VENTILATION IN KITCHEN AEROSOL CONCENTRATION AND KEY COMPONENTS IN THE VAPOUR

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1 Proceedings: Indoor Air 22 VENTILATION IN KITCHEN AEROSOL CONCENTRATION AND KEY COMPONENTS IN THE VAPOUR BAndrejs *, JFauss, MWeigl, PRietschel Berufsgenossenschaft Nahrungsmittel und Gaststätten, Mannheim, Germany ABSTRACT When frying, grilling and deep-frying in kitchens, vapours and aerosols are released into the surrounding air. The aerosol is air- born and can contain an array of noxious substances. The purpose of the work was to develop a simple method for calculating the loading resulting from kitchen vapours. Of the low-molecular aldehydes, the acrolein in the air contributed most to the load in the kitchen due to its pungent odor and toxic properties. In kitchens, aerosols and aldehydes (low molecular aldehydes) up to trans 2-hexenal and unsaturated fatty aldehydes (decenal, decadienal, undecenal) form the main components of the extraneous substances in the air. The aerosols consist in part of ultra fine particles and are deposited in the lungs. Up to 9% of these consist of triglycerides and fatty acids.other components include furans and polymer or oxidised triglycerides. The concentration of aldehydes and aerosols changes in the same ratio. INDEX TERMS Decomposition products, Aerosol concentration, Kitchen, VOC`s, Ventilation. INTRODUCTION When frying, grilling and deep-frying in kitchens, vapours and aerosols are released into the surrounding air. These are pyrolysis products of fat and fatty aerosols of previously unknown composition. The aerosol is air-borne and can contain an array of noxious substances. The particles serve as vehicles for transporting these hazardous substances deep into the lungs when they are less-than 8µm in diameter, where they are deposited Ross et al. 1999, Andrejs et al ). The substances in the kitchen vapours which are toxicologically relevant are those with chemically irritative, carcinogenic and mutagenic properties (Rogge et al. 1991, Vainiotalo and Matveinen 1993). Edible oils and fats consist primarily of triglycerides. When fats are heated, as happens when frying and deep-frying, three basic types of chemical reactions are known ( Gertz, 2): 1.Hydrolysis, 2. Oxidation, 3. Pyrolysis. Triglycerides are triesters of glycerine with fatty acids of different chain lengths and double bond content (Doberganes et al., 2).Of the usual fatty acid components of triglycerides, oleic acid with one double bond is the most stable, while linolenic acid (with 3 double bonds) is the easiest to oxidise. Limit concentrations in deep-fry fats and oils must therefore be complied with. Linoleic acid oxidises 1 times faster than oleic acid. The triglycerides of the normal vegetable fats and oils contain up to 6% oleic acid and up to 3% linoleic acid. The linolenic acid content should be below 1%; the remainder consists of palmitic acid, stearic acid, arachidic acid and arachidonic acid. The purpose of the work was to develop a simple method for calculating the loading resulting from kitchen vapours. Both gas chromatography determination of the triglycerides and gravimetric calculation of the aerosol quantities require very little data gathering and analysis * Contact author brigitte_andrejs@bgn.de 292

2 Proceedings: Indoor Air 22 work. All that needed to be examined was whether a correlation existed between vaporous decomposition products of the triglycerides (e.g. short-chain and long-chain aldehydes) and the aerosols which are produced when fat and other products are heated in the kitchen. METHODS Sampling was performed using a combination of glass-fibre filters for collecting the triglycerides and polyurethane foam, cleaned (PU foam), for absorbing the volatile components ( figure 1). A commercially available cartridge filled with impregnated silica gel was used for calculating the short-chain aldehydes, while silica gel tubes were used for other volatile organic compounds and fatty aldehydes. Workplaces were selected in kitchens at points where fats and foodstuffs are subjected to elevated temperatures (up to approx. 2ºC). These included a workplace near the frying pan, or grill plate and another near the deep fryer. Figure 1. Collection systems (1 Filter holder, 2 Filter, 4 Cartridge ) The triglyceride pattern of a fat results from the fatty acid pool which is available for fat biosynthesis. This in turn depends on the type of plant which the fat or oil was produced from. Most of the triglyceride fraction measured in the air was triglyceride 54 (this includes all triglycerides whose fatty acid components are aggregated to 54 C atoms). This is a result of the C18 fatty acids which are generally dominant. The other triglycerides exhibited far smaller concentrations, similar to a normal distribution. The smallest values were calculated for the triglycerides with the largest and smallest molecular weights (generally triglyceride 46 and 6 respectively). After dissolution with Hexane they were analysed by high-resolution gas chromatography with flame ionisation detector (GC/FID ) ( Mayer and Lorbeer, 1997). Palmitic acid, oleic acid and stearic acid were found to be the main fatty acids in the aerosols. In a few cases, traces of linoleic acid were also found. Fatty aldehydes is a term used in this report to describe saturated and unsaturated aldehydes with more than 6 C-atoms. The main elements of the medium-volatility components which accompanied the aerosols and which were deposited on the PU foam and on silica gel were as follows: heptenal, octanal, nonanal, nonadienal, decanal, 2-decenal, 2,4-decadienal and 2-undecenal. After dissolution with hexane or acetone the analysis was done by GC/MS (gas chromatography/mass spectrometry)oxicological studies conducted in conjunction with absorption through the food chain also revealed mutagenic properties, e.g. for the decadienal which, among other things, is a decomposition product of linoleic and linolenic acid. 293

3 Proceedings: Indoor Air 22 The following high-volatility aldehydes were quantified: acetaldehyde, acrolein, butanal, caproaldehyde, crotonaldehyde, formaldehyde, valeraldehyde, trans-2-hexenal. Low molecular aldehydes were sampled by silica gel cartridges impregnated with dinitrophenyl hydrazine and analysed in HPLC ( High Performance Liquid Chromatography ).. The kitchen aerosols can be sorted into a particle size distribution ranging from.18µm to 1µm using a 1-stage Bern cascade impactor. The composition of the particles deposited on the separator foil was analysed by GC after eluting with hexane. RESULTS On installation of ventilation systems in kitchens the amount of airborne aerosols and vapours should be known to calculate the air exchange, to find a suitable aerosol filter and to measure the efficiency of the ventilation system. The measurements were performed in 1 kitchens of various size and workload in order to obtain different layouts for the cooking utensils, different room sizes, different ventilation systems and different foodstuffs. In all cases, samples were only taken while the cooking utensils were actually being used. 12,4. Concentration of Aerosols (mg/m³) Aerosoles Acrolein,35,3,25,2,15,1,5 Acrolein Concentration (mg/m³) Kitchen Number Figure 2. Acrolein ( right axis) and Aerosol Concentration (left axis) (mg/m³) near pans The measuring equipment was set up at breathing height, approx. 2 cm from the cooking utensils. Of the low-molecular aldehydes, the acrolein in the air contributed most to the load in the kitchen due to its pungent odour and toxic properties ( Figure 2). Alongside the lowmolecular aldehydes, the concentration of fatty aldehydes in the air was also determined (Figure 3). The aldehyde concentrations of the unsaturated high-molecular fatty aldehydes (2- decenal, 2,4-decadienal and 2-undecenal) of both the frying pan and deep fryer were also calculated. The 2,4-decadienal, one of the main components of the fatty aldehydes, is analysed in particular at the deep fryer. This aldehyde is an auto oxidation product of the linoleic and linolenic acid. Here, too, the long storage life of the deep fryer fat at temperatures in excess of 16 C plays an important role. The aerosol concentration measured at the same time changes in the same ratio as the highly volatile aldehydes and fatty aldehydes. Values of between.5 294

4 Proceedings: Indoor Air 22 and 11 mg/m³ aerosol were measured in the kitchen. From what we have seen above, we can derive that calculating the aerosol concentration at highly loaded workplaces in the kitchen could be adequate for assessing the risk posed by substances extraneous to the air. This naturally assumes that the composition of the aerosols is known and that they do not contain any chemical compounds of high toxicity. Aerosol Concentration (mg/m³) Figure 3. pans Aerosoles Fatty Aldehydes Kitchen Number 1,4 1,2 1,8,6,4,2 Fatty Aldehyde Concentration (mg/m³) Fatty Aldehydes (right axis) and Aerosol Concentration (left axis)( mg/m³) near Concentration (mg/m³) Triglycerides Aerosoles free fatty Acids Kitchen Number Figure 4. Triglycerides and free fatty Acids in Aerosols near pans The aerosols consist of triglycerides and their oxidation products, plus water, as seen in figure 4. The concentration of free fatty acids in the aerosols is also calculated as a third component. These are only slightly volatile and, in part, are dissolved in the fat globules. They can therefore be quantified on the sampling filters. In the kitchen number 8 in figure 4 the 295

5 Proceedings: Indoor Air 22 concentration of free fatty acids was very high. In this case fish was fried. In the majority of cases, the aerosols consist of up to 9 % triglycerides and free fatty acids. Butyl esters and isopropylesters of fatty acids, diacylglycerides and other minor components of vegetable fats (squalene, vitamin derivatives, sterol) were also found in aerosol fractions. The kitchen aerosols can be sorted into a particle size distribution ranging from.18µm to 1µm using a 1-stage Bern cascade impactor. In the measurements performed above the cooking utensils, the largest mass was released in the area of the extractor hood (measuring height 2.5m) at stage 6 of the impactor, which corresponds to a particle fraction over the range.5-1µm. With this fraction, 7% of the mass was identified as triglycerides and 2% as fatty acids. The maximum triglyceride component referred to the total amount of collected aerosols applies to aerosol particles over the range 8-16µm. 85% (averaged over 2 experiments) of the aerosols deposited on the filter consist of undecomposed triglycerides. The largest absolute mass of triglycerides was identified over the size range 4-8µm. The situation is different with fatty acids. Here a maximum of 2% related to the mass of aerosols deposited on the filter was identified for very small particle diameters of.3-.6µm. The largest absolute mass of fatty acids is obtained for particle diameters of.5 1 µm as shown in figure Mass of Triglycerides Mass of free Fatty acids mass in µg ,3µm,6µm,125m,25µm,5µm 1µm 2µm 4µm 8µm 16µm Particle size µm Figure 5. Content of Triglycerides and free Fatty acids in oil droplet of different particle size It must also be emphasised that the larger particles >2µm consist primarily - and in some cases exclusively - of triglycerides. However, the free fatty acids predominate up to a particle size of 1µm. One possible reason for the triglyceride distribution lies in the fact that the substances containing water immediately release water when they come into contact with hot fat, vaporising in an almost explosive way and taking with it the surrounding fat. In the deep frying process, impactor measurements reveal that the maximum yield of the triglycerides or fatty acids occur at comparable stages to those obtained during frying. Here, too, the maximum of the percentage mass component of triglycerides can be found at stage 9 or 1, while the maximum level of fatty acids appears at far smaller particle sizes (<1µm). Unlike 296

6 Proceedings: Indoor Air 22 frying, more free fatty acids than triglycerides are identified when all fractions are totalled together. CONCLUSION In kitchens, aerosols and aldehydes (low molecular aldehydes) up to trans 2-hexenal and unsaturated fatty aldehydes (decenal, decadienal, undecenal) form the main components of the extraneous substances in the air. Vainiotalo et al.. discussed the toxic effect of aldehydes, polycyclic aromatic hydrocarbons and aerosols in kitchen workplaces, but they did not investigate the correlation between aerosol concentration and the concentration of other vaporous components. Rogge et al. analysed kitchen aerosols collected at the exit to the exhaust duct and recommended cholesterol as a marker for food cooking operation especially in the atmosphere. In this paper the aerosols and vapours in kitchens are collected near pans and deep fryer. Due to determine whether a ventilation system in kitchen is needed or what kind of system is recommended the aerosol concentration is an easy to measure key component. The aerosols consist in part of ultra fine particles. These are deposited in the lungs. Up to 9% of the aerosols consist of triglycerides and fatty acids. Other components include furans and polymer or oxidised triglycerides. The concentration of aldehydes and aerosols changes in the same ratio. An aerosol concentration of mg/m³ can be used as a guideline value for a well ventilated kitchen. Complex measurements of other toxic substances can be dispensed with. Measuring of acrolein is recommended. REFERENCES Andrejs B, Huber J, Rietschel P, et al., 1999, Ventilation in kitchen, Proceedings of the 8 th International Conference on Indoor Air Quality and Climate Indoor Air 99, Vol. 2pp , Edinburgh, Indoor Air `99Doberganes C, Marquez Ruiz G, Velasco J,2, Interaction between fat and food during deep- frying, European Journal of Lipid Science and Technology, Vol. 12,pp Gertz Ch, 2, Chemical and physical parameters as quality of used fats, Eur. J. Lipid Sci. Technol.,Vol 12, pp Mayer B.X, Lorbeer E, 1997, Triacylglycerol mixtures for testing capillary columns for hightemperature Gaschromatography, J. Chromatogr. Vol. A758, pp Ross D. J, Upton S. L, Hall D. J et al., 1999, Preliminary Measurement of ultrafine Aerosol Emission from gas cooking, Proceedings of the 8 th International Conference on Indoor Air Quality and Climate Indoor Air 99, Vol. 2, pp , Edinburgh, Indoor Air `99 Rogge F.W, Hildemann M.L, Mazurek M.A et al., 1991, Sources of Fine organic Aerosols. 1. Charbroilers and Meat Cooking Operations, Environ. Sci. Technol. Vol.25, pp Vainiotalo S, Matveinen K, 1993, Cooking Fumes as a Hygienic Problem in the Food and Catering Industries, Am. Ind. Hyg. Assoc. J., Vol.54, pp

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