« Return

NUTRITIONAL COMPOSITION OF GREEK FOODS
AND TRADITIONAL DISHES BY LABORATORY ANALYSES

In the context of the overall research activity on the systematic investigation of traditional Greek foods (see www.nut.uoa.gr – Traditional foods), the nutrient value of the composite food as well its main ingredients was determined. The recipes of the composite foods appear as the censor passes over the name of each food. The techniques used for the preparation of the laboratory samples should ensure the validity of the derived results. Thus, the selected techniques should minimize the possible deterioration of ingredients and achieve the highest degree of homogeneity. Therefore, the Ultra-Turrax T25 apparatus of the German firm ΙΚΑ LABORTECHNIK was chosen for homogenizing foods under investigation. In the case of vegetables, due to their sensitive texture, a household blender was used (multi-moulinette, ΜOULINEX).

Freeze drying is considered as the most appropriate preparation method, since it leads to the production of dried samples, which, thus, allows for further analyses, while preventing the deterioration of the nutritional components. For sample distribution, glass airtight vessels were used to ensure the safe maintenance of the freeze dried samples.

Standard and valid methods from the international literature were used for the laboratory analyses. More specifically, the following laboratory methods were applied:

Determination of water content: For the freeze dried samples, the water content was determined by difference, from the loss of water during the freeze drying procedure (Flink & Knudsen, 1983). For the samples that were analyzed in their original state, the water content was determined by the oven method (AOAC, 1990).

Determination of nitrogen: The determination of nitrogen was carried out using the Kjeldahl method (AOAC, 1990). Protein was calculated by multiplying the total nitrogen value by FAO/WHO nitrogen conversion factors. (FAO/WHO, 1973).

Determination of total lipids: Total lipids of the samples were determined by the Soxhlet method after acid hydrolysis. (Egan et al., 1987; AOAC, 1984; ISO 659:1988). Determination of fatty acids: The determination of fatty acids was accomplished using gas chromatography methods, according to EU Regulation 2568/91 (EU, 1991). The fatty acid methyl esters were converted to g of fatty acids per 100 g of total lipids, by applying the appropriate for each food fatty acid conversion factor (Paul & Southgate, 1978). For the composite foods, the selection of the appropriate fatty acid conversion factor was made based on the analogy of fatty acids indicated by the analyses.

Calculation of carbohydrates: Carbohydrates were calculated “by difference”. The values reported correspond to available carbohydrates and were calculated based on analytical values and literature data (Trichopoulou, 1992; Souci-Fachmann-Kraut, 1986), in the cases where analytical values were not available.

Determination of dietary fiber: The determination of dietary fiber was carried out by the Englyst method. (Englyst et al., 1994).

Measurements of energy value: The available energy value of the foods was calculated following the determination of the gross energy value through an adiabatic colorimeter (Box & Cameron, 1982).

Determination of inorganic components: Atomic absorption spectrometry with flame and with graphite oven was applied. (AOAC, 1990).

All laboratory analyses were carried out in duplicate or triplicate. Moreover protein and fatty acid determination were externally validated through reference material used in quality control testing conducted by the Food Analysis Performance Assessment Scheme (FAPAS- Ministry of Agriculture, Fisheries and Foods (MAFF) of the United Kingdom) and the International Olive Oil Council respectively.

The analyses were implemented in the context of research projects, which have been co-financed by the Hellenic General Secretariat of Research and Technology, and the European Union. The sources of the analytical values appear as the censor passes over each individual value. The names of the collaborating partners are presented below.

Collaborating partners:

Dept. of Hygiene and Epidemiology, School of Medicine, University of Athens; Dept. of Nutrition and Biochemistry, Athens School of Public Health; Laboratory of Chemistry and Food Analysis, Agricultural University of Athens; Food Industrial Research and Technological Development Company S.A. (ETAT S.A.); General Chemical State Laboratory; Yiotis nourishing products industry S.A.; Elaiourgiki; Elais S.A.; Hellenic Catering S.A.; Olympic Catering S.A.

REFERENCES

- Association of Official Analytical Chemists (AOAC). (1984). Official methods of analysis of the AOAC. 14th ed. Association of Official Analytical Chemists. Washington DC, U.S.A.
- Association of Official Analytical Chemists (AOAC). (1990). Official methods of analysis of the AOAC. 15th ed. Association of Official Analytical Chemists. Arlington, Va., U.S.A.
- Box, B.A. and Cameron, A.G. (1982). Food Science: a chemical approach. 4th ed. Hodder and Stoughton Ltd. U.K.
- Egan H, Kirk RS, Sawyer R. (1987) Pearson’s Chemical Analysis of Foods, 8th ed., Longman Scientific &Technical, U.K. p.22
- Englyst, H.N., Quiley, M.E. and Hudson, G.J. (1994). Determination of dietary fibre as Non-starch Polysaccharides with Gas Liquid Chromatographic, High Performance Liquid Chromatographic or Spectrophotometric Measurements of Constituent Sugars. Analyst. 119:1497-1509.
- European Union Regulation. (1991). Method for the preparation and analysis of methyl esters of fatty acids. Method: EE 2568/91. Official Newspaper of the European Community. L248/36-43.
- FAO/WHO Expert Group (1973) Energy and protein requirements. Report of a Joint FAO/WHO Ad Hoc Expert Committee. FAO Nutrition Meeting Report Series No. 52. Rome:FAO/WHO.
- Flink, M.J. and Knudsen, H. (1983). An Introduction to freeze-drying. Strandberg Bogtryk/Offset a.s; ISBN 87-872-0084-8. Denmark. - International Organization for Standardization (ISO 659) (1988) Oil seeds-Determination of hexane extract (or light petroleum extract), called "oil contant"
- Paul, A.A. and Southgate, D.A.T. (1978). McCance &Widdowsons’ The Composition of Foods, 4th ed., Her Majesty’s Stationer Office, London and Elsevier/North-Holland Biomedical Press, Amsterdam, The Netherlands.
- Souci-Fachmann-Kraut, (1986) “Food composition and nutrition tables”, Ed. 3, 1986/87, Wissenschaftliche Verlagsgesellschaft mbH, Post-fach 40, D-7000, Stuttgart, Germany.
- Trichopoulou, A. (1992). Greek Food Composition Tables. 2nd ed. Litsas publications. Athens, Greece.

COMPOSITION TABLES