Submitted Successfully!
To reward your contribution, here is a gift for you: A free trial for our video production service.
Thank you for your contribution! You can also upload a video entry or images related to this topic.
Version Summary Created by Modification Content Size Created at Operation
1
Goreti Botelho
 + 1647 word(s) 1647 2020-12-17 05:00:34 |
2 format change
Lily Guo
 Meta information modification 1647 2021-01-20 12:04:23 | |
3 format change
Lily Guo
 Meta information modification 1647 2021-01-20 12:06:01 |

Video Upload Options

Do you have a full video?
Send video materials Upload full video

Confirm

Are you sure to Delete?
Yes No
Cite
If you have any further questions, please contact Encyclopedia Editorial Office.
Botelho, G.; Anjos, O. Methanol. Encyclopedia. Available online: https://encyclopedia.pub/entry/6423 (accessed on 24 April 2024).
Botelho G, Anjos O. Methanol. Encyclopedia. Available at: https://encyclopedia.pub/entry/6423. Accessed April 24, 2024.
Botelho, Goreti, Ofélia Anjos. "Methanol" Encyclopedia, https://encyclopedia.pub/entry/6423 (accessed April 24, 2024).
Botelho, G., & Anjos, O. (2021, January 14). Methanol. In Encyclopedia. https://encyclopedia.pub/entry/6423
Botelho, Goreti and Ofélia Anjos. "Methanol." Encyclopedia. Web. 14 January, 2021.
Methanol
Edit
This entry is adapted from the peer-reviewed paper 10.3390/pr8121609

Methanol, an alcohol with an odor similar to that of ethanol, has been described to exist in low concentrations in the human organism and occurs naturally at a low level in most spirits, without conferring health risk if it exists within the legal limits. 

Methanol Spirits Quantification

1. Introduction

Spirits are alcoholic beverages commonly consumed in European countries. Their raw materials are diverse and include fruits, cereals, honey, sugar cane, or grape pomace. The main aim of this work is to present and discuss the source, quality control, and legal limits of methanol in spirits produced using fruit and honey spirits.

2. Methanol: Source and Impact on Human Health

Methanol is an alcohol, a small molecule with a boiling point of 64.7 °C, which is formed naturally from pectic substances, which exist in plants and fruits, particularly in the solid parts of the fruits[1][2]. Pectin is a branched heteropolysaccharide consisting of long-chain galacturonan segments and other neutral sugars such as arabinose, xylose, rhamnose, and galactose. It contributes to the cell structure and forms a matrix with cellulose and hemicellulose fibers[3][4]. In healthy individuals’ methanol and formaldehyde, its short-lived oxidized products are naturally occurring compounds. The main sources of exogenous methanol in the healthy human organism are fruits, vegetables, and alcoholic beverages[5]. Indeed, methanol is usually present in alcoholic beverages (yet in much lower concentrations in the honey spirit) in a concentration that depends on the raw material used in their production [6].

When juices are extracted and during fermentation, the hydrolysis of chemical groups of pectic substances occurs naturally, through the action of pectin methylesterases (PME), enzymes that naturally exist in plants. Cleavage of methyl-ester bonds of the galacturonic acid units of the pectin backbone leads to the release of free methanol into the medium, which, being volatile, passes easily to the distillate during the distillation process [1].

In humans, methanol is metabolized by the alcohol dehydrogenase 1b (ADH1b) into toxic formaldehyde [7]. This metabolite is responsible for carcinogenesis and age-related damage to neurons in the brain[8].

Methanol and ethanol are very similar compounds from a biological point of view. Indeed, they have the same target structures, possessing a very similar organic effect[9]. However, while ethanol is oxidized to harmless acetate in the process including conversion to acetyl-coenzyme A and further oxidation via the Krebs cycle, formate is the last product of methanol oxidation. Formate is a chemical toxicant that can react with several target structures such as the mitochondrial cytochrome oxidase[9]. Besides that, formate is responsible for two typical manifestations of methanol poisoning: dysfunction of the retina followed by irreversible damage and metabolic acidosis [10][9]. Accumulation of methanol in the blood can cause hyperosmolality, and accumulation of its metabolites can cause an increase in the anion gap and a decrease in serum bicarbonate concentration and this abnormality is an important diagnostic clue in methanol intoxication. Furthermore, the accumulation of lactic and formic acids, formaldehyde, and ketones leads to metabolic acidosis and favors retinal damage [11].

Inhaled methanol is eliminated mainly by metabolism (70–97% of the absorbed dose); only a small fraction is eliminated unchanged in the urine and expired air (3–4%) [12]. The quantification of methanol and ethanol contents in the human breath after the consumption of different amounts of fruits and alcoholic beverages showed that methanol concentrations increased from a physiological level (0.4 to 2 ppm) a few hours after eating approximately 0.5 kg of fruits. Similar levels were found after drinking 100 mL brandy containing 24% ethanol and 0.19% volume of methanol[9].

As methanol is a neurotoxic substance, especially affecting the human retina, several situations of methanol poisoning have been detected, associated with the consumption of adulterated alcoholic beverages. For this reason, it is very important to know the factors that can influence the content of methanol in spirits, as well as to always determine its content before reaching the final consumer. Of paramount importance is also the establishment of legal limits for the concentration of methanol in alcoholic beverages (Table 1).

The maximum tolerable concentration (MTC) of methanol in an alcoholic beverage would be 2% (v/v) by volume in an adult who consumes 425 mL standard measures of an alcoholic beverage containing 40% alcohol by volume over a period of two hours. Nevertheless, this value only allows a safety factor of 4 to cover variation in the volume consumed and for the effects of folate deficiency, illness, and other personal factors such as ethnicity. For example, the EU general limit for naturally occurring methanol is 10 g methanol/L ethanol (corresponding to 0.4% (v/v) methanol at 40% alcohol volume)[13].

The ingestion of alcoholic beverages, even those of high analytical quality, always results in ethanol, methanol, and formaldehyde contents increasing in the human blood. Recently, a review paper[10] devoted particular attention to lifestyle diseases related to ethanol and methanol, toxicology, and metabolic disruptions of situations where ethanol is inadvertently or criminally replaced by methanol.

3. Methanol Quantification in Spirits

3.1. Current Methods

Methanol is a volatile compound that should be well monitored in spirit drinks. The determination of methanol is usually carried out using high-performance gas-liquid chromatography[14]. Methanol concentrations expressed in grams or milligrams per liter (mg/L) or mg/L of 100% vol. alcohol is usually evaluated using the Internal Standard (IS) method[15][16]. The IS more frequently used are the 4-methyl-2-pentanol or 2-octanol as IS [17][18][19][20]. However, 1-octanol [21], 2-pentanol [22], or 4-nonanol [23] could also be used as the IS.

Because the introduction of the IS compound in low dose is not easy given its volatility, the method of External Standard (ES) is also used[24]. Nevertheless, in both methods, it is mandatory to determine alcohol strength by volume (% v/v) of the analyzed sample[15][16].

In summary, the fulfillment of good manufacturing practices in the production of spirits, whatever its origin, has two advantages that should be highlighted: the reduction of the content of methanol and other constituents harmful to its quality (analytical and sensory) and to increase the guarantee of a final product complying with the legal limits.

3.2. Methanol Quantification by Vibrational Spectroscopy

Methanol content could also be detected by vibrational spectroscopy (namely NIR, FTIR ad RAMAN). This methodology has been used in numerous studies to forecast the chemical composition of different beverages due to the accessibility of quick results, the minimum sample preparation, and the consequent low associated costs[25][26]. Besides, the use of vibrational spectroscopy leading to a specific and characteristic spectrum for each sample or matrix to be connected to the molecular bonds of its chemical constituents [26] and different methodologies give additional information. As an example, in Figure 2, there is spectra of wine spirit aging in oak for six months, acquired with Fourier transform infrared (FTIR) spectroscopic method with attenuated total reflectance (ATR), near-infrared spectroscopy (NIR), and FT-RAMAN. These techniques have been used to assess spirits’ features and some studies are focused in the methanol determination given their importance and legal limits.

Processes 08 01609 g002 550

Figure 2. Spectra of wine spirit with 3 months of aging in wood collected in (A) FTIR-ATR [27]; (B) FT-RAMAN [28] and (C) NIR [29].

The NIR technique has been used to estimate the alcohol and methanol contents in brandies and other distilled beverages[30][31]. Nordon et al.[32] in their work made the comparison between Raman spectrometry and NIR to assess the alcohol strength of whiskies, vodkas, and other alcoholic drinks. Only a small number researchers used vibrational techniques to quantify or identify methanol content in spirits and are listed below separated by technique.

(a)

Using FTIR-ATR:

 

  • Lachenmeier[33] applied the FTIR spectroscopy in combination with multivariate data analysis to assess the quantification of parameters density, ethanol, methanol, ethyl acetate, propanol-1, isobutanol, and 2-/3-methyl-1-butanol of spirit drinks. The calibration model obtained presented an r2 of 0.997 for cross-validation and 0.981 test-set validation;
  • Coldea et al. [34] applied FTIR spectroscopy and chemometrics techniques to evaluate the quality of fruit spirits traditionally produced in Romania. In this study, the methanol fingerprint was identified in the 1020 and 1112 cm-1. Using PLS regression, these authors found that the FTIR spectra could be useful for authenticity control of the provenience region and the type of the fruit spirit;
  • Anjos et al.[35] used FTIR-ATR in the spectral region of 4000 to 400 cm−1 to forecast the alcoholic strength, methanol content, acetaldehyde, and fusel alcohol content of grape mark and wine spirits, applying partial least square (PLS). For methanol content, a very good model was obtained using the peaks at 1085 and 1043 cm−1 corresponding to the C–O stretch absorption bands, with r2 of 99.2 and ratios of performance to deviation (RPD) of 11.1.

 

(b)

Using RAMAN:

 

  • Boyaci et al. [36] proposed a method for direct quantification of ethanol and methanol in distilled alcoholic beverages. In this research, calibration models for ethanol and methanol concentrations in the ranges of 0–7 M and 0–10 M, respectively, were performed. An r2 value of 0.998 for ethanol and 0.998 for methanol for linear correlations were plotted. The aforementioned authors used the important bands of methanol at 1019 cm–1 that corresponded to C–O stretching;
  • Goes et al. [37] used Raman spectroscopy and a statistical procedure based on principal component analysis to determine the presence of methanol content in beverages;
  • Song et al. [38] used handheld Raman spectroscopy, with an excitation laser emitting at 1064 nm to online detect methanol content in a spirit. For their analysis, they used the spectral information located at 1074.6 cm−1 (bending vibration of C-O-H). The prediction of methanol concentration was made with an r2 of 0.999. More recently, Ellis et al. [39] proposed a methodology for through-container detection of fake spirits and methanol quantification with handheld Raman spectroscopy. These authors used the peak at 1030 cm−1 assigned to the methanol C–O stretching vibration, to make their validation. In this study, the PLS model developed had an r2 between 0.9518 and 0.9734.

 

(c)

Using NIR:

  • Yang et al. [31], applied multivariate calibration in data collected with two-dimensional NIR, to make the determination of methanol in white spirit. In this study, the N-way partial least squares technique was applied to the impure methanol solution; the obtained average relative error and root mean square error was 2.97 and 0.064%, respectively. They concluded that the adulteration level by methanol was taken in the region of 4300– 4450 cm−1.

References

  1. Wormit, A.; Usadel, B. The multifaceted role of pectin methylesterase inhibitors (PMEIs). Int. J. Mol. Sci. 2018, 19, 1–19, doi:10.3390/ijms19102878.
  2. Komarova, T.V.; Sheshukova, E.V.; Dorokhov, Y.L. Cell wall methanol as a signal in plant immunity. Front. Plant Sci. 2014, 5, 2012–2015, doi:10.3389/fpls.2014.00101.
  3. Vanitha, T.; Khan, M. Role of pectin in food processing and food packaging. In Pectins-Extraction, Purification, Characterization and Applications; IntechOpen, London, UK: 2020, doi: 10.5772/intechopen.83677
  4. Broxterman, S.E.; Schols, H.A. Interactions between pectin and cellulose in primary plant cell walls. Carbohydr. Polym. 2018, 192, 263–272, doi:10.1016/j.carbpol.2018.03.070.
  5. Dorokhov, Y.L.; Shindyapina, A.V.; Sheshukova, E.V.; Komarova, T.V. Metabolic methanol: Molecular pathways and physiological roles. Physiol. Rev. 2015, 95, 603–644, doi:10.1152/physrev.00034.2014.
  6. Deitrich, R.; Zimatkin, S.; Pronko, S. Oxidation of ethanol in the brain and its consequences. Alcohol Res. Heal. 2006, 29, 266–273.
  7. Cederbaum, A.I. Alcohol metabolism. Clin. Liver Dis. 2012, 16, 1–11, doi:10.1016/j.cld.2012.08.002.ALCOHOL.
  8. Tulpule, K.; Dringen, R. Formate generated by cellular oxidation of formaldehyde accelerates the glycolytic flux in cultured astrocytes. Glia 2012, 60, 582–593, doi:10.1002/glia.22292.
  9. Bouchard, M.; Brunet, R.C.; Droz, P.O.; Carrier, G. A biologically based dynamic model for predicting the disposition of methanol and its metabolites in animals and humans. Toxicol. Sci. 2001, 64, 169–184, doi:10.1093/toxsci/64.2.169.
  10. Seme, M.T.; Summerfelt, P.; Henry, M.M.; Neitz, J.; Eells, J.T. Formate-induced inhibition of photoreceptor function in methanol intoxication. J. Pharmacol. Exp. Ther. 1999, 289, 361–70.
  11. Kraut, J.A.; Kurtz, I. Toxic alcohol ingestions: Clinical features, diagnosis, and management. Clin. J. Am. Soc. Nephrol. 2008, 3, 208–225, doi:10.2215/CJN.03220807.
  12. Horton, V.L.; Higuchi, M.A.; Rickert, D.E. Physiologically based pharmacokinetic model for methanol in rats, monkeys, and humans. Toxicol. Appl. Pharmacol. 1992, 117, 26–36, doi:10.1016/0041-008X(92)90213-C.
  13. Paine, A.J.; Dayan, A.D. Defining a tolerable concentration of methanol in alcoholic drinks. Hum. Exp. Toxicol. 2001, 20, 563–568, doi:10.1191/096032701718620864.
  14. Wiśniewska, P.; Śliwińska, M.; Dymerski, T.; Wardencki, W.; Namieśnik, J. Application of gas chromatography to analysis of spirit-based alcoholic beverages. Crit. Rev. Anal. Chem. 2015, 45, 201–225, doi:10.1080/10408347.2014.904732.
  15. OIV (International Organisation of Vine and Wine). Compendium of international methods of wine and must analysis. In EC Regulation (EU) 2019/787; 2009; Volume 1 and Volume 2. Available online: http://www.oiv.int/en/technical-standards-and-documents/methods-of-analysis/compendium-of-international-methods-of-analysis-of-wines-and-musts-2-vol (accessed on 5 May 2020).
  16. AOAC International. Official Methods 972. Methanol in distilled liquors. In Gas Chromatographic Method; AOAC: Maryland, USA; 1973. Available online: http://www.aoacofficialmethod.org/index.php?main_page=product_info&cPath=1&products_id=2090 (accessed on 12 November 2020).
  17. Luís, A.C.P.M.N.; Mota, D.; Anjos, O.; Caldeira, I. Single-laboratory validation of determination of acetaldehyde, ethyl acetate, methanol and fusel alcohols in wine spirits, brandies and marc spirits using GC-FID. Ciência Téc. Vitiv. 2011, 26, 69–76.
  18. López-Vázquez, C.; Herminia Bollaín, M.; Berstsch, K.; Orriols, I. Fast determination of principal volatile compounds in distilled spirits. Food Control 2010, 21, 1436–1441, doi:10.1016/j.foodcont.2010.03.008.
  19. Granja-Soares, J.; Roque, R.; Cabrita, M.J.; Anjos, O.; Belchior, A.P.; Caldeira, I.; Canas, S. Effect of innovative technology using staves and micro-oxygenation on the odorant and sensory profile of aged wine spirit. Food Chem. 2020, 333, 127450, doi:10.1016/j.foodchem.2020.127450.
  20. López-Vázquez, C.; García-Llobodanin, L.; Ricardo Pérez-Correa, J.; López, F.; Blanco, P.; Orriols, I. Aromatic characterization of pot distilled kiwi spirits. J. Agric. Food Chem. 2012, 60, 2242–2247, doi:10.1021/jf204310v.
  21. Wechgama, K.; Laopaiboon, L.; Laopaiboon, P. Quantitative analysis of main volatile and other compounds in traditional distilled spirits from Thai rice. Biotechnology 2008, 7, 718–724, doi:10.3923/biotech.2008.718.724.
  22. De León-Rodríguez, A.; González-Hernández, L.; De La Rosa, A.P.B.; Escalante-Minakata, P.; López, M.G. Characterization of volatile compounds of mezcal, an ethnic alcoholic beverage obtained from Agave salmiana. J. Agric. Food Chem. 2006, 54, 1337–1341, doi:10.1021/jf052154+.
  23. Dragone, G.; Mussatto, S.I.; Oliveira, J.M.; Teixeira, J.A. Characterisation of volatile compounds in an alcoholic beverage produced by whey fermentation. Food Chem. 2009, 112, 929–935, doi:10.1016/j.foodchem.2008.07.005.
  24. Madrera, R.R.; Valles, B.S. Determination of volatile compounds in cider spirits by Gas Chromatography with direct injection. J. Chromatogr. Sci. 2007, 45, 428–434.
  25. Lohumi, S.; Lee, S.; Lee, H.; Cho, B.-K. A review of vibrational spectroscopic techniques for the detection of food authenticity and adulteration. Trends Food Sci. Technol. 2015, 46, 85–98, doi:10.1016/j.tifs.2015.08.003.
  26. Downey, G. Tutorial review. Qualitative analysis in the near-infrared region. Analyst 1994, 119, 2367, doi:10.1039/an9941902367.
  27. Anjos, O.; Comesaña, M.M.; Caldeira, I.; Pedro, S.I.; Oller, P.E.; Canas, S. Application of functional data analysis and FTIR-ATR spectroscopy to discriminatewine spirits ageing technologies. Mathematics 2020, 8, 896, doi:10.3390/MATH8060896.
  28. Anjos, O.; Santos, R.; Estevinho, L.M.; Caldeira, I. FT-RAMAN methodology for the monitoring of honeys’ spirit distillation process. Food Chem. 2020, 305, 1–7, doi:10.1016/j.foodchem.2019.125511.
  29. Anjos, O.; Caldeira, I.; Roque, R.; Pedro, S.I.; Lourenço, S.; Canas, S. Screening of different ageing technologies of wine spirit by application of Near-Infrared (NIR) Spectroscopy and volatile quantification. Processes 2020, 8, 736, doi:10.3390/pr8060736.
  30. Palma, M.; Barroso, C.G. Application of FT-IR spectroscopy to the characterisation and classification of wines, brandies and other distilled drinks. Talanta 2002, 58, 265–271, doi:10.1016/S0039-9140(02)00244-8.
  31. Yang, Y.R.; Ren, Y.F.; Dong, G.M.; Yang, R.J.; Liu, H.X.; Du, Y.H.; Zhang, W.Y. Determination of methanol in alcoholic beverages by Two-Dimensional Near-Infrared Correlation Spectroscopy. Anal. Lett. 2016, 49, 2279–2289, doi:10.1080/00032719.2016.1144060.
  32. Nordon, A.; Mills, A.; Burn, R.T.; Cusick, F.M.; Littlejohn, D. Comparison of non-invasive NIR and Raman spectrometries for determination of alcohol content of spirits. Anal. Chim. Acta 2005, 548, 148–158, doi:10.1016/j.aca.2005.05.067.
  33. Lachenmeier, D.W. Rapid quality control of spirit drinks and beer using multivariate data analysis of Fourier transform infrared spectra. Food Chem. 2007, 101, 825–832, doi:10.1016/j.foodchem.2005.12.032.
  34. Coldea, T.E.; Socaciu, C.; Fetea, F.; Ranga, F.; Pop, R.M.; Florea, M. Rapid quantitative analysis of ethanol and prediction of methanol content in traditional fruit brandies from romania, using FTIR spectroscopy and chemometrics. Not. Bot. Horti Agrobot. Cluj-Napoca 2013, 41, 143–149, doi:10.15835/nbha4119000.
  35. Anjos, O.; Santos, A.J.A.; Estevinho, L.M.; Caldeira, I. FTIR–ATR spectroscopy applied to quality control of grape-derived spirits. Food Chem. 2016, 205, 28–35, doi:10.1016/j.foodchem.2016.02.128.
  36. Boyaci, I.H.; Genis, H.E.; Guven, B.; Tamer, U.; Alper, N. A novel method for quantification of ethanol and methanol in distilled alcoholic beverages using Raman spectroscopy. J. Raman Spectrosc. 2012, 43, 1171–1176, doi:10.1002/jrs.3159.
  37. De Góes, R.E.; Fabris, L.V.M.; Muller, M.; Fabris, J.L. Light-assisted detection of methanol in contaminated spirits. J. Light. Technol. 2016, 34, 4499–4505, doi:10.1109/JLT.2016.2522656.
  38. Song, L.M.; Liu, L.W.; Yang, Y.G.; Xi, J.T.; Guo, Q.H.; Zhu, X.J. Online detection of distilled spirit quality based on laser Raman spectroscopy. J. Inst. Brew. 2017, 123, 121–129, doi:10.1002/jib.399.
  39. Ellis, D.I.; Muhamadali, H.; Xu, Y.; Eccles, R.; Goodall, I.; Goodacre, R. Rapid through-container detection of fake spirits and methanol quantification with handheld Raman spectroscopy. Analyst 2019, 144, 324–330, doi:10.1039/C8AN01702F.
  40. Wiśniewska, P.; Śliwińska, M.; Dymerski, T.; Wardencki, W.; Namieśnik, J. Application of gas chromatography to analysis of spirit-based alcoholic beverages. Crit. Rev. Anal. Chem. 2015, 45, 201–225, doi:10.1080/10408347.2014.904732.
More
© Text is available under the terms and conditions of the Creative Commons Attribution (CC BY) license; additional terms may apply. By using this site, you agree to the Terms and Conditions and Privacy Policy.
Upload a video for this entry
Information
Subjects: Agriculture, Dairy & Animal Science
Contributors MDPI registered users' name will be linked to their SciProfiles pages. To register with us, please refer to https://encyclopedia.pub/register :
Goreti Botelho
,
Ofélia Anjos
View Times: 1.6K
Revisions: 3 times (View History)
Update Date: 20 Jan 2021
Table of Contents
    1000/1000
    Hot Most Recent
    Feedback