Journal of Food Processing & Technology

D_g : geometric mean diameter (mm); T_a: beginning value of the torque (N cm); L: length of caper seed (mm); T_m: average value of the torque (N cm); M: mass of caper seed (g); V: volume of seed (mm³); m1000: thousand of caper seed (g); V_t: terminal velocity (m/s); A: projected area (cm²); W: width of seed (mm); ρb: bulk density (kg/ m³); W_s: sample weight (10N); ρk: seed density (kg/m³); Ø: sphericity of seed; p₁: initial pressure (kg/cm²); ε porosity of seed (%); p₂: final pressure (kg/cm²); μ_s: static coefficient of friction; μ_d: dynamic coefficient of friction; T: thickness of caper seed (mm); q: torque arm (cm) (10.5 cm)

Caper is a plant with medicinal and aromatic properties. It is a long-lasting shruby plant that belongs to the Capparaceae family; capers occurs in various types (more than 350) and grows naturally in all the continents in many different regions of the world [1-3]. It is a tropical/subtropical plant [1,4]. The caper plant, which is called bubu, gebre, gabar, gevil, kapari, keper, kebere, tursuotu and Sebellah in differetnt parts of Turkey, is an economically valuable plant. In various regions of the world different organs of caper species have been profitable for several purposes since ancient times. Young shoots, flower buds, and fruit are used for human nutrition. Capers have very important roles in the food industry; the flower buds are stored in brine and have become a costly product during recent years [2,5-9]. Capers have been an important economic plant in Spain and Italy for the last 3 decades [1,2,6].The species has been cultivated from varieties growing wild in large parts of Turkey [2], and product technology has been developed [10,11]. There is limited information on physical and chemical properties of seeds of Caper plants used as food and as a condiment [3,4,7,12]. Also, no study on technological properties of seeds of C.spinosa plants were carried out hitherto.But limited study was made on C.ovata seeds [9]. The aim of this work is to establish the proximate composition, and some technological properties such as projected area, bulk density, seed density, 1000 seed mass, static and dynamic coefficient of friction, etc.

Material

Ripened caperberries (fruit) of wild growing plants of C.ovata and C.spinosa were collected from Konya (Selçuklu) and Mersin (Silifke), respectively. The seeds were obtained from ripened fruit. The seed samples were put into paper bags for transport to the laboratory. The seeds were dried under the air condition, and cleaned in an air screen cleaner to remove all foreign matter such as dust, dirt and chaff as well as immature and damaged seeds. The initial moisture content of seeds was determined by using a Standard method [13]. The remaining material was packed in a 2000 ml hermetic glass vessel and kept in cold storage until use.

Chemical properties

Chemical properties of both caper plant seeds picked in August were analysed according to AOAC [14]. The dried seeds were finely powdered. The oil was extracted with petroleum ether (50°C) in a soxhlet apparatus. The extract was evaporated in vacuum. The lipid extract was collected in a flask. The extracted lipid was weighed to determine the oil content and stored under nitrogen at 4°C for further analyses.

Determiation of mineral contents

About 0,5g of dried and ground caperberry seeds were put into burnig cup with 15 ml of pure NHO₃. The sample was incinerated in a MARS 5 microwave oven at 200°C. Distilled deionized water and ultrahigh-purity commercial acids were used to prepare all reagents, standards, and walnut samples. After digestion treatment, samples were filtrated through whatman No 42. The filtrates were collected in 50 ml Erlenmayer flasks [15] and analysed by ICP-AES. The mineral contents of the samples were quantified against standard solutions of known concentrations which were analyzed concurrently [16].

Working conditions of ICP-AES

Instrument : ICP-AES (Varian-Vista

RF Power : 0, 7-1, 5 kw (1, 2-1, 3 kw for Axial)

Plasma gas flow rate (Ar) : 10, 5-15 L/min. (radial) 15 “(axial)

Auzilary gas flow rate (Ar) :1, 5 “

Viewing height : 5-12 mm

Copy and reading time : 1-5 s (max.60 s)

Copy time : 3 s (max. 100 s)

Determination of fatty acids

Fatty acid composition for caperberry seeds samples was determined using a modified fatty acid methyl ester method as described by Akgül and Özcan [7]. The oil was extracted three times from 2 g air-dried seed sample by homogenization with petroleum ether. The oil sample (about 0.15-0.20 g) was converted to its fatty acid methyl esters (FAME). The methyl esters of the fatty acids (0.5 μl) were analysed in a gas chromatograph (Shimadzu GC-2010, Japan) equipped with a flame ionising detector (FID), a fused silica capillary column (MN FFAP (60 m x 0.25 mm i.d.; film thickness 0.20 μm). It was operated under the following conditions: oven temperature program, 90°C for 7 min. Raised to 240°C at a rate of 6°C/min and then kept at 240°C for 15 min); injector and detector temperatures, 260 and 260°C; respectively, carrier gas, nitrogen, at flow rate of 14 psi; split ratio 1/50 ml/min. A Standard fatty acid methyl ester mixture (Sigma Chemical Co.) was used to identify sample peaks. Commercial mixtures of fatty acid methyl esters were used as reference data for the relative retention times [14]. Quantitative analyses of the fatty acids were performed using the heptadecanoic acid methyl ester as internal standard. The results are mean values of three replicates

Determination of physical properties

All physical properties of C.spinosa 5.18 % m.c.d.b and C. ovata 4.93 % were determined at natural moisture content at 20 repetitions, respectively. To determine the size of the seeds, ten groups of samples consisting of 1000 seeds have been selected randomly. 100 grains have been taken from each group and their linear dimensions – length (L), width (W) and thickness (T) - and projected areas have been measured. Linear dimensions were measured by a micrometer to an accuracy of 0.01mm.

Projected area (A) of seeds was determined by using a digital camera (Kodak DC 240) and Sigma Scan Pro 5 program [17,18].

The mass (M) of seeds and a thousand seeds mass (m₁₀₀₀) were measured by an electronic balance to an accuracy of 0.0001g. To evaluate 1000 seed mass, 100 randomly selected seeds from the bulk were averaged.

The bulk density (P_b) was determined with a hectoliter tester which was calibrated in kg per hectoliter [19-21]. The seeds were dropped down into a bucket from a height of approximately 15 cm. The excess seeds were removed by sweeping the surface of the bucket. The seeds were not compressed in any way.

The caperberry seed volume (V) and its seed density (Pk) were determined by using the liquid displacement method. Toluene (C7H8) was used instead of water because it is absorbed by seeds to a lesser extent. Also, its surface tension is low, so that it fills even shallow dips in a seed and it’s dissolution power is low [22-24].

The rupture strength of seeds, were determined with Test Instrument of Biological Materials (Figure 1) using the procedure described by Aydin and Ögüt [25].

Figure 1: Biological material test unit (B.M.T.U.).

The terminal velocities (Vt) of caper seeds were measured using an air column (Figure 2).

Figure 2: Unit for measuring terminal velocity.

For each test, a sample was dropped into the air stream from the top of the air column, up which air was blown to suspend the material in the air stream. The air velocity near the location of the seed suspension was measured by electronic anemometer having a least count of 0.1 m/s [26].

The porosity of the bulk (ε) were measured using a porosity device [27,28]. Which consists of two identical tanks, one containing air under pressure (p₁) and the other one containing the samples of seed. When the valve between the two tanks opened, the air pressure in the two tanks equalized to a value p₂. Porosity was calculated from the following equation;

ε = (p₁-p₂)/p₁.100

The rupture strength values of caper seeds were measured by forces applied through three axis (length, width and thickness). The device, has three main components which are stable up and motion bottom of platform, a driving unit (AC electric motor and electronic variator) and the data acquisition (Dynamometer, amplifier and XY recorder) system. The rupture force of seeds was measured by the data acquisition system. The seed was placed on the moving bottom platform and was pressed with stationary platform. Experiment was conducted at a loading velocity at 50 mm min^-1 .

Geometric mean diameter (D_g) and sphericity (Ø) values were found using the following formula; [20,22]

D_g = (LWT)^0.333

Ø = (LWT)^0.333 /L

The coefficient of friction caperberry seed was measured using a friction device modified by Tsang-Mui Chung, Verma & Wright [29] and improved by Chung and Verma [30]. Also, both the static and dynamic coefficient of friction was measured and calculated using the equation [30].

μ_s = Ta / Ws.q

μ_d = Tm / Ws.q

Where μ_s equals static coefficient of friction, T_a equals beginning value of torque, μ_d equals dynamic coefficient of friction, T_m equals average value of the torque, q the length of torque arm, and W is the weight of seeds to calculate the dynamic and static coefficients of friction. The average value of the torque during the rotation of the disk and the maximum value of torque obtained as the disk started to rotate were used.

Statistical analyses

Results of the research were analysed for statistical significance by analysis of variance [31].

Chemical properties

The chemical properties of caperberry seeds are given in Table 1. The crude oil, crude fibre, ash, crude energy and ether soluble extract contents of C.ovata seeds were higher than that of C.spinosa. But, protein content (8.71%) of C.spinosa was high compared with C.ovata. Also, crude protein contents of both seeds was higher than those caperberries fruits (17.4% and 18.6% for C.spinosa and C.ovata, respectively) reported by Özcan and Aydin [32]. The moisture, crude oil and crude energy contents were similar to those for caperberry seeds reported by Akgül and Özcan [7].

Table 1: Chemical properties of caper seeds.

The mineral contents of caperberry seeds were determined by ICPAES (Table 2) and found to be excellent. The seeds were composed Mg, K, P and Ca. The Fe, K, Mg, Na, P and Zn contents of C.spinosa seeds were found high compared with C.ovata seeds. Contents in seeds of some minerals were determined to be higher compared with those of caper (C.ovata) seeds reported by Özcan [3]. Mineral contents were determined to vary widely depending on the different species and locations of caper plant. The soil, fertilizers and other cultural factors effect the presence of minerals in oil-bearing seeds [33]. The fatty acid composition of caperberries seed oils was determined by gas chromatography (Table 3).

Table 2: Some mineral contents of C.spinosa and C.ovata seeds (mg/kg).

Table 3: Fatty acid composition of caper seeds (%).

Oleic acid (38.45% and 44.62% for C.spinosa and C.ovata, respectively) was present in the highest concentration, followed by linoleic (23.71% and 18.26%), palmitic (10.23% and 8.41%), stearic (2.61% and 2.07%) and linolenic (1.17% and 0.56%) acids. Akgül and Özcan [7] found that the contents of the main fatty acids of caperberries seeds of C.spinosa and C.ovata were 13.2% and 11.3% palmitic, 3.2% and 2.7% stearic, 49.87% and 34.66% oleic, 25.2% and 24.5% linoleic and 1.0% and 0.3% linolenic, respectively. Mannina et al. established that the contents of the main fatty acids of hazelnut oils were 5.1-6.4% palmitic, 2.2-2.5% stearic, 77.8-84.2% oleic, 6.4-12.0% linoleic and 0.10-0.18% linolenic acids. The main fatty acids identified by gas chromatography were oleic (52.3%), palmitic (21.3%) and linoleic (19.7%) acids for P.terebinthus fruits [34].

As a result, the differences in chemical properties, mineral contents and fatty acid composition of caper seed and seed oil belong to both plants were probably due to environmental conditions in conjunction with the analytical methods used. The analytical values revealed nutritional properties such as protein, oil, ash, fibre, mineral contents and fatty acid composition. These findings may be useful for dietary information, which requires prior knowledge of the nutritional composition of caperberry seeds.

Physical properties

Dimensional properties, sphericity and the values of geometric mean diameter of C.spinosa and C.ovata seeds are given in Table 4.

Table 4: Dimensional properties of C.spinosa and C.ovata seeds.

The frequency distributions of these seeds and dimensional properties are given in Figure 3.

Figure 3: Frequency distribution curves for mass of C. spinosa (Silifke-Mersin) and C. ovata (Selçuklu-Konya) (a), (b) lenght, Width and Thickness of C. spinosa at a moisture content of 5.18% d.b., (c) lenght, Width and Thickness of C.ovata at a moisture content of 4.93% dry basis.

The 89% of the measured C.spinosa is between 0.011 to 0.013g in terms of moisture content of 5.18 % in weight, 85% of them is between 3.5 to 4 mm in length, 96% of them is between 2.6 to 3.5 mm in width, and 93% is between 2.0 to 2.50 mm in thickness. The 96% of C.ovata is between 0.012 to 0.013 g in terms of moisture content of 4.93 % in weight, 91% of them is between 3.2 to 4.0 mm in length, 96% of them is between 2.6 to 3.5 mm in width, and 96 % is between 1.90 to 2.50 mm in thickness.

The relationship between length, width, thickness, weight, geometric mean diameter and sphericity of C.spinosa has been determined. This relationship was found to be as the follows.

L=298.41xM=1.24xW=1.72xT=1.29xDg=4.83x Ø

The same comparison between length, width, thickness and weight, the relationships for C.ovata has been established. This relationship for this seed was found to be as the follows.

L= 2 8 7 . 5 xM= 1 . 2 3 xW= 1 . 7 0 x T = 1 . 2 8 x D g = 4 . 7 1 x Ø Correlation coefficients for these relations are given Table 5.

Table 5: The correlation coefficient of C.spinosa and C.ovata seeds.

L/M For both seeds these relations are found statistically insignificant, the relationships between L/W, L/T , L/Dg and L/Ø have been found to be statistically significant. Similar results were reported by Demir etal. [35], Gezer et al. [36], Carman [26], Joshi et al. [37].

This indicates that the length, mass, the geometric mean diameter and sphericity are closely related to the diameter of seed. Some technological properties of seeds used in experiment are shown in Table 6.

Table 6: Some technological properties of C.spinosa and C.ovata seeds

Similar investigations have been made to evaluate the projected area, volume, bulk density, fruit density and terminal velocity by Özcan et al. [8] for caper buds. The static and dynamic coefficients of friction for caperberry seeds determined with respect to iron sheet and galvanized steel surfaces are represented in Table 7. At the same moisture contents, both the static and dynamic coefficients of friction were greatest for seeds on iron sheet.

Table 7: Relationships between friction coefficients and moisture content of C.spinosa and C.ovata seeds for various material surfaces.

It is important, however, to know, the physical properties of equipment used in plantation, harvesting, transportation, storage and processing of caperberry seeds.

Also length, mass, geometric mean diameter, sphericity, volume, seed density, bulk density, porosity, projected area, terminal velocity and seed hardness values were at 5.18% and 4.93% moisture content levels for C.spinosa and C.ovata seeds, respectively. The values of mass, length, width, geometric mean diameter and sphericity of C.spinosa and C.ovata seeds established were 0.01-0.01 mm, 3.76-3.68 mm, 2.92- 2.87 and 0.78-0.78, respectively. At the same moisture content, fruit density, bulk density, projected area and terminal velocity of both species were determined as 728.44 and 794.50 kg/m3, 502.88 and 488.48 kg/m3, 0.09 and 0.09 cm2 and 4.01 and 3.91 m/s, respectively. The coefficient of static and dynamic on galvanized steel, iron sheet, plywood and rubber ranged between 0.35-0.67 and 0.29-0.56; 0.37-0.66 and 0.31-0.56 for C.spinosa and C.ovata seeds, respectively.

Authors thank to Mrs Perihan (Büyük) Özcan due to her helps for seed extraction. This work was supported by Selçuk Üniversity Scientific Research Project (S.Ü.-BAP, Konya-TURKEY).