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Article

The Impact of Date Syrup on the Physicochemical, Microbiological, and Sensory Properties, and Antioxidant Activity of Bio-Fermented Camel Milk

by
Magdy Ramadan Shahein
1,
El Sayed Hassan Atwaa
2,
Wael F. Elkot
3,
Hayfa Hussin Ali Hijazy
4,
Rami B. Kassab
5,6,
Mohamed A. Alblihed
7 and
Ehab Kotb Elmahallawy
8,*
1
Department of Food Science and Technology, Faculty of Agriculture, Tanta University, Tanta 31527, Egypt
2
Food Science Department, Faculty of Agriculture, Zagazig University, Zagazig 44511, Egypt
3
Dairy Science and Technology Department, Faculty of Agriculture & Natural Resources, Aswan University, Aswan 81528, Egypt
4
Department of Family Education, Faculty of Education, Umm Al-Qura University, Makka Al-Mukarama 21955, Saudi Arabia
5
Department of Zoology and Entomology, Faculty of Science, Helwan University, Cairo 11795, Egypt
6
Department of Biology, Faculty of Science and Arts, Al Baha University, Almakhwah, Al Baha 1988, Saudi Arabia
7
Department of Microbiology, College of Medicine, Taif University, P.O. Box 11099, Taif 21944, Saudi Arabia
8
Department of Zoonoses, Faculty of Veterinary Medicine, Sohag University, Sohag 82524, Egypt
*
Author to whom correspondence should be addressed.
Fermentation 2022, 8(5), 192; https://doi.org/10.3390/fermentation8050192
Submission received: 25 February 2022 / Revised: 3 April 2022 / Accepted: 19 April 2022 / Published: 22 April 2022
(This article belongs to the Special Issue Fermented and Functional Food)
Versions Notes

Abstract

:
Fermented camel milk is rich in nutrients and vitamins necessary for the health of humans and has therapeutic properties. Date palm camel milk has been reported to be beneficial for preventing and treating various diseases in Arab countries. This study targeted the production of probiotic fermented camel milk fortified with date syrup. In addition, the effect of adding date syrup as a prebiotic and flavoring agent to probiotic fermented camel milk on the physicochemical, phytochemical, microbiological, and sensory properties of probiotic fermented camel milk during storage was investigated. Probiotic fermented camel milk without adding date syrup served as a control, and the other two treatments were supplemented with date syrup at ratios of 6.0% and 8.0%. Probiotic fermented camel milk was analyzed after 1 day and 15 days from storage at 5 ± 1 °C. Interestingly, the present study revealed that the addition of date syrup significantly (p ≥ 0.05) increased total solids (TS), ash, Na, K, Fe, acetaldehyde, total phenolic contents, and titratable acidity, viscosity, and antioxidant values of resultant synbiotic fermented camel milk, and this increase was proportional to the level of date syrup fortification. In addition, non-significant changes in these components were observed during the storage period. However, total protein and fat content did not show significant changes. Furthermore, the addition of date syrup significantly increased (p ≥ 0.05) the total bacterial and Bifidobacteria counts, and this increase was associated with the level of the addition of date syrup. The addition of date syrup also significantly (p ≥ 0.05) improved the sensory scores for flavor, consistency, appearance, and total scores of resultant products. Moreover, the addition of date syrup at a level of 8% showed the highest sensory scores. In conclusion, probiotic fermented camel milk could be produced using a probiotic strain and flavored with date syrup at a level of 8%.

1. Introduction

Camels play a major role in supplying desert dwellers with milk of high nutritional quality under extremely hostile conditions of temperature, drought, and lack of pasture. In addition, camel milk is characterized by its higher content of vitamin C and potassium salts compared to other mammals’ milk [1]. Most camel milk is traditionally consumed fresh as raw milk or when soured. However, camel milk has been recently gaining more popularity and several commercial farms are being established to supply fresh pasteurized camel milk to consumers in the Middle East and the Arab territory [2,3]. Camel milk contains reasonable amounts of lysozyme, lactoferrin, lactoperoxidase, immunoglobulin G, and immunoglobulin A [4,5]. Camel milk has more free amino acids and peptides than bovine milk [6]. Moreover, non-protein-bound amino acids in camel milk are easily digested by microorganisms, and therefore, camel milk has a higher metabolic activity when used in a starter culture preparation [7]. The importance of free amino acids and peptides for the growth of bifidobacteria has been studied by Wada et al., 2020 [8]. In addition, camel milk could be used to produce fermented milk because of the high amount of peptides, which might be easily attacked by Bifidobacterium species containing peptidase enzymes [9].
Recent interest has focused on using probiotic bacteria (Lactobacillus acidophilus and bifidobacteria) as dietary adjuncts. Therefore, these organisms are normal inhabitants of the intestine [10,11,12]. The same interest has been shown in active foods and their supplementation with functional ingredients [13,14,15,16]. Probiotic products have become increasingly popular, and the consumption of such products has increased dramatically throughout the world. The introduction of probiotic action to various dairy products has been the point of many studies, such as with fermented milk [17,18], yogurt [18,19], cheese [20,21], cream [22], ice cream [23], and dried dairy products [24]. Camel milk is characterized by a saltier taste compared to cow’s milk due to its higher content of both Na and K salts. Therefore, it is of great interest to produce flavored camel milk products that mask salty taste [9].
Date syrup is an important food source of sugars, minerals, vitamins, and antioxidants [25]. Research has proven dates to have a low glycemic index when eaten alone or in mixed meals with plain yogurt [26]. Date fruit has anti-tumor activity [27], antioxidant, anticancer, and anti-mutagenic properties [28]. Aqueous date extract has been shown to significantly inhibit lipid peroxidation and protein oxidation in a dose-dependent manner [29]. Furthermore, date palm may be considered an almost ideal food, providing a wide range of essential nutrients and potential health benefits [30]. Date syrup (dibs) has been utilized to manufacture some dairy products. Gad et al. [31] used date syrup to manufacture date juice fermented milk of good nutrition quality. Tammam et al., 2013 [32] also used date syrup as a sweetening and flavoring agent in yogurt making. Abdel-Ghany and Zaki (2018) [33] manufactured date juice yogurt with a long shelf life from date syrup and low fat milk. Given the above information, the present study has been planned to produce functional probiotic fermented camel milk using date syrup (dibs) as a sweetening and flavoring agent to improve the health and nutritional quality of the resultant product.

2. Materials and Methods

2.1. Materials

Fresh camel milk was obtained from a private farm in El-Arish, North Sinai Governorate. Milk was collected early in the morning from a healthy herd of camels. Date syrup was obtained from a local market in El-Arish, North Sinai Governorate, Egypt. Starter cultures containing Bifidobacterium bifidum B-12 as a probiotic strain and Streptococcus salivaris ssp. thermophillus and Lactobacillus bulgaricus as yogurt starters were used in this study, these strains were obtained from Hansen’s Laboratories Copenhagen/Denmark.

2.2. Experimental Procedure

2.2.1. Preparation of Probiotic Fermented Camel Milk

Probiotic fermented camel milk was manufactured according to the method reported by Tamime and Robinson, 1999 [34]. The samples prepared were as follows:
  • Whole camel milk as a control (C).
  • Whole camel milk fortified with 6.0% date syrup (S1).
  • Whole camel milk fortified with 8.0% date syrup (S2).
All samples—control camel milk and camel milk with date syrup samples—were pasteurized in a water bath, at 72 °C for 15 s, then cooled to 40 °C. At this temperature, each sample was inoculated with 2% yogurt culture + 5% probiotic culture of B. bifidum, and then incubated at 37 °C until complete coagulation (around 12 h). The curd obtained was refrigerated overnight at 5 ± 1 °C in a refrigerator (Toshiba Model GR-EF37), then stirred with an electric mixer (Moulinex LM2411EG Blender—400 W, 1.25 L, Grinder, Stick), filled in 100 g plastic bottles, and stored at 5 ± 1 °C, for 15 days.

2.2.2. Examination of Physicochemical Properties

Samples of fermented camel milk of both control (yogurt from camel milk) and synbiotic product (yogurt from camel milk with date syrup addition) were analyzed for total solids, fat, total protein, ash content, and acidity values according to the standard methods [35]. Total solids of camel milk, date syrup, and fermented camel milk samples were determined in a drying oven for 24 h at 100 °C. The percentage of moisture content was calculated by the following formula.
% moisture = W1 − (W2 × 100)/W1
where, W1 = initial weight of sample; W2 = weight of the dried sample
Total solids % = 100 − moisture content.
For fat content of camel milk and fermented camel milk samples, the Gerber method was applied, whereas for date syrup, the Soxhelt apparatus method was used. The total nitrogen content (TN) was determined using the micro-Kjeldahl method, and protein content was calculated by multiplying the percentage of TN by 6.38 for milk components and 6.25 for date syrup. To determine ash content, a 5 g sample was heated in a muffle furnace at 550 °C overnight. The titratable acidity was determined by mixing 10 g of fermented milk with 10 mL of distilled water and titrating with 0.1 N NaOH using phenolphthalein as an indicator to an end point of faint pink color, then the values were expressed as a percentage of lactic acid. The changes in pH in the samples were measured using a laboratory pH meter with glass electrode (HANNA, Instrument, Portugal). Acetaldehyde was determined by Less and Jago, 1969 [36]. After the reaction of acetaldehyde with a semi-carbazide solution, 5 g of the well-mixed sample was pipetted into the outer compartment, the cell was covered, and then incubated at 30 °C for 90 min, then the solution was transferred into a cuvette to measure the absorbance at 224 nm. The concentration of acetaldehyde was calculated from the standard curve of the acetaldehyde solution, which ranged from 1 to 30 µmol/100 mL. Viscosity was determined by the method of Aryana, 2003 [37] using Rotational Viscometer Type Lab. Line Model 5437. Measurements were determined at a temperature of 30 °C after 15 s and the results were expressed as centipoise (cP).

2.2.3. Determination of Mineral Content

The content of minerals of fermented camel milk for both the control (yogurt from camel milk) and yogurt from camel milk with the date syrup addition were determined according to protocol described by Horwitz (2010) [38]. Samples were kept in oven at a temperature of 450 °C for 6 h, then cooled and dissolved in concentrated HNO3 for analysis, then diluted two times. The flame atomic absorption with variant spectrophotometer (JENWAY PFP7) was used to determine the macro-elements, Na and K, and micro-elements, Fe. Atomic absorption (UNICAM 929 AA Spectrometer) using hollow cathode lamp differs according to each measured element.

2.2.4. Determination of Total Phenolic Compounds (TPC)

Camel milk yogurt samples were centrifuged at 20,000× g for 60 min at 4 °C. The supernatants were filtered using a 0.45 µm syringes filter and kept at -20 °C until further testing. The total phenolic compounds (TPC) were determined by the Folin–Ciocalteu method [39]. Briefly, 100 μL of each concentration for the test samples was mixed with 1 mL of diluted FC reagent (1:10). After 10 min of formation of this mixture, 1 mL of 7.5% (w/v) sodium carbonate solution was added to the mixture and incubated in the dark for 90 min. The absorbance was recorded at 725 nm. The TPC was calculated from the calibration curve of gallic acid Y = 0.2808 X + 0.0301; R2 = 0.9983. The results were expressed as gallic acid equivalents in mg/g of extract.

2.2.5. Determination of Total Flavonoids

Total flavonoid content was determined by using the aluminum chloride calorimetric method, as described in previous study [40]. Briefly, 100 μL of different concentrations of each tested sample was dissolved in 80% methanol. The dissolved sample solution (0.5 mL) was then mixed with 95% methanol (1.5 mL), 10% aluminum chloride (0.1 mL), 1 M potassium acetate (0.1 mL), and deionized water (2.8 mL). After 30 min, the absorbance was measured 30 min later using spectrophotometry (Beckman DU 640B, Nyon, Vaud, Switzerland) at 415 nm. The results were expressed as catechin equivalents (CE) in mg/g of extract.

2.2.6. Determination of Antioxidant Activity

The antioxidant activity of free and bound phenolic extracts was measured by using DPPH scavenging as previously described by Van Hung and Morita (2008) [41]. The extracted solution (0.1 mL) was mixed with 3.9 mL of 0.075 mM DPPH. The mixture was left in the dark at room temperature for exactly 30 min. The absorbance was then measured using a spectrophotometer (6405 UV/VIS–Jenway, England) at 525 nm. The blank was made by replacing the extracted solution by methanol (0.1 mL) and then measured at T = 0. The DPPH scavenging was calculated according to the following equation:
% DPPH scavenging = [Abs (T0) − Abs (T30) × 100]/Abs (T0)
where: Abs. (T = 0) is the absorbance of DPPH radical and methanol at T = 0 and Abs. (T = 30) is the absorbance of DPPH radical and extracts at T = 30.

2.2.7. Determination of Vitamin C

Vitamin C content in camel milk of both the control (yogurt from camel milk) and yogurt from camel milk with the date syrup was determined as described by Htay et al., 2020 [42], which is based on the oxidation of ascorbic acid after its extraction from the product to dehydroascorbic acid by oxalic acid in an acidic medium and titration using a dye 2,6-dichlorophenolindophenol.

2.2.8. Microbiological Examinations

Each sample (1.0 mL) was added to 9.0 mL of 0.85% sterile saline (sodium chloride) and further dilutions were carried out according to requirements. The standard pour plate method was employed to determine the counts of microorganisms. Samples of probiotic and synbiotic fermented camel milk were examined for total bacterial counts according to the protocol previously described [43]. Plate counts of B. bifidum were performed in Bifidobacterium agar under anaerobic incubation at 37 °C for 72 h. The enumeration of the microbial counts was performed on plates containing 30–300 colonies, and the results were recorded as log number of colony-forming units per mL (Log cfu/mL).

2.2.9. Sensory Evaluation

All fermented camel milk treatments (all yogurt samples without data syrup (control) and with data syrup) were organoleptically examined after refrigerated storage for 1 day and 15 days according to Tamime and Robinson, 1999 [34]. Samples were scored for flavor out of 50 point consistency out of 30 points and appearance out of 20 points. The sensory evaluation was performed by a team of 10 trained panelists, aged (25–30 years). The samples were packed and coded with a 3-digit code. The encoded samples were then presented in a tray to the panelists. After each sample testing, the panelists were offered plain water to clean their palate before moving on to the next sample.

2.2.10. Statistical Analysis

All data were subjected to one-way analysis of variance (ANOVA) software [44]. Significant treatment means were separated by Duncan’s new multiple range tests. Differences were considered significant at (p ≤ 0.05).

3. Results and Discussion

3.1. Chemical Composition, Mineral Content, and Phytochemical Properties of Fresh Camel Milk and Date Syrup

The present work reveals baseline information about the impact of the addition of different concentrations (6% and 8%) of date syrup on the physicochemical, microbiological, and sensory properties, and antioxidant activity of fermented camel milk. A review of the available literature finds most previous studies using date syrup in the manufacture of yogurt at rates between 5% and 15% [45,46,47]. In the present work, as shown in Table 1, date syrup (dibs) has relatively lower protein (1.76%) and fat content (0.96%) compared to camel milk (3.26% and 3.18%, respectively), while a higher total solids content (80.42%) was observed in date syrup than in camel milk (11.42%). The date syrup is characterized by the unique presence of fibers and much higher levels of Na, K, and Fe than camel milk, i.e., 78.62, 272.36, and 4.78 mg/100 g for date syrup compared to 62.5, 152.40, and 0.34 mg/100 g for camel milk, respectively. Additionally, the date syrup is characterized as containing much higher levels of vitamin C (mg·L−1), total phenolic (mg GAE/100 g), total flavonoids (TF) mg/100 g, and antioxidant activity (AO)% than camel milk, i.e., 66.48 mg·L−1, 472.14 mg/100 g, 16.52 mg/100 g, and 72.84% for date syrup compared to 32.96 mg·L−1, 6.34 mg/100 g, 0.42 mg/100 g, and 5.24% for camel milk, respectively. These results are in line with those reported by Atwaa et al. (2020) [5] who found that total solids, protein, fat, ash, and fiber content of camel milk were 12.58, 3.18, 4.12, 0.82, and 0.0%, respectively. Furthermore, Farahnaky et al. (2018) [48] found that moisture, protein, and ash content of date syrup were 24.07, 1.43, and 2.18%, respectively.
Aludatt et al., 2010 [49] reported that Na, K, and Fe content of camel milk ranged from 217.9–488, 1106–19, 895 and 0.42–3.46 mg/100 g, respectively, while, Ganbi (2012) [30] found that the potassium, sodium, and iron content of date syrup were 771, 14.4, and 4.36 mg/100 g, respectively.
Ahmed et al., 2018 [50] found that the vitamin C and antioxidant activity of camel milk were 8.4 ± 0.44 mg/dl and 3.6 ± 0.14 mmol/l, respectively, while Farahnaky et al., 2018 [48] found that total phenolic, total flavonoids, and antioxidant activity of date syrup were 453.04 mg/100 g, 11.93 mg/100 g, and 68.20%, respectively. Additionally, Ganbi [30] found that total phenolic, total flavonoid, and antioxidant activity for the date dibs of the extract of water were 66.03 mg/100 g, 13.85 mg/100 g, and 61.49%, respectively.

3.2. Influence of Date Syrup Addition on the Chemical Composition of Camel Milk Yogurt

It is noteworthy that various factors are responsible for a wide variation in milk compositions, including healthy status of the animal, stage of lactation, genetic factors, and environmental factors. The various fermented products are some of the typical milk products with different chemical compositions [51]. In the present work, as shown in Table 2, camel milk contained 11.42%, 3.26%, 3.18%, and 0.72% total solids, protein, fat, and ash, respectively. Meanwhile, the date syrup contained 80.42%, 1.67%, 0.98%, and2.08% total solids, protein, fat, and ash, respectively. It is clearly evident that the addition of date syrup, in small percentages, to camel milk leads to an obvious increase in the proportions of some components of the resulting fermented milk. The addition of date syrup significantly (p ≥ 0.05) increased TS, and ash contents of the resultant synbiotic product. This increase was associated with the level of addition of date syrup. However, fat and protein content did not show significant changes. Moreover, insignificant changes in these components were observed during storage period. The increase in TS and ash of fermented camel milk following the addition of date syrup is likely due to the high ash and total solids content of date syrup (Table 1) [48]. These results are in agreement with those reported by Gad et al., 2010 [31], who reported that the addition of date syrup to skim milk increased TS, protein, and ash contents of the resultant fermented milk. Furthermore, Abdel-Ghany and Zaki 2018 [33] reported similar results for their study on a production of functional yogurt fortified with date syrup. Tammam et al., 2013 [32] also reported similar results due to the addition of date syrup to stirred yogurt.

3.3. Influence of Date Syrup Addition on the pH, Acidity, Viscosity Values, and Acetaldehyde Content of Camel Milk Yogurt

The impact of the date syrup addition on the pH, acidity, viscosity values, and acetaldehyde content of camel milk yogurt is shown in Table 3. Data indicated that the addition of date syrup to camel milk showed a significant (p ≥ 0.05) increase in total acidity, viscosity, and acetaldehyde content of resultant synbiotic products. This was associated with a significant (p ≥ 0.05) decrease in pH values. In addition, this effect was associated with the level of added dibs. On the first day, the titratable acidity (TA) values for control fermented camel milk (C), fermented camel milk fortified with 6% date syrup (S1), and fermented camel milk fortified with 8% date syrup (S2) were 0.78, 0.84, and 0.87, respectively, However, these values experienced a significant increase (p ≥ 0.05) after 15 days of storage period and reached 0.91, 0.97, and 1.14, for the control fermented camel milk (C), fermented camel milk fortified with 6% date syrup (S1), and fermented camel milk fortified with 8% date syrup (S2), respectively. Clearly, these values show that the TA of date syrup fermented camel milk increased compared to the control fermented camel milk as the storage period progressed. The possible explanation is that the activity of the yogurt starter culture, which converted lactose into lactic acid as well as the fact that date syrup contains simple sugars (glucose and fructose) and also some nutrients, may stimulate the bacterial activity [52,53]. In addition, date syrup may contain some oligosaccharides which increase the viscosity of the resultant products. The pH values of all fermented camel milk treatments significantly decreased (p ≥ 0.05) during the 15 days of storage and the acidity significantly (p ≥ 0.05) increased with the advance of storage period. This difference might be attributed to the effect of camel milk on the growth of microorganisms and subsequently on pH values. The pH reduction during storage could be because of the starter culture variety, lactic acid conversion into lactose, storage duration, and temperature of fermentation [54]. Moreover, the addition of date syrup to camel milk showed a significant (p ≥ 0.05) increase in viscosity of resultant synbiotic products and this effect was associated with the level of added dibs. It seems that date syrup increased the fiber content of fermented camel milk, which changes its structure and improves the viscosity by binding to water molecules [55]. Acetaldehyde is considered a flavor compound of fermented milk [56]. It is evident from Table 3 that, the addition of date syrup to fermented camel milk increased these compounds. On the other hand, a significant (p ≥ 0.05) decrease in acetaldehyde values were reported during the storage period, which might be attributed to the ability of lactic organisms to hydrolyze acetaldehyde and diacetyl into acetone [57]. These results are in agreement with those reported by Aljasass et al., 2010 [58] and Abdel-Ghany and Zaki 2018 [33], who reported that the addition of date syrup significantly increased the acidity and viscosity of yogurt and probiotic dairy food.

3.4. Influence of Date Syrup Addition on the Mineral Content of Camel Milk Yogurt

Milk contains inorganic and organic salts. All the minerals are distributed between a soluble and a colloidal phase and their interaction with milk proteins has important consequences for the stability of milk and milk products [51]. Results presented in Table 4 show the average content of Na, K, and Fe of camel milk were 62.50, 152.40 and 0.34 mg/100 g, respectively, while the Na, K, and Fe content of date syrup was 78.62, 272.36, and 4.78 mg/100 g respectively. As shown in Table 4, the addition of date syrup to camel milk significantly (p ≥ 0.05) increased Na, K, and Fe content of the resultant synbiotic products. These results could be due to the higher levels of these salts in date syrup (dibs), according to Al-Rwaily et al., 2005 [53] and Ganbi 2012 [30]. With the advance of storage period, values of Na, K, and Fe content of probiotic fermented camel milk of all samples were significantly increased. These results are in agreement with Gad et al., 2010 [31] and Abdel-Ghany and Zaki 2018 [33], who reported that the addition of date syrup significantly increased Na, K, and Fe content of the resultant yogurt.

3.5. Influence of Date Syrup Addition on the Phytochemical Properties of Camel Milk Yogurt

Polyphenols are phytochemicals from plants and are being used for the prevention of various diseases. The higher polyphenol content exhibits stronger inhibition of free radicals and high antioxidant activity [59]. Taken into consideration is the antioxidant activity which is dependent on the purity of active compounds, the test system, and substrate to be protected by the antioxidant [60]. Results presented in Table 5 show vitamin C, total phenolic, and antioxidant activity of probiotic fermented camel milk treatments. As shown, the vitamin C, total phenolic, total flavonoid, and antioxidant activity of camel milk were 32.96 mg·L−1, 6.34 mg/100 g, 0.42 mg/100 g, and 5.24%, respectively, while vitamin C, total phenolic content, total flavonoid, and antioxidant activity of date syrup were 66.48 mg·L−1, 472.14 mg/100 g, 96.52 mg/100 g, and 72.84%, respectively. The addition of date syrup to camel milk significantly (p ≥ 0.05) increased vitamin C, total phenolic, and antioxidant activity of resultant synbiotic products. These results could be due to the higher levels of total phenolic and vitamin C content in date syrup, according to Farahnaky et al., 2018 [48]. With the advance in storage period, values of vitamin C, total phenolic, and antioxidant activity of probiotic fermented camel milk of all treatments were significantly decreased. Similar results were reported by Alhamdan et al., 2021 [45], who reported that the addition of date syrup significantly increased total phenolic and antioxidant activity of fermented milk drink. Gad et al., 2010 [31] observed that the addition of date syrup to functional yogurt significantly increase vitamin C content.

3.6. Influence of Date Syrup Addition on the Total Bacterial and Bifidobacteria Counts of Camel Milk Yogurt

Investigation of the total bacterial and bifidobacteria counts of probiotic fermented camel milk is critical for the assessment of the microbiological quality of the resulting product. Data presented in Table 6 shows the average total bacterial and bifidobacteria counts in probiotic fermented camel milk treatments. The results indicated that the addition of date syrup significantly increased (p ≥ 0.05) the total bacterial and bifidobacteria counts. The increase was associated with the level of addition of date syrup. These results could be due to the presence of some components in date syrup which may stimulate the bacterial growth, especially oligosaccharides, as prebiotic [61], which in turn enhances the viability and survival of bifidobacteria in the resultant probiotic fermented camel milk. Furthermore, date syrup contains simple sugars which stimulate the growth and activity of bacteria. These results are in agreement with those reported by Aljasass et al., 2010 [58]. The present results also indicated that total bacterial and bifidobacteria counts of all treatments gradually decreased with the advance of storage period.

3.7. Influence of Date Syrup Addition on the Sensory Evaluation of Camel Milk Yogurt

To the best of the authors’ knowledge, the sensory quality of the incorporated product is considered the final measurement of its success. The sensory analysis takes into consideration a range of powerful and sensitive tools included to measure human and other product responses. The optimal testing, circumstances, and data analysis lead to powerful and repeatable results. The sensory tests apply to a particular product that illustrates consumer visions and interpretation of volatile compound analyses for flavor perception [62]. Results presented in Table 7 show the average scores for sensory evaluation of probiotic fermented camel milk treatments. Data indicated that the addition of date syrup significantly (p ≤ 0.05) improved the sensory scores for flavor, consistency, appearance, and total scores of resultant synbiotic products. Moreover, the addition of date syrup at a level of 8% showed the highest sensory scores. These results could be explained on the basis that the addition of date syrup masked the salty flavor of camel milk. These results are in agreement with those reported by Gad et al., 2010 [31] and Abdel-Ghany and Zaki 2018 [33], who stated that the addition of date syrup or dried date extracts improved the flavor of fermented milk.

4. Conclusions

The present study revealed the utilization of camel milk and date syrups to produce a natural, sweet, healthy, synbiotic, and high nutritional value fermented camel milk. The work also involved assessment of the nutritional, microbial, and organoleptic quality attributes of the developed fermented camel milk during cold storage for 15 days. The study found that the addition of 8.0% date syrup to fermented camel milk improved the nutritional quality, as it increased the levels of total solids, ash, and potassium of the developed product. Furthermore, incorporation of date syrup fermented camel milk controlled the microbial quality of the product and improved the sensory quality of the developed product. Overall, this innovative new flavored fermented camel milk can be of high nutritional and health value and could attract consumers, as it did not contain refined sweeteners, artificial additives, and preservatives. Further future research is suggested to highlight the potential effects of the addition of date syrup on fermented camel milk with prebiotic activities due to the presence of oligosaccharide and polyphenols, among others.

Author Contributions

M.R.S., E.S.H.A. and W.F.E. were involved in the conception of the research idea and methodology design, supervision, data analysis, and interpretation; H.H.A.H., R.B.K., M.A.A. and E.K.E. were involved in the methodology, and drafted and prepared the manuscript for publication and revision. All authors read and approved the final manuscript. The funders had no role in data collection and analysis, decision to publish, or preparation of the manuscript. All authors have read and agreed to the published version of the manuscript.

Funding

Thanks and appreciation to the Saudi Ministry of Environment, Water, and Agriculture, facilitated by General Administration of Animal Productions for enabling research and using its facilities.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The data that support the findings of this study are available on request from the corresponding author.

Acknowledgments

The authors thank the Taif University Researchers supporting project number (TURSP-2020/93), Taif University, Taif, Saudi Arabia, for support.

Conflicts of Interest

The authors declare no conflict of interest.

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Table
Table 1. Chemical composition, minerals content, and phytochemical properties of fresh camel milk and date syrup.
Table 1. Chemical composition, minerals content, and phytochemical properties of fresh camel milk and date syrup.
Components (%)Camel MilkDate Syrup (Dibs)
Total Solids11.42 ± 0.4880.42 ± 4.36
Protein3.26 ± 0.121.76 ± 0.18
Fat3.18 ± 0.140.98 ± 0.04
Ash0.72 ± 0.022.08 ± 0.06
Fiber-2.44 ± 0.32
Minerals (mg/100 gm)
Na62.50 ± 3.8478.62 ± 4.08
K152.40 ± 9.12272.36 ± 14.26
Fe0.34 ± 0.034.78 ± 0.84
Phytochemical properties
Vitamin C (mg·L−1)32.96 ± 2.1466.48 ± 2.65
Total phenolic (TP) mg/100 g6.34 ± 0.84472.14 ± 9.12
Total Flavonoids (TF) mg/100 g0.42 ± 0.0216.52 ± 5.64
Antioxidant activity (AO)%5.24 ± 1.0472.84 ± 3.06
Table
Table 2. Influence of the addition of date syrup on the chemical composition of fresh camel milk, date syrups, and fermented camel milk of both the control (yogurt from camel milk) and yogurt from camel milk with the date syrup during the cooled storage period.
Table 2. Influence of the addition of date syrup on the chemical composition of fresh camel milk, date syrups, and fermented camel milk of both the control (yogurt from camel milk) and yogurt from camel milk with the date syrup during the cooled storage period.
Storage Period (Days)Fresh Camel Milk and Date SyrupFermented Camel Milk Samples
Camel MilkDate Syrup (Dibs)Control
(0.0% Date Syrup)		Fermented Camel Milk
(6% Date Syrup)		Fermented Camel Milk
(8% Date Syrup)
Total Solids %
111.42 ± 0.48 c80.42 ± 4.36 a11.67 ± 2.52 c16.52 ± 1.00 bc17.73 ± 1.01 b
15--11.85 ± 3.26 c16.72 ± 2.23 b17.92 ± 1.57 a
Fat (%)
13.18 ± 0.14 ab0.98 ± 0.04 b3.32 ± 0.24 a3.31 ± 0.10 a3.30 ± 0.24 a
15--3.41 ± 0.35 a3.35 ± 0.22 a3.36 ± 0.184 a
Protein (%)
13.26 ± 0.12 a1.76 ± 0.18 b3.26 ± 0.31 a3.31 ± 0.10 a3.38 ± 0.35 a
15--3.18 ± 0.14 b3.35 ± 0.22 a3.31 ± 0.06 a
Ash (%)
10.72 ± 0.02 c2.08 ± 0.06 a0.74 ± 0.05 c0.88 ± 0.10 b0.91 ± 0.05 b
15--0.80 ± 0.06 b0.95 ± 0.11 a0.98 ± 0.04 a
a,b,c Means followed by different letters in the same row are significantly different (p ≥ 0.05).
Table
Table 3. Influence of the addition of date syrup on the pH, acidity, viscosity values, and acetaldehyde content of camel milk yogurt during cooled storage period.
Table 3. Influence of the addition of date syrup on the pH, acidity, viscosity values, and acetaldehyde content of camel milk yogurt during cooled storage period.
Control
(0.0% Date Syrup)		Fermented Camel Milk
(6% Date Syrup)		Fermented Camel Milk
(8% Date Syrup)
pH
14.80 ± 0.05 a4.53 ± 0.03 b4.41 ± 0.02 c
154.38 ± 0.08 a4.22 ± 0.02 b4.20 ± 0.01 c
Acidity (as lactic acid %)
10.78 ± 0.03 c0.84 ± 0.05 b0.87 ± 0.020 a
150.91 ± 0.02 c0.97 ± 0.01 b1.14 ± 0.03 a
Acetaldehyde (µg/100 g)
124 ± 1.27 c36 ± 1.25 b42 ± 1.80 a
1522 ± 1.38 c30 ± 1.95 a34 ± 1.0 b
Viscosity (as cp)
130 ± 4.84 d57 ± 3.74 b61 ± 2.00 a
1541 ± 2.58 c67 ± 2.08 b74 ± 1.70 a
a,b,c,d Means followed by different letters in the same row are significantly different (p ≥ 0.05).
Table
Table 4. Na, K, and Fe content of the camel milk (control) and fermented camel milk with date syrup during the cooled storage period.
Table 4. Na, K, and Fe content of the camel milk (control) and fermented camel milk with date syrup during the cooled storage period.
Storage Period (Days)Fresh Camel Milk and Date SyrupFermented Camel Milk Samples
Camel MilkDate Syrup (Dibs)Control
(0.0% Date Syrup)		Fermented Camel Milk
(6% Date Syrup)		Fermented Camel Milk
(8% Date Syrup)
Na (mg/100 gm)
162.50 ± 3.84 e78.62 ± 4.08 c69.6 ± 1.64 d86.8 ± 1.09 b95.2 ± 1.26 a
15--77.4 ± 1.59 c114.2 ± 1.08 b122.6 ± 2.76 a
K (mg/100 gm)
1152.40 ± 9.12 e272.36 ± 14.26 a198.3 ± 2.00 d224.7 ± 2.00 c238.7 ± 1.64 b
15--217.2 ± 2.39 c227.5 ± 3.02 b249.3 ± 3. 36 a
Fe (mg/100 gm)
10.34 ± 0.03 e4.78 ± 0.84 a0.486 ± 0.07 d0.795 ± 0.09 c1.135 ± 0.15 b
15--0.528 ± 0.13 c0.953 ± 0.05 b1.777 ± 0.23 a
a,b,c,d,e Means followed by different letters in the same row are significantly different (p ≥ 0.05).
Table
Table 5. Influence of the addition of date syrup on the phytochemical properties of camel milk yogurt during the cooled storage period.
Table 5. Influence of the addition of date syrup on the phytochemical properties of camel milk yogurt during the cooled storage period.
Storage Period (Days)Fresh Camel Milk and Date SyrupFermented Camel Milk Samples
Camel MilkDate Syrup (Dibs)Control
(0.0% Date Syrup)		Fermented Camel Milk
(6% Date Syrup)		Fermented Camel Milk
(8% Date Syrup)
Total phenolic (TP) mg/100 g
16.34 ± 0.84 e472.14 ± 9.12 a1.68 ± 0.12 d22.40 ± 1.98 c40.28 ± 1.86 b
15--0.94 ± 0.11 c17.32 ± 1.74 b36.56 ± 2.16 a
Total Flavonoids (TF) mg/100 g
0.42 ± 0.02 e16.52 ± 5.64 a0.54 ± 0.02 d3.42 ± 0.94 c4.86 ± 0.90 b
--0.42 ± 0.03 c2.58 ± 0.74 b4.02 ± 0.88 a
Antioxidant activity (AO) %
15.24 ± 1.04 e72.84 ± 3.06 a6.33 ± 1.0 d24.70 ± 2.18 c29.84 ± 1.94 b
15--4.42 ± 0.13 c20.55 ± 1.89 b25.38 ± 1.76 a
Vitamin C (mg/1000 gm)
032.96 ± 2.14 e66.48 ± 2.65 a21.53 ± 0.08 d24.12 ± 0.28 c25.05 ± 0.09 b
15--20.07 ± 0.03 c23.18 ± 0.12 b24.20 ± 0.13 a
a,b,c,d,e Means followed by different letters in the same row are significantly different (p ≥ 0.05).
Table
Table 6. Influence of date syrup addition on the total bacterial and bifidobacteria counts of camel milk yogurt during the cooled storage period.
Table 6. Influence of date syrup addition on the total bacterial and bifidobacteria counts of camel milk yogurt during the cooled storage period.
Storage
Period (Days)		Control
(0.0% Date Syrup)		Fermented Camel Milk
(6% Date Syrup)		Fermented Camel Milk
(8% Date Syrup)
Total bacterial counts (Log10 cfu/mL)
17.982 ± 0.39 b8.461 ± 0.60 a8.476 ± 0.60 a
157.389 ± 0.57 b7.687 ± 0.36 a7.653 ± 0.22 a
Bifidobacteria counts (Log10 cfu/mL)
17.789 ± 0.45 b8.459 ± 0.06 a8.598 ± 0.11 a
156.554 ± 0.72 c8.129 ± 0.17 a7.581 ± 0.76 b
a,b,c Means followed by different letters in the same row are significantly different (p ≥ 0.05).
Table
Table 7. Influence of date syrup addition on the sensory evaluation of camel milk yogurt during cooled storage period.
Table 7. Influence of date syrup addition on the sensory evaluation of camel milk yogurt during cooled storage period.
Control
(0.0% Date Syrup)		Fermented Camel Milk
(6% Date Syrup)		Fermented Camel Milk
(8% Date Syrup)
Flavor (50)125.43 ± 4.0 c40.14 ± 2.51 b45.43 ± 3.51 a
1525.15 ± 2.33 c37.35 ± 2.28 b42.25 ± 2.35 a
Consistency (30)123.57 ± 2.36 c25.28 ± 1.72 b26.14 ± 1.05 a
1520.63 ± 3.28 c24.27 ± 1.57 b27.74 ± 2.40 a
Appearance (20)115.57 ± 1.25 c18.24 ± 1.06 b19.35 ± 1.50 a
1514.13 ± 1.23 c16.35 ± 1.06 b17.28 ± 1.21 a
Total (100)164.57 ± 2.42 c84.66 ± 2.06 b90.92 ± 2.78 a
1559.91 ± 3.65 c77.97 ± 6.09 b87.272 ± 3.72 a
a,b,c Means followed by different letters in the same row are significantly different (p ≥ 0.05).
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Shahein, M.R.; Atwaa, E.S.H.; Elkot, W.F.; Hijazy, H.H.A.; Kassab, R.B.; Alblihed, M.A.; Elmahallawy, E.K. The Impact of Date Syrup on the Physicochemical, Microbiological, and Sensory Properties, and Antioxidant Activity of Bio-Fermented Camel Milk. Fermentation 2022, 8, 192. https://doi.org/10.3390/fermentation8050192

AMA Style

Shahein MR, Atwaa ESH, Elkot WF, Hijazy HHA, Kassab RB, Alblihed MA, Elmahallawy EK. The Impact of Date Syrup on the Physicochemical, Microbiological, and Sensory Properties, and Antioxidant Activity of Bio-Fermented Camel Milk. Fermentation. 2022; 8(5):192. https://doi.org/10.3390/fermentation8050192

Chicago/Turabian Style

Shahein, Magdy Ramadan, El Sayed Hassan Atwaa, Wael F. Elkot, Hayfa Hussin Ali Hijazy, Rami B. Kassab, Mohamed A. Alblihed, and Ehab Kotb Elmahallawy. 2022. "The Impact of Date Syrup on the Physicochemical, Microbiological, and Sensory Properties, and Antioxidant Activity of Bio-Fermented Camel Milk" Fermentation 8, no. 5: 192. https://doi.org/10.3390/fermentation8050192

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