ANALYSIS AND CALCULATIONS

In order to generate new and reliable analytical data for TürKomp, the analysis methods were selected based on appropriateness of the analysis; national legislations, most advanced methods, cost of the methods, technological facilities of partner laboratories, budget and timeline of the project. Analysis were performed according to sampling procedures and in the edible portion of 100 g foods. The data on liquid food products represent the amount of each consituent in weight (g) of the food. In order to calculate the nutrients in volume (ml), food density should be considered. Analysis methods are given in Standard Operation Procedures (SOP), and their principals are indicated below.

Energy and carbohydrate

Energy and carbohydrate calculation (SOP 045.01): Energy was calculated by Atwater extensive general factor system. Some of the conversion factors used in energy calculation are given in Table 1. Energy values in beer and wine is determined by methods, 971.10 and 979.07 of AOAC (AOAC, 2011), respectively. Food labeling information were used for energy and carbohydrate calculation of non-analysed food additives in food products.

Carbohydrate (available) was determined by the difference between 100 and the sum of water, ash, protein, fat, and when present, dietary fibre, sugar alcohols, ethyl alcohol, and food additive content in 100 g food. Because the analyses of dietary fiber, total sugars, and individual sugars are performed separetly and reflect the analytical variability inherent to the measurement process, the sum of these carbonhydrate fractions may not equal to the carbonhdrate-by-difference value. Carbohydrate data on meat and fish samples were theoretically indicated with zero values. Carbohydrate in beer and wine is determined by methods, 979.06 and 985.10 of AOAC International (AOAC, 2011), respectively.

References:

AOAC International, Official Methods of Analysis, 18th ed. (2005) Revision 4, 2011 (on-line). AOAC International, Gaithersburg, MD, (2011).

Table 1. Energy conversion factors

Water

The water content of foods were determined by different analytical methods indicated below which were selected according to food matrix.

Determination of moisture-air drying method (SOP 001.01): The principle of method is calculating the moisture content from the loss of weight due to drying process in air-oven under a specific temperature.

Determination of moisture-vacuum drying method (SOP 001.02): The principle of method is based on principle of calculating the moisture content from the loss of weight after drying sample in vacuum oven under specific conditions.

Determination of moisture-distillation method (SOP 001.03): The principle of method is distilling and collecting water content of sample by azeotropic distillation using a solvent which is immiscible with water and measuring the water content.

Ash

The ash (inorganic component) content of foods was determined by gravimetric method indicated below.

Determination of ash-dry ashing method (SOP 003.01): The principle of the method is to ash organic materials in ash-oven at elevated temperatures (550±25ºC or 900± 10°C), and weghing the dry mineral residue.

Protein

The values of protein are calculated from the amount of total nitrogen (N) in food which was determined by analytical methods indicated below. Total nitrogen content is multiplied by a nitrogen-to-protein conversion factor which is specific for each food. The nitrogen-to-protein conversion factors used to calculate protein are listed in Table 2.

Table 2. Factors for the conversion of nitrogen values to protein

References:

Jones, D.B., Factors for Converting Percentages of Nitrogen in Foods and Feeds into Percentages of Protein, United States Department of Agriculture Washington D.C., Circular No:183, August 1931, Rev. February, (1941).

Watt, B.K. and Merrill, A.L., Composition of Foods Raw, Processed, Prepared. U.S. Department of Agriculture, Agriculture Handbook 8, (1963).

Determination of total nitrogen''Kjeldahl digestion'' method (titrimetric) (SOP 002.01): The principle of method is to digest samples with acid and determine the total organic nitrogen content by "Kjeldahl" titration after converting organic matter to the free ammonia.

Determination of total nitrogen (thermal conductivity) (SOP 002.02): The principle of method is to carry nitrogen releasing as a result of burning homogenized food sample at elevated temperatures (850-950°C) with pure oxygen (99.9%) by the contribution of helium to the thermal conductivity detector, to measure and calculate protein content by multiplying with appropriate protein factor.

Fat, total

The total fat content of foods were determined by the methods indicated below which were selected according to matrix.

Determination of fat by Soxhlet (classical) and gravimetric methods (SOP 004.01, 004.04): The principle of method is extraction of fat from food sample in an appropriate solvent by soxhlet apparatus.

Determination of fat by acid hydrolysis and gravimetry (extraction) (SOP 004.02, 004.05): The principle of method is decomposition of the sample and extraction of fat in an appropriate solvent by soxhlet apparatus.

Determination of fat in milk by Gerber method (SOP 004.03): The principle of method is to determine the fat content of milk and dairy products by solvation in concentrated sulfuric acid, centrifuge and directly measurement via a special calibrated butyrometer.

Fiber, total dietary

The value of total dietary fiber is the sum of water-soluble and insoluble fibers which were determined by the method indicated below.

Determination of total, soluble and insoluble fiber enzimatic-gravimetric method (SOP 005.01): The principle of method is to determine the amount of soluble, insoluble and total dietary fibre by enzymatic-gravimetric analysis using MES/TRIS buffer solution.

Starch

Starch is analysed by the enzymatic method indicated below.

Determination of starch by enzymatic method (SOP 029.01): The principle of method is to hydrolize starch into glucose molecules enzymatically and calculate the starch concentration through the amount of glucose.

Individual sugars

Individual sugars in the database are fructose, glucose, sucrose, maltose and lactose. Sugars are analysed by chromatographic method indicated below.

Determination of monosaccharides (fructose, glucose) and disaccharides (sucrose, maltose, lactose) by high performance liquid chromatography (HPLC) (SOP 027.01): The principle of method is centrifuging or applying to a C18 cartridge followed by the proper solvent system extraction, which is depend on the type of the product, and determination of sugars by using a HPLC system with a refractive index (RI) detection.

Food additives

Food additives in the database; aspartame, acesulfame-K and sodium saccharin were analysed in foods containing food additives (sweeteners) by chromatographic method indicated below.

Determination of aspartame, acesulfame-K, sodium saccharin by high performance liquid chromatography (HPLC) (SOP 007.01): Water diluted sample is extracted using an ultrasonic water bath. If necessary, the sample solution is purified using centrifuge followed by the addition of carrez reagents and applied to a C18 cartridge. Sweeteners are quantitated by HPLC system with an ultra viole (UV) detection.

Sugar alcohols

Sugar alcohols in the database; mannitol, xylitol and sorbitol were analysed in foods containing sugar alcohols by chromatographic method indicated below.

Determination of sugar alcohols (mannitol, xylitol and sorbitol) by high performance liquid chromatography (HPLC) (SOP 044.01): The principle of method is analysis of foods mannitol, xylitol and sorbitols' followed by extraction of the HPLC peak area measurement of the fluorescence (FL) detector.

Alcohol

The values of alcohol (ethanol) were determined by the method indicated below and given in 100 g weight of food which does not correspond to food volume (%vol).

Determination of alcohol by gas chromatography-mass spectrometry (GC-MS) "headspace" (SOP 026.01): The principle of method is to determine the amount of alcohol by using GC-MS.

Salt

Salt is calculated according to the sodium content of food (1 g sodium = 2.5 g salt).

Minerals

Minerals in the database are iron, phosphorus, calcium, magnesium, potassium, sodium, zinc, iodine and selenium. Concentrations of minerals were determined by various mass spectrometric methods which are indicated below.

Determination of minerals by inductively coupled plasma optical emission spectroscopy (ICP-OES) (SOP 034.01): The principle of method is based on the dissolution of minerals in all kinds of food materials by using the closed system microwave digestion method and the measurement of sodium, potassium, calcium, magnesium, iron, zinc and phosphorus concentrations by ICP-OES.

Determination of minerals by inductively coupled plasma optical emission spectroscopy (ICP-MS) (SOP 035.01): The principle of method is based on the dissolution of minerals in all kinds of food materials by using the closed system microwave digestion method and the measurement of sodium, potassium, calcium, magnesium, iron, zinc, selenium and phosphorus concentrations by ICP-MS.

Determination of iodine by inductively coupled plasma optical emission spectroscopy (ICP-OES) (SOP 032.01): The principle of method is based on the dissolution of minerals in all kinds of food materials by using the closed system microwave digestion method and the measurement of iodine concentrations by ICP-OES.

Vitamins

Water soluble vitamins in the database are; vitamin C, B1, B2, niacin, B6, folate, B12. Fat soluble vitamins in the database are; A, D, E, K1, K2.

Vitamin C

Vitamin C; L-ascorbic acid and L-dehydroascorbic acid forms were determined by chromatographic method indicated below.

Determination of vitamin C by high performance liquid chromatography (HPLC) (SOP 017.01): The principle of method is based on extraction with metaphosphoric acid and quantification by HPLC UV detection after reduction L-dehydroascorbic acid to L-ascorbic acid.

Vitamins B1, B2, B6 and B12

B group vitamins were determined by chromatographic methods indicated below. Vitamin B6 is the sum of pyridoxine, pyridoxal and pyridoxamine forms of vitamin B6.

Determination of vitamin B1 (thiamine) by high performance liquid chromatography (HPLC) (SOP 040.01): The principle of method is an acid hydrolysis (0.1 M HCl, autoclaving at 121°C, 30 minutes) combined with an enzymatic digestion to liberate bound forms of thiamine and quantification by HPLC system with FL detection after pre-column conversion of thiamine to thiochrome.

Determination of vitamin B2 (riboflavin) by high performance liquid chromatography (HPLC) (SOP 041.01): The principle of method is an acid hydrolysis (0.1 M HCl, autoclaving at 121°C, 30 minutes) combined with an enzymatic digestion to liberate bound forms of riboflavin and quantification by HPLC system with FL detection.

Determination of vitamin B6 by high performance liquid chromatography (HPLC) (SOP 042.01): The principle of method is an acid hydrolysis (0.1 M HCl, autoclaving at 121°C, 30 minutes) combined with an enzymatic digestion to liberate bound forms of vitamin B6 and quantification by HPLC system with FL detection.

Determination of vitamin B12 (cyanocobalamin) by high performance liquid chromatography (HPLC) (SOP 016.01): The principle of method is extraction with sodium acetate buffer in the presence of sodium cyanide and pepsin treatment and quantification by HPLC UV detection after purification and enrichment on an immunoaffinity column.

Folate

For folate determination, folic acid (synthetic) and folate (food, natural) are analysed separately by chromatographic method indicated below. Folate, was calculated as "dietary folate equivalent (DFE)" by using these compounds. Following dietary folate equivalens are used;

DFE = folate, food + (1.67 x folic acid, synthetic)

Determination of folates by high performance liquid chromatography (HPLC) (SOP 025.02): The principle of method is tri-enzyme extraction steps for naturally occuring foods and/or single extraction with phosphate buffer for added foods and quantification by HPLC with a FL/UV detection after purification with strong anion-exchange solid-phase extraction (SPE) column.

Niacin

Niacin was analysed by the chromatographic method indicated below. Niacin is calculated by using the contribution of tryptophan which can be converted into niacin. Total niacin activity is expressed as "niacin equivalent (NE)". Following equivalents are used;

1 niacin equivalent (NE) = 1 mg niacin = 60 mg tryptophan

For cereals and cereal products, only tryptophan's contribution is used in the calculation of the niacin equivalents.

Determination of niacin by high performance liquid chromatography (HPLC) (SOP 039.01): The principle of method is an acid/alkaline treatment steps (autoclave at 121°C for 1 hour) and quantification by HPLC with a FL detection after a post-column derivatization with UV irradiation.

Vitamin A

Vitamin A active components; retinol and β-carotene were analysed by chromatographic methods indicated below. Vitamin A was determined by using these compounds and calculated as "retinol equivalent (RE)". Retinol equivalents used for determination of vitamin A are indicated below. Beside β-carotene, other carotenoids; lycopen and lutein are also analysed.

Determination of vitamin A (retinol) by high performance liquid chromatography (HPLC) (SOP 008.01): The principle of method is saponification and extraction steps and quantification by HPLC with a FL detection.

Determination of carotenoids (lutein, lycopene, β-carotene) by high performance liquid chromatography (HPLC) (SOP 013.01): The principle of method is saponification with KOH:methanol and/or direct extraction with THF:methanol and quantification by HPLC UV detection.

Vitamin D

Vitamin D3 (cholecalciferol) was analysed in animal, plant based products and fortified foods. Vitamin D is calculated as unit "IU". Following calculation and analysis method was used.

Vitamin D, IU = Vitamin D3, µg x 40

Determination of vitamin D3 (cholecalciferol) by high performance liquid chromatography (HPLC) (SOP 015.01): The principle of method is saponification, extraction and purification using semipreparative HPLC steps and quantification by HPLC UV detection.

Vitamin E

Vitamin E active component, α-tocopherol was analysed. Vitamin E was determined by using α-tocopherol and calculated as "d-α-tocopherol equivalent (α-TE)" and international unit (IU). Following calculation and analysis method was used:

1 mg d-α-tocopherol = 1 α-TE = 1.49 IU

Determination of vitamin E (α-tocopherol) by high performance liquid chromatography (HPLC) (SOP 009.01): The principle of method is saponification and extraction steps and quantification by HPLC with a FL detection.

Vitamin K

Two major form of vitamin K, vitamin K1 (phylloquinone) and vitamin K2 (menaquinone) are analysed. Vitamin K is expressed as vitamin K1 (in plant based foods) and vitamin K2 (in animal origin foods), respectively. Following analyses methods were used:

Determination of vitamin K1 (phylloquinone) by high performance liquid chromatography (HPLC) (SOP 010.01): The principle of method is extraction with hexane:1-propanol and quantification by HPLC with FL detection after zinc post-column reduction.

Determination of vitamin K2 (menaquinone) by high performance liquid chromatography (HPLC) (SOP 024.01): The principle of method is lipase digestion and extraction with hexane and quantification by HPLC with FL detection after zinc post-column reduction.

Fatty Acids

Fatty acids and cholesterol were analysed by chromatographic method indicated below. Fatty acids expressed in g per 100 g of food. Fatty acid conversion factors (Table 3) are used for converting percentages of total fatty acids to fatty acids per 100 g of food.

Table 3. Fatty acid conversion factors

References:

Greenfield, H., Southgate, D.A.T., Food Composition Data: Production, Management and Use, 2nd Edition, FAO Rome, (2003).

*Sen, D.P., Advences in Fish Processing Technology, Allied Publishers Private Limited, s.79, (2005).

David, F., Sandra, P., Vickers, A.K., Column Selection fort for the Analysis of Fatty Acid Methyl Esters, Agilent Technologies, Inc., 2005.

Determination of fatty acid composition by gas chromatography (SOP 011.01): The principle of method is the peak area measurement resulted from the conversion of fatty acid in foods to its methyl esters by potassium hydroxide generated by the flame ionization detector (FID) using GC.

Determination of cholesterol by gas chromatography (SOP 006.01): The principle of method is the peak area measurement of chloresterol, the component of unsaponified matter that is the result of cholesterol saponification of food cholesterol, generated by the FID using GC.

Amino acids

Amino acids are analysed by the chromatographic methods indicated below.

Determination of amino acid composition-ultra fast liquid chromatoraphy (UFLC) (SOP 012.02): The principle of method is hydrolyzing the protein content of sample to amino acid components and detection by UFLC (UV) detector after derivating with phenyl isothiocyanate solution.

Determination of tryptophan-high performance liquid chromatoraphy (HPLC) (SOP 043.01) :The principle of method is hydrolyzing tryptophan in protein structure of sample to free state by using alkaline solution and detection with HPLC FL detector.

SAMPLING

The definitions and sampling plans used for generic, processed and traditional foods in TürKomp are indicated below. Standardisation of sampling was provided by sampling protocols (continuously revised) which were prepared for each food and in order to prevent risks, risk plans were prepared.

Sampling Plan of Generic Foods: In TürKomp, generic foods were described as foods which are able to consume directly after the harvest (such as tomatoes, bread, dried fruits). All generic foods, exclude fish and fisheries were sampled from 3 vegetation regions in Turkey. Samplings were repeated for 2 years (n=2). Foods were prepared according to instructions in sampling protocols of each food and mixed in equal amounts for the generation of composite sample. The minimum number of samples in each regional composite is 6. The minimum number of samples in each country specific composite is 18.

Fish and fisheries were sampled from 4 different seas and provided 4 sea composites. The minimum number of samples in each sea composite is 6. The minimum number of samples in each country specific composite is 24. Mean of composite values are given as nutrient value.

Sampling Plan of Processed Foods: In TürKomp, processed foods were described as foods and food products which were selling under a brand and/or produced with a technological process (such as pasteurised milk, biscuit, tomato paste). Sampling of processed foods were planned according to current food legislations and standardised production techniques. Therefore, the sampling was carried out in 3 market/gross market which had highest annual sales and were located in 3 different socio-economic regions (low, medium, high income) of 3 largest cities in Turkey (Ankara-İstanbul-İzmir). In each market, 3 products were sampled from 3 different brands according to price (low, medium and high). Food products were prepared based on instructions in sampling protocols and mixed in equal amounts for composite sample. The minimum number of samples in each country specific composite is 27. Processed foods were sampled once (n=1). Additional plans were applied for specific food products which were not able to supply based on current sampling procedures.

Sampling Plan of Traditional Foods: In TürKomp, the definitions generated by European Union and European Food Information Resource Network (EuroFIR) www.eurofir.org were taken into consideration for traditional foods. Traditional food is a food of a specific feature or features, which distinguish it clearly from other similar products of the same category in terms of the use of "traditional ingredients" (raw materials or primary products) or "traditional composition (a time period showing transmission between generations which means a minimum of 25 years)" or "traditional type of production and/or processing method" (European Commission, 2007; Weichselbaum et al., 2009). For sampling of traditional foods; 3 (for some other foods 4) main geographical area of origin of the traditional food production was identified for collection of each traditional food. Traditional foods were sampled from the 3 local producers which were selected within the defined geographical region. One of the local producers was visited for recording of the traditional food processed. The local producers were selected according to various criteria such as; using the traditional production method, keeping related regulations, using local ingredients, pass down the production method through generations was preferred. Prior to traditional food sampling, information on the traditional food was traced from related publications and outlined registration files of project group, and main geographical areas of origin were identified. In each location, local food producers were informed with "collaboration letters", and the producers were selected according to feedbacks and criteria. "Collaboration protocols" were used for some recipe recordings. For some foods, recipe recording was provided from semi-industrial producers which were not completely far from traditional production techniques, or from home or boutique type producers. Traditional foods were sampled once during the project (n = 1).

References:

European Commission, European Policy for Quality Agricultural Products. Fact Sheet. Office for Official Publications of the European Communities, Luxembourg, (2007).

Weichselbaum, E., Benelam, B.,Costa, H.S., EuroFIR Synthesis Report No 6, Traditional Foods in Europe, ISBN 0 907667 67 8, (2009).

DATABASE SPECIFICATIONS

All data given in TürKomp is produced under “TürKomp, Data Quality Evaluation Procedure”, “Quality Index Confidence Code” is at the level of A class.

FOOD GROUPS: TürKomp contains food composition data on the most produced and consumed foods in Turkey. The foods are represented under 13 food groups (Table 1). Analytical data for traditional foods will be availabe after application for intellectual property registration.

Table 1. Food groups

NUTRIENTS: There are approximately 100 nutrients, analysed in TürKomp. The nutrients were individualised for each food, according to food type. Description and abbreviation of nutrients were indicated based on "EuroFIR Component Thesaurus version 1.3".

PRESENTATION OF DATA: Food composition values and their units were presented based on "Greenfield and Southgate, 2003. In the database, there are no missing values for foods which were not analysed. The foods which are not theoretically contain; protein, fat and fiber, dietary total were presumed as zero (0). The analyse results found as zero or under the limit of quantification “LOQ” (trace values) were given as zero (0).

FOOD DESCRIPTION: All foods were indexed according to "Langual Thesaurus, Food Product Indexer Version 3.91, October 2008". Description of all codes was translated into Turkish.

MULTI LANGUAGE: Turkish (Tr) and English (En) are available.

SEARCH: Different ways can be performed to search the data. Beside the alphabetical food list, a free text search for foods from their English, scientific, and traditional names are available. The ‘by components’ link can be used to obtain the listed foods through the content of the nutrient. The ‘by dietary uses’ link can be used to obtain the listed foods according to their content of specific nutrients and indicated as low calorie, low fat, no fat, high fiber and high protein.

COMPARISON: The comparison of two different foods in terms of nutrients is available.

"LUNCH BOX" APPLICATION: The food composition of multiple foods can be obtained by the selection of more than one food and typing the amount for each food.