Investigating the effect of sucrose with a suitable level of licorice as a native Iranian sweetener on the quality of ice cream

Introduction: Ice cream is the most popular dessert in the category of dairy products. The definition of ice cream varies from country to country (Goff et al., 2013). According to the definition of Iranian National Standard No. 2450, ice cream is a nutritious product that is prepared by freezing and aerating a homogeneous and pasteurized mixture of ingredients such as milk, fat, sugar, additives, and other optional ingredients in order to increase the quality and nutritional value of ice cream. The desired sweetness of ice cream is approximately equivalent to 13 to 16% of sucrose in the composition of 36 to 38% of total solids. Different types of sugar do not have the same sweetness, sweetness cannot be precisely defined and measured (Goff et al., 2013). High sucrose consumption causes cardiovascular diseases, obesity, and diabetes (Ozdemir et al., 2015). Therefore, much effort has been focused on using natural sweeteners in ice cream production (Alizadeh et al., 2014). Sugar plays many roles in food. Its most obvious function is sweet sugar, but it also helps improve flavor performance and affects mouthfeel and textural properties. All sweeteners can be used only as partial replacements for sugar since complete replacement significantly changes the structural properties (Goff et al., 2013). The genus Glycyrrhiza is a well-known traditional medicinal plant that grows in several regions of the world. The stolons and roots of these plants have been used in traditional medicine for more than 4000 years. Rhizomes and roots are the most important medicinal parts of licorice, which have been reported alone or in combination with other plants to treat many gastrointestinal disorders (such as peptic ulcer, hyperplasia, flatulence and colic), respiratory disorders such as cough, asthma, tonsillitis, and It is used for sore throat, epilepsy, fever, impotence, paralysis, rheumatism, leukorrhea, psoriasis, prostate cancer, malaria, bleeding diseases and (Öztürk et al., 2018). Licorice is mainly used as a sweetener because it is 50 times sweeter than sucrose and also has medicinal properties (Bahmani et al., 2015). Licorice is widely used in the food industry as a sweetener, flavor enhancer, and flavor modifier. Therefore, licorice extract is usually used in sweet foods such as sweet snacks, ice cream and syrup to increase their sweetness (Alfaumi et al., 2020).
Material and methods: The dried licorice root was cut into small pieces (1-0.5 cm in diameter and 1-0.5 cm in length). The dried roots were ground using a laboratory mill and after passing through a sieve (mesh 35) they were stored in polyethylene bags at -18°C (Shabkhiz et al., 2016). For the preparation of extract, 25 grams of powdered licorice root mixed with 50% (v/v) ethanol-water solvent at a ratio of 1:5 and subjected to 37 kHz ultrasound waves for 30 minutes at a temperature of 45°C and after filtering with Whatman No. 1 paper, then the solution was evaporated at 45°C in an oven and after freeze drying, the resulting powder was homogenized and stored in a dark container at -18°C until the experiments were carried out and For the preparation of different licorice extracts (0.5, 1, 1.25, 1.5, 1.75, and 2%) was used as a substitute for sucrose in ice cream formulation. Ice cream formulation based on 7% fat, sweetness equivalent to 15% sucrose (mixture of sucrose and licorice extract), 9% dry matter fat-free milk, 0.1% vanilla, and 0.3% salep, treatment, and control samples are prepared. For the preparation of ice cream First, the milk was heated to a temperature of 40-45 degrees Celsius, then the milk and cream were homogenized for one minute, sucrose was added to the mixture along with other dry components including licorice, milk powder, salep and mixed for 5 minutes with a mechanical stirrer at 70 rpm. The resulting mixture was pasteurized for 30 minutes at 70°C in a bain-marie and finally cooled to 5°C with the help of antifreeze (ice and salt). Then, the Aging stage was carried out at a temperature of 4-6 degrees Celsius in a refrigerator for 24 hours. Vanilla was also added to the mixture and the mixture was frozen in a non-continuous ice cream maker (Cuisinart, USA) for 30 minutes at a temperature of -4 degrees and the physicochemical characteristics of ice cream including pH, specific gravity, viscosity, Overrun, Dry matter, time of first melting drop, colorimetric and sensory evaluation were investigated.
Results and discussion: The physicochemical characteristics of ice cream showed that by adding different concentrations of licorice (0.5, 1, 1.25, 1.5, 1.75, and 2%) along with sucrose in ice cream, the pH of the samples decreased significantly and the lowest pH in The sample containing 2% licorice was observed (6.38). The reason for the decrease in pH can be attributed to the acidic compounds in licorice such as saponin. By increasing the licorice extract concentration to 1.5%, the viscosity decreased significantly (P<0.05). The highest viscosity was related to the control treatment (1238 cp) and the lowest viscosity was related to the treatment containing 1.5% extract (cp 377.93). By increasing the licorice concentration up to 1.5% levels, there was a significant decrease in the specific gravity of the treatments, and by increasing the amount of extract at higher levels, the specific gravity increased significantly. Thus, the highest amount of specific gravity was observed in the concentration of 2% licorice (1.11). Also, With the increase of licorice concentration, the increase in volume in the treatments increased significantly, so that the treatment containing 2% licorice with Overrun (42.60%) caused a significant increase in ice cream volume. Because licorice root is a rich source of saponins, and foam formation is one of the prominent properties of saponins, and it can be said that the lipophilicity-hydrophilicity of saponins is responsible for foam formation. Levels of 0.5 to 1.25% licorice decrease the time of the first drop of melting and increase the speed of melting, and then by increasing the concentration of licorice extract at levels of 1.5 to 2%, the speed of melting decreased significantly, so that the treatment containing 2% licorice, the time of first melting drop (11 minutes) was equivalent to the control treatment (P<0.05). The highest amount of dry matter was seen in the control treatment (35.82) and with increasing the concentration of the extract up to 1.5%, the amount of dry matter in the samples decreased significantly (P<0.05) and with increasing the concentration of more than 1.5% of licorice extract powder, the amount of dry matter has shown an increasing trend. With increasing licorice extract concentration, brightness indices decreased. Thus, the highest level of brightness index belongs to the control treatment (73.85) and the lowest level of brightness index is related to the treatment with 2% licorice extract (47.59). It was also observed that with the increase of licorice percentage in the ice cream formulation, the highest amount of yellow/blue index was related to the treatment of 2% licorice (21.26) that these changes can be related to the presence of the predominant yellow (brownish) color of licorice extract. Also, with increasing concentration of licorice, (a*) it increased, so that 2% licorice treatment had the highest amount of redness (7.15). Also, In terms of sensory characteristics, high licorice concentrations scored very low and the reason was the bitter aftertaste of this extract. Among the different concentrations of this extract, 1% concentration of licorice extract was chosen to add to ice cream.
Conclusion: The results demonstrated that the addition of different concentrations of licorice with sucrose in the ice cream formulation, significantly reduced the pH, first melting drop, and dry matter in different samples, as well as with the replacement of licorice up to 1.5% viscosity and specific gravity were reduced, and increase of overrun was observed. With the increase of licorice, the brightness index decreased, and a*, b* increased. in terms of sensory characteristics, a very low score can be considered for ice cream containing licorice, and the reason for this is the bitter taste of this extract. Among the different concentrations of extract, 1% licorice extract was selected to add to ice cream and prepare a healthy and safe product. In general, considering the nativeness of the licorice plant and its food and medicinal use since ancient times in our country, this review can be an introduction to the practical use of this extract in dairy food products, especially ice cream, So that the possibility of using an available and affordable source is provided and also leads to the production of food products with new taste characteristics, which will ultimately be a step towards improving the health and safety of society.