Development of camel and cow's milk, low‐fat frozen yoghurt incorporated with Qodume Shahri (Lepidium perfoliatum) and cress seeds (Lepidium sativum) gum: Flow behavior, textural, and sensory attributes' assessment

Abstract In this study, the effect of different concentrations (0.2%, 0.1%, and 0%) of some plant seed gums (Qodume Shahri (Lepidium perfoliatum) and cress (Lepidium sativum)) as the stabilizer on the flow behavior, textural, and sensory properties of frozen yoghurt produced from camel and cow's milk was investigated. The results showed that plant seed gums significantly affected the viscosity, overrun and melting rate, textural, and sensory properties of frozen yoghurt samples prepared from camel and cow's milk. Also, no significant differences were observed in pH and acidity of the samples. The highest overrun value was observed in the control sample. Frozen yoghurt containing 0.2% Qodume Shahri seed gum (QSSG) had the highest viscosity and the longest first dripping time. This is an indication that frozen yoghurt mixes are non‐Newtonian at all added concentrations. Finally, Herschel–Bulkley model well described the rheological behavior of frozen yoghurt mixtures due to the higher correlation coefficient. In general, cow's frozen yoghurts containing 0.2% cress seed gum (CSG) and 0.1% QSSG were more acceptable among panelists than camel frozen yoghurt sample.


| INTRODUC TI ON
Camel milk is one of the very important source of nutrient for human in numerous arid and semiarid environment (Agrawal et al., 2011), and it has been used in the treatment of many diseases including the tuberculosis and other lung ailments in Russia, dropsy, jaundice, and anemia in India (Hashim et al., 2009) and finally glycemic control and reduced insulin dose in patients with type-I diabetes (Agrawal et al., 2011). Camel milk is a complex mixture of total solid (9.8%-14.4% w/w), fat (3.2%-5.5% w/w), protein (2.7%-4.5% w/w), lactose (3.4%-5.5% w/w), and ash (0.6%-0.9% w/w) (Tamime & Robinson, 2013). Since the physicochemical properties of camel milk differ from those of cow's milk, thus, the products manufactured from camel milk can be different from cow's milk. Usually, camel milk is consumed fresh or fermented (Singh et al., 2017). Frozen dairy desserts can be made from milk of different animals such as cow's and camel milk (Kavas & Kavas, 2016), sheep's milk (Elisangela et al., 2016), and goat's milk (Ranadheera et al., 2013).
Frozen yoghurt is a refreshing and nutritious dessert, with or without the flavor that combines the texture of ice cream and yoghurt (Goff, 2018). Like most frozen dairy desserts, frozen yoghurt contains milk fat, milk solids-not-fat, sweetener, stabilizer, emulsifier, and water. It is low in fat, typically 2%-4% (Goff & Hartel, 2013).
Furthermore, there are many factors that influence the body and texture of the ice cream and similar products. Stabilizers are one of the main ingredients that have important functions on the final product quality. For example, they are used in the ice cream mixture to increase mixture viscosity; prevent the separation of clear serum during meltdown; and restrict the growth of ice and lactose crystals during storage periods, especially during periods of temperature fluctuation. They also produce a stable foam with easy cutoff and stiffness in the barrel freezer for packaging; provide uniformity to the product and increase resistance to melting; and finally improve the feeling of smoothness texture during consumption in the final product (Clarke, 2012;Goff & Hartel, 2013).
Recently, the trend in the enrichment of the dairy products with herbal extract particularly food hydrocolloids from natural gums obtained from various sources with different physical and functional properties in the food industry has been increased significantly Mirhosseini & Tab atabaee Amid, 2012).
Fortified food with the herbal additives can be unique and provide more health benefits (Panesar & Shinde, 2012). Lepidium perfoliatum and Lepidium sativum both types of herb belong to the Cruciferae family where is originated from Iran and locally called Qodume Shahri and cress, respectively. The parts of the plant which are used are the roots, leaves, and seeds (Amin, 2005). The L. perfoliatum and L. sativum seeds contain a large amount of mucilaginous substances which diffuses out when soaked in water under optimal conditions (Seyedi et al., 2014). Therefore, the aim of the present study was to investigate the possibility of producing low-fat frozen yoghurt from camel and cow's milk by applying these gums and comparing the rheological, textural, and sensory characteristics of produced low-fat frozen yoghurt samples.

| Extraction procedure of QSSG and CSG gums
The Qodume Shahri and cress seeds were purchased from the Attari, herbal medicine shop, in Gorgan, Iran. The seeds were cleaned by hand to remove all foreign material. The Qodume Shahri seed gum (QSSG) and cress seed gum (CSG) were extracted under optimal conditions (pH = 8; 48°C and water to seed ratio of 30 (ml):1 (g); pH = 10; 35°C, at a water to seed ratio of 30 (ml):1 (g), respectively).
The pH was adjusted constantly by the addition of 0.1 mol/L NaOH and/or HCl. The seed-water slurry was stirred with an electric stirrer throughout the entire extraction period (1.5-3.5 hr); then, the seeds were discarded, and remained gum slurry was dried to overnight by oven at 50 ± 1°C. The obtained powder was milled and sieved by using a mesh 18 sifter to get the same particles then packed and stored in cool and dry conditions Razavi et al., 2011).
The flow diagram of frozen yoghurt manufacturing stages is presented in Figure 1 and described as below (Rezaei et al., 2011): -Blending of Sugar (16%), stabilizer-emulsifier mixture (0.2%), cow skim milk powder (to adjust total solid to 30%), and different F I G U R E 1 The flow diagram of low-fat frozen yoghurt production Blending of Sugar (16%), stabilizer-emulsifier mixture (0.2%), cow skim milk powder (to adjust total solid to 30%) and different concentration ( Packaging in plastic cups (50 ml) and hardening at -18 °C concentration (0, 0.1, and 0.2% w/w) of QSSG and CSG (depending on the type of treatment for both types of milk).
-Pasteurization in laboratory water bath (at 85°C for 30 min).
-Blending yoghurt with prepared frozen yoghurt mixture.
-Cooling to refrigerator temperature (4°C) for 24 hr (to ensure complete hydration of the mixed ingredients).
-Freezing in laboratory batch home ice cream maker (Musso, made in Italy) having 1.5 L capacity, for 20 min.

| The pH and acidity measurement
The pH was measured using a Metrohm-827 pH meter (Metrohm,

| Viscosity and flow behavior characteristic of frozen yoghurt mixture
After aging process (kept at 5°C overnight), the apparent viscosity of the prepared frozen yoghurt mixtures made by different concentration of two gums was measured using a Brookfield Viscometer where τ is shear stress (Pa), γ is the shear rate (s −1 ), k is the consistency coefficient (Pa s n ), n is the flow behavior index (dimension less), and τ 0 is yield stress (Pa). For shear-thinning fluids, n < 1 and for shear-thickening fluids, n > 1.

| Overrun
The overrun of frozen yoghurt samples was calculated using the following equation (Akın et al., 2007;.
where W 1 = the weight of unit mixture; W 2 = the weight of same volume of frozen yoghurt.

| Melting characteristics
Melting behavior expressed as the first (1st) dripping time and melting rate was evaluated on frozen yoghurt samples stored after 1 day at −18°C. Blocks of frozen yoghurt with weight of 30 ± 1 g were placed on a sieve with a mesh diameter of 2 mm and incubated at 25 ± 1°C.
After 60 min, depending on the weight of the melted liquid, melting rate was measured as a percentage of initial weight. The time of the first drop was recorded during melting process (Akalın & Erişir, 2008).

| Textural analysis
Instrumental texture profile analysis (TPA) was performed on the frozen yoghurt samples using a Texture Analyzer TA-XT-plus (Stable Micro Systems, Surrey, UK), equipped with a 2 mm diameter stainless steel cylindrical probe and set up to record the desired forces for penetrating distance = 15 mm, force = 5 g, probe speed during penetration = 3.3 mm/s, probe speed pre-and postpenetration = 3 mm/s.
Factors evaluated in this test were hardness (maximum force during penetration), adhesiveness (negative area of peak force during withdrawal), gumminess (hardness × cohesiveness (that describes how well a food retains its form between the 1st and 2nd chew)), and chewiness (springiness (that is a textural parameter, which is related to elasticity of the sample) × gumminess (that describes being soft and sticky)). Before testing, samples were stored at −10°C for 24 hr .

| Sensory evaluation of frozen yoghurt
Evaluation of sensory properties of the produced frozen yoghurt was done, after maintenance at −18°C for 1 day. All samples were tempered for 5 min at 20 ± 2°C prior to sensory testing. In order to evaluate sensory attributes, 8 trained panelists were tested the samples. After initial training of the panelists to acquaint the desired properties, the samples were evaluated in term of texture, flavor, color, and total acceptability Mehrinejad Choobari et al., 2020). In this test, the 5-point hedonic scale (excellent sample = 5, good = 4, average = 3, bad = 2, and too bad = 1) was used.

| Statistical analysis
In order to evaluate obtained physical and chemical properties, results were analyzed based on a completely randomized design by using SPSS software (version 21). Average data were compared using the Duncan multiple range test at the 5% level, and graphs were plotted using Microsoft Excel (version 2013) and Curve Expert 1.3. All tests and experiments were performed in three replicates.

| pH and acidity
As shown in Table 1, no significant differences (p > .05) were observed on the pH and acidity of frozen yoghurt samples containing gums. Results showed that the pH ranged from 5.23 to 5.42 and the acidity ranged from 7.5 to 7.65 as a percentage of lactic acid. These observations are in agreement with the study of Rezaei et al. (2011) and Bahramparvar et al. (2009) which showed that the addition of stabilizers had no effect on pH and acidity of samples. As presented in Table 1, there are significant difference between produced yoghurt from camel and cow milk in terms of the pH and acidity which are in agreement with the results of Al-Saleh et al. (2011). That may be due to the differences in buffering capacities between the mixes made from cow's and camel milk. Generally, the total amount of protein in cow's milk is more than camel milk; therefore as a result, the buffering capacity of cow's milk can be higher than the camel milk.

| Overrun
The amount of overrun of frozen yoghurt samples was different from 20.13% to 54.47% (Table 1). The type of milk, type and concentration of gums had a significant effect on the amount of overrun (p < .05). Results showed that in all samples, the amount of overrun was reduced with increasing the stabilizers' concentration. Cow's frozen yoghurt containing 0.2% QSSG and control sample made from camel milk (without gum) had lowest and highest overrun values than the other samples, respectively. Also, QSSG is more effective in reducing the overrun than CSG in the same concentration (p < .05) for both frozen yoghurt produced from cow and camel milk.
One of the most important properties of the stabilizers is increasing ice cream volume through increasing the viscosity by keeping the air bubbles (Bahramparvar & Mazaheri Tehrani, 2011). But this trend was not observed in the present study.  and Bahramparvar et al. (2009)

| Melting properties
Besides overrun, the melting rate also is an important quality index for frozen dairy dessert. The amount of melting rate and first dripping time are presented in Table 1 in ice cream products is improving the melting properties. Stabilizers due to their water-holding and microviscosity enhancement ability increase the melting resistance of frozen yoghurt (Bahramparvar & Mazaheri Tehrani, 2011). In this case, other researchers reported that the addition of stabilizers not only increased ice cream mix viscosity, but also resulted in a lower melting rate and consequently improved the melting resistance (Milani & Koocheki, 2011;Moeenfard & Tehrani, 2008).
The melting rate of the frozen yoghurt made from camel milk was significantly higher than the produced frozen yoghurt from cow's milk with the same values (p < .05). These results also may be due to the fact that yoghurt made from camel milk had a fragile structure compared to the yoghurt made from cow's milk, which forms a weak network around of the air cells and lead to decrease meltdown resistance in these samples. Stabilizers can form a sticky network in yoghurt ice cream that results in more resistance to melting (El-Nagar et al., 2002). The same reasons that mentioned for melting rate is also true for the first dripping time of the frozen yoghurt. According to Milani and Koocheki (2011) and Rezaei et al. (2011), hydrocolloid stabilizers lead to an increase in the first dripping time.

| Viscosity
The apparent viscosity of frozen yoghurts mixtures made from both types of milk (cow and camel) is shown in Table 1. There were significant differences between all mixtures in term of viscosity (p < .05).
As can be seen, the apparent viscosity of frozen yoghurt mixtures was enhanced by increasing the gum concentration. Addition of QSSG and CSG lead to different apparent viscosity and samples containing QSSG had the higher apparent viscosity than samples containing CSG.
Several studies were conducted on the both types of gums previously. They found that the apparent viscosity of produced samples from QSSG was higher than CSG. These results may be related to the chemical structure and molecular weight of these gums (Karazhiyan et al., 2011;Koocheki et al., 2013;Razavi et al., 2011). Basically, whatever the size and molecular weight of hydrocolloid is high, the friction between the molecules and so the viscosity will be the greater . Similarly, Rezaei et al. (2011)  On the other hand, the cow's frozen yoghurt mixture had higher apparent viscosity (

| Flow behavior
The Figures 2a,b and 3a,b showed the data curve of the shear stress versus shear rate and apparent viscosity versus shear rate in camel and cow's frozen yoghurts containing QSSG and CSG, respectively.
The Herschel-Bulkley, Power Law, and Casson models adequately were fitted the data curve for all mixtures. Consistency coefficients (k) and flow behavior index (n) are also shown in Table 2 The flow properties of Lepidium perfoliatum gum, extracted from Qodume Shahri seeds and Lepidium sativum gum, extracted from cress seeds as a function of the concentrations were investigated by Koocheki et al. (2013) and Karazhiyan et al. (2011) respectively. They showed that, these extracts exhibited strong shear-thinning behavior and Qodume Shahri extract showed the sharper shear-thinning behavior compared to cress seed extract. Several studies have investigated the rheological properties of frozen dairy desserts by various stabilizers, which is in agreement with the results of this study (Cakmakci & Dagdemir, 2013;Karazhiyan et al., 2011;Koocheki et al., 2013).
Since, production of fermented products from camel milk is difficult because of the problem of milk coagulation, therefore frozen yoghurts made from camel milk in contrast to cow's milk has lower viscosity ( Figure 2). Camel milk has a similar protein content, lower lactose and fat content with saturated fatty acids and greater total cholesterol compared to cow's milk (Hashim et al., 2009). Thus, strong shear-thinning behavior in cow's frozen yoghurt than camel frozen yoghurt might be due to the interaction between gums and F I G U R E 2 (a) The effect of QSSG and CSG on the flow curve of camel frozen yoghurts. (b) The effect of QSSG and CSG on the flow curve of cow frozen yoghurts milk components in both milk types that are different from each other.

| Hardness
Hardness is another very important property that directly affects the frozen products final quality (degree of smoothness, intensity of coldness, appearance and overall acceptability). Table 3 presents the effect of QSSG and CSG on the hardness amount of frozen yoghurt made from cow's and camel milk. As can be seen, such as other factors cow's frozen yoghurt containing 0.2% QSSG and control frozen yoghurt made from camel milk (without gum) have the highest (124.6 ± 0.8) and lowest (46.5 ± 1.2) hardness, respectively.
Numerous studies have found that, increasing stabilizers concentration increase the hardness of the frozen yoghurt sample. Increasing the gum concentration led to increase apparent viscosity of the serum phase of the ice cream mixture, mostly due to the high waterholding capacity, which led to increase of the hardness of the final frozen yoghurt product (Azari-Anpar, Soltani Tehrani, et al., 2017).
Another factor has been found to influence hardness of the ice cream is the overrun (Goff & Hartel, 2013). The results of this study showed that the overrun of sample decreased by increase gum concentration. Goff and Hartel (2013) have found that increase overrun lead to decreases the hardness of the final ice cream. Similarly, Martinou-Voulasiki and Zerfiridis (1990) also reported that the addition of natural stabilizers increased the hardness of frozen yoghurt ice cream. As a result, the presence of a QSSG and CSG improved F I G U R E 3 (a) The effect of QSSG and CSG on the apparent viscosity of camel frozen yoghurt. (b) The effect of QSSG and CSG on the apparent viscosity of cow frozen yoghurt the hardness of frozen yoghurt with increasing apparent viscosity (Rezaei et al., 2015).

| Adhesiveness
Adhesiveness is defined as the amount of required work in order to overcome the attractive forces among the surface of the food product and the surface of the material with which it comes in contact (Bahramparvar et al., 2013). Except than the control sample in cow's frozen yoghurt and camel frozen yoghurt containing 2% CSG, gums have a significant effect on adhesiveness in other treatments  (Table 3). On the other hand, results showed that the adhesiveness of frozen yoghurt samples produced by QSSG was higher than produced sample from CSG (in the equal values in frozen yoghurt made with camel milk).

| Gumminess
Gumminess is defined as the required energy to disintegrate a semisolid product to make it ready for swallowing. Gumminess is unattractive parameter that affects the appearance and texture of dairy desserts such as ice cream and frozen yoghurt (Bahramparvar et al., 2013). Results showed that, the gumminess of samples, increased noticeably by the addition of gums to the frozen yoghurt formulation (Goff & Hartel, 2013). Similar results have also been TA B L E 2 Rheological parameters of the flow curves of the frozen yoghurt containing QSSG and CSG reported in the case of frozen yoghurt produced by xanthan gum and hydroxylpropyl methylcellulose (Soukoulis et al., 2010).
In addition, the effect of both gums on the increase of gumminess in cow's frozen yoghurt was higher than camel frozen yoghurt (with equal values). About this subject, Varelaet al. (2014) reported that correlation among gumminess and the viscosity of the samples containing guar gum leads to an increase in samples gumminess (Table 3). According to the obtained results from the gumminess, it could be concluded that it linked to the strong textural network of the produced frozen yoghurt samples from cow's milk compared to produce samples from camel milk.

| Chewiness
Chewiness is defined as the required energy to chew a solid food product until it is ready for swallowing. As can be seen from  Wittinger and Smith (1986) also reported that the presence of locust bean and guar gums interacted to enhance chewiness of the ice cream. Based on these results, excessive use of stabilizer leads to increasing gumminess, in which the product cannot melt quickly in the mouth and retains excessive chewiness (Goff & Hartel, 2013).

| Sensory evaluation
The results obtained from the data mean comparison of sensory attributes are illustrated in Table 4. Results showed that the addition of QSSG and CSG had a significant effect on the color, flavor, texture and total acceptance of the frozen yoghurt samples. Moeenfard and Tehrani (2008) and Rezaei et al. (2011) studied the relationship between the type and concentration of stabilizers with viscosity, body and texture, and total acceptance of the produced ice cream.
These researchers stated that the type and concentration of stabilizers were highly affected the viscosity, body and texture of frozen yoghurt mixtures. The results of other studies also showed that QSSG and CSG improved the rheological attributes of foods and provide the suitable texture and mouth feel for industrial application Behrouzian, Razavi, & Phillips, 2014;Koocheki et al., 2013). However, the increase of the QSSG and CSG gum concentration lead to increase in the sensory scores of color, texture and total acceptability but in lower concentration these differences were not significant.
As can be seen from

| CON CLUS IONS
The results showed that the addition of QSSG and CSG to yoghurts mixture improved the viscosity, first dripping times, complete melting times, textural, and sensory properties, but had no significant effect on the pH and acidity of the final product. Therefore, the gums obtained from Lepidium perfoliatum and Lepidium sativum seeds have the potential to be applied as a new source of polysaccharides for producing frozen yoghurts with improved properties. The cow's frozen yoghurt mixture had the higher apparent viscosity than the camel frozen yoghurt mixture at the equal concentration of gums.
This is an indication that frozen yoghurt mixes are non-Newtonian at all added concentrations. Along with increase in gum concentration,
Results showed that the addition of QSSG and CSG had a significant effect on the color, flavor, texture, and total acceptance of the frozen yoghurt samples and by the increase of the QSSG and CSG gum concentration, sensory scores of cow's frozen yoghurt samples were higher than camel frozen yoghurt samples.

CO N FLI C T O F I NTE R E S T
The authors declare that they do not have any conflict of interest.

E TH I C A L A PPROVA L
This study does not involve any human or animal testing.

I N FO R M E D CO N S E NT
Written informed consent was obtained from all study participants.

DATA AVA I L A B I L I T Y S TAT E M E N T
Research data are not shared.