MATERIALS AND METHODS

Experimental design: The experiment was conducted during 2010 at the Laboratory of Dairy Sciences and Technology Department, College of Animal production Sciences and Technology. In this study four treatments were carried out as follows: First treatment is the control in which goat’s milk cheese had no additive. In the second, third and fourth treatments 0.02% of fenugreek, cinnamon and cardamom powder were added to the curd after coagulation, respectively.

Materials: Forty liters of goat’s milk were obtained from the local farm at Khartoum State. Seeds of cardamom, cinnamon and fenugreek were obtained from local spices market (Attar) at Khartoum. They were grinded to fine powder before use. Commercial edible grade table Salt (Sodium Chloride) was obtained from the local market. Rennet tablet from (Ch. Hansen’s Lab., Copenhagen, Denmark) were added at the rate of one tablet per 100 pounds of milk.

Cheese manufacture: The cheese was made according to the traditional method (Hamid, 2005). Raw goat’s milk was thermized at 40°C then salt was added at the rate of 3% and rennet tablet was added at the rate of one tablet per 45 kg milk with stirring then, the milk left until complete coagulation. The first treatment was control cheese (C) without any spices and the other three treatment were supplemented with different spices as follows: in the second, third and fourth portions 0.02% of Fenugreek (FN), Cinnamon (CN) and Cardamom (CR) powder were added, respectively to the curd of each ones. Then the curd of each treatment was left for drainage, after whey drainage in each treatment the cheese was packed into plastic containers (three replicates) then the cheese stored at 5°C for 30 days. The chemical analysis and sensory evaluation were carried out in duplicates at zero, 10, 20 and 30 days of storage for each treatment.

Chemical analysis: Titratable acidity was determined according to AOAC (2000), total solids was determined as described by AOAC (2000), protein was determined by Kjeldahl method as determined by AOAC (2000), fat and the ash contents of milk and cheese were determined according to AOAC (1990).

Sensory evaluation: The quality of the cheese samples stored under different conditions were judged by 10 untrained panelists for color, flavor, texture, odour and taste using sensory evaluation sheet according to Larmond (1987).

Statistical analysis: Statistical analysis was done using SPSS (1998) program (version 17). General linear models were used to estimate the effect of storage periods, flavoring materials and interaction between them on the chemical and sensory characteristics of goat’s white cheese. Least Significance Difference (LSD) was used for mean separation between the treatments. The level of significance (0.05) was used in this study.

RESULTS

Chemical composition of milk: The average chemical composition of the milk used for cheese making in this study were as follows: 0.11, 9.8, 3.2, 3.5 and 0.5% for titratable acidity, total solid, protein, fat and ash content, respectively.

Effect of the storage on the chemical composition of the goat’s cheese: Results in Table 1 show the main effect of the storage period on chemical composition of the goat’s cheese. The results indicated that fat contents of the cheese was affected significantly (p<0.05) by the storage period. It was decreased from 14.88±3.47% at day zero to 12.03±1.51 at day 10, then increased to 18.25±4.93% at day 20 and finally decreased to 13.68±1.62 at day 30.

Total solid contents of the goat’s cheese significantly (p<0.05) affected by storage period (Table 1). Total solids decreased from 41.813±3.66% at day zero to 27.43±4.25% at day 10. Then the value increased to 44.94±6.8% at day 20 and decreased to 33.81±3.02% at day 30.

Table 1:	Effect of storage period on the chemical composition (%) of goat’s cheese

The ash contents of the cheese increased significantly (p<0.05) with storage time from 2.88±0.92% at zero days to 3.063±0.496% at day 10, then slightly decreased to 2.19±0.65 at day 20 followed by a slightly increase to 2.31±1.34 at day 30. The protein contents of the goats cheese significantly (p<0.05) affected by storage period it decreased from 13.03±1.47% at day zero to 9.68±1.767 at day 10. Then it Increased to 15.260±2.06% at day 20 and decreased to 13.026±2.413% at day 30. The storage period affected the acidity of the cheese significantly (p<0.05), with an increase in storage time till 20 day thereafter no changes were observed at day 30.

Effect of spice types on the chemical composition of goat’s cheese: Results in Table 2 illustrated the effect of the additive types on the chemical composition of the goat’s cheese. The results indicated that there were no significant difference (p<0.05) in the fat content between all treatments. The results showed that the highest protein content (14.07±2.42%) was in the goat’s milk cheese with cinnamon while the lowest protein content was in the goat’s milk cheese without additive (Table 2). The results revealed that there was significant difference (p = 0.05) in the protein content between the control and the goat’s milk cheese with cinnamon. The ash content was highest in the cheese with fenugreek (3.38±0.84%). However, the lowest ash content was in the cheese with cardamom (2.38±1.25%). The statistical analysis showed that there was no significance difference (p = 0.05) in the total solids contents of the goat cheese in all treatments (Table 2). The results indicated that the acidity did not significantly (p = 0.05) affected by spices addition (Table 2).

Sensory evaluation: Results in Table 3 showed the main effect of the storage period on sensory characters of the goat’s cheese. The result indicated that the best value for all characters was at 20 day. The colour of the cheese was affected significantly (p<0.05) by the storage period.

Table 2:	Effect of spices types on chemical composition of goat’s cheese
Means within columns bearing different superscripts are significantly different (p≤0.05), S: Significantly different, NS: Not significantly different, C: Control, FN: Cheese with fenugreek, CN: Cheese with cinnamon, CR: Cheese with cardamom, LS: Level of significance

Table 3:	Effect of storage period on sensory evaluation of goat's cheese
Means within columns bearing different superscripts are significantly different (p≤0.05)

Table 4:	Effect of spices type on the sensory evaluation of goat’s cheese
Means within columns bearing different superscripts are significantly different (p≤0.05), S: Significantly different, NS: Not significantly different, C: Control, FN: Cheese with fenugreek, CN: Cheese with cinnamon, CR: Cheese with cardamom, LS: Level of significance

No changes were observed between day 0 and day 10 after that colour scores increased at day 20 and no change at day 30. The lowest value of the Colour scores recorded at day zero and the highest value at days 20 and 30.

Table 3 showed that the taste of the cheese samples improved from day 10 till the end of storage period. The results indicated that the odour of the cheese significantly (p<0.05) affected by the storage period (Table 3). There were no changes at day 0 and day 10, thereafter it increased at day 20 and no changes at day 30. The flavour of the cheese affected significantly (p = 0.05) by storage period (Table 3) the highest value (6.52) was at day 30 while the lowest one was at day 0 (5.68). The texture of the cheese during the storage period showed the same trend as the odour of the cheese done.

Effect of spices types on sensory characteristics of goat’s milk cheese: Table 4 showed the main effect of spices types on sensory characteristics of goat’s milk cheese. The color of the cheese affected significantly (p≤0.05) by spices type, the best value of the colour was for control and the lowest one was for the cheese with cinnamon and there were no change in fenugreek and cardamom cheeses colours. Spices types had no significant (p≥0.05) effect on the flavor and odour of the cheese in all treatments. The values of the texture decreased significantly (p<0.05), the best texture scores was for the control cheese while the lowest one was for the cheese with the cinnamon. The results indicated that the taste of the control cheese was significantly different (p<0.05) from the other treatments.

DISCUSSION

Effect of storage period and spices type on the chemical composition of the goat’s milk cheese: The chemical composition of the goat’s milk cheese was significantly (p≤0.05) affected during storage period (Table 1). The fat contents of the cheese samples significantly decreased during storage period. The decrease in fat content during storage from day 20 to 30 was probably due to the lipolytic activity of microorganisms on fats resulting in leakage of some fat from curd into the pickling whey. The findings in this study agreed with those of Khalid (1991), Abbasi (1992) and Nuser (2001), who reported that there was decrease in fat contents during storage period. Although, the decreased in fat content from day 0-10 was attributed to decrease in the total solid (Khalid, 1991). Total solids contents of the goat cheese increased from day 10 to day 20 then decreased throughout the storage period (Table 1). The findings were in accordance with the work of Babiker (1987), Abdel-Razig (1996), Hamid (2005) and Bilal (2000) who found that the total solid content of the white soft cheese increased during storage. The increase could be due to continuous loss of moisture from the curd as a result of lactic acid development which causes curd contraction. However, the decrease of total solids content from days 20-30 possibly due to proteolytic effect of microorganisms on the proteins and dissolution of fat and salt into the pickling solution (Nuser, 2001). The results of ash content confirmed the finding of Abdel-Razig (1996); Hamid (2005) and Nuser (2001) who reported that the increased in the ash content during storage might be due to decrease in moisture content and absorption of salt by curd. The decrease in ash content was possibly due to diffusion of salt from the curd into the pickling solution (Abbasi, 1992).

The results in protein contents in this study were in accordance with the findings of Kur (1992), Abdel-Razig (1996) and Hamid (2005) that showed the protein contents of cheese increased during ripening due to decrease in moisture contents. Other results demonstrated that the protein contents decreased during storage due to protein degradation leading to formation of water soluble compounds Nuser (2001). Titratable acidity of the cheese affected significantly (p = 0.05) by storage period (Table 1). These results were in agreement with those reported by Kur (1992), Nuser (2001) and Bilal (2000). The development of titratable acidity during storage till day 20 could be attributed to growth of lactic acid bacteria which increased the level of lactic acid in the cheese (Walstra et al., 1999). On the other hand the decrease in titratable acidity at day 30 might be due to utilization of lactic acid by other micro flora during storage. Increase of fat (Table 2) in cheese with cinnamon could be due to the contents of essential oils in its components (Valero and Salmeron, 2003; El-Tantawy et al., 2006). The highest total solids content of the cheese with cinnamon might be due to high retention of moisture from the curd and high level of fat while the low total solids content of the control cheese could be attributed to the high moisture contents in curd (Table 2). The highest value of ash content of cheese with fenugreek could be due to high level of minerals it content while the lowest ash content of the cheese with cardamom probably due to high moisture content in the curd. The decrease of protein in control cheese may be due to the degradation of protein by micro organisms (Table 2). The highest titratable acidity in cheese with fenugreek could be due to high level of lactic acid produced by lactic acid bacteria. On the contrary the low titratable acidity in cheese with cardamom was due to inactivation of lactic acid bacteria by cardamom. Present results were consistent with those of El-Tantawy et al. (2006), Bilal (2000) and Hamid (2005).

Effect of storage period and spices types on sensory characteristics of white goat cheese: The sensory evaluation (Table 3) affected significantly (p≤0.05) by storage period. The colour, taste, texture and flavour of the cheese improved during storage period this could be due to proteolytic and lipolytic processes occurred during storage.

Results showed that the best colour of the control cheese (Table 4) could be due to consumer acceptability of the white colour in cheese. Statistical analysis showed that the spices types had no significant effect on the flavour and odour of the cheese in all treatments, probably due to low percent of all additives. These results were in accordance with the results of El-Tantawy et al. (2006).

CONCLUSION

Chemical composition and sensory characteristics of goat’s milk white soft cheese were significantly (p<0.5) affected by storage period. Sensory evaluation results showed that addition of spices improve flavour and odour of the goat’s milk cheese. Fat, protein and ash contents of the cheese were significantly (p<0.5) affected by storage period and spices types. While, total solids and acidity were not affected by spices types. The use of some spices powders improved the quality of goat’s milk cheese.