Patent Office: 1,254 Days
• Field of Search: 422/82.05, 436/20, 436/23, 436/21, 436/60, 436/71, 436/142, 436/164, 436/172, 250/910, 356/301, 426/87, 426/231
• US Class Current: 436/21
• CPC Class Codes: G01N 21/3563 for analysing solids; Preparation of samples therefor
• CPC Class Codes: G01N 21/359 using near infrared light
• CPC Class Codes: G01N 33/03 Edible oils or edible fats
• CPC Class Codes: Y10S 250/91 Food sample analysis using invisible radiant energy source
• CPC Class Codes: Y10T 436/216 Unsaturated [e.g., ethylene, diene, etc.]
• CPC Class Codes: Y10T 436/24 Nuclear magnetic resonance, electron spin resonance or other spin effects or mass spectrometry

Abstract

Systems and methods for material analysis are disclosed in which an organic sample (e.g., a foodstuff, tissue sample or petroleum product) is illuminated at a plurality of discrete wavelengths which are absorbed by fatty acid and fatty acid oxidation products in the sample. Measurements of the intensity of reflected or absorbed light at such wavelengths are taken, and a analysis of absorbance ratios for various wavelengths is performed. Changes in the reflection ratios are correlated with the oxidative state of fatty acids present in the material.

Claims

1. A method for determining the oxidation state unsaturated fatty acids or long-chain hydrocarbons in a food sample by Raman spectroscopy, comprising the steps of:

(i) irradiating the food sample with electromagnetic radiation at a plurality of wavelengths including a reference wavelength and a sample wavelength, wherein the sample wavelength is an infrared wavelength and absorption of light at the sample wavelength varies with the state of oxidation of unsaturated fatty acids or hydrocarbons in the food sample, and the reference wavelength is sufficiently removed from the sample wavelength so that absorption of light at the reference wavelength is substantially insensitive to the concentration of oxidized unsaturated fatty acids or long-chain hydrocarbons;

(ii) optically detecting radiation absorbed or scattered by the food sample at each of the sample and reference wavelengths, wherein the spectrophotometric detection of radiation absorbed or scattered by the sample is performed using Raman spectroscopy;

(iii) determining the ratio of absorbance at the sample wavelength to the absorbance at the reference wavelength;

(iv) comparing the ratio to a predetermined value from a control specimen to determine the oxidation state of unsaturated fatty acids or long-chain hydrocarbons in the food sample by Raman spectroscopy.

2. The method of claim 1, wherein the sample wavelength is a near-infrared wavelength.

3. The method of claim 1, wherein the sample wavelength detects the abundance of an allylic proton of an unsaturated fatty acid or long-chain hydrocarbon.

4. The method of claim 1, wherein the sample wavelength is about 3000 cm^-1.

5. The method of claim 1, wherein the food sample is a sample of fish meat.

6. A method for determining the oxidation state of unsaturated fatty acids or long-chain hydrocarbons in a load sample, comprising the steps of:

(i) irradiating the food sample with electromagnetic radiation at a plurality of wavelengths including a reference wavelength and a sample wavelength, wherein the sample wavelength is an infrared wavelength and absorption of light at the sample wavelength varies with the state of oxidation of unsaturated fatty acids or hydrocarbons in the food sample, and the reference wavelength is sufficiently removed from the sample wavelength so that absorption of light at the reference wavelength is substantially insensitive to the concentration of oxidized unsaturated fatty acids or long-chain hydrocarbons;

(ii) optically detecting radiation absorbed or scattered by the food sample at each of the sample and reference wavelengths;

(iii) determining the ratio of absorbance at the sample wavelength to the absorbance at the reference wavelength;

(iv) comparing the ratio to a predetermined value from a control specimen to determine the oxidation state of unsaturated fatty acids or long-chain hydrocarbons in the food sample

wherein the sample wavelength detects the abundance of an allylic proton of an unsaturated fatty acid or long-chain hydrocarbon.

7. The method of claim 6, wherein the sample wavelength is a near-infrared wavelength.

8. The method of claim 6, wherein the sample wavelength is selected from the group consisting of about 3350 nm, about 1677 nm, about 2115 nm, and about 2175 nm.

9. The method of claim 6, wherein the food sample is a sample of fish meat.