Table 1 compares the chemical composition of CM and BM and shows major differences in the relative casein proportions and micelle properties. CM is very different from BM, including the paler (whitish) color, slightly salty flavor, and lower density (1.029 g/mL) (Izadi et al., 2019). The distinct composition of CM results in a relatively weaker response to traditional gel production methods used with BM, such lactic acid fermentation or renin treatments (Attia et al., 2001). Because texture has a major impact on sensory and quality parameters such as mouth feel, appearance, and customer acceptance, the poor coagulation properties of CM render commercial fermented CM products, including yogurt and cheese, with generally low acceptance by consumers (Patel et al., 2022). Although stabilizers, skim milk powder, calcium chloride, and commercial yogurt culture have been used in a series of initiatives to produce high-quality yogurt from CM, the texture and consistency of the gels remain undesirable (Al-Zoreky and Al-Otaibi, 2015). Another disadvantage is that the fermentation of CM generally takes longer than required for BM fermentation (Galeboe et al., 2018). Therefore, further research is needed to optimize the operating parameters and standardize procedures to improve the production process and acceptability of fermented CM (Seifu, 2023).

In a previous study, conducted by our research team, showed that the properties of fermented CM and BM are affected by the milk type, bacteria, temperature, and their interactions (Chelladhurai et al., 2024). Compared to BM, CM is void of β-lactoglobulin, has lower κ-casein and higher β-casein contents, has larger casein micelles, smaller fat globules, and higher levels of proteolytic products (Mohamed et al., 2020; Mbye et al., 2022; Chelladhurai et al., 2024; Tsermoula et al., 2021). As discussed above (Figure 2), β-lactoglobulin and κ-casein play a very important role in yogurt quality. The size of casein micelles in CM (20–300 nm) is two-folds larger than that of the micelles in BM (40–160 nm) (Swelum et al., 2021), which may potentially influence the final texture and consistency of fermented CM. Differences in protein profiles and amino acid sequences between CM and BM can also significantly influence the composition of their fermented products (Izadi et al., 2019). The relative composition of αS1-, αS2-, β-, and κ-caseins in CM was found to be 26:4:67:3 compared to a ratio of 38:10:36:12 in BM (Mohamed et al., 2020). This difference results in higher concentrations of β-casein and lower levels of α-caseins in CM. Furthermore, CM lacks β-lactoglobulin and has lower levels of κ-casein (3.5%) than BM (10%), which are the two most important proteins for the initial formation of yogurt gels (Mohamed et al., 2022a). Moreover, CM exhibits a higher content of whey proteins (20–25%) than BM (18–20%) (Mohamed et al., 2020; Fabiano et al., 2013). Together, these variations contribute to differences in the ultimate rheological properties of fermented CM, such as weaker coagulation and gel structure, from those of BM yogurt (Hailu et al., 2016).

A crucial factor that affects the fermentability of CM and BM is the degree of proteolysis of the milk proteins by the bacteria and indigenous factors (Chelladhurai et al., 2024). CM shows a higher degree of proteolysis than BM, which correlates negatively to the bacterial count (Figure 5). In addition, β-casein, which is highly abundant in CM, is more susceptible to proteolysis than the other caseins. CM contains shorter β-casein chains with more proline residues, and its hydrolysis produces bioactive peptides and releases antioxidative amino acids such as phenylalanine and tryptophan (Izadi et al., 2019). Such an increase in proteolytic products enhances the water holding capacity and the watery consistency of Fermented CM and influences the gel’s internal stability (Abdeldaiem et al., 2022).

CM exhibits antimicrobial activities that may affect bacterial growth during fermentation (Swelum et al., 2021; Hamed et al., 2024). CM significantly surpasses BM in serum albumin content (26% vs. 6.2%) (Mbye et al., 2022) and in the contents of immunoglobulins A, G, and M (18% vs 3.5%) (Hailu et al., 2016). Moreover, CM is significantly richer in lactoferrin and lysozyme compared to BM (639.4–2094.9 μg/mL vs 76.7–140 μg/mL), making it more potent in immune defense and antimicrobial activities (El-Agamy, 2000; Kappeler et al., 1998). The lactoferrin in CM has been shown to exhibit antibacterial, antiviral, anticancer, anti-inflammatory, and immunomodulatory effects. Similarly, CM contains higher levels of lysozyme, in the range of 23.3–71.4 μg/mL compared to only 7 μg/mL lactoferrin found in BM (Elagamy et al., 1996). This elevated lysozyme concentration enhances CM’s antibacterial properties, further contributing to its potential health benefits (Mohamed et al., 2022a). These notable differences in protein composition might contribute to a denser texture of CM compared to BM.

In casein micelles, calcium binds to αS1-, αS2-, and β-caseins in the core, while κ-casein forms a “brush” on the micelle surface (de Kruif and Zhulina, 1996; Dalgleish and Corredig, 2012). CM caseins are characterized by lower degree of phosphorylation and micelle stability compared to those of BM (Sobti and Kamal-Eldin, 2019; Ryskaliyeva et al., 2018; Kumar et al., 2015). The higher levels of β-casein and their greater chaperone activity in CM compared to BM (Kumar et al., 2015) can further increase the amphiphilicity and detergent-like properties of CM proteins, which impairs their aggregation and refolding (Raynes et al., 2015). In addition, the structure and properties of fermented CM were improved by adding bovine casein and whey proteins (Sobti and Kamal-Eldin, 2019).

The functional properties of fermented CM may also be affected by the milk lipids. Compared to BM, CM exhibits a slightly higher fat content (Table 1) and smaller fat globule size (Khalesi et al., 2017), which may be linked to the slower and more thorough creaming process (Lean, 2011). In particular, CM has a higher concentration of branched-chain fatty acids (3.03%) than BM (1.82%) (Dreiucker and Vetter, 2011) and also has a markedly lower carotene content (Claeys et al., 2014). These differences result in a “waxy texture” and whiter color of fermented CM (Ereifej et al., 2011), possibly influencing its digestibility and sensory attributes (Tomotake et al., 2006). The CM fat composition is dominated by higher-molecular-weight triacylglycerols (≥C40 carbons), with low levels of C24–C40 and high levels of C48–C52, resulting in a higher melting temperature (32.6 °C) compared to that of BM (22.8 °C) (Smiddy et al., 2012). Goat milk (GM) yogurt exhibits higher water-holding capacity than BM yogurt due to its higher protein (3.27% vs. 3.14%) and fat (3.69% vs. 3.33%) contents (Ragab et al., 2021). Although understanding the role of fat is essential for developing CM products with desired characteristics, the effects of fat content on the textural and rheological properties of fermented CM remain to be thoroughly investigated.

CM producers worldwide have developed diverse traditional fermented products, each with its own microbiological, physicochemical, and flavor characteristics (Table 2). These products vary according to fermentation conditions and microbial properties, which are then reflected in the unique sensory characteristics (Hamed et al., 2024; Shori, 2017; Seifu, 2023). Compared to fermented BM yogurts, the majority of fermented CM products are beverages (i.e., drinkable yogurts) (Sobti et al., 2021; Sobti et al., 2023; Kamal-Eldin et al., 2020). For example, Chal, a slightly thick beverage popular in Bulgaria, Iran, and Turkey, is fermented by a complicated bacterial consortium mainly consisting of L. plantarum, Lactobacillus kefiri, and Enterococcus faecium (Hamed et al., 2024; Seifu, 2023; Soleymanzadeh et al., 2016). Doogh, which is consumed in Iran, Afghanistan, and Turkey, is a drinkable yogurt fermented with Bifidobacterium bifidum and frequently enriched with salt, ginger extract, pectin, or gum Arabic (Azarikia and Abbasi, 2010). Gariss, which is produced by spontaneous fermentation in Sudan, has a liquid to slightly thick consistency (Hamed et al., 2024; Shori, 2017). Camel kefir is obtained by spontaneous fermentation of kefir grains under approximately room temperature, resulting in a thick, creamy product that is usually chilled for consumption (Hamed et al., 2024; Shori, 2017; Seifu, 2023). Other traditional fermented CM products include Laban, Shubat, Susuac, and Zrig (Muthukumaran et al., 2023; Seifu, 2023; Chammas et al., 2006).

Figure 6 illustrates the mutualistic interaction between Lb. delbrueckii subsp. bulgaricus and S. thermophilus in the fermentation of milk. These interactions are crucial for establishing the appropriate microbial ecosystem in milk fermentation, ensuring the quality and safety of the final product (Yang et al., 2025). Synergistic interactions between these bacteria involve metabolite exchange, protein and amino acid metabolism, lactic acid and acidity regulation, urea activity, pH regulation, exopolysaccharide production, and glutathione production (Ayivi and Ibrahim, 2022). S. thermophilus enhances the growth of Lb. bulgaricus and metabolism by producing ammonia, formic acid, and folic acid, while Lb. bulgaricus hydrolyzes milk proteins into the growth-promoting peptides and amino acids used by S. thermophilus (Yang et al., 2025). S. thermophilus consumes oxygen (O₂) in the fermentation medium, producing carbon dioxide (CO₂), which is preferred by Lb. bulgaricus (Sasaki et al., 2014). Additionally, Lb. bulgaricus produces lactic acid, which adds to the acidity of the yogurt, by breaking down casein into peptides and amino acids through the expression of proteases (Ayivi and Ibrahim, 2022). Lb. bulgaricus and S. thermophilus produce long-chain fatty acids and glutathione, which maintain membrane stability and oxidative stress resistance (Yang et al., 2025). This proto-cooperation ensures optimal growth, metabolite exchange, and stability in yogurt fermentation (Ayivi and Ibrahim, 2022). Bacteria produce several fermentation products such as lactic acid, flavor components, and EPS, enhancing the yogurt’s texture and mouthfeel. Their mutual metabolic exchange ensures stability and optimal growth, driving efficient milk fermentation (Wang J. et al., 2025). This symbiosis highlights the importance of microbial interactions in achieving stable coexistence and efficient substrate conversion in food fermentation. Therefore, understanding the connection between Lb. bulgaricus and S. thermophilus may contribute to enhancing the texture, flavor, and quality of fermented dairy products by optimizing strain selection or process conditions.

As schematically outlined in Figure 7, bacterial cells quickly sense their surroundings and initiate transcription during the different phases of bacterial growth. A transcriptomic analysis of the lag phase helped to identify the regulatory mechanisms that govern the transitions from the stationary to lag phases and from the lag to exponential phases, where aerobic respiration is fully established and tricarboxylic acid (TCA) cycle enzymes and metal uptake systems support growth (Rolfe et al., 2012). The stationary phase is characterized by low TCA cycle components, active Fe–S cluster formation, strong expression of genes involved in the stress response systems and protein repair pathways, and anaerobic respiration. Increased protein repair and the production of Fe–S clusters occur as a result of the oxidative stress response that is initiated during the lag phase (Rolfe et al., 2012). Two exponential growth phases, each distinguished by significant interactions and metabolic alterations, are separated by a transition phase.

S. thermophilus can withstand neutral pH and efficiently uptake amino acids (Sieuwerts, 2016), which may promote its faster growth in the lag phase as an adaption to the milk environment. The first exponential phase (Figure 7) is the most common, which generates carbon dioxide, lactic acid, formic acid, and folic acid. S. thermophilus provides folic acid and formic acid, which Lb. bulgaricus requires for its growth (Lecomte et al., 2016), while the bacterium’s consumption of oxygen, and consequent production of carbon dioxide, promotes the anaerobic growth of Lb. bulgaricus (Sasaki et al., 2014). S. thermophilus hydrolyzes lactose by utilizing β-galactosidase, resulting in the production of glucose and galactose, which are then glycolyzed to generate lactic acid in milk (Tarrah et al., 2018). The limited availability of amino acids slows bacterial growth during the transition phase. Lb. bulgaricus activates the prtB gene, generating an extracellular protease that breaks down casein into peptides and amino acids, providing nitrogen sources to promote the growth of both bacteria (Liu et al., 2016). The second exponential phase during milk fermentation involves the growth of Lb. bulgaricus and S. thermophilus, which upregulate pathways for the synthesis of long-chain fatty acid and glutathione (Yang et al., 2025). These conditions offer advantages to the growth of Lb. bulgaricus by raising pH and improving acidification, lactose utilization, and lactic acid production (Yu et al., 2020). During the stationary phase, bacterial growth is delayed due to acid accumulation; nevertheless, the metabolic synergy between the two species ensures efficient fermentation (Yang et al., 2025). Future research could explore the effect of various probiotic strains on fermentation and their contributions to improving the techno-functional properties of fermented dairy products. S. thermophilus plays a major role in lactose utilization, producing lactic acid, which lowers pH and enhances proteolysis, resulting in the liberation of peptides and amino acids with antimicrobial and antioxidant properties (Elhamid and Elbayoumi, 2017). S. thermophilus also generates EPS by facilitating water-binding capacity and casein network rigidity, resulting in viscosity improvement and reducing syneresis in BM yogurt (Yang et al., 2014; Daba et al., 2021). Moreover, strains ST-3021 and ST-4845 are EPS-producing strains that enhance the hardness and texture of yogurt, resulting in a creamier yogurt with a superior mouthfeel (Folkenberg et al., 2006). The bacterium interacts synergistically with Lb. bulgaricus, further highlighting its importance in commercial yogurt production. Thermophilic lactobacilli, particularly Lb. bulgaricus, surpass the fermentation performance other bacteria by exhibiting strong proteolytic activities (proteinases and peptidases), which contribute to flavor development and the formation of bioactive peptides with antimicrobial and antioxidant properties (Kieliszek et al., 2021). Strain GL03-1 of Lb. bulgaricus was reported to substantially improve the viscoelastic properties of buffalo yogurt, exhibiting a three-dimensional mesh-like gel structure (Yang et al., 2014). The combination of Lb. fermentum and Lb. bulgaricus in BM yogurt increased acid generation and adhesiveness, while decreasing the degree of whey separation, offering an effective fat replacer (Tiwari et al., 2021).

Some studies have investigated the influence of other lactobacilli on the fermentation time and yogurt quality. For instance, the addition of Lb. helveticus H9 as a starter culture in BM yogurt fermentation led to shorter fermentation times and higher levels of volatile compounds (Zhou et al., 2019). Lb. helveticus is a probiotic bacterium that can be used as a starter culture in fermented CM and exhibits high proteolytic activity, producing bioactive peptides with therapeutic benefits and antibacterial properties (Chelladhurai et al., 2024). Notably, selective strains of Lb. helveticus are also considered for imparting nutty and anti-bitter flavors and improving the sensory appeal of fermented CM (Chelladhurai et al., 2023). Lb. helveticus-fermented CM exhibited high levels of auto-aggregation, coaggregation, and adhesion, demonstrating the ability to adhere to intestinal epithelial cells and offer defense against infections (Mahmoudi et al., 2019).

Probiotic Lactobacillus strains (L. plantarum-KX881772, L. plantarum-KX881779, Lb. reuteri-KX881777) of CM performed better than non-CM strains (Hati, 2018). Research on the incorporation of L. plantarum in CM fermentation suggests its potential for industrial utilization. L. plantarum HUM19, Lb. fermentum, and Lb. rhamnosus showed high proteolysis and sensory characteristics in both fermented CM and BM (Moslehishad et al., 2013). As a probiotic adjunct culture in yogurt production, L. plantarum exhibits strong capacity to enhance functional attributes such as flavor and probiotic viability without compromising sensory profiles, making it a suitable and considerable option for the creation of innovative functional dairy products (Li et al., 2017). L. plantarum exhibited proficiency in suppressing the proliferation of foodborne pathogens in fermented CM (Li et al., 2017), rendering it a secure choice as a primary fermentative. L. plantarum was also found to enhance secondary proteolysis in CM, releasing peptides and amino acids that act as flavor precursors (Mishra et al., 2019). Mixed starters of L. plantarum and S. thermophilus exhibited enhanced casein breakdown and modified proteolysis patterns (Li et al., 2019). Moreover, L. plantarum KX041 produces EPS with free radical-scavenging activity during fermentation (Xu et al., 2019). These results highlight the significance of adopting a careful approach when selecting probiotic strains for co-cultures in fermented dairy production (Li et al., 2019).

According to Bandiera et al. (2013), Lb. casei can be effectively incorporated into yogurt without negatively affecting other starter cultures. The probiotic strain Lb. casei (Bai et al., 2020) shortened the fermentation time and increased beneficial EPS production, resulting in higher bacterial viability, improved viscosity and enhanced gel structures in fermented CM (Bai et al., 2020; Lee and Lucey, 2004; Wang D. et al., 2025). Lb. casei and Lb. acidophilus enhanced the antioxidant capacity in probiotic BM yogurt by releasing potent peptides with free radical-scavenging and metal-chelating properties (Fardet and Rock, 2018; Tadesse and Emire, 2020). In commercial products such as Yakult^® and Actimel^™, fermentation with Lb. casei alone generated volatile compounds dominated by acetic acid, acetoin, and butyric acid. When combined with other yogurt cultures, Lb. casei increased the levels of 3-hydroxy-2-butanone and hexanoic acid in BM yogurt, thereby enhancing the yogurt-like aroma (Chen et al., 2017; Zaręba et al., 2014). Table 3 summarizes the techno-functional effects of various LAB strains and species on the properties of yogurts and fermented camel milk products.

In addition to the milk type and bacterial strain, the processing conditions such as heat treatment, pressure, homogenization, and additives are key variables that affect yogurt quality. Conventional heat treatments prior to fermentation have detrimental effects on the organoleptic qualities of fermented milk products (i.e., texture, creation of off-flavors, and color) (Asaduzzaman et al., 2021; Yirda et al., 2020). In addition to deactivating enzymes and extending the shelf life of milk by destroying pathogenic microbes and spoiling either completely or partially (Hattem et al., 2011), heat treatment has major effects on the composition of fermented CM and the release of bioactive peptides (Izadi et al., 2019). As previously mentioned, the denaturation of milk whey proteins and their bonding with κ-casein are the most significant consequences of heating milk (Genene et al., 2018). κ-Casein interacts with sulfhydryl-disulfide bonds during heating above 70 °C to produce micelle-bound and soluble thermal co-aggregates (Asaduzzaman et al., 2021), which has an impact on the protein network and the gelation characteristics of casein micelles (Mohamed et al., 2022b). Compared to BM, CM was reported to be less stable and more susceptible to heat treatments (Mohamed et al., 2022b). A typical pasteurization procedure for CM is 60 °C for 30 min, 63 °C for 30 min, and 75 °C for 15 s (Alhaj et al., 2013). Thermally treated CM (63 °C for 30 min, 72 °C for 15 s, and 100.5 °C for 10 min) reduced the overall acceptability, taste score, and texture compared to those of untreated milk (Lund et al., 2019). Moreover, CM exhibited poor heat stability when autoclaved for 15 min at 121 °C, resulting in sedimentation and whey separation (Alhaj et al., 2013). Prior heating of the milk for 10–15 min at 80 °C–95 °C promotes protein network development, water retaining capabilities, enzyme denaturation, and the destruction of unavoidable microbes. Whey separation and textural flaws may be reduced by optimizing the incubation temperature (∼40 °C), which can eventually improve the yogurt texture (Lee and Lucey, 2004).

Table 4 shows the effects of various fermentation pre-treatments, including thermal processing, homogenization, HPP, fermentation, and thermosonication (Kenari and Razavi, 2021). By adopting non-thermal technology, most of the adverse effects of thermal treatment can be avoided, leading to higher-quality food products (Ahmad et al., 2019). Milk homogenization was reported to improve BM yogurt quality by reducing the size of fat globules (Ho et al., 2022b; Trujillo et al., 2016). However, since CM is naturally characterized by smaller and more homogeneous fat globules than BM, it does not require homogenization (Table 1). HPP can enhance the rheological characteristics of fermented BM by modifying milk proteins, such as whey protein denaturation and casein micelle disruption due to colloidal calcium phosphate solubilization (Nassar et al., 2020). HPP treatment at 300 and 600 mPa for 10 min at 10 °C could maintain the greatest bacterial counts. While high-temperature short-time and UHT treatments increase the particle size in BM, the opposite effect is found in CM (Ayyash et al., 2022). HPP treatment lowered the particle size in both CM and BM and produced yogurts with creamier mouthfeels and smoother textures (Ayyash et al., 2022). Furthermore, fermented heat-treated CM produced stronger gels with better storage properties and less modulus loss than HPP-treated milk, notably with treatment at 85 °C, whereas ultrafiltration increased only the viscosity and not the gel strength (Sobti et al., 2024). Therefore, HPP is inferior to heat treatment in enhancing fermented CM texture. Thus, the observed difference can be attributed to the differences between CM and BM in the original micelle structure and how these are affected by heating and HPP treatments.

The combination of low incubation temperatures and moderate to high inoculation rates can enhance the gel strength and storage modulus, thereby enhancing the texture of BM yogurt (Lee and Lucey, 2004). In the dairy sector, the application of ultrasound has been used to regulate the functional qualities of dietary proteins as well as the microstructure and texture of fat-containing items, including yogurt, cheese, and ice cream (Ahmad et al., 2019). Moreover, ultrasound inactivates microorganisms and enzymes (Ahmad et al., 2019), develops a sweetening effect in yogurt (Wu et al., 2000), enhances emulsification and homogenization by decreasing the size of milk fat globules, and shortens fermentation times by enhancing lactose hydrolysis in yogurt production (Akdeniz and Akalın, 2019). High-intensity ultrasound treatment was reported to improve various characteristics of BM, including the denaturation of casein micelles, formation of aggregates between κ-casein and whey proteins (β-lactoglobulin), viscosity, texture, fat globule size, and surface membrane area (Akdeniz and Akalın, 2019).

Thermosonication considerably improved the qualities of fermented CM, providing a potentially viable method for improving yogurt quality. The ideal parameters for thermosonication of CM are 55 °C for 10 min at 75 amplitudes (Kenari and Razavi, 2021). The texture of set and stirred yogurt was also influenced by sonication during BM fermentation, which may result in improved smoothness and creaminess (Körzendörfer et al., 2017). By comprehensively understanding the impacts of manufacturing processes on the final product, the processes may be optimized to produce fermented CM with desired textural features. Figure 8 presents a summary overview of processing and fermentation conditions that enhance, have limited influence on, degrades the quality of fermented CM.

Table 5 summarizes the effects of coagulants and texture-enhancing additives on the quality of fermented products: these additives result in more calcium, phosphorus, and saturated fatty acids in fermented CM, whereas the protein, lactose, and total solids are enhanced in BM yogurt, contributing to its preferred flavor and texture (Galeboe et al., 2018). Fortifying CM with milk from other species such as sheep, buffalo, and bovine has been proposed as a potential strategy to enhance the texture and minimize syneresis (Kamal-Eldin et al., 2020; Ait El Alia et al., 2023; Ibrahem and El Zubeir, 2016). Compared to the yogurt produced entirely with CM, yogurt manufactured using a combination of CM and BM had better physicochemical properties and sensory profile (Kamal-Eldin et al., 2020; Mustafa, 2015). Sheep milk (40–60%) (Ibrahem and El Zubeir, 2016) and buffalo milk (90%) (Khalifa and Zakaria, 2018) increased the total solids content and acceptability of fermented CM, while oat milk (40%) improved the antioxidants, viscosity, and sensory qualities (Atwaa et al., 2020). The enhancement of fermented CM quality by the fortification with milks from other animals was attributed to the differences in composition of third portions, especially the contents of β-lactoglobulin and κ-casein. Fortification of CM with BM powder improved the hardness and consistency of fermented CM gels and minimize syneresis during the processing and storage phases (Sobti and Kamal-Eldin, 2019; Atwaa et al., 2020; Salih and Hamid, 2013; Omar et al., 2019). Acid gelation of fermented CM was shown be aided by sodium caseinate prepared from CM casein micelles, which lead to improved texture and rheological properties of the gel (Wang J. et al., 2025), suggesting that casein source and structural compatibility are significant factors for effective coagulation. Supplementation with high levels of casein or whey protein was shown to increase syneresis by creating larger porous and less linked aggregates (Puvanenthiran et al., 2002) suggesting the need for optimized levels of added milk proteins.

Efforts have been made to improve fermented CM quality by adding hydrocolloids such as gelatin, sodium alginate, gum Arabic, and xanthan gum (Table 5). Gelatin (0.75–1.0%) (Mudgil et al., 2018), and xanthan gum (0.75%) (Mohsin et al., 2019), oat β-glucan (2%) (Ladjevardi et al., 2016), modified starch (3%) (Ibrahim and Khalifa, 2015) improved hardness, viscosity, water holding capacity, and sensory perception and sweet potato powder (3%) reduced syneresis and extended shelf-life (Omar et al., 2019). Adding hydrocolloids (gelatin, alginate, gum Arabic, and pectin) to CM containing casein, whey protein, and calcium chloride produced different effects. While alginate and pectin improved texture and rheology and reduced syneresis, gum Arabic and gelatin had small negative effect on hardness and rheology (Sobti et al., 2020). When mixed with hydrocolloids (gelatin, gum Arabic, pectin, and sodium alginate), calcium chloride (CaCl₂) was shown to cause excessive protein aggregation in fermented CM leading to coarse gels, enhanced syneresis, and unwanted stiffness, which reduced consumer acceptance (Sobti et al., 2020; Oselu et al., 2022b; Ramasubramanian et al., 2008). Fat substitutes such as gelatin, k-carrageenan, pectin, inulin, fibers, and starch increased the viscosity, decreased syneresis, and improved overall sensory qualities (Saleh et al., 2018; Atwaa et al., 2020). Some ingredients were effective primarily in combination, such as whey protein isolate (3%) with κ-carrageenan (0.1%), samphire molasses (3%), and xanthan gum (0.5%) improved rheological properties (Kavas, 2016).

Enzymatic modifications are also being tested to improve the quality and properties of fermented CM products. For example, microbial transglutaminase (MTGase, EC 2.3.2.13), a natural alternative to gelatin for yogurt stabilization, proved to be more effective than the dairy powder components (Abou-Soliman et al., 2017). MTGase was shown to enhance the structural, textural, and sensory qualities of fermented CM by improving the microstructure and volatile compounds content (Bulca et al., 2022; Chen et al., 2019; Hovjecki et al., 2021). MTGase is commonly added to fermented dairy products at below 1% concentration (Arslan Amin et al., 2023) to strengthen the gel matrix by generating cross links between lysine and glutamate residues of proteins (Gharibzahedi and Chronakis, 2018). However, MTGase alone cannot fully improve the poor texture of fermented CM, necessitating milk protein enrichment (Abou-Soliman et al., 2017; Ma et al., 2019; Metwalli et al., 2023; Han et al., 2020). Further research is needed to optimize the texture of fermented MTGase-treated CM and testing its interaction with milk proteins and hydrocolloids.

Fruit-based ingredients remain popular among consumers because of added color, flavor, taste, and texture (Alia et al., 2023; Sobti et al., 2023; Ramasubramanian et al., 2008; Kavas, 2016). Flavored CM labans supplemented with fruit purees (25% apricot, blueberry, mango, peach, pineapple, and strawberry) showed higher storage moduli, loss moduli, and viscosity values; enhanced gel structures; and improved acceptable sensory properties (Sobti et al., 2023). Monk fruit sweetener (0.42–2.54%) can be used in fermented CM to change its color and viscosity, while providing a calorie-free, healthy alternative to traditional sweeteners (Buchilina and Aryana, 2021). Plant-based additives including pea protein (3–6%) resulted in enhancement of yogurt texture and antioxidant qualities (Olaimat et al., 2023), while carob fiber (2%) improved cohesion and water-holding capacity (Jrad et al., 2021). Date and orange dietary fiber (4.5%) also improved the texture and probiotic development (Ibrahim and Khalifa, 2015) and persimmon pulp (5%) promoted gel formation (Alia et al., 2023).