Introduction What we know and what we should know about virgin oils a general introduction

Transcription

1 Eur. J. Lipid Sci. Technol. 2008, 110, Introduction What we know and what we should know about virgin oils a general introduction Bertrand Matthäus 1 and Friedrich Spener 2 1 Max Rubner-Institute, Federal Research Institute for Nutrition and Food, Münster, Germany 2 Department of Molecular Biosciences, University of Graz, Graz, Austria On international scale the Codex Alimentarius Standard for Named Vegetable Oils differentiates between virgin oils and cold-pressed oils, while in Germany virgin, non-refined and refined oils are available. Here cold-pressed is an additional quality feature. The paper explains and comments the various definitions for vegetable oils other than olive oil obtained by mechanical extraction only, because they are partly contradictory. Resulting from gentle processing virgin oils are often appreciated by the consumers as the better oils. The answer of the present paper to the question which type of oil is better is that there is no better or worse oil, but only a better or worse suitability of an oil for application in food processing or the kitchen. Finally, the paper picks up the upcoming debate on the potential new contaminant, 3-MCPD-fatty acid esters, which were found in refined oils. Keywords: 3-MCPD-fatty acid esters / Codex Alimentarius / German guidelines for edible fats and oils / Virgin oil / Cold-pressed oil Received: May 14, 2008; accepted: May 5, 2008 DOI /ejlt Background and rationale It is a truism to state that virgin olive oil is a big success on the market. The consumer associates this oil to be healthier than refined vegetable oils, due to less processing by mechanical extraction only, the deep colour, and the typical taste and smell. Over the last years, however, other vegetable oils that are produced by mechanical extraction without use of any solvent emerged and are now available for the consumer, resulting in increased competition for market shares. While virgin olive oil is clearly defined by regulation EEC/2568/91 [1] of the European Union, we face a remarkable confusion about naming and characterisation of all these other vegetable oils. Apart from virgin, labels like cold-pressed, not-refined can be found, in non-english speaking countries also the label native. The aim of this introductory paper to this special issue is to explain and comment the various definitions for vegetable Correspondence: Max Rubner-Institute, Federal Research Institute for Nutrition and Food, Piusallee 68/76, D Münster, Germany. bertrand.matthaus@mri.bund.de oils other than olive oil obtained by mechanical extraction only. In fact, some international and national definitions exist, yet are partly contradictory. Finally, the question which oil is better will be addressed, including the upcoming debate on a potential new contaminant of the oils. 2 Definitions according to Codex Alimentarius 2.1 Virgin oils On international scale the Codex Alimentarius Standard for Named Vegetable Oils, Codex-Stan 210 [2], defines virgin oils as obtained without altering the nature of the oil, by mechanical procedures, e.g. expelling or pressing and the application of heat only. Subsequent purification of the oil by washing with water, settling, filtering and centrifugation is possible. Thus, application of heat in the course of the whole process is allowed. But the limitation is that the nature of the oil must not to be changed. As several constituents of the oil are very susceptible to heat, e.g. chlorophyll in rapeseed oil [3], such heating is highly restricted.

2 598 B. Matthäus and F. Spener Eur. J. Lipid Sci. Technol. 2008, 110, Cold-pressed oils Codex Alimentarius does not allow applying heat in the course of any production step of cold-pressed oils. Thus, coldpressed oil is also virgin oil, but virgin-oil not necessarily coldpressed oil. 2.3 Definition according to German guidelines for edible fats and oils In Germany, in addition to Codex Alimentarius, a guideline is available, which describes good-manufacturing-practice (GMP) for edible fats and oils jointly defined by industry, science, official food control and consumer protection [4]. Besides refined oils, the guideline differentiates between virgin and non-refined oils. It has no legally binding status, but in the case of a complaint by official food authorities a deviation from it requires an explanation Virgin oils Most important, applying heat in preparing the raw material, during pressing and post-pressing is prohibited. In the latter, treatment of the oil by washing, filtering or centrifugation is allowed. A limit for temperature resulting from heat arising in the course of pressing itself is not given. It follows that the term virgin in the German guideline on the one hand is identical to the term cold-pressed as defined by Codex Alimentarius, on the other hand differs from the Codex definition of virgin by the exclusion of heat. The key point is, however, that in both definitions of virgin oil, the composition must not be altered in the course of the production process. This implies that in practice analytical standards available today preclude the use of heat, because sensitivities and detection limits of present sensory and analytical methods track any changes in oil composition Non-refined oils The position of non-refined oils is between refined and virgin oils. In addition to mechanical extraction by pressing, centrifugation and melting of the raw material is allowed. Preheating of the raw material to increase oil yield, or to obtain a special roasty sensory perception is not forbidden. Another processing step which is allowed for not refined oils is the use of hot water steam, but only to the extent necessary to improve shelf life of the oils. In practice temperatures between 100 and 1507C are in use. The problem of such a treatment is that aroma compounds responsible for the typical taste and smell of the oil are removed first [5], while unpleasant fusty and musty aroma remains in the oil. Only higher temperatures remove unpleasant components, the result being nearly tasteless oil. Such oil would be neither virgin nor non-refined oil, because the German guideline defines that both types of oil must preserve the typical taste of respective seed or fruit. So far, Codex Alimentarius has no provisions for a nonrefined oil, although these types of oil are available on the market in form of oils from roasted raw material, e.g. pumpkin seed oil or oils treated with hot water steam Cold-pressed oils According to the German guideline both, virgin oil and nonrefined oil, also can be labelled cold-pressed, if a careful, gentle mechanical extraction of the raw material without application of heat was carried out. But heat-treatment is allowed during preparation of the raw material and/or of the oil after the pressing process. In fact, the term cold-pressed by the guidelines is meant as an additional quality feature, indicating gentle extraction conditions. This is at variance with the definition of coldpressed by Codex Alimentarius, where application of heat is strictly forbidden through-out the whole production process. 3 Confusion and possible remedy For the non-expert, all this is hard to grasp as consumers consider the terms virgin and cold-pressed to be synonymous. Producers and retailers in present practice, regrettably, label oils from heat-treated seed material or oils treated with hot water steam as virgin or cold-pressed without using the term non-refined additionally. This is also to the disadvantage for producers of genuine virgin oils, because under the definitions of Codex Alimentarius or the German guideline they have no possibility to improve oil quality in case optimum raw material was not available. Fraud by heat treatment of either raw material or resulting oil can be detected by sensory evaluation if the oil becomes roasty or burnt, or by determination of chemical parameters like oligomer triacylglycerols, trans fatty acids, steradienes or a certain ratio of chlorophyll degradation products. The latter applies particularly to virgin rapeseed oil [6]. In order to improve transparency in product labelling for the market, a working group of the German Society of Fat Science (DGF) pushes for an update of the existing German Guidelines:. The term virgin oil is reserved for oils obtained in native or raw form; no heat treatment at all, only pressing of untreated raw material by a screw press or other mechanical extraction and purification of resulting oil by sedimentation, centrifugation, or filtration. This definition is comparable to the definition for cold-pressed of the Codex Alimentarius.. Delete the definition of non-refined.. In contrast to Codex Alimentarius the term coldpressed in the German guidelines refers only to the extraction process, i.e. no application of heat in this step. Therefore, cold-pressed oil can be processed from roasted seeds, or the

3 Eur. J. Lipid Sci. Technol. 2008, 110, Virgin oils 599 use of hot water steam is allowed for the oil obtained from cold-pressing. But such treatment has to be indicated on the product label. An oil from roasted seeds would be labelled as coldpressed from roasted seeds or an oil treated by hot water steam would be labelled as cold-pressed, steam-treated. Strictly speaking, virgin oil could be labelled as cold-pressed, virgin, but the term virgin according to this new proposal comprises already the term cold-pressed. Moreover, from this it can be concluded that virgin oils are also cold-pressed, but cold-pressed oils are not stringent virgin. 4 Which type of oil is better? What does better mean? As opposed to refined oil, is a virgin oil better with regard to nutrition and health, with regard to taste and smell, with regard to processing and contaminants? These questions are commonly asked by consumers and hotly debated by producers, the prevalent question being for nutrition and health. The answer to the latter is, however, that there is no better or worse oil, but only a better or worse suitability of oil for application in food processing or kitchen. 4.1 Aspects of processing Virgin oil is a natural product whose quality depends not so much on processing but on the quality of raw material used. As alluded to before the producer has no chance to improve oil quality when starting from bad raw material. It follows that high seed quality is of utmost importance for virgin oils quality. The problem is that the quality of raw material is subject to great variation, resulting in a great variation of virgin oil quality on the market. These differences can be judged by sensory evaluation and by the presence of minor components like free fatty acids, metal ions or chlorophyll which negatively affect the oxidative stability of the virgin oil. Unfortunate for the consumer, visual assessment of the bottle does not give any hint about quality of the virgin oils contained therein. In contrast to virgin oils, refined oils have undergone comprehensive processing, resulting in a product with standardised quality. By appropriate quality management systems established in big facilities, it is possible to produce oil having always the same high quality. To the advantage for the consumer he can buy refined vegetable oils throughout the year and can be sure that he gets the quality he wants for preparing food. 4.2 Environmental aspects Processing of virgin oils in small and medium-sized facilities for the production of virgin oils is often based on regional material circulation and short distances of transportation. This adds to consumer s acceptance of virgin oils [7, 8]. 4.3 Aspects of composition Different extraction processes result in certain differences in the composition of the oil which lead to consumers assumption that virgin oils are healthier than refined oils. Indeed, the gentle extraction procedure during processing of virgin oils preserves all oil-soluble components, like tocopherols, sterols, carotinoids and phenolic compounds representative for the natural composition. This results in sensory perceptions of taste and smell as well as in colours of virgin oils indicative for the plant material they originate from. Cold-pressed oils from roasted seed material present a special aspect, because such heat treatment results in a better oxidative stability of the oil that can be explained by better extractability of antioxidants during pressing. In contrast, refined oils are neutral in taste and smell and only pale in colour. Carotinoids and phenolic compounds are removed almost totally, while vitamin E-active compounds and phytosterols are reduced by about 10% to 40% [9]. From a nutritional point of view it is important to note that refined edible oils still contain sufficient amounts of tocopherols and phytosterols for the supply of humans; and with respect to carotinoids and phenolic compounds these oils are not the main suppliers to fill human needs. In virgin oils the amount of trans fatty acids is below 0.2%, while during refining up to 1% trans fatty acids can be formed. In cold-pressed oils treated afterwards by hot water steam, depending on temperature higher amounts of trans fatty acids can be found; levels do not exceed 1%, however which is generally regarded as safe in nutritional terms [10]. 4.4 Aspect of application The main consumption of virgin oils appears to be via salads or something similar. The important factor here is that the typical smell and taste of the virgin oil is taken up by the food and increases its sensation. The use of virgin oils described in this special issue in pan-frying or deep-fat frying is not recommended, yet partly possible due to individual quality of the oil [11]. Clearly, pan-frying and deep-fat frying is the domain of refined oils. 5 3-Monochloropropane-1,2-diol fatty acid esters (3-MCPD-esters) in heat-treated oils Hydrolysis of 3-MCPD-esters results in 3-MCPD, which in high doses applied to animals led to a carcinogenic effect; a genotoxic potential was observed in vitro, but not confirmed in vivo [12-15]. From these data the Joint FAO/WHO Expert Committee on Food Additives (JECFA) defined in 2001 the daily tolerable intake as 2 mg 3-MCPD/kg body weight [16]. The formation of kidney tumours in animal experiments arose only at 500-fold higher concentrations.

4 600 B. Matthäus and F. Spener Eur. J. Lipid Sci. Technol. 2008, 110, In December 2007 two German institutions reported the finding of high amounts 3-MCPD-esters in refined vegetable oils [17, 18]. A provisional assessment by the Federal Institute for Risk assessment (BfR), one of the two institutions, assumes that 3-MCPD-esters are decomposed completely during digestion to which the European Food Safety Authority (ESFA) agrees [19]. Although no acute health hazard is seen, BfR recommends (a) investigating the reasons for the formation of 3-MCPD-esters and (b) searching for alternatives in the production [18]. Preliminary data from the Chemisches und Veterinäruntersuchungsamt (CVUA) in Stuttgart and the Max Rubner-Institute in Münster reveal that deodorisation during refining is the critical step for the formation of 3-MCPDesters. From this it becomes clear that the appearance of 3- MCPD-esters is mainly a problem of refined oils. Yet, in coldpressed oils 3-MCPD-esters can be found if the temperature during treatment of the oil with water steam is high. By the same token, this applies to the oil from roasted pumpkin seeds as well. 6 Conclusions For olive oil strict, internationally acknowledged definitions for the various quality levels exist. These criteria and the oil s availability allow to use it in salad dressings and as cooking and baking ingredients. Virgin olive oil, in particular, is big business already and still bound to grow further. In contrast, the market for virgin and cold-pressed oils from all other plants still is rather small and local; in fact, the market needs to take off from this niche. The main stumbling block for further market growth of these oils is the lack of transparency for the parties involved of the definition of product quality. At the moment we have the international standard Codex Alimentarius that defines the terms virgin and cold-pressed, but another category of oils, which are produced from roasted seeds or by treatment with hot water steam are not taken into consideration. We also have the German guideline defining the terms virgin, nonrefined, and cold-pressed. There are contradictions within and between these two systems, which confuse not only the consumer, but also producer and retailer. With the aim to arrive at an internationally acknowledged system of quality criteria for all virgin and cold-pressed oils, except for those from olive, a DGF working group proposes the following: The definition virgin oil means, it is obtained by mechanical extraction and heat is not applied through-out the whole production process. This implies that this oil, per definition, is also cold-pressed oil. The second definition pertains to cold-pressed oil. This term refers to the pressing process of the oil only and says nothing about a treatment of the seed material before pressing and about a treatment of the oil after pressing. However, it is mandatory that cold-pressed is accompanied by terms describing specific processing before and/or after pressing, e.g. virgin, from roasted seeds, steam-treated. Consumers associate virgin oils with healthier nutrition resulting. Yet in spite of some differences in the composition of virgin and refined vegetable oils, these differences do not result in significant nutritional-physiological differences between both types of oil. Up to now no scientific investigation is available showing that virgin oils have a higher nutritional value than refined oils. The main point why humans need fats and oils, are fatty acids and these are comparable for both types of oil. The application of pesticides or biocides to oil crop plants is not separately regulated by present and proposed definitions of quality criteria for virgin oils and refined oils either. Thus the question, which type of oil is better, virgin or refined, can not be answered on the basis of composition or health effect, rather the area of food production tells us which oil is preferable. Conflict of interest statement The authors have declared no conflict of interest. References [1] European Commission: Characteristics of Olive Oil and Olive- Residue Oil and on the Relevant Methods of Analysis. Commission Regulation EEC/2568/91 as amended. Off J Eur Communities 1991, 310, L248, [2] Food and Agriculture Organization of the United Nations/ World Health Organization, Joint FAO/WHO Food Standards Programme: Codex Alimentarius Commission, (1993) Codex Alimentarius Volume 8, Fats, Oils and Related Products, 2nd Edition, Rome Codex Standard for named Vegetable Oils Codex-STAN 210 (Amended 2003, 2005).. [3] K. Aitzetmüller: Chlorophyll-Abbauprodukte in pflanzlichen Ölen. Fat Sci Technol. 1989, 91, [4] Leitsätze für Speisefette und -öle. vom (BAnz. Nr. 239a vom , GMBl. Nr. 45 S. 864 vom ), geändert am (BAnz. Nr. 199 vom , GMBl Nr. 38; 754 ff vom ) [5] B. Matthäus, L. Brühl, S. Krüger: Lässt sich eine Wasserdampfbehandlung von kaltgepressten Rapsspeiseölen nachweisen? Lebensmittelchemie. 2006, 60, [6] B. Matthäus, L. Brühl, D. Reinhold: Detection of a heat-treatment of native edible rapeseed oil by chlorophyll degradation products? 5th Euro Fed Lipid Congress September, Gothenburg (Sweden) [7] B. A. 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5 Eur. J. Lipid Sci. Technol. 2008, 110, Virgin oils 601 wirtschaft und Forsten Bayer. Staatsministerium für Ernährung,. Gelbes Heft [9] S. Ramamurthi, A. R. McCurdy, R. T. Tyler: Deodorizer distillate: A valuable byproduct. In: Proc. World Conf Oilseed Edible Oils Process Vol. 1. Eds. S. S. Koseoglu, K. C. Rhee, R. F. Wilson, AOCS Press, Champaign, IL (USA) 1998, pp [10] Deutsche Gesellschaft für Ernährung, Österreichische Gesellschaft für Ernährung, Schweizerische Gesellschaft für Ernährungsforschung, Schweizerische Vereinigung für Ernährung (Hrsg): Referenzwerte für die Nährstoffzufuhr, 1 st edn. Umschau Braus, Frankfurt am Main (Germany) 2000, p. 56B. [11] B. Matthäus: Are cold-pressed rapeseed oils suitable for deepfat frying of potatoes? Lipid Technology. 2005, 17, [12] B. S. Lynch, D. W. Bryant, G. J. Hook, E. R. Nestmann, I. C. Munro: Carcinogenicity of monochloro-1,2-propanediol (achlorohydrin, 3-MCPD). Intern J Toxicol. 1998, 17, [13] S. Robjohns, R. Marshall, M. Fellows, G. Kowalczyk: In vivo genotoxicity studies with 3-monochloropropan-1,2-diol. Mutagenesis. 2003, 18, [14] L. Silhankova, F. Smid, M. Cerna, J. Davidek, J. Velisek: Mutagenicity of glycerol chlorohydrins and of their esters with higher fatty acids present in protein hydrolysates.mutation Research. 1982, 103, [15] G. Sunhara, L. Perrin, M. Machessini: Carcinogenicity study on 3- monochloropropane-1,2-diol (3-MCPD) administered in drinking water to Fischer 344 rats. 1993, Report No. RE- SR (Switzerland: Nestec Ltd., Research and Development). [16] Scientific Committee on Food: Opinion on 3-Monochloro- Propane-1,2-Diol (3-MCPD) updating the SCF opinion of 1994 adopted on 30 May [17] 2&ID=717: 3-MCPD-Ester in raffinierten Speisefetten und Speiseölen ein neu erkanntes, weltweites Problem [18] Stellungnahme Nr. 047/2007 des BfR vom 11. Dezember 2007: Säuglingsanfangs- und Folgenahrung kann gesundheitlich bedenkliche 3-MCPD-Fettsäureester enthalten. [19] European Food Safety Authority: Statement of the Scientific Panel on Contaminants in the Food chain (CONTAM) on a request from the European Commission related to 3-MCPD esters (Question No EFSA-Q ) Adopted by written procedure on 28 March 2008.