Lokum industry, or the so-called Turkish delight, is one of the oldest popular sweets that were made in Turkish Anatolia since the fifteenth century, after which its industry spread in the Balkans, the Middle East and Greece. It is a jelly sweet made of starch and sucrose with the addition of nuts such as walnuts, pistachios, hazelnuts, coconut and peanuts, as well as coloring agents and flavors according to Turkish Standard Specifications [1]. Pocan et al. [2], added that gelatin and pectin can be added to contribute to the Giving the required sweets texture, as it was mentioned that most of the sweets manufacturers prefer to use corn syrup in the permissible quantities with sucrose as an anti-crystallization substance and improve the shelf life of sweets, as well as improve the sensory and structural properties and reduce the cost. In Bulgaria, there are two types of lokum, ordinary which corn syrup is added and Extra which the syrup is not added. The lokum are sold in the markets in the form of small cubes with a soft gel texture. Eating different types of sweets containing sucrose or corn syrup, including lokum, with lack of movement, led to an increase in the emergence of many diseases such as diabetes, heart disease, atherosclerosis and others, which led food manufacturers to find alternatives of sucrose with safe sweeteners [3]. Therefore, it was necessary to find alternative sweeteners to sucrose that are safe and do not cause the aforementioned diseases, such as sorbitol, which is one of the sugar alcohols that contribute to the formation and stabilization of textures. The Food and Drug Administration (FDA) has set the sweetness of sucrose and the acceptable daily intake of sorbitol as 50 g/day, confirming that what is more than that has laxative effect [4]. The study aimed to the possibility of producing low-calorie lokum by practically replacing sucrose with 25% sorbitol, 25% each of sorbitol and xylitol and 25% each of sorbitol and stevia and studying the effect of the treatment type and storage period on some Physicochemical and sensory properties for the produced lokum. Reaching to the best replacement ratio so that it gives similar properties to those which sweetened with sucrose.

It was used four types of sweeteners in research, sucrose that has white fine crystals, purchased from the local market/Mosul city/Iraq. Sorbitol, xylitol and stevia are in white powder form, its purity is 98%. citric acid, which were purchased from the chemical sales offices in the city of Mosul and imported from the Chinese company Jiangxi Congcongle Food Industry Co.ltd. Modified corn starch and flavoring materials (mastic and cardamom) from the local market/Mosul city/Iraq.

Lokum (Turkish Delight) Manufacturing 

A standard treatment of lokum was manufactured according to the method of Gönül [5], with some modifications. To manufacture low-calorie lokum, it is necessary to find a method for manufacturing lokum that are close to the standard method in terms of texture and flavour, so gelatin was used in this study (3,4 and 5 g/100g) Which was mixed with starch homogeneously, cold water was added to them to disperse in. In the first treatment, the sucrose was replaced by sorbitol (sugar alcohol) at a ratio of 25%, the second treatment was replaced by sorbitol and xylitol (sugar alcohols) at a rate of 25% for both and the third treatment was replaced by sorbitol and the natural sweetener stevia 25% for both, too. Each treatment was separately mixed with water and citric acid was added to it. The quantities were determined in the preliminary experiments to determine the strength of the resulting gel, as well as to determine the appropriate cooking time and temperature. The prepared solution of starch and gelatin was added to the sugar solution with sweeteners and continued boiling with stirring until the color changed to transparent. The mastic and cardamom were added while continuing to stir until reaching to the desired texture that was tested by taking a small amount of it, placing it in cold water. It was found that it does not disperse in it. This mean, the cooking process was end which was found to have taken 30 minutes and the temperature had reached 90°C. After manufacturing of the treatments were completed, they were poured into trays covered with greaseproof paper, then cooled and left for 24 hours, Then the lokum was cut into cubes, packed in tightly closed plastic containers and stored at 20-25°C for 30 days.

Physical, Chemical and Sensory Analyses

The pH was measured using the manual pH2- Singapore Eco Tester, No. 374, after the treatments were prepared, by taking 10 gm of lokum and mixing it with 90 ml of distilled water in a volumetric flask. The mouth of the flask was covered with a film and left for 30 minutes, after which the solution was mixed well. The pH value was recorded after the sensor remained in the mixture for 15 minutes at 20°C. The percentage of total acidity TA% was estimated on the basis of citric acid, by titration with 0.1 N of NaOH solution. The moisture content was estimated in a German vacuum oven, all of these tests were estimated according to AOAC [6]. The color of the lokum (Turkish delight) piece was measured by spectrophotometer model Fm-721 imported from the Chinese company, the absorption of the clear extract was read at a wavelength of 425 nm, sensory evaluation was conducted at the beginning and end of the storage period according to the method mentioned by Kurtcan and Gönül [7], with some modifications. The hardness of the treatments was also estimated using a penetrometer, the cone was immersed at an angle of 45 degrees in the treatment to be analyzed, the duration took 5 seconds according to the method of Hadjikinova and Hasan [3], with some modifications. Finally, the statistical analysis of the data was carried out according to the factorial system of experiments using the complete randomized design (C.R.D) and the different coefficients were marked with different alphabets using Duncan's Multiple Range Test under the probability level of 5% [8].

Some Physicochemical Indicators of Lokum

It is noted from the results of Table 2, that the pH value of all replacement treatments T1, T2 and T3 was significantly high at the level (p≤0.05) in zero days of storage, it reached 4.11, 4.18 and 4.33, respectively, compared to the standard treatment T0, which decreased in the same value Which it reached 4.02. The reason for the high pH in the substitution treatments may be due to the increase in the amount of water or moisture in it. The results agreed with Batu and Arslan [9], as he mentioned in his study that the low acidity and high pH is caused by the increase in the amount of water in the lokum, this negatively affected on the properties of the produced lokum (Turkish delight). The same table indicates that the total acidity TA% decreased significantly (p≤0.05) in all replacement treatments (p≤0.05) and reached 0.09, 0.07 and 0.05% respectively. While that percentage increased significantly in the standard treatment T0 and reached 0.12 % for the same reason mentioned in pH.

Table 1: Turkish Delight Ingredients

*T0 = Standard(sucrose), T1 = 25% Sorbitol, T2 = 25% Sorbitol+25%xylitol, T3 = 25% Sorbitol+25% stevia, *The coefficients that took the same letter are not significantly different from each other under the 0.05 probability level

Table 2: Some of Physicochemical Indicators of Lokum (Turkish Delight)

*T0 = Standard(sucrose), T1 = 25% Sorbitol, T2 = 25% Sorbitol+25% xylitol, T3 = 25% Sorbitol+25% stevia, *The coefficients that took the same letter are not significantly different from each other under the 0.05 probability level

As for the color index, it is noted from the table also that the absorbance value of the substitution treatments T1, T2 and T3 decreased significantly (p≤0.05) and reached 1.38, 1.32 and 1.28 nm respectively, then the standard treatment T0 in which the same value increased and reached 1.42 nm. This means that the color of standard treatment was slightly darker compared to the replacement treatments. The reason may be due to a slight caramelization of sucrose during cooking due to the higher amount of sucrose in it compared to the mentioned treatments according to the study plan [10].

Effect of the Type of Treatment and Storage Period on the Hardness of the Lokum (Turkish Delight)

It is notice from the results of Table 3, that there are significant (p≤0.05) differences in the texture of the lokum (Turkish delight), as its hardness decreased significantly (p≤0.05) in all the substitution treatments T1, T2 and T3 and it amounted to 202, 176 and 151 respectively compared to the standard treatment T0 which was of high significantly in hardness value, it reached to 255. 

Table 3: Effect of Treatment Type and Storage Period On Hardness of Lokum (Turkish Delight)

*T0 = Standard (sucrose), T1 = 25% Sorbitol, T2 = 25% Sorbitol+25% xylitol, T3 = 25% Sorbitol+25% stevia, *The coefficients that took the same letter are not significantly different from each other under the 0.05 probability level

The reason for the low stiffness of the substitution treatments may be due to the decrease in the amount of sucrose in them according to the study plan, which plays an important role with starch and gelatin in the formation of the gelatinous network and thus the formation of elastic texture and moderate stiffness of the lokum. Also, the sugar alcohols, sorbitol and xylitol, have the ability to absorb water (moisture) and retain it [11], while stevia sweetener does not have this property, so the gel formed was weak even with the addition of gelatin. From these results it can be said that gel formation increases with higher sucrose amount [12]. The same table indicates that the standard treatment T0 of lokum was the most hardness in 30 days of storage, while the treatment T3 was less hardness compared to the other replacement treatments and the standard treatment, For the same reasons mentioned above. It is also noted from the same table that the hardness of the lokum increased significantly in the standard treatment T0, that its flexibility decreased.

The reason for the increase in hardness and loss of elasticity in it may be due to the increase in moisture loss and dryness of its outer surface [13], while the hardness of the replacement treatments were gradually decreased with the progression of storage periods. From this it can be concluded that the hardness of the lokum is closely related to its moisture content [1].

Effect of Treatment Type and Storage Period on the Moisture Content of Lokum (Turkish Delight)

The results of Table 4, indicate that there were significant differences (p≤0.05) in the moisture content of lokum in the standard sample T0 containing sucrose and the rest of the replacement treatments T1, T2 and T3, as the moisture content increased significantly in all of the replacement treatments at the beginning of storage, amounted to 27.55, 29.67 and 31.33%, respectively, while the same percentage decreased in the standard treatment, reached to 26.92%. 

Table 4: Effect of Treatment Type and Storage Period On Moisture% Of Lokum (Turkish Delight)

*T0 = Standard (sucrose), T1 = 25%Sorbitol, T2 = 25% Sorbitol+25% xylitol, T3 = 25% Sorbitol+25% stevia, *The coefficients that took the same letter are not significantly different from each other under the 0.05 probability level

The reason may be due to the ability of sugar alcohols such as sorbitol and xylitol to bind and retain free water, despite of their ability to stabilize starch in water systems, while the ability of sucrose is weak [11]. It is noted from the same table that the highest moisture content reached by the treatment T3 amounted to 32.92% at the end of the storage period and the lowest moisture content reached by the standard treatment T0 amounted to 23.77% at the end of the storage period. It also appears from the same table that the moisture content increased significantly (p≤0.05) in all substitution treatments, while it decreased significantly in the standard treatment T0 with the progression of storage periods. The reason may be due to sugar alcohols continuing to absorb and retain moisture from the surrounding atmosphere, despite of their ability to synergize with other sweeteners such as stevia, making them improve the taste of products containing them and prevent the product from losing its moisture [14].

Effect of Treatment Type and Storage Period On the Sensory Evaluation Properties (Taste, Chewing Ability, Flexibility and Appearance) Of The Lokum

There are no definite properties of the lokum in the literature, but some physical properties of the lokum, such as elasticity and chewability, can be identified so that the lokum should not be too hard or too soft, nor sticky or difficult to chew. Since the steps for making lokum differ from one manufacturer to another, it can be asserted that there is no product similar to the other [15].

It is noticeable from the results of Table 5, that there are significant differences (p≤0.05) between all the treatments in the degree of acceptance of the lokum taste at the beginning of storage. All the substitution treatments T1, T2 and T3 obtained an acceptance degree of 9.58, 9.32 and 9.12, respectively. It is approach to the standard treatment T0, which amounted to 9.76, this means that the replacement with alternative sweeteners and the addition of gelatin in these treatments did not affect in its taste significantly, perhaps due to the appearance of the mastic and cardamom flavor making it taste close to the standard treatment, in addition to that the added sugar alcohols gave a wonderful taste and a sense of coldness in oral and its synergistic effect with other sweeteners such as stevia improved the taste [14]. At the end of the storage period (30 days), the degree of lokum acceptance decreased significantly (p≤0.05) in all treatments T0, T1, T2 and T3, especially the substitution treatments compared to the standard treatment, perhaps because of the loss of water that led to changes in texture that affected on the taste of the produced lokum (Dereli et al., 2014). It is also noted from the same table that the chewing ability was significantly (p≤0.05) high at the beginning of storage in the standard treatments T0 and T1 in which sucrose was replaced by 25% with sorbitol, they were reached 9.61 and 9.52, respectively. While the chewing ability of the two treatments T2 replaced sucrose with sorbitol and xylitol by 25% for both and the treatment T3 replaced sucrose with sorbitol and stevia by 25% for both, which they amounted to 8.82 and 8.61, respectively. perhaps due to Moisture in it, thus increasing its softness a lot. This is return to the ability of sugar alcohols (xylitol and sorbitol) to absorb and retain water more than sucrose in starch systems [11], In addition to the decrease in the amount of sucrose in these two treatments according to the study plan, which plays an important role in forming textures with starch. As for the end of the storage period, it was noticed that the two treatments T0 and T1 decreased in the chewing ability and reached 8.55 and 8.23 respectively. The reason may be due to the loss of water or moisture with long storage that made the surface of the lokum somewhat hard and the chewing ability decreased to a lesser extent in the two treatments T2 and T3 and were 7.69 and 7.12 respectively, probably due to the softness of lokum [1,16].

Table 5: Effect of Treatment Type and Storage Period On Sensory Evaluation Properties of Lokum (Turkish Delight)

*T0 = Standard(sucrose),T1 = 25%Sorbitol,T2 = 25%Sorbitol+25%xylitol,T3 = 25%Sorbitol+25% stevia, *The coefficients that took the same letter are not significantly different from each other under the 0.05 probability level

It is also noted from the table that the degree of elasticity of the lokum (Turkish delight) was highly acceptable (p≤0.05) at the beginning of storage, especially in the two treatments T0 and T1, which amounted to 9.76 and 9.65, respectively, as the high amount of sucrose in these two treatments, according to the study plan, contributed with starch to the formation of the appropriate flexibility of the lokum, which is one of the main factors affecting the quality of the product [1]. It is also noted that the elasticity decreased in the two treatments T2 and T3 compared to the two treatments mentioned above due to the increase in their moisture percentage and the decrease in the amount of sucrose in them. At the end of storage, the degree of flexibility of the lokum decreased in all the treatments T0, T1, T2 and T3, they were 8.57, 8.43, 7.32 and 7.10, respectively. The reason for the loss of elasticity over time could be attributed to the increase in water loss from the lokum samples, especially on the surface of the lokum, which became more cohesive, reached to this results Kavak and Akpunar [1]. It was noted from Table 5, that the appearance of the lokum (Turkish delight) was highly acceptable, despite the occurrence of significant differences (p≤0.05) between all treatments T0, T1, T2 and T3, but they are not practically important at the beginning of storage, which amounted to 9.81, 9.60, 8.44 and 8.23, respectively. May be due to the quality of the color and softness of the produced lokum, but at the end of storage, the degree of acceptance of the appearance decreased by the assessors for all treatments, especially the two treatments T2 and T3, which amounted to 7.86 and 7.37 respectively. The reason may be due to their softness and lack of cohesion with the dryness of the surface. As for the decrease in the degree of acceptance of the two treatments T0 and T1, which were 7.86 and 7.37, respectively, the reason for the hardness of their external surface due to moisture loss with the extension of the storage period [1,9]. It can be concluded from the results of sensory evaluation that the treatment T1 that was sweetened with sorbitol was acceptable in terms of the characteristics of taste, chewing ability, flexibility and appearance and did not differ much from the standard treatment T0, the treatment T2 was moderately accepted by some assessors at the beginning and end of storage, while the treatment T3 did not receive accepted by the assessors for the aforementioned reasons.

Replacing sucrose with the sweetener sorbitol, xylitol and stevia partially resulted low calories lokum (Turkish delight). The treatment that partially replaced sucrose with sorbitol in the replacement ratios 25 %, gave acceptance in sensory properties until the end of storage. Sorbitol gave a good and suitable flexibility and improved of chewability, While the replacement with sorbitol and xylitol or sorbitol and stevia did not give acceptance in the mentioned properties.

1. Kavak, D.D. and E.B. Akpunar. “Quality characteristics of Turkish delight (Lokum) as influenced by different concentrations of cornelian cherry pulp.” Journal of Food Processing and Preservation, vol. 42, no. 7, 2018, e13656.

2. Pocan, P. et al. “Detection of authenticity and quality of Turkish delights (Lokum) by means of conventional and fast field cycling nuclear magnetic resonance Relaxometry.” Journal of Agricultural and Food Chemistry, vol. 69, no. 41, 2021, pp. 12089–12101.

3. Hadjikinova, R. and Y. Hasan. “Isomaltulose as an alternative to sucrose in the composition of Turkish Delight (Lokum).” BIO Web of Conferences, vol. 45, EDP Sciences, 2022.

4. Zhang, W. et al. “Sugar alcohols derived from lactose: Lactitol, Galactitol and sorbitol.” Applied Microbiology and Biotechnology, vol. 104, no. 22, 2020, pp. 9487–9495.

5. Gönül, M. Türk Lokumu Yapım Tekniği Üzerine Araştırmalar. Ders Kitapları 1. Baskı. Yayın No: 8. Bornova: Ege Üniversitesi Mühendislik Fakültesi, 1985.

6. AOAC. Official Methods of Analysis of the Association of Official Analytical Chemists. 17th ed., Washington, D.C., 2012.

7. Kurtcan, Ü. and M. Gönül. “Gıdaların Duyusal Değerlendirilmesinde Puanlama Metodu.” Ege Üniversitesi Mühendislik Fakültesi Dergisi, vol. 5, 1987, pp. 137–146.

8. Antar, S.H. Statistical Analysis in Scientific Research and the SAS Program. University of Mosul, Dar Ibn al-Atheer for Printing and Publishing, 2010.

9. Batu, A. and A. Arslan. “Biochemical and sensory evaluations of Turkish delight (Lokum) enriched with black grape and sour cherry syrups.” Turkish Journal of Agriculture and Forestry, vol. 38, no. 4, 2014, pp. 561–569.

10. Batu, A. et al. Changes in the Gastronomic Characteristics of Plain Turkish Delight (Lokum) During Production. Aydın Gastronomy, vol. 2, no. 2, 2018, pp. 9–20.

11. Ding, S. and J. Yang. “The effects of sugar alcohols on rheological properties, functionalities and texture in baked products – A review.” Trends in Food Science and Technology, vol. 111, 2021, pp. 670–679.

12. Muñoz-Almagro, N. et al. “Effect of sucrose substitution with stevia and saccharin on rheological properties of gels from sunflower pectins.” Food Hydrocolloids, vol. 120, 2021, p. 106910.

13. Kaya, S. and G.Ö. Tattan. “Thermal and textural changes of Turkish delight with storage relative humidity.” Journal of Food Science and Engineering, vol. 7, 2017, pp. 186–191.

14. Grembecka, M. “Sugar Alcohols – their role in the modern world of sweeteners: A review.” European Food Research and Technology, vol. 241, no. 1, 2015, pp. 1–14.

15. Batu, A. “Production of Turkish delight (Lokum) with Its additives and quality.” ICEF11 International Congress on Engineering and Food, May 2011, pp. 22–26.

16. Dereli, Z. et al. “Effects of modified atmosphere packaging on shelf life of Turkish delight (Lokum).” Journal of Food Protection, vol. 77, no. 10, 2014, pp. 1799–1803.

17. Jamieson, P.R. et al. Sorbitol and Mannitol. Alternative Sweeteners. CRC Press, Taylor and Francis Group, Boca Raton, 2012.