determination of nutritional and physical properties of myrtle (myrtus communis l.) fruits growing...

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Journal of Food Engineering 79 (2007) 453–458

Determination of nutritional and physical properties of myrtle(Myrtus communis L.) fruits growing wild in Turkey

Cevat Aydın a,*, M. Musa Ozcan b

a Department of Agricultural Machinery, Faculty of Agriculture, Selcuk University, 42031 Konya, Turkeyb Department of Food Engineering, Faculty of Agriculture, Selcuk University, 42031 Konya, Turkey

Received 11 April 2005; accepted 2 February 2006Available online 11 April 2006

Abstract

In this study, some nutritional and physical properties of myrtle fruits (Myrtus communis L.) growing wild in Mersin region weredetermined. Nutritional properties such as protein, oil, fibre, reducing sugar, tannin, ash and water-soluble extract and physical prop-erties such as dimensions, weight, thickness, geometric mean diameter, sphericity, bulk density, porosity, projected area, 100 fruit weight,terminal velocity and the rupture strength of myrtle fruits used in the experiment were established. The crude oil, crude protein, crudefibre, crude energy, reducing sugar, tannin, ash, water-soluble extract and essential oil values of fruit were determined as 2.37%, 4.17%,17.41%, 11.21 kcal/g, 8.64%, 76.11 mg/100 g, 0.725%, 52.94% and 0.01%, respectively. Some physical properties of myrtle fruits wereevaluated as functions of moisture content. The average length, width, thickness, the geometric mean diameter of myrtle fruits were13.75 mm, 8.11 mm, 7.57 mm, 10.53 mm at a moisture content of 8.32% d.b., respectively.� 2006 Elsevier Ltd. All rights reserved.

Keywords: Myrtle; Myrtaceae; Physical and chemical properties; Essential oil

1. Introduction

Myrtle (Myrtus communis L.) is a typical representativeof the Mediterranean flora. Myrtle, belonging to the Myrt-aceae family, is a pleasant annual shrub which grows in sev-eral regions all over the world (Akgul, 1993; Davis, 1982;Ozek, Demirci, & Bas�er, 2000). In Turkey, myrtle tree isfound growing in pine forests and riversides, particularlyin the Taurus mountains, from just above sea level to500–600 m. Myrtle is called as ‘‘hambeles’’, ‘‘mersin’’ or‘‘murt’’ in Turkish. Its leaves are commonly known dueto its presence of essential oils and their composition deter-mine the specific aroma of plants and the flavour of the con-diment. Several uses of this plant oil are known for culinary

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doi:10.1016/j.jfoodeng.2006.02.008

* Corresponding author.E-mail address: [email protected] (C. Aydın).

purposes. Its fresh and/or dried leaves oils are used in cos-metics sauces, confectionery and beverage industry (Akgul,1993; Akgul & Bayrak, 1989; Boelens & Jimenez, 1992;Karamanoglu, 1972; Ogur, 1994; Ozek et al., 2000).

At the folk medicine, leaf and fruits decoction or infu-sion of this plant are used as stomachic, hypoglycemic,cough and oral diseases, antimicrobic, for constipation,appetizing, antihemorrhagic and externally for woundhealing (Baytop, 1984; Duke, 1988; Ogur, 1994; Ozeket al., 2000; Twaij, Elisha, & Khalid, 1989). The oilsextracted by steam distillation of fruits are used both in fla-vour and fragrance industries (Dogan, 1978; Lawrence,1989). Fruits rich in tannin. The fruits are very astringentand are used as a condiment as a substitute for pepperand considered a rich source of tanin (Canhoto, Lopes, &Cruz, 1998).

The aim of this study was to report chemical composi-tion and physical properties of maturated myrtle fruitsgrown wild in Turkey.

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Nomenclature

Dp geometric mean diameter (mm)Fr rupture force (N)L length, mmMc moisture content (% d.b.)Pa projected area (mm2)R2 determination coefficientT thickness (mm)

Vt terminal velocityW width (mm)Wf 100 fruit weight (g)e porosity (%)qb bulk density (kg/m3)qk kernel density (kg/m3)U sphericty (%)

454 C. Aydın, M. M. Ozcan / Journal of Food Engineering 79 (2007) 453–458

2. Material and methods

2.1. Material

Myrtle tree (Myrtus communis L.) fruits were collectedfrom plants growing wild in Mersin province (Buyukeceli–Gulnar) of Turkey in October 2004. The fruits were cleanedby a all foreign matter and crushed and immature fruits.The initial moisture content of fruits was determined byusing a standard method (USDA, 1970) and was foundto be 74.44% d.b.

The samples were transported in polypropylene bags,and were dried to constant weight in room temperaturefor analyses. Moisture content was immediately measuredon arrival.

2.2. Chemical analyses

Chemical composition (moisture, crude fibre, crude oil,crude protein, energy, ash, non-soluble HCl acid ash,reducing sugar, pH, acidity and water-soluble extract) wereanalysed according to AOAC (1984), tannin content wasdetermined according to Horwitz (1975).

2.3. Isolation of essential oil

Fresh fruits (about 200 g) were cut into small pieces andsubjected to hydrodistillation for 3 h using a Clevenger-type apparatus and the oils obtained were dried over anhy-drous sodium sulfate.

2.4. Methods of physical properties

The fruit samples of the desired moisture levels were pre-pared by adding calculating amounts of distilled water,through mixing and then sealing in separate polyethylenebags. The samples were kept at 278 K in a refrigeratorfor 7 d for the moisture to distribute uniformly throughoutthe sample. Before starting a test, the required quantity ofthe fruit was allowed to warm up to room temperature(Carman, 1996; Deshpande, Bal, & Ojha, 1993).

All the physical properties of the fruits were assessed atmoisture levels of 8.32%, 21.24% and 74.44% d.b. withthree replications at each level. To determine the average

size of the fruit a sample of 100 fruits was randomlyselected. Measurements of the three major perpendiculardimensions at the fruit were carried out with a micrometerto an accuracy of 0.01 mm.

The geometric mean diameter (Dp) of the fruit was cal-culated by using the following relationship (Mohsenin,1970):

Dp ¼ LWTð Þ1=3; ð1Þ

where L is the length, W, the width and T, the thickness.According to Mohsenin (1970), the degree of sphericity

(U) can be expressed as follows:

U ¼ ðLWT Þ1=3

L100. ð2Þ

This equation was used to calculate the sphericity ofmyrtle fruit in the present investigation. To obtain theweight, each fruit was weighed by a chemical balance read-ing to 0.001 g.

The kernel density of a fruit is defined as the ratio of themass of a sample of a fruit to the solid volume occupied bythe sample (Deshpande et al., 1993). The fruit volume andits fruit density were determined using the liquid displace-ment method. Toluene (C7H8) was used rather than waterbecause it is absorbed by fruits to a lesser extent. Also, itssurface tension is low, so that it fills even shallow dips in afruit and its dissolution power is low (Ogut, 1998; Sitkei,1986). The bulk density is the ratio of the mass of a sampleof a fruit to its total volume. It is a moisture dependentproperty. The bulk density was determined with a weightper hectolitre tester which was calibrated in kg per hectoli-tre (Deshpande et al., 1993). The fruits were poured in thecalibrated bucket up to the top from a height of about15 cm and excess fruits were removed by strike off stick.The fruits were not compacted in any way.

The porosity (e) of bulk fruit was computed from thevalues of fruit density and bulk density using the relation-ship given by Mohsenin (1970) as follows:

e ¼ qk � qb

qk

100 ð3Þ

where qb is the bulk density and qk the kernel density.

C. Aydın, M.M. Ozcan / Journal of Food Engineering 79 (2007) 453–458 455

The projected area of a fruit was measured by placing itunder a thin transparent paper and using a planimeterequipped with a magnifying glass (Makanjuola, 1972).

The terminal velocities of fruits and fractions at differentmoisture content were measured using an air column. Foreach test, a small sample was dropped into the air streamfrom the top of the air column, up which air was blownto suspend the material in the air stream. The air velocitynear the location of the fruit suspension was measured byan electronic anemometer having an accuracy of 0.1 m/s(Joshi, Das, & Mukherjee, 1993). Three replications weremade for each fruit sample.

To determine the rupture strength of fruits, biologicalmaterial test device was used. The device developed byAydın and Ogut (1992) has three main components whichare stable up and motion bottom of platform, a drivingunit and the data acquisition system. The fruit was placedon the stable up platform and pressed with motion probe(diameter 2.2 mm). The rupture force of seed was measuredby the data acquisition system.

Table 2Means and standard errors of the myrtle fruits dimensions at moisturecontent at 8.32% d.b.

Properties Values

Length (mm) 13.75 ± 1.90Thickness (mm) 7.57 ± 1.14Width (mm) 87.11 ± 0.74Geometric mean diameter (mm) 10.53 ± 0.71Sphericity (%) 58.32 ± 4.00

3. Results and discussion

3.1. Chemical properties

The chemical properties of myrtle fruits are given inTable 1. The moisture, crude oil, crude protein, crude fibre,crude energy, reducing sugar, pH, acidity, ash, non-solubleHCl acid ash, water soluble extract and essential oil yieldwere determined in fruits. Moisture, crude protein, reduc-ing sugar, pH, acidity and water-soluble extract containsof fruits were found to be higher compared with those ofsimilar fruits (Cemeroglu & Acar, 1986). For myrtle fruitessential oil content was low compared with Spanish myrtlefruit oil reported by Boelens and Jimenez (1992). Also,reducing sugar, pH and water-soluble extract values ofsample were higher compared with that of raw caperberies(Ozcan, 1999). It is thought to be helping the fruit process-ing technology to be known the chemical composition ofmyrtle fruits.

Table 1Chemical composition of myrtle fruits

Properties Values

Moisture, d.b. (%) 74.44Crude oil (%) 2.37Crude protein (%) 4.17Crude fiber (%) 17.41Crude energy (kcal/g) 11.21Reducing sugar (%) 8.64Tannin (mg/100 g) 76.11pH 6.56Acidity (%, malic) 0.14Ash (%) 0.725Non-soluble HCl acid ash (%) 0.0041Water-soluble extract (%) 52.94Essential oil (%) 0.01

3.2. Dimensions of fruit

Table 2 shows the means and standard errors of themyrtle fruits. The average values of geometric mean diam-eter and sphericity were calculated 10.53 mm and 58.32%,respectively. The relationship between dimensions andmoisture content Mc in d.b. can be represented by the fol-lowing equations:

L ¼ 0:0475Mcþ 14:954 ð4ÞW ¼ 0:1149Mcþ 7:411 ð5ÞT ¼ 0:1016Mc þ 6:2157 ð6Þ

3.3. Bulk density

The bulk density of fruits at different moisture levelsvaried from 619 to 573 kg/m3 and indicated a decrease inbulk density with an increase in moisture content(Fig. 1). The negative linear relationship of bulk densitywith moisture content was also observed by Shepherdand Bhardwaj (1986) and Visvanathan et al. (1996) forpigeon pea and neem nut, respectively. The statistical anal-ysis of experimental data showed that relationship betweenbulk density and moisture content was significant(p < 0.05).

3.4. Kernel density

The kernel density at different moisture levels variedfrom 953 to 1083 kg/m3 (Fig. 2). The effect of moisture

ρb = -0.641Mc + 619.55

R2 = 0.9444

560

570

580

590

600

610

620

630

0 20 40 60 80

Moisture content, % d.b.

Bul

k de

nsity

, kg

/ m3

Fig. 1. Variation of bulk density of myrtle fruits with moisture content.

Pa = 1.7587Mc + 83.297

R2 = 0.9722

1

51

101

151

201

251

0 20 40 60 80


Pro

ject

ed a

rea,

mm

2

Fig. 4. Variation of projected area of myrtle fruits with moisture content.

ρk = 2.0066Mc + 932.77

R2 = 0.9967

920

940

960

980

1000

1020

1040

1060

1080

1100

1120

0 20 40 60 80


Ker

nel d

ensi

ty, k

g / m

3

Fig. 2. Variation of kernel density of myrtle fruits with moisture content.


content on kernel density of myrtle showed an increasewith moisture content. Gupta and Das (1997) alsoobserved the linear increase in kernel density with increasein seed moisture in the range 4–20% d.b. for sunflowerseed.

3.5. Porosity

Since the porosity depends on the bulk as well as true orkernel densities, the magnitude of variation in porositydepends on these factors only. The porosity of myrtle fruitwas found to slightly increase with increase in moisturecontent from 8.32% to 74.44% d.b. (Fig. 3). The form ofthe plot is similar to that for pigeon pea as found by Shep-herd and Bhardwaj (1986). Carman (1996) reported a sim-ilar increase in porosity from 27.4% to 32.0% for lentil.

3.6. Projected area

The projected area of myrtle increased by about 138%,when the moisture content of seed increased from 8.32%to 74.44% d.b. (Fig. 4). Similar trends were reported formany other seeds (Mohsenin, 1970; Sitkei, 1986). Desh-pande et al. (1993) found that the surface area of soybeangrain increased from 0.813 to 0.952 cm2, when the moisture

ε = 0.1768Mc + 33.937

R2 = 0.9944

0

10

20

30

40

50

60

0 20 40 60 80


Por

osity

, %

Fig. 3. Variation of porosity of myrtle fruits with moisture content.

content was increased from 8.7% to 25% d.b. The relation-ship between projected area and moisture content wasfound significantly.

3.7. Hundred fruit weight

The 100 fruit weight of myrtle fruit was found to slightlyincrease with increase in moisture content from 8.32% to74.44% d.b. (Fig. 5). The form of the plot is similar to thatfor vetch seed found by Yalcın and Ozarslan (2004).

3.8. Terminal velocity

The experimental results for the terminal velocity ofthe myrtle at various moisture levels are plotted in Fig. 6.As moisture content increased, the terminal velocity wasfound to increase linearly. The results are similar tothose reported by Kural and Carman (1997). Yalcın andOzarslan (2004) found that the terminal velocity of vetchseed increased from 9.94 to 10.33 m/s when the moisturecontent was increased from 10.57% to 20.63% d.b. Theincrease in terminal velocity with increase in moisture con-tent can be attributed to the increase in mass of an individ-ual fruit per unit frontal area presented to the air stream.

Wh = 1.3907Mc + 30.457

R2 = 0.9912

0

20

40

60

80

100

120

140

160

0 20 40 60 80Moisture content, % d.b.

Hun

dred

frui

t wei

ght,

g

Fig. 5. Variation of 100 fruit weight of myrtle fruits with moisturecontent.

Vt = 0.0159Mc + 6.8172

R2 = 0.9601

6

6.5

7

7.5

8

8.5

0 20 40 60 80


Ter

min

al v

eloc

ity, m

/s

Fig. 6. Variation of terminal velocity of myrtle fruits with moisturecontent.

C. Aydın, M.M. Ozcan / Journal of Food Engineering 79 (2007) 453–458 457

3.9. Sphericity

The sphericity of myrtle fruit was found to slightlyincrease with increase in moisture content from 8.32% to74.44% d.b. (Fig. 7). The form of the plot is similar to thatfor vetch seed found by Yalcın and Ozarslan (2004).

3.10. Rupture force

The results of the rupture force tests are presentedFig. 8. The results show that the rupture force is highly

φ = 0.4477Mc + 53.48

R2 = 0.9967

40

50

60

70

80

90

100

0 20 40 60 80


Sph

eric

ity, %

Fig. 7. Variation of sphericity of myrtle fruits with moisture content.

Fr = -0.4625Mc + 33.365

R2 = 0.7371

0

5

10

15

20

25

30

35

40

45

0 20 40 60 80


Rup

ture

forc

e, N

Fig. 8. Variation of rupture force of myrtle fruits with moisture content.

dependent on moisture content for the range moisture con-tent investigated (8.32–74.44% d.b.). For curve, greaterforces were necessary to rupture the fruits at less moisturecontent. The highest force was obtained from less moisturecontent. The small rupturing forces at higher moisture con-tent might have resulted from the fact that the fruit tendedto be very brittle at high moisture content. The relationshipbetween the rupture strengths and moisture content of themyrtle fruits presented at Fig. 8.

4. Conclusions

(1) The hundred fruit weight increased from 38.0 to132.66 g with the increase in moisture content.

(2) The terminal velocity increased from 6.85 to 7.98 m/swith the increase in moisture content from 8.32% to74.44%.

(3) The rupture force decreased from 38.5 to 0.98 Nwith the increase in moisture content from 8.32% to74.44%.

Acknowledgements

Authors thank to Mr. H. _Ibrahim Ates� and Mrs. N.Ozcan for their material collection. Also, this work wassupported by Selcuk University Scientific Research Project(S. U-BAP-Konya, Turkey).

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