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Abstract

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS AND DISCUSSION
  6. ACKNOWLEDGMENTS
  7. REFERENCES

ABSTRACT

The fat and fatty acid content of three traditional Greek cheeses were determined monthly for a period of 1 year. The analyzed cheeses, feta, graviera and manouri, are traditional Greek dairy products made exclusively or primarily from sheep milk. In all cheeses, the content of the fatty acids varies during several months, especially the conjugated linoleic acid (CLA) content of feta, graviera and manouri ranged between 0.5 and 0.9, 0.5 and 1.0 and 0.4 and 0.8 g/100 g total fatty acids, respectively. The average content of CLA in graviera and feta was similar (0.75 and 0.72 g/100 g fatty acids, respectively). On the other hand, the CLA content of manouri (0.54 g/100 g fatty acids) was less than that of the other two cheeses. In every case, the analyzed cheeses can be characterized as good or very good CLA sources.

PRACTICAL APPLICATIONS

No data exist about the variation in the fatty acid composition of standardized cheeses during the various months of the year. Several investigations were carried out in order to determine the fatty acid composition and especially the conjugated linoleic acid (CLA) content of various kinds of cheese. However, cheeses were produced from milk and it is suggested that the milk composition is affected by seasonal factors. In the present investigation, we tried to find out if the beneficial fatty acid content of cheeses, which were previously found as rich CLA sources, is season dependent. The results of this research are a potential tool for food technologist in order to provide CLA-enriched diets.


INTRODUCTION

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS AND DISCUSSION
  6. ACKNOWLEDGMENTS
  7. REFERENCES

Interest in the fatty acid composition of dairy products is continuously increasing, as some fatty acids that are present in milk fat are recognized as bioactive substances (Molketin 1999). One of these, conjugated linoleic acid (CLA), has been related in experiments with animals with the inhibition of tumorgenesis (Ip 1997; Ip et al. 1991; Belury 1995), atherogenesis (Lee et al. 1994; Nicolosi et al. 1997; Kritchevsky et al. 2000), normalization of glucose tolerance (Houseknecht et al. 1998) and the reduction of body fat (Park et al. 1997; West et al. 1998).

Since the early characterization of CLA as a protective agent against chemically induced cancer (Pariza et al. 1986), many studies have examined the factors that affect the CLA content of ruminant meat, milk and dairy products (Lin et al. 1998; Jahreis et al. 1999; Maranesi et al. 2005). The type of animal feeding influences the fatty acid content of milk (Stanton et al. 1997; Dhiman et al. 1999; Mir et al. 1999) and especially the CLA content. The initial milk composition, in turn, influences the CLA content of dairy products, as has been reported for cheeses (Zlatanos et al. 2002).

However, the CLA content of dairy products is not affected only by the milk composition, as cheeses contain different amounts of CLA from the milk they are made from (Chin et al. 1992). Other important factors that can affect the CLA content of dairy products are aging time (Lin et al. 1998; Zlatanos et al. 2002), processing (Garcia-Lopez et al. 1994) and the lactic cultures (Sieber et al. 2004).

In the present study, the fat and fatty acid content of three traditional Greek cheeses (feta, graviera and manouri) were determined monthly for a period of 1 year. These represent three common categories of Greek cheeses. Feta is the most produced Greek cheese (ESYE 1996) and belongs to the brine cheeses; graviera is a popular hard cheese and manouri a whey cheese.

The cheeses that were analyzed are produced in different ways. Sheep milk is used for the production of graviera, sheep's whey milk with a surplus of fresh sheep milk is used for the production of manouri and feta is produced mainly from sheep milk with addition of goat milk. The usual aging time of feta is 2 months. Graviera is a common Greek hard cheese with long aging time (approximately 3 months), while Manouri is produced without aging. However, the sheep milk production in Greece is seasonal. Therefore, besides the fact that the analyzed cheeses were bought during the whole year, they were produced mainly during the months with the highest milk availability.

MATERIALS AND METHODS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS AND DISCUSSION
  6. ACKNOWLEDGMENTS
  7. REFERENCES

Sampling

Three kinds of Greek cheeses were collected monthly from a supermarket in Thessaloniki (Northern Greece). In particular, three samples of every kind were bought. These cheeses were brine cheese (Feta from Dodoni), hard cheese with long aging time (Graviera from Crete) and whey cheese (Manouri from Tirnavos). All three kinds are cheeses with Controlled denomination of origin and only one brand was selected for every cheese.

Lipid Extraction and Methylation

Approximately 100 g of every cheese sample were weighed and homogenized. The fat of 1-g (exactly weighted) cheese was extracted according to the Schmidt–Bondzynski–Ratzlaff method (DIN 1981). According to this method, the sample was hydrolyzed with HCl and then extracted in three repeated steps with diethyl ether and petroleum ether. The fat content was measured gravimetrically.

The fatty acids were methylated according to the specific method for fatty acids with four or more carbon atoms (British Standards 1980). According to this method, 500 µL of trimethylsulfonium hydroxide (methanolic solution, 0.2 mol/L), 500 µL of margaric acid (C17:0) hexane solution (2 mg/ml), as an internal standard, and 10 mg of the extracted fat were put in a glass tube and were shaken for 1 min with a vortex shaker. After methylation, the fatty acid methyl esters (FAME) were determined with gas chromatography.

Gas Chromatography of the FAME

The FAME of the methylated fat aliquots were determined using a gas chromatograph (Sigma 2B, Perkin Elmer, Norwalk, CT), equipped with a flame ionization detector. A DB-5 column (J & W Scientific, Folsom, CA; length 60 m, film 0.25 µm, diameter 0.32 mm) was used. The flow rate of the carrier gas was 1 mL/min, the injection temperature was 250C and the detector temperature was 300C. The temperature program was as following: initial temperature 80C isothermally for 5 min, temperature ramp 5C/min until 180C isothermally at 180C for 16 min, temperature ramp 5C/min until 220C isothermally at 220C for 15 min.

Identification of the FAME was performed from the comparison of the retention times with the retention times of the FAME standards. The standards were purchased by Sigma-Aldrich Ltd. except for the CLA standard, which was purchased by Trofocell Research and Trade Ltd. Hamburg/Germany. The gas chromatographic spectra were converted to weight percentages utilizing response factors. The response factors were previously determined empirically in our laboratory.

Moisture Content Determination

For the measurement of the moisture content, 10 g of the homogenized cheese were exactly weighed and then heated at 102C until constant weight.

Statistical Analyses

Three samples of each brand were collected, and data were reported as average (n = 3) ± standard deviation (n = 3). The data were considered significant at P < 0.05. For the determination of the P value, one-way analysis of variance was conducted.

RESULTS AND DISCUSSION

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS AND DISCUSSION
  6. ACKNOWLEDGMENTS
  7. REFERENCES

The average moisture and fat content of the analyzed cheeses during the 1-year period are shown in Table 1. Among the analyzed cheeses, feta has the most stable fat and moisture composition. On the other hand, the manouri cheese showed the largest variations. Especially, the fat content variation is characteristic for the various cheeses. The fat content shows small variation for feta, greater variation for graviera and the greatest variation for manouri.

Table 1.  FAT AND MOISTURE CONTENT (g/100 g sample) IN GREEK CHEESES DURING THE 1-YEAR PERIOD
 MoistureFat
Feta52.30 ± 2.7721.12 ± 2.50
Graviera34.33 ± 2.3129.86 ± 5.50
Manouri38.60 ± 4.6446.18 ± 12.95

The mean, standard deviation and the range of the analyzed fatty acids during the 1-year period are presented in Table 2. The most common fatty acids (C16:0, C18:1, C10:0, C14:0, C18:0) in the three investigated cheeses account for 70% of total fatty acid content. These results are similar to the results reported for sheep milk, where these five fatty acids accounted for around 75% of the total fatty acid content (Goudjil et al. 2004).

Table 2.  FATTY ACIDS (g/100 g FATTY ACIDS) IN GREEK CHEESES DURING THE 1-YEAR PERIOD
 FetaGravieraManouri
A.SDA.SDA.SD
  1. CLA, conjugated linoleic acid; SFA, saturated fatty acids; MUFA, monounsaturated fatty acids; PUFA, polyunsaturated fatty acids.

C 4:05.130.894.830.445.070.75
C 6:04.130.583.910.503.980.48
C 7:00.070.050.040.030.040.02
C 8:03.600.623.420.413.700.50
C 9:00.080.050.060.020.060.03
C 10:010.632.179.581.1810.441.05
C 11:00.080.050.090.050.080.02
C 12:04.801.064.240.604.620.56
C 13:00.090.030.060.040.060.03
C 14:010.390.7710.480.869.890.66
C 14:10.360.100.350.100.400.11
C 15:00.770.270.710.150.830.26
C 16:022.321.6222.380.9622.671.60
C 16:1w9c0.690.100.700.110.610.13
C 16:1w7t0.320.090.300.110.340.07
C 16:1w7c0.410.100.380.100.420.09
C 18:09.021.389.521.4310.291.26
C 18:118.802.7520.841.6918.482.77
C 18:22.200.302.180.202.250.52
C 19:00.210.050.190.080.320.06
C 20:00.280.060.240.070.350.10
C 18:30.750.180.580.240.500.14
C 20:10.00.00.00.00.00.0
CLA0.720.150.750.160.540.12
ΣSFA71.803.0069.951.8972.503.19
ΣMUFA20.582.8222.571.7120.252.84
ΣPUFA3.770.483.610.423.390.67

According to the average values of the investigated cheeses during the 1-year period, graviera contain lower amounts of saturated fatty acids (SFA) (69.95 ± 1.89 g/100 g fatty acids) but higher amounts of monounsaturated fatty acids (MUFA) (22.57 ± 1.71 g/100 g fatty acids) and CLA (0.75 ±  0.16 g/100 g fatty acids) than the other two cheeses. On the other hand, manouri contains the highest amounts of SFA (72.50 ± 3.19 g/100 g fatty acids) and the lowest amounts of MUFA (20.25 ± 2.84 g/100 g fatty acids), polyunsaturated fatty acids (PUFA; 3.39 ± 0.67 g/100 g fatty acids) and CLA (0.54 ± 0.12 g/100 g fatty acids). Finally, feta contains the highest amount of PUFA (3.77 ± 0.48 g/100 g fatty acids) and average amounts of the other fatty acid categories (SFA: 71.80 ± 3.0, MUFA: 20.58 ± 2.82 and CLA: 0.72 ± 0.15 g/100 g fatty acids).

The CLA content was found analog to the aging time of the cheeses. In fact, graviera cheese, which has the longest aging time (at least 3 months), contains the highest content of CLA, followed by feta, which has intermediate aging time (at least 2 months). Finally, manouri contains the lowest content of CLA and is produced without aging. The same tendency, about the categories of fatty acids and the CLA content, was presented in a previous study for Greek cheeses (Zlatanos et al. 2002). Especially, the CLA content of hard cheeses (among others, graviera) was slightly higher than the CLA content of brine cheeses (mainly feta) and significantly higher than the CLA content of whey cheeses (among others, manouri).

Variation of the Fatty Acid Content

Tables 3, 4 and 5 present the fatty acid contents of the investigated cheeses for each month. Every fatty acid of each cheese type shows a statistically significant variation (P < 0.05) during the 1-year season. However, it can be concluded that feta shows a period (between November and February) in which the CLA content is higher than the average CLA content of the year. During this period, the variation in the CLA content did not show a significant variation (P > 0.05). Graviera shows also a period with higher amounts of CLA between December and March (P < 0.05) and a period with lower amounts of CLA (P < 0.05) between August and November. Finally, the 6 among 7 months in which the manouri cheese shows CLA values higher than the 1-year average are between March and September (P < 0.01). To understand these results, it is necessary to take into account the way of cheese making in Greece. As it is reported in the introduction, the availability of sheep milk differs from month to month. In general, the milk production during the last months of the year may be up to 100 times lower than the production in late spring, when the availability of milk is the maximum for the year. Therefore, the production of several cheeses is strongly dependent on the season. Usually, the available (at the time) milk, during the months with small milk production, is primarily used to produce cheeses with small aging time and/ or limited production, as milk industries avoid reserving such cheeses as stock products. On the contrary, the surplus of milk from the season with high milk production is used to produce cheeses with greater consumption and cheeses able to be reserved for several months in storage. This kind of cheese is mainly feta cheese, which makes up almost half of the total annual production of cheese in Greece. Also, important quantities of graviera are produced mainly during the months with high milk availability. The maximum reserve of feta and graviera as stock products are sufficient approximately for 5 months. On the other hand, manouri has no aging time and is produced each month of the year.

Table 3.  AVERAGE FATTY ACID COMPOSITION (g/100 g FATTY ACIDS) IN FETA CHEESE DURING THE 1-YEAR PERIOD
 JanuaryFebruaryMarchAprilMayJuneJulyAugustSeptemberOctoberNovemberDecember
C 4:05.26 ± 0.284.80 ± 0.364.80 ± 0.235.61 ± 0.354.50 ± 0.345.09 ± 0.286.25 ± 0.426.60 ± 0.336.29 ± 0.334.09 ± 0.284.10 ± 0.314.18 ± 0.26
C 6:03.17 ± 0.183.15 ± 0.244.17 ± 0.224.50 ± 0.264.31 ± 0.194.71 ± 0.274.69 ± 0.304.85 ± 0.224.53 ± 0.173.97 ± 0.283.97 ± 0.393.57 ± 0.32
C 7:00.000.030.070.050.070.070.060.060.060.000.190.00
C 8:02.57 ± 0.132.72 ± 0.23.84 ± 0.324.01 ± 0.264.22 ± 0.293.81 ± 0.343.96 ± 0.214.14 ± 0.264.46 ± 0.343.07 ± 0.203.30 ± 0.173.12 ± 0.24
C 9:00.000.040.110.090.010.110.080.090.080.000.210.05
C 10:07.66 ± 0.457.59 ± 0.3812.04 ± 0.5611.27 ± 0.4312.98 ± 0.5214.54 ± 0.6811.01 ± 0.7111.19 ± 0.4711.03 ± 0.6210.09 ± 0.7110.58 ± 0.597.56 ± 0.58
C 11:00.000.050.050.030.130.050.100.080.100.070.130.17
C 12:03.44 ± 0.212.96 ± 0.275.56 ± 0.365.93 ± 0.386.15 ± 0.276.1 ± 0.415.01 ± 0.305.06 ± 0.294.44 ± 0.354.51 ± 0.414.76 ± 0.383.64 ± 0.27
C 13:00.000.080.110.110.100.100.080.100.090.100.140.10
C 14:010.10 ± 0.428.82 ± 0.3510.94 ± 0.5110.83 ± 0.6110.97 ± 0.3410.59 ± 0.4710.72 ± 0.519.92 ± 0.359.94 ± 0.379.74 ± 0.4211.86 ± 0.5110.20 ± 0.63
C 14:10.61 ± 0.080.38 ± 0.020.32 ± 0.050.41 ± 0.040.36 ± 0.040.37 ± 0.020.33 ± 0.040.20 ± 0.050.38 ± 0.020.30 ± 0.010.23 ± 0.040.44 ± 0.05
C 15:00.000.84 ± 0.020.80 ± 0.080.91 ± 0.070.79 ± 0.080.78 ± 0.050.75 ± 0.070.75 ± 0.060.85 ± 0.110.68 ± 0.081.11 ± 0.071.01 ± 0.04
C 16:024.35 ± 0.7723.85 ± 0.8222.72 ± 1.0120.63 ± 0.8220.85 ± 0.6419.71 ± 0.8921.74 ± 1.2321.31 ± 0.7121.74 ± 0.8222.30 ± 0.8725.01 ± 0.9623.60 ± 0.81
C 16:10.87 ± 0.120.72 ± 0.040.64 ± 0.030.53 ± 0.080.71 ± 0.060.66 ± 0.040.68 ± 0.040.81 ± 0.050.64 ± 0.050.51 ± 0.060.71 ± 0.070.74 ± 0.04
C 18:011.47 ± 0.3710.66 ± 0.428.90 ± 0.258.44 ± 0.578.60 ± 0.366.78 ± 0.457.79 ± 0.417.22 ± 0.528.89 ± 0.399.75 ± 0.549.64 ± 0.6210.04 ± 0.39
C 18:122.16 ± 0.5824.75 ± 0.7116.83 ± 0.6416.85 ± 0.8215.67 ± 0.7716.35 ± 0.6716.54 ± 0.5818.08 ± 0.6317.93 ± 0.9220.41 ± 0.5519.36 ± 0.8120.69 ± 0.31
C 18:22.09 ± 0.052.25 ± 0.172.16 ± 0.183.00 ± 0.232.02 ± 0.142.14 ± 0.242.15 ± 0.182.09 ± 0.171.99 ± 0.222.35 ± 0.261.76 ± 0.142.36 ± 0.24
C 18:2 conj.0.87 ± 0.090.85 ± 0.050.56 ± 0.010.83 ± 0.040.55 ± 0.040.75 ± 0.080.58 ± 0.030.75 ± 0.090.54 ± 0.040.62 ± 0.020.88 ± 0.060.91 ± 0.04
C 18:30.92 ± 0.070.96 ± 0.060.60 ± 0.040.83 ± 0.060.54 ± 0.020.65 ± 0.040.56 ± 0.030.75 ± 0.070.63 ± 0.040.65 ± 0.030.89 ± 0.051.07 ± 0.06
Table 4.  AVERAGE FATTY ACID COMPOSITION (g/100 g FATTY ACIDS) IN GRAVIERA CHEESE DURING THE 1-YEAR PERIOD
 JanuaryFebruaryMarchAprilMayJuneJulyAugustSeptemberOctoberNovemberDecember
C 4:04.61 ± 0.384.21 ± 0.515.38 ± 0.335.32 ± 0.375.08 ± 0.284.59 ± 0.415.16 ± 0.294.54 ± 0.325.52 ± 0.264.36 ± 0.184.47 ± 0.284.66 ± 0.32
C 6:03.48 ± 0.333.45 ± 0.284.70 ± 0.284.35 ± 0.254.65 ± 0.363.38 ± 0.244.01 ± 0.223.93 ± 0.184.26 ± 0.243.84 ± 0.273.15 ± 0.243.77 ± 0.18
C 7:00.020.040.000.000.000.040.040.010.050.090.060.05
C 8:02.89 ± 0.363.23 ± 0.313.28 ± 0.273.58 ± 0.224.13 ± 0.362.98 ± 0.273.91 ± 0.213.42 ± 0.253.85 ± 0.173.43 ± 0.182.86 ± 0.323.50 ± 0.12
C 9:00.050.070.000.060.070.050.080.030.060.070.030.07
C 10:08.51 ± 0.7110.01 ± 0.529.57 ± 0.589.72 ± 0.5111.85 ± 0.577.70 ± 0.3210.81 ± 0.589.44 ± 0.417.95 ± 0.269.58 ± 0.319.32 ± 0.4210.53 ± 0.51
C 11:00.060.080.070.120.10.060.090.010.070.070.210.08
C 12:03.58 ± 0.214.11 ± 0.284.08 ± 0.334.42 ± 0.235.64 ± 0.223.56 ± 0.174.57 ± 0.363.62 ± 0.283.68 ± 0.384.43 ± 0.274.50 ± 0.364.65 ± 0.24
C 13:00.060.070.110.000.070.000.020.130.070.040.080.06
C 14:09.25 ± 0.429.94 ± 0.4610.47 ± 0.3710.07 ± 0.6210.75 ± 0.549.48 ± 0.8410.23 ± 0.7411.53 ± 0.669.81 ± 0.7412.15 ± 0.5810.94 ± 0.8711.18 ± 0.41
C 14:10.36 ± 0.010.35 ± 0.060.40 ± 0.070.26 ± 0.010.30 ± 0.030.37 ± 0.020.30 ± 0.050.59 ± 0.040.36 ± 0.020.23 ± 0.010.21 ± 0.010.42 ± 0.01
C 15:00.76 ± 0.040.72 ± 0.040.770.54 ± 0.040.77 ± 0.060.66 ± 0.020.59 ± 0.041.06 ± 0.030.68 ± 0.020.45 ± 0.010.69 ± 0.020.83 ± 0.02
C 16:023.08 ± 1.0422.53 ± 1.1723.03 ± 1.2021.31 ± 0.9321.62 ± 0.4922.56 ± 0.8621.77 ± 0.8820.65 ± 1.0121.94 ± 1.0723.92 ± 1.1722.56 ± 1.0423.57 ± 0.99
C 16:10.70 ± 0.130.70 ± 0.020.68 ± 0.040.68 ± 0.050.70 ± 0.030.41 ± 0.030.65 ± 0.020.77 ± 0.010.86 ± 0.020.76 ± 0.030.73 ± 0.040.70 ± 0.02
C 18:011.22 ± 0.4510.65 ± 0.339.67 ± 0.689.10 ± 0.467.25 ± 0.5510.47 ± 0.587.59 ± 0.3610.11 ± 0.3710.41 ± 0.419.82 ± 0.5510.81 ± 0.367.18 ± 0.71
C 18:122.62 ± 0.5220.51 ± 0.6018.95 ± 0.9821.53 ± 0.8718.01 ± 0.8423.44 ± 1.0520.76 ± 0.8722.24 ± 1.1222.57 ± 0.8718.92 ± 0.9720.48 ± 0.8120.07 ± 0.89
C 18:22.21 ± 0.242.15 ± 0.222.03 ± 0.222.11 ± 0.082.65 ± 0.142.17 ± 0.172.31 ± 0.192.28 ± 0.131.95 ± 0.141.96 ± 0.242.30 ± 0.122.02 ± 0.21
C 18:2 conj.0.97 ± 0.020.86 ± 0.100.84 ± 0.060.72 ± 0.010.6 ± 0.080.99 ± 0.070.78 ± 0.040.58 ± 0.070.60 ± 0.030.52 ± 0.050.66 ± 0.070.83 ± 0.06
C 18:30.85 ± 0.050.75 ± 0.060.79 ± 0.060.29 ± 0.030.64 ± 0.020.95 ± 0.030.44 ± 0.040.31 ± 0.040.37 ± 0.050.37 ± 0.040.37 ± 0.020.78 ± 0.04
Table 5.  AVERAGE FATTY ACID COMPOSITION (g/100 g FATTY ACIDS) IN MANOURI CHEESE DURING THE 1-YEAR PERIOD
 JanuaryFebruaryMarchAprilMayJuneJulyAugustSeptemberOctoberNovemberDecember
C 4:05.17 ± 0.485.32 ± 0.385.00 ± 0.515.40 ± 0.415.63 ± 0.534.20 ± 0.365.72 ± 0.443.61 ± 0.364.97 ± 0.284.12 ± 0.286.13 ± 0.425.58 ± 0.36
C 6:04.33 ± 0.343.61 ± 0.323.76 ± 0.333.84 ± 0.314.42 ± 0.323.76 ± 0.274.60 ± 0.332.95 ± 0.284.55 ± 0.333.68 ± 0.294.28 ± 0.313.93 ± 0.41
C 7:00.050.040.020.010.060.050.040.030.050.000.000.05
C 8:04.09 ± 0.393.46 ± 0.263.65 ± 0.273.71 ± 0.454.4 ± 0.283.69 ± 0.294.54 ± 0.342.88 ± 0.314.07 ± 0.413.02 ± 0.273.52 ± 0.303.42 ± 0.32
C 9:00.080.070.060.080.020.080.010.050.060.000.000.07
C 10:011.21 ± 0.4510.83 ± 0.5510.01 ± 0.4211.45 ± 0.6210.75 ± 0.4710.37 ± 0.6312.46 ± 0.748.80 ± 0.629.00 ± 0.5210.82 ± 0.459.51 ± 0.6610.02 ± 0.63
C 11:00.090.090.070.100.100.110.080.060.050.000.080.07
C 12:04.45 ± 0.325.27 ± 0.334.45 ± 0.345.04 ± 0.115.29 ± 0.324.85 ± 0.364.61 ± 0.363.81 ± 0.263.35 ± 0.234.83 ± 0.364.76 ± 0.184.74 ± 0.22
C 13:00.07 ± 0.010.090.060.040.070.080.020.040.080.000.000.08
C 14:08.94 ± 0.6110.45 ± 0.419.43 ± 0.3610.05 ± 0.719.39 ± 0.4210.02 ± 0.8810.00 ± 0.489.95 ± 0.518.75 ± 0.5510.11 ± 0.6110.88 ± 0.7110.72 ± 0.36
C 14:10.40 ± 0.020.41 ± 0.010.31 ± 0.050.34 ± 0.010.28 ± 0.40.36 ± 0.040.36 ± 0.020.46 ± 0.030.63 ± 0.040.59 ± 0.030.31 ± 0.020.32 ± 0.03
C 15:00.77 ± 0.050.86 ± 0.060.61 ± 0.300.61 ± 0.030.68 ± 0.050.73 ± 0.070.81 ± 0.060.95 ± 0.121.57 ± 0.200.96 ± 0.600.70 ± 0.020.71 ± 0.04
C 16:020.01 ± 0.5124.01 ± 0.0321.97 ± 1.0120.33 ± 0.9622.84 ± 0.5822.30 ± 0.8122.69 ± 0.8423.4 ± 0.8521.30 ± 1.2125.37 ± 1.1224.29 ± 1.0423.54 ± 0.72
C 16:10.67 ± 0.020.31 ± 0.010.49 ± 0.010.77 ± 0.020.74 ± 0.040.48 ± 0.060.62 ± 0.020.69 ± 0.060.72 ± 0.040.63 ± 0.030.54 ± 0.040.68 ± 0.02
C 18:010.08 ± 0.558.80 ± 0.3611.43 ± 0.228.25 ± 0.559.23 ± 0.4110.60 ± 0.6412.67 ± 0.8311.4 ± 0.579.31 ± 0.3611.03 ± 0.5210.13 ± 0.3710.58 ± 0.56
C 18:120.26 ± 0.7217.23 ± 1.0219.10 ± 0.7721.97 ± 1.0517.98 ± 0.6619.52 ± 0.7521.10 ± 0.2121.08 ± 0.6320.28 ± 1.0517.84 ± 0.7717.63 ± 0.6917.80 ± 0.72
C 18:21.92 ± 0.112.30 ± 0.112.96 ± 0.312.66 ± 0.142.47 ± 0.222.24 ± 0.112.64 ± 0.171.94 ± 0.113.02 ± 0.241.36 ± 0.111.63 ± 0.041.85 ± 0.11
C 18:2 conj.0.79 ± 0.050.41 ± 0.020.60 ± 0.030.66 ± 0.030.46 ± 0.080.55 ± 0.040.61 ± 0.030.55 ± 0.080.61 ± 0.010.39 ± 0.020.42 ± 0.060.44 ± 0.03
C 18:30.66 ± 0.040.39 ± 0.030.39 ± 0.020.64 ± 0.020.4 ± 0.050.48 ± 0.030.57 ± 0.040.69 ± 0.030.66 ± 0.070.25 ± 0.010.36 ± 0.040.47 ± 0.03

The time period with the highest CLA content of manouri is between March and September, a season in which animals take their food mainly from grazing. On the contrary, for the other months (between middle autumn and winter), the grazing of animals is limited and a surplus of conventional foods is added to the animal diets. As it is reported, grazing is a factor that can lead to increased values in the CLA content. In addition, at the beginning of the grazing period, the CLA content of milk and butter is smaller than at the end of the grazing period (Lock and Garnsworthy 2003; Ledoux et al. 2005).

The feta samples that were bought during November and February were produced during June and September. Graviera that were bought between December and March were also produced between June and September. From the seasonal variation in the CLA content of both graviera and feta, we can finally conclude that cheeses that are produced at the end of the grazing period are excellent sources of CLA.

The results show that Greek cheeses are good sources of CLA during the whole year. However, the CLA content is affected by seasonal factors. Especially, cheeses that were produced during the grazing period of animals show increased CLA amounts. On the other hand, only the seasonal factors cannot explain the variation of the CLA content in some months. The influence of other factors, like storage, can be proposed for future investigation.

Manouri shows the smallest SFA contents during August and September, feta cheese during the months October, December, January and February and finally graviera during the three summer months and January. In months in which the SFA is less, the MUFA content is increased. For most of the cases in months with the lowest SFA content, an increased content of CLA was found. This indicates that some of the factors that lead to an increased CLA content also lead to a low SFA content. This is only a first indication; however, if this supposition could be established in the future, it would be of great importance, as the increased SFA consumption is correlated with an increased health risk.

ACKNOWLEDGMENTS

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS AND DISCUSSION
  6. ACKNOWLEDGMENTS
  7. REFERENCES

Significant information about milk availability during the year and the milk and stock management of Greek cheese manufactories was given by Dr. A. Karakatsanis, former technical manager of the milk industry Evrofarma.

REFERENCES

  1. Top of page
  2. Abstract
  3. INTRODUCTION
  4. MATERIALS AND METHODS
  5. RESULTS AND DISCUSSION
  6. ACKNOWLEDGMENTS
  7. REFERENCES
  • BELURY, M.A. 1995. Conjugated dienoic linoleate: A polyunsaturated fatty acid with unique chemoprotective properties. Nutr. Rev. 53, 8389.
  • BRITISH STANDARDS. 1980. 684, sec. 2.34. Methods of analysis of fats and fatty oils. Other methods. Preparation of methyl esters of fatty acids.
  • CHIN, S.F., LIU, W., STORKSON, J.M., HA, Y.L. and PARIZA, M.W. 1992. Dietary sources of conjugated dienoic isomers of linoleic acid, a newly recognized class of anticarcinogens. J. Food Comp. Anal. 5, 185197.
  • DHIMAN, T.R., ANAND, G.R., SATTER, L.D. and PARIZA, M.W. 1999. Conjugated linoleic acid content of milk from cows fed different diets. J. Dairy Sci. 82, 21462156.
  • DIN (GERMAN INSTITUTE FOR STANDARIZATION). 1981. Determination of fat content of cheese and processed cheese products (reference method). Norm DIN 10 313.
  • ESYE (NATIONAL STATISTIC OFFICE OF GREECE). 1996. Statistiki Erevna Biomihanias Etous 1992 [Statistical Research of Manufacture for the Year 1992], ESYE, Athens, Greece.
  • GARCIA-LOPEZ, S., ECHEVERRIA, E., TSUI, I. and BALCH, B. 1994. Changes in the content of conjugated linoleic acid (CLA) in processed cheese during processing. Food Res. Int. 27, 6164.
  • GOUDJIL, H., FONTECHA, J., LUNA, P., DE LA FUENTE, M.A., ALONSO, L. and JUAREZ, M. 2004. Quantitative characterization of unsaturated and trans fatty acids in ewe's milk fat. Lait 84, 473482.
  • HOUSEKNECHT, K.L., VAN DEN HEUVEL, J.P., MOYA-CAMARENA, S.Y., PORTOCARRERO, C.P., PECK, L.W., NICKEL, K.P. and BELURY, M.A. 1998. Dietary conjugated linoleic acid normalizes impaired glucose tolerance in the Zucker diabetic fatty fa/fa rat. Biochem Biophys. Res. Commun. 244, 678682.
  • IP, C. 1997. Review of the effects of trans fatty acids, oleic acid, n-3 polyunsaturated fatty acids, and conjugated linoleic acid on mammary carcinogenesis in animals. Am. J. Clin. Nutr. 66, 1523S1529S.
  • IP, C., CHIN, S.F., SCIMECA, J.A. and PARIZA, M.W. 1991. Mammary cancer prevention by conjugated dienoic derivative of linoleic acid. Cancer Res. 51, 61186124.
  • JAHREIS, G., FRITSCHE, J., MOCKEL, P., SCHONE, F., MOLLER, U. and STEINHART, H. 1999. The pontential anticarcinogenic conjugated linoleic acid, cis-9, trans-11 C18:2, in milk of different species: Cow, goat, ewe, sow, mare, woman. Nutr. Res. 19, 15411549.
  • KRITCHEVSKY, D., TEPPER, S.A., WRIGHT, S., TSO, P. and CZARNECKI, S.K. 2000. Influence of conjugated linoleic acid (CLA) on establishment and progression of atherosclerosis in rabbits. J. Am. Coll. Nutr. 19, 472S477S.
  • LEDOUX, M., CHARDIGNY, J.M., DARBOIS, M., SOUSTRE, Y., SEBEDIO, J.L. and LALOUX, L. 2005. Fatty acid composition of French butters, with special emphasis on conjugated linoleic acid (CLA) isomers. J. Food Comp. Anal. 18, 409425.
  • LEE, K.N., KRITSCHEVSKY, D. and PARIZA, M.W. 1994. Conjugated linoleic acid and atherosclerosis in rabbits. Atherosclerosis 108, 1925.
  • LIN, H., BOYLSTON, T.D., LUEDECKE, L.O. and SHULTZ, T.D. 1998. Factors affecting the conjugated linoleic acid content of cheddar cheese. J. Agric. Food Chem. 46, 801807.
  • LOCK, A.L. and GARNSWORTHY, P.C. 2003. Seasonal variation in milk conjugated linoleic acid and Δ9-desaturase activity in dairy cows. Livestock Prod. Sci. 79, 4759.
  • MARANESI, M., BOCHICCHIO, D., MONTELLATO, L., ZAGHINI, A., PAGLIUCA, G. and BADIANI, A. 2005. Effect of microwave cooking or broiling on selected nutrient contents, fatty acid patterns and true retention values in separable lean from lamb rib-loins, with emphasis on conjugated linoleic acid. Food Chem. 90, 207218.
  • MIR, Z., GOONEWARDENE, L.A., OKINE, E., JAEGAR, S. and SCHEER, H.D. 1999. Effect of feeding canola oil on constituents, conjugated linoleic acid (CLA) and long chain fatty acids in goats milk. Small Rumin. Res. 33, 137143.
  • MOLKETIN, J. 1999. Bioactive lipids naturally occurring in bovine milk. Nahrung 43, 185189.
  • NICOLOSI, R.J., ROGERS, E.J., KRITCHEVSKY, D., SCIMECA, J.A. and HUTH, P.J. 1997. Dietary conjugated linoleic acid reduces plasma lipoproteins and early aortic atherosclerosis in hypercholesterolemic hamsters. Artery 22, 266277.
  • PARIZA, M.W., HARGRAVES, W.A., BENJAMIN, H., CHRISTOU, M., JEFCOATE, C.R., STORKSON, J., ALBRIGHT, K., KRAUS, D., SHARP, P., BOISSONNEAULT, G.A. et al. 1986. Modulation of carcinogenesis by dietary factors. Environ. Health Perspect. 67, 2529.
  • PARK, Y., ALBRIGHT, K.J., LIU, W., STORKSON, J.M., COOK, M.E. and PARIZA, M.W. 1997. Effect of conjugated linoleic acid on body composition in mice. Lipids 32, 853858.
  • SIEBER, R., COLLOMB, M., AESCHLIMANN, A., JELEN, P. and EYER, H. 2004. Impact of microbial cultures on conjugated linoleic acid in dairy products – a review. Int. Dairy J. 14, 115.
  • STANTON, C., LAWLESS, F., KJELLMER, G., HARRINGTON, D., DEVERY, R., CONNOLLY, J.F. and MURPHY, J. 1997. Dietary influences on bovine milk cis-9, trans-11 conjugated linoleic acid content. J. Food Sci. 62, 10831086.
  • WEST, D.B., DELANY, J.P., CAMET, P.M., BLOHM, F., TRUETT, A.A. and SCIMECA, J. 1998. Effects of conjugated linoleic acid on body fat and energy metabolism in the mouse. Am. J. Physiol. 275, 667672.
  • ZLATANOS, S., LASKARIDIS, K., FEIST, C. and SAGREDOS, A. 2002. CLA composition of Greek feta and hard cheeses. Food Chem. 78, 471477.