The impact of varying the level of salt (@ 1.75 and 2.25% w/w of cued) with the exclusive focus on the survivability of S. boulardii adjunct culture (incorporated @ 3.5 g/100 kg milk) during Pizza cheese making and on the proximate composition, physico-chemical characteristics, yield, textural attributes, baking properties and sensory quality of cheese (i.e. as pizza topping) were explored in this investigation.
Temperature of plasticized mass
Based on the plasticizing conditions adopted in preparing cheeses CCUM and CBHM, the temperatures of the cheese mass during plasticizing were 61.5°C and 59.5°C respectively. The plasticizing conditions for the two cheeses, in the same order as specified above, were 84.5°C for 2.5 min. and 79°C for 2.5 min. Pizza cheese was able to have a lower pH as a result of cheddaring (i.e. stretching the curd at 0.75% LA), leading to colloidal calcium phosphate dissolution, which made the curd susceptible to plasticization at lower temperatures (Jana and Upadhyay, 1997). Cheese made from a blend of milk (unhomogenized: homogenized, 1:1 w/w) has a higher protein content in the homogenized milk fraction, which is due to the greater fat surface area. Additionally, the pH of the curd during stretching (where the acidity of the whey was 0.44% LA) was lower than in the control cheese. These two factors caused the cheese curds to become more pliable at a lower temperature (Jana and Upadhyay, 1993)
Effects on the proximate composition, physicochemical characteristics and yield of cheese as influenced by two levels of salt
The proximate composition and physicochemical characteristics of experimental Pizza cheeses (i.e. CCUM1.75, CBHM1.75, CCUM2.25 and CBHM2.25) are shown in Table 1.
Table 1
Proximate composition, physicochemical characteristics and yield of Pizza cheeses as affected by the level of salt
Parameters | CCUM1.75 | CBHM1.75 | CCUM2.25 | CBHM2.25 |
Proximate composition |
Moisture, % | 47.99 ± 0.19d | 52.20 ± 0.23b | 48.95 ± 0.25c | 52.95 ± 0.47a |
Fat, % | 22.90 ± 0.14a | 22.20 ± 0.27b | 22.62 ± 0.24a | 22.35 ± 0.22b |
FDM1, % | 44.03 ± 0.27c | 46.45 ± 0.72b | 44.31 ± 0.44c | 47.50 ± 0.82a |
Protein, % | 23.35 ± 0.14 a | 22.46 ± 0.60c | 22.87 ± 0.08b | 22.44 ± 0.11c |
Salt, % | 0.96 ± 0.03b | 0.95 ± 0.02b | 1.22 ± 0.05a | 1.19 ± 0.02a |
Ash, % | 2.37 ± 0.07a | 2.22 ± 0.08b | 2.35 ± 0.01a | 2.21 ± 0.06b |
Physico-chemical properties |
Acidity, (% LA) | 0.56 ± 0.03b | 0.64 ± 0.03a | 0.49 ± 0.01c | 0.56 ± 0.01b |
pH | 5.23 ± 0.01a | 5.14 ± 0.01b | 5.25 ± 0.05a | 5.15 ± 0.04b |
Yield |
kg cheese/100 kg milk | 12.20 ± 0.10d | 12.62 ± 0.09b | 12.43 ± 0.23c | 13.11 ± 0.18a |
The subscripts 1.75 and 2.25 represent the salt addition rate; CCUM and CBHM = Cheese made employing Protocol I and Protocol II respectively; Figures placed after ± indicate standard deviation, the values in each row that have different superscript letters are significantly (p < 0.05) different from each other; n = 5 |
All four Pizza cheeses complied with the FSSR compositional standard for Pizza cheese (FSSR 2023). The values shown in Table 1 revealed a significant (p < 0.05) difference with respect to all the constituents studied for the Pizza cheeses. The moisture content of CBHM2.25 was markedly higher than that of the other three cheeses. The sequence of cheeses in decreasing order of moisture content was as follows: CBHM2.25 > CBHM1.75 > CCUM2.25 > CCUM1.75 (Table 1).
With respect to fat and ash contents as well as pH, cheeses CCUM1.75 and CCUM2.25 as well as CBHM1.75 and CBHM2.25 were statistically similar. The salt content of cheeses CCUM1.75 and CBHM1.75 as well as CCUM1.75 and CBHM2.25 were also statistically similar. With regard to FDM content, cheeses CCUM1.75 and CCUM2.25 were statistically similar. However, cheese CBHM2.25 had a markedly higher FDM content compared to the remaining three cheeses. Both CBHM cheeses, irrespective of the salting rate, were at par with regard to the protein content. The highest values of protein and acidity (% LA) were associated with the cheeses CCUM1.75 and CBHM1.75 respectively (Table 1).
Table 1
The lowest moisture level (i.e., 47.99%) of cheese CCUM1.75 could be the reason for its noticeably greater fat, ash and protein content. Likewise, the minimum fat, protein, salt content and pH associated with cheese CBHM1.75 as well as CBHM2.25 were due to the markedly higher moisture content (i.e. 52.20 and 52.95% respectively). The lowest acidity value was associated with cheese CCUM2.25; this value was markedly lower in comparison to the other remaining three cheeses (Table 1).
Mozzarella cheese that was dry salted at a higher level (1.0% vs. 0.5%) had a higher moisture content (Paulson et al. 1998). The decrease in the fat and protein content of Pizza cheeses when salting was carried out at a higher level (i.e. 1.75%) could be attributed to the markedly higher moisture content associated with such cheeses. Pizza cheeses testing higher moisture content had marginally lower fat content (18.5%) but had similar protein content when compared with cheeses testing lower (46.4%) moisture content (Rowney et al. 2004).
The maximum yield was noted for cheese CBHM2.25 (i.e. 13.11%) among all cheeses. Likewise, cheese CCUM2.25 had a markedly higher yield than cheese CCUM1.75. The plausible reason for the enhanced yield of cheeses made using a higher salting rate (i.e. 2.25%), irrespective of the method adopted (i.e. protocols CCUM and CBHM), was due to the greater moisture content associated with such products; possibly the losses of milk constituents were also lower. The rate at which cheese is salted is known to affect the water-holding capacity of casein, which in turn can affect the cheese yield (Guinee and Fox 2004).
Pande (2016) found that the yield of Mozzarella cheese was not considerably affected by salting the cheese curd at different levels (2.0%, 2.5%, and 3.0%).
Effect of salting rate on the textural properties of cheese as influenced by two levels of salt
The textural properties of Pizza cheeses as influenced by the salting rate are shown in Table 2. The hardness, cohesiveness and springiness values of cheeses CCUM1.75 and CCUM2.25 as well as of cheeses CBHM1.75 and CBHM2.25 were statistically similar. All four cheeses differed significantly (p < 0.05) from each other with regard to gumminess, chewiness and adhesiveness. Cheese CCUM1.75 was associated with the maximum values for hardness (i.e. 21.80 N), cohesiveness (i.e. 0.258), springiness (i.e. 4.77 mm), gumminess (i.e. 562.07 N) and chewiness (i.e. 26.78 N-mm). The minimum hardness, cohesiveness and springiness were associated with cheese CBHM2.25 (Table 2). However, Pande (2016) did not note any marked difference in the textural properties of Mozzarella cheese prepared using salt levels of 2.00 and 2.25% salt by weight of curd.
Table 2
Textural properties of Pizza cheeses as influenced by salt level
Parameters | CCUM1.75 | CBHM1.75 | CCUM2.25 | CBHM2.25 |
Hardness (N) | 21.80 ± 1.12a | 16.96 ± 0.42b | 20.93 ± 0.92a | 16.00 ± 0.70b |
Cohesiveness | 0.258 ± 0.012a | 0.226 ± 0.008b | 0.252 ± 0.026a | 0.213 ± 0.008b |
Springiness (mm) | 4.77 ± 0.08a | 4.27 ± 0.15b | 4.73 ± 0.20a | 4.21 ± 0.17b |
Gumminess (N) | 562.07 ± 22.11a | 382.50 ± 16.10c | 526.56 ± 33.51b | 340.55 ± 25.78d |
Chewiness (N-mm) | 26.78 ± 1.00a | 16.34 ± 1.13c | 24.89 ± 1.35b | 14.30 ± 0.60d |
Adhesiveness (N-mm) | 0.312 ± 0.007c | 0.429 ± 0.005a | 0.296 ± 0.008d | 0.410 ± 0.008b |
The subscripts 1.75 and 2.25 represent the salt addition rate; CCUM and CBHM = Cheese made employing Protocol I and Protocol II respectively; Figures placed after ± indicate standard deviation, the values in each row that have different superscript letters are significantly (p < 0.05) different from each other; n = 5 |
Table 2
Cheese CBHM1.75 had the maximum adhesiveness (i.e. 0.429 N-mm) values (Table 2). Cheese CCUM1.75 had significantly (p < 0.05) higher gumminess and chewiness values than the other three cheeses. The maximum hardness associated with cheese CCUM1.75 could be attributed to the lowest moisture and higher content of protein and ash in such cheese compared to the rest of the three cheeses (Table 2).
Effect of salting rate on the baking characteristics of cheese
The baking characteristics relevant to the end-use application of Pizza cheese as affected by the salting rate are shown in Table 3.
Table 3
Baking characteristics of Pizza cheeses as influenced by salt levels
Baking characteristics | CCUM1.75 | CBHM1.75 | CCUM2.25 | CBHM2.25 |
Shredability | Excellent | Very Good | Excellent | Very Good |
Melting time in oven at 230oC (s) | 420.00 ± 10.00b | 484.00 ± 5.48a | 426.00 ± 2.24b | 488.60 ± 6.15a |
Schreiber meltability (Arbitrary value) | 4.21 ± 0.32a | 3.49 ± 0.29b | 4.09 ± 0.05a | 3.33 ± 0.11b |
Fat leakage (cm2) | 5.96 ± 0.83a | 3.73 ± 0.83b | 5.51 ± 0.23a | 3.78 ± 0.24b |
Stretch length (cm) | 52.80 ± 1.79a | 47.30 ± 0.84c | 50.00 ± 2.00b | 44.20 ± 2.39d |
The subscripts 1.75 and 2.25 represent the salt addition rate; CCUM and CBHM = Cheese made employing Protocol I and Protocol II respectively; Figures placed after ± indicate standard deviation, the values in each row that have different superscript letters are significantly (p < 0.05) different from each other; n = 5 |
Table 3
Shredability
To ensure proper distribution and melting of cheese on pizza pie and for other applications, the cheese needs to be sliced, diced, or shredded into separate entities of uniform size. Hence, the determinants of the overall functional properties of Pizza cheese involve shredability and resistance to clumping, post shredding (Jana and Tagalpallewar 2017). The cheese should be easy to shred into thin, long shreds.
Shredded cheeses are classified into various categories viz., ‘Excellent’, ‘Very Good’, ‘Good’ and ‘Fair’. ‘Excellent’ shredded cheeses shred easily and form thin, long shreds that do not mat. ‘Good’ shredded cheeses are slightly more difficult to shred and form thick, short shreds that may mat slightly. The cheeses that behaved in a manner that was construed to be midway between the previous two categories were labelled as ‘Very Good’ and those that behaved very poorly were categorized in the ‘Fair’ category. Pizza cheeses having the desired firmness yielded a greater proportion of longer shreds during the shredding process (Banville et al. 2014).
Figure 1
The shredability of the two CCUM cheeses was rated as ‘Excellent’, while the rating for the two CBHM cheeses was ‘Very Good’ (Table 3).
Meltability (including melting period)
‘Meltability’ is defined as the ability of cheese shreds to coalesce into a uniform, continuous layer at the heat of the baking oven. The cheese should melt easily (Jana and Tagalpallewar 2017). Cheese meltability is concerned with the disintegration of the protein matrix as a consequence of heating, with consequent melting of entrapped fat and weakening of the protein-protein linkages culminating in the flowability of cheese (Lucey et al. 2003). Any delay in the melting of the cheese in the heat of the oven is unfavourable, as it may lead to browning and blistering of the cheese (Jana and Tagalpallewar 2017).
The melting periods of cheeses prepared by the same method (i.e. CCUM or CBHM) were statistically similar, irrespective of the level of salting. As expected, the two CBHM cheeses required a markedly higher melting period as compared to the two CCUM cheeses (Table 3).
Fat leakage
The tendency for liquid fat to separate from melted cheese and form oil pockets on the surface of baked cheese is known as ‘oiling-off’ or ‘free oil formation’. While a small amount of free fat is desirable in pizza cheese, excessive free fat can detract from its appearance, palatability and crispness (Rudan et al. 1999).
As noted for the meltability character, the fat leakage values of cheeses prepared using same method (i.e. CCUM, CBHM) were rated statistically alike. As anticipated, cheeses CBHM1.75 and CBHM2.25 had lower fat leakage values (i.e. 3.73 and 3.78 respectively); such values were significantly (p < 0.05) different from those associated with the two CCUM cheeses (Table 3).
Mozzarella cheese made using a higher (i.e. 3.0%) salt rate exhibited reduced fat leakage compared to cheeses containing a lower (0.4–2.5%) salting rate (Rowney et al. 1999; Pande, 2016).
Stretchbility
The ability of melted pizza cheese to form long, thin strands that do not break when stretched is known as ‘stretchability’. The United States Department of Agriculture has set a standard for mozzarella cheese in the United States, requiring a minimum stretch of 3.0 inches (7.62 cm) of continuous string (USDA 2013).
The stretch lengths of all the cheeses markedly differed from each other. The maximum stretch length (i.e. 52.80 cm) was associated with cheese CCUM1.75; the cheeses exhibiting still lower stretch, in descending order, were as follows: CCUM2.25 > CBHM1.75 > CBHM2.25 (Table 3).
The impaired stretch character noted for the two CBHM cheeses (vs. CCUM cheeses) could be ascribed to the negative influence on such properties as a result of ‘mixed milk’ containing homogenized milk. Homogenization treatment meted to cheese milk is reported to impair the stretchability of Pizza/Mozzarella cheeses (Rowney et al. 2003; Patel 2022).
Effect of salting rate on the sensory scores of cheeses judged as pizza topping
To ascertain the sensory acceptability of the four Pizza cheeses viz., CCUM1.75, CCUM2.25, CBHM1.75 and CBHM2.25, the cheeses topped on pizza pie were subjected to sensory evaluation. The sensory scores of all four cheeses evaluated as pizza topping are represented in Fig. 2.
Figure 2
The rate of salting of cheese curd affects the final salt content of Pizza cheese. The salt content of cheese has been observed to have an impact on baking characteristics including shredding, melting, fat leakage, stretching and the sensory perception of chewiness when it is used in pizza pies (Rowney et al. 1999; Jana and Tagalpallewar 2017). Hence, the Pizza cheeses made using two manufacturing protocols (i.e. to yield cheeses CCUM and CBHM), salted at two levels (viz. 1.75 and 2.25%) at the salting stage, were subjected to sensory evaluation as a topping on pizza pie.
Figure 3
The appearance scores of the Pizza cheeses remained unaffected by the two salting rates applied during their manufacture. All the sensory scores of the two CCUM cheeses were statistically similar. The flavour score of cheese CBHM2.25 (i.e. 7.30) was markedly higher than that of counterpart cheese CBHM1.75. The two CBHM cheeses had statistically similar scores for attributes such as stringiness, chewiness and total sensory aspects (Table 4).
Table 4
Microbial count of cheeses as influenced by the two levels of salt
Microbial count (log10 cfu/g) | CCUM1.75 | CBHM1.75 | CCUM2.25 | CBHM2.25 |
Lactic Acid Bacteria count | 8.40c ± 0.05 | 9.02b ± 0.02 | 8.16d ± 0.06 | 8.91a ± 0.14 |
S. boulardii count | 4.91c ± 0.17 | 6.02a ± 0.11 | 4.69d ± 0.12 | 5.78b ± 0.10 |
The subscripts 1.75 and 2.25 represent the salt addition rate; CCUM and CBHM = Cheese made employing Protocol I and Protocol II respectively; Figures placed after ± indicate standard deviation, the values in each row that have different superscript letters are significantly (p < 0.05) different from each other; n = 5 |
The highest flavour and total scores were associated with cheeses CCUM1.75 (i.e. 8.15 out of 10.0) and CCUM2.25 (i.e. 40.37 out of 50.0) respectively, while the lowest scores for such attributes were associated with cheese CBHM1.75 (i.e. 7.30 and 38.32 respectively).
The total sensory score (i.e. 41.63 out of 50.0) as well as scores for flavour (i.e. 8.40 out of 10.0) and stringiness (i.e. 8.58 out of 10.0), were superior for Mozzarella cheese prepared utilizing 2.5% salt in contrast to cheeses made using lower (i.e. 2.0, 3.0%) levels. The Mozzarella cheeses made using dry salting at a level of 2.0 or 2.5% had sensory scores (judged as pizza topping) for appearance, melting and chewiness that were statistically similar (Pande 2016).
Microbial count of cheeses as influenced by the salting rate
The main objective of studying the two levels of salt in producing Pizza cheese was to ascertain the survivability of the adjunct S. boulardii culture (purported to be a probiotic) in addition to the thermophilic LAB used in its manufacture. The microbial counts of Pizza cheeses as influenced by the levels of salt addition are shown in Table 4.
Table 4
The LAB as well as the S. boulardii count of the cheeses (viz., CCUM and CBHM) were significantly (p < 0.05) influenced by the salt addition rate and the two protocols of cheese manufacturing. The highest and lowest counts of both LAB were associated with cheeses CBHM1.75 (i.e. 9.02 log10 cfu/g) and CCUM2.25 (i.e. 8.16 log10 cfu/g) respectively. In a similar fashion, the highest and least count of S. boulardii were associated with cheeses CBHM1.75 (i.e. 6.02 log10 cfu/g respectively) and CCUM2.25 (i.e. 4.69 log10 cfu/g) respectively (Table 4). This clearly indicated that the use of a higher salt level (i.e. 2.25%) was somewhat inhibitory to the growth of both S. boulardii and LAB.
The microbial count displayed in Table 4 also revealed that cheeses prepared from ‘mixed milk’ involving 50.0% homogenized milk (i.e. CBHM) had a significantly (p < 0.05) higher count of both LAB and of S. boulardii than the counterpart cheeses made using another method (i.e. CCUM). Such responses regarding LAB and S. boulardii count of cheeses held true at each level of salting used in the preparation of Pizza cheese. However, a comparison of the microbial count of cheeses could not be made in light of the availability of the literature.
The S. boulardii and LAB counts of Pizza cheese tended to be lower when using higher levels (i.e. 2.25 vs. 1.75% w/w of curd) of salt. It is recommended to use salt @ 1.75% when employing S. boulardii culture as an adjunct starter for Pizza cheese making.