Characteristics of Mulberry Pekmez with Cornelian Cherry

Abstract

This study was conducted to determine some properties of mulberry pekmez containing 0% (control group-without Cornelian cherry), 10% and 20% Cornelian cherry (Cornus mas L.) fruit. Significant differences were determined between the samples in terms of water, soluble dry matter, sucrose, total sugar, pH, titratable acidity, electrical conductivity, and viscosity (p < 0.05). Sensory analysis indicated that Cornelian cherry added-pekmez has higher scores than control group. In addition, the panellists favoured the pekmez with 20% of Cornelian cherry added. The addition of Cornelian cherry produced a new type of pekmez, which retains acceptable quality, that Cornelian cherry may enhance invert sugar, some minerals including Ca, K, Fe, and Zn and sensory quality. Element analyses were performed by X-ray fluorescence spectrometry; K, Ca, and Fe concentrations of the mulberry pekmez were increased by increasing levels of Cornelian cherry.

Keywords:

• Mulberry pekmez
• Mulberry
• Cornelian cherry
• Concentrated fruit juices
• Sensory analysis
• Properties

INTRODUCTION

Pekmez is a traditional Turkish food made by using different fruits such as grape, mulberry, fig, plum, apple, and harnup, and it is named after the fruit from which it is obtained (i.e., grape pekmez, mulberry pekmez). However, the grape and mulberry are the most common fruits used in processing pekmez in Turkey. Pekmez is consumed mainly for breakfast instead of jam, marmalade, or honey particularly in winter. Pekmez is healthy food due to its mineral content and is used as a main source of energy based on its chemical composition.[1–3] Pekmez contains copper, and zinc at definite levels especially it is very rich with iron.[4] In fact, the production of pekmez has been continuously and rapidly increasing because of its composition.

Recently, the pekmez produced from mulberry and is more popular because of its medicinal properties. Mulberry pekmez is highly recommended for colds, stomach complaints, and anemia. Therefore, the price of mulberry pekmez is higher than the other types.[5] Fresh or dried mulberry is used as a raw material to produce mulberry pekmez. Mulberry juice is concentrated usually in open vessels. Then product is cooled. It is packaged after cooling to room temperature. Storage is carried out at this temperature. Vacuum concentration method is rarely used in traditional production.[6,7]

White mulberry (Morus alba L.) is widely grown throughout Turkey. It is used fresh or dried consumption and in mulberry pekmez, juices and pestil (a locally dried fruit pulp product) in Turkey. Mulberry fruit is a good source of antioxidant and minerals.[8] Cornelian cherries (Cornus mas) are used in the preparation of beverages in Europe and to treat diabetes-related disorders in Asia. In Europe, C. mas or Cornelian cherry fruits were reported to have food and cosmetic applications.[9] The Cornelian cherry fruits contain a high amount of vitamin C.[10] Anthocyanins and ursolic acid purified from C. mas fruits have biological activities that improve certain metabolic parameters associated with diets high in saturated fats and obesity.[11] In addition, C. mas was reported to has antioxidant effect.[12] Furthermore, the fruits are not only consumed fresh but also used to produce jam, marmalade, pestil, syrup, and several types of soft drinks. These are also used for medicinal purposes.[11,13] The fruit are also rich in sugar, organic acid, and tannin.[4–16] It is well known in Turkish folk medicine and has been used antimicrobial, antihelminitic drug, anti-inflammatory, and constipation effects.

Pekmez has been produced since ancient time but its production technique has not been developed and mechanized. There have been several studies about production, composition, standardization and health benefits of pekmez,[4,17–29] but negligible work was conducted for compositional characteristics of Cornelian cherry fruit adding mulberry pekmez. Today, farmers produce small amounts of Cornelian cherry fruits added mulberry pekmez in order to supply their own requirements. This type of pekmez has been produced by adding Cornelian cherry fruits to the liquid mulberry pekmez at the end of making processes (Fig. 1). Therefore, the purpose of the study was to determine some chemical, physical and sensory properties of Cornelian cherry added-pekmez.

Figure 1 The process routes for mulberry pekmez with Cornelian cherry making in the research.

MATERIALS AND METHODS

Materials

White mulberry and Cornelian cherry was provided from Yedigöl (Yolbilen) Village/İspir-Erzurum-Turkey, and pekmez samples were made at the same village. The process routes for mulberry pekmez with Cornelian cherry making are given in Fig. 1. There were two replicates for each three Cornelian cherry treatments (control 0%, 10%, and 20% Cornelian cherry).

Chemical and Physical Analysis Methods

Soluble solids content, pH and titratable acidity were determined according to standard method AOAC[30]; soluble solids content was determined with an Abbe refractometer (2WA model); pH was measured with a WTW inolab model pH meter; titratable acidity was measured with 0.1 N NaOH up to pH 8.1 and expressed as percentage of citric acid. Total ash was determined by weighing portions of homogenized pekmez and drying it for 12 h at 75°C in an oven; then the crucible was transferred to a muffle furnace. The temperature was gradually raised to 550°C, and the samples were incinerated for 24 h until white ash resulted.[26] The electrical conductivity of each pekmez solution at 20% (dry matter basis) in CO₂-free deionised distilled water was measured at 20°C in a conductimeter (WTW 720 model conductimeter). Results are expressed as mS cm⁻¹.[31,32] Total sugar, invert sugar and sucrose contents were analysed by the Lane-Eynon Method.[33] Moisture was determined according to Cemeroglu[33] and AOAC.[30]

The viscosity (cp) of pekmez samples were determined at 20°C using a Fungilab rotational viscometer (Model Visco Basic L) equipped with spindle 2 at the speed of 20 rpm. Three readings were recorded per sample at 30 s intervals and viscosity expressed as cp.

Mineral Analysis Methods

For elemental analysis was used X-ray fluorescence spectrometry. The samples dropped on the filter papers have been analyzed by using Rigaku ZSX 100e Wavelength Dispersive X-Ray Fluorescence (WDXRF) spectrometer. The spectrometer has a 4 kW end window x-ray tube with Rh anode.[34] All measurements were made in duplicate.

Sensory Analysis

The sensory properties of the pekmez samples were assessed at 7–10 d of storage by 50 consumer panellists who were experienced and familiar with pekmez. Coded pekmez samples were stored at the room temperature (25 ± 2°C) before analysis. The tests conducted at a convenient central location (Yedigöl Village/İspir Erzurum/Turkey) or in homes, students of Oltu Technical Vocational School Food Technology Department (Atatürk University, Erzurum, Turkey) in the laboratory, and food teaching staffs in homes. The pekmez samples (approx. 20 mL) were placed on white plates. Each panel member assessed the pekmez samples for six sensory attributes including colour, odour, viscosity, flavour, acidity, and overall acceptability. All sensory attributes were recorded on point scales with 1 (poor) to 9 (excellent). Water and bread were also provided to the panel members to cleanse their palates between samples.

Statistical Analysis

Experimental data were statistically analyzed by SPSS.[35] Means with a significant difference were compared by Duncan's multiple range tests.

RESULTS AND DISCUSSION

Chemical and Physical Properties

Significant differences were determined between the samples in terms of water, soluble solids, sucrose, total sugar, pH, titratable acidity, electrical conductivity, and viscosity (p < 0.05); however, total ash content of the samples was not found different statistically (p < 0.05)

Some physical and chemical properties of pekmez samples are shown in Table 1. The sucrose, total sugar and pH of pekmez with Cornelian cherry were lower but invert sugar higher than that of control. This decrease may be proportional due to an increasing level of water for mulberry pekmez by Cornelian cherry added or because these parameters could be decreased relatively.

Table 1 The chemical and physical characteristics of pekmez samples

Pekmez samples	Water (%)	Soluble solids content (°Brix)	Invert sugar (%)	Sucrose (%)	Total sugar (%)	Total ash (%)	pH	Titratable acidity (citric acid %)	Electrical conductivity (mS cm^−1)
control (without Cornelian cherry)	25.8 ± 0.1c	72.7 ± 0.1a	53.7 ± 0.1b	5.90 ± 0.23a	59.6 ± 0.2a	1.92 ± 0.06a	5.18 ± 0.01a	0.66 ± 0.01c	3.13 ± 0.00 b
10% Cornelian cherry added pekmez	27.4 ± 0.1b	71.1 ± 0.2b	54.8 ± 0.0a	4.55 ± 0.02b	59.3 ± 0.0ab	1.87 ± 0.01a	4.81 ± 0.02b	0.94 ± 0.00b	3.21 ± 0.00 a
20% Cornelian cherry added pekmez	29.2 ± 0.3a	69.3 ± 0.3c	54.7 ± 0.3a	4.27 ± 0.17b	59.0 ± 0.1 b	1.73 ± 0.06a	4.71 ± 0.00c	1.04 ± 0.02a	3.19 ± 0.01 a
Values are means ± SE; values followed by different letters in a column were significantly different (p < 0.05), using Duncan's multiple range test.

The changes in acidity in pekmez after the addition of Cornelian cherry are given in Table 1. Addition of Cornelian cherry significantly (p < 0.05) enhanced the development of acidity in pekmez, but 20% Cornelian cherry added pekmez samples were more favoured than 10% Cornelian cherry added pekmez samples. There were no significant differences in the concentration invert sugar, sucrose, and electrical conductivity in the pekmez samples containing different amount of Cornelian cherry.

Invert sugar content of Cornelian cherry added pekmez was higher than that of control sample. It may be due to invert sugar content of Cornelian cherry. Our results showed that pH of pekmez decreased with 10% and 20% Cornelian cherry. pH of 20% Cornelian cherry added pekmez samples were different from that of 10% Cornelian cherry added pekmez.

The effect of Cornelian cherry concentration on viscosity of mulberry pekmez was found to be statistically significant (p < 0.01) and the viscosity for mulberry pekmez at different addition were shown in Fig. 2. The viscosity of mulberry pekmez decreased by increasing level of Cornelian cherry. The increase total sugar and sucrose contents resulted in higher viscosity in all samples.

Figure 2 Viscosities of the pekmez samples (speed of 20 rpm), the different letters mean significant differences (p < 0.01).

Mineral Contents

The results are tabulated in Table 2. K, Ca, Fe, and Zn concentrations of Cornelian cherry added (10 and 20%, w/w) the mulberry pekmez samples were definitely higher control group. The increasing levels of Cornelian cherry concentration also increased the concentrations of same minerals. K, Ca, and Fe concentrations of the mulberry pekmez were increased by the Cornelian cherry addition by 34.6–37.9, 29.7–34.7, and 42.4–72.7%, respectively, in the concentrations 10 and 20%.

Table 2 Element concentration of pekmez with and without Cornelian cherry (ppm)

Element	Control (without Cornelian cherry)	10% Cornelian cherry added pekmez	20% Cornelian cherry added pekmez
Na	42a	38a	34a
Mg	1490a	1310b	1160c
Al	43a	27b	23b
Si	254a	231ab	162b
P	828a	862a	821a
S	187a	182a	180a
Cl	184a	182a	160a
K	7100b	9560a	9790a
Ca	118b	153a	159a
Fe	33c	47b	57a
Zn	4b	8ab	9a
Sn	8a	7a	6a
Values followed by different letters in the same row were significantly different (p < 0.05), using Duncan's multiple.

Table 2 showed that there was no significant difference in the concentration of Na, P, S, Cl, and Sn in the mulberry pekmez between treatments. In general, K, Ca, Fe, and Zn concentrations of mulberry pekmez were increased when increasing concentration of Cornelian cherry. Cornelian cherry addition 10 and 20%, however, decreased concentrations of Mg up to 12.1 and 22.1%; Al 37.2 and 46.5% and Si by 9.1 and 36.2%, respectively. These results indicate that decreasing the elements of pekmez was due in particular to their increasing relative water ratio.

Sensory Characteristics

Sensory quality evaluation of pekmez, with and without Cornelian cherry, was carried out by a consumer panel of 50 persons. Generally, all of pekmez samples were favoured by the panellists. As shown in Table 3, the addition of 10% and 20% Cornelian cherry to pekmez improved the sensory quality characteristics of the pekmez. Colour, flavor, and overall acceptability scores were significantly (p < 0.05) higher for pekmez containing Cornelian cherry than control samples. However, score ratings for sensory qualities of the pekmez containing 20% Cornelian cherry were slightly higher than 10%. It was concluded that the rate of Cornelian cherry added in this research was enough to flavour and overall acceptability, and these Cornelian cherry ratio may be preferred by consumers. Adding of Cornelian cherry did not show any significant differences in odour, with respect to the control pekmez. Colour, flavor, and overall acceptability scores were increased due to the increasing levels of Cornelian cherry, but decreased viscosity values. Increasing Cornelian cherry concentration also increased overall acceptability of pekmez. In addition, 20% Cornelian cherry added pekmez were favoured by the panelists. It is stated that pekmez with Cornelian cherry additive has slightly sour aroma.

Table 3 Sensory quality evaluation of mulberry pekmez with and without Cornelian cherry

Samples	Colour	Odour	Viscosity	Flavour	Acidity	Overall acceptability
Without Cornelian cherry (control)	8.21 ± 0.16b	7.11 ± 0.09a	8.14 ± 0.10a	7.87 ± 0.11c	5.72 ± 0.14c	7.68 ± 0.12c
10% Cornelian cherry added pekmez	8.38 ± 0.13 b	7.18 ± 0.10a	7.32 ± 0.13b	8.28 ± 0.08b	6.58 ± 0.12b	8.23 ± 0.13b
20% Cornelian cherry added pekmez	8.92 ± 0.08a	7.22 ± 0.07a	7.18 ± 0.08b	8.64 ± 0.11a	8.82 ± 0.08a	8.68 ± 0.18a
Values are means ± SE; values followed by different letters in a column were significantly different (p < 0.05), using Duncan's multiple range test.

The addition of Cornelian cherry produced a new type of pekmez, which retains acceptable quality. The results suggest that the levels of Cornelian cherry tested this study have great potential, which will contribute in pekmez production technology and customer's taste expectation.

CONCLUSIONS

The results suggested that the sensory characteristics of pekmez can be improved by the use of Cornelian cherry. However, addition of 20% Cornelian cherry showed comparatively higher sensory scores than 10% Cornelian cherry added pekmez. Therefore, it is suggested that overall acceptability of pekmez could be increased by the addition of Cornelian cherry at elevated rates. Colour is an important quality attribute of pekmez, but during processing or storage, very dark brown colours develop because of either Maillard or caramelization reactions. Cornelian cherry may provide a desirable colour. In addition, it could be utilized as fruit juice with a delicious aroma and its consumption could be increase by diluting with water as fruit juice with high-energy value. The Cornelian cherry may enhance invert sugar, some minerals, and sensory quality. As a result, Cornelian cherry added mulberry pekmez production and its chemical composition should be adapted to the mechanized production.

ACKNOWLEDGMENTS

The authors are grateful to Yedigöl (Yolbilen) Village (İspir/ Erzurum, Turkey) villager for their help, advice, and sensory analysis. We thank to students of Oltu Technical Vocational School for their help sensory analysis. We thank Dr. Ali Gurol, Dr. Faruk Demir, and Prof. Dr. Yusuf Sahin (Department of Physic, Atatürk University, Erzurum, Turkey) for their help in the mineral determination, and Prof. Dr. Ramazan Cakmakci (Atatürk University, Faculty of Agriculture, Department Agron, Erzurum, Turkey) for his kind help with the statistical analysis.