Abstract:
Objective: The study was carried out to compare the production and composition of Sudanese white cheese (Gibna Mudaffara) in four different localities in North Kordofan states. Materials and Methods: A total of 24 samples of white cheese were collected from four cities of North Kordofan. The samples were characterized for their chemical and microbial properties. Data were analyzed using the SPSS software. Results: Significant (p<0.05) variations were observed in the chemical composition and microbial load of the cheese samples although the production techniques were slightly different from each other. The average chemical composition of the cheese gave the following results: 52.88% total solids, 23.8% fat, 20.4% crude protein, 0.37% water soluble protein, 5.33% ash and 1.057% titratable acidity. The total viable bacteria count was the highest in samples collected from EL Rahad city, while the highest Coliform bacteria counts was recorded in Mudaffara cheese samples obtained from Kazgail city. The total viable bacteria, Coliform bacteria and Staphylococci counts was the lowest in the sample obtained from Abuharaz city. Conclusion: A significant difference in the chemical composition and microbial load was observed in the cheese samples. The yeast, mold, Staphylococcus aureus, total viable count and coliform bacteria was the highest in the Mudaffara cheese samples.
INTRODUCTION
Sudan has one of largest livestock populations in Africa. It makes a major contribution to the national economy and export revenue. Traditional dairy products are not only economically important but they also represent a cultural heritage for the production area. Knowledge of microbial communities may help in the specification and characterization of these products. To date, few studies are conducted on Sudanese dairy foods. Important protocols and procedures for safety, storage and production of dairy products must be taken into account1.
In Sudan, cheese is produced throughout the country, particularly in Eldueim, White Nile State; Elobied, North Kordofan State; Nyala, South Darfur State and other locations1. However, in the rural areas of Sudan, cheese production is the most commonly practiced method of preservation of surplus milk, especially during the rainy season when milk is relatively plentiful1,2. Traditional Sudanese fermented foods are the main source of nutrition for rural and urban people. Dairy products help in boosting economic growth, finance and business3. Sudanese cheese is a traditional product made from raw milk and without the use of starter culture with added salt (6-20%) and is usually packed in plastic containers, a practice that leads to deterioration of quality4. This high salt content (6-20%) may have an immediate impact on health and blood pressure5. Salt acts as a preservative and protect cheese from rapid deterioration before ripens6. Mudaffara cheese is a braided, un-matured semi-hard cheese from the Mediterranean region with a close texture, yellowish color, slightly acidic and salty taste that is popular among Sudanese rural communities. Rennet or rennet extract is added to produce a firm coagulum in four to six hours. Ripening takes place while the cheese is immersed in whey. The purpose of coagulation is to catalyze the conversion of liquid milk into gel using various proteases7.
In Sudan, cheese making is the main conservation method for excess milk in rural areas particularly during the rainy season when plenty of milk is available and about 152,000 tons of cheese is produced annually2 and accordingly many types of cheese are produced throughout the country. Of them, braided cheese locally known as Muddaffara is now being produced in Sudan. Muddaffara cheese is among the most popular cheese in Sudan and other Middle Eastern countries. It is estimated that about 7500 t of Muddafara cheese is manufactured in Sudan each year and this cheese is sold in the local markets8. Cow milk or sheep milk or a mixture of cow, sheep and goat milk is used to prepare Mudaffara cheese9. Increasing demand of Mudaffara cheese in Sudan and its short shelf life at room temperature (15 days), make it so important to enhance its taste and quality. No previous studies have been carried out to investigate the nutritional value and microbiological characteristics of white cheese (Gibna Mudaffara), therefore, the present study was conducted to evaluate the nutritional value, chemical and microbiological composition of Modaffara cheese produced in Sudan.
MATERIALS AND METHODS
Collection of samples: North Kordofan is one of the 18 states of Sudan. It has an area of 185,302 km2. Twenty-four samples were collected from four cities (El Obaied, El Rahad, Kazgail and Abuharaz) in North Kordofan State.
Chemical analysis of Gibna Mudaffara samples: Gibna Mudaffara were tested for titratable acidity, total solids, crude protein and ash content in accordance with AOAC10 guidelines. Soluble protein was determined according to the procedure described by Ling11 while salt content was estimated according to the method described by IDF12. The amount of volatile fatty acids was measured according to the procedure described by Kosikowski's13. The fat content was evaluated according to the procedure described by Foley et al.14.
Microbiological analysis of cheese samples: Samples were maintained aseptically under refrigerated condition (4°C) before being serially diluted by adding 25 g of Gibna samples to 225 mL of sterile peptone water in a clean 500 ml sterile flask and shaking to generate a 10–1 dilution. For enumerating diverse groups of spoilage and harmful bacteria, appropriate dilutions were surface plated on appropriate agar plates15.
Aerobic colony bacterial count (ACC): The whole bacteria count was determined using plate count agar medium (2006) as described by Laird et al.16 and Ramakant17.
Coliform bacteria count: To enumerate coliforms and E. coli, Violet Red Bile Agar (VRBA, Oxoide) and Eosin Methylene Blue Agar (EMB, Oxoide) Agar medium were used. For coliforms enumeration the plates were incubated at 37°C for 48 h while the plates carrying E. coli were incubated at 44°C for 24 and 48 h15.
Staphylococci count: Only 0.1 mL of the tested samples from the prepared dilutions was transferred and lightly spread at the floor of mannitol salt agar medium (OXOID, Hampshire, United Kingdom). Inoculated plates were incubated at 37°C for 48 h and Staphylococci counts per g of examined product was calculated and recorded15.
Enumeration of molds and yeasts: Sabouraud dextrose agar medium was used for the enumeration of yeasts and molds count as described by Harriagan and McCance15.
Statistical analysis: This study used a Completely Randomized Design. All statistical analyses were performed using the Statistical Package for Social Science (SPSS)18 version 10.0 for windows (SPSS Inc., Chicago, IL, USA).
RESULTS AND DISCUSSION
The highest total solids content was recorded for cheese samples obtained from El Rahad (North Kordofan) which was significantly higher (p<0.001) than those of the other cheese samples obtained from other three areas. The total solids contents of most cheese samples obtained from El Obaied, Kazgali and Abuharaz showed non-significant variations (p>0.05).
The highest protein content, recorded for the cheese sample from El Rahad and Kazgail, while the lowest was observed in the cheese sample obtained from Abuharaz city. However, no significant variations were found in protein contents of the cheese samples between producers in El Obaied and Abuharaz.
The highest water-soluble protein content was observed in cheese sample that obtained from Kazgail city, whilst the lowest was recorded for a cheese sample obtained from El Rahad. Enormous (p<0.001) variation was discovered in soluble protein contents of the cheese in special areas.
The ash content for the cheese sample from El Rahad was the highest, while the lowest was for a cheese sample from Abuharaz. The acidity of cheese samples from El Rahad was significantly higher (p<0.001) than those of the other cheese samples. The lowest acidity value was recorded for the cheese sample obtained from El Obaied city, higher salt contents was found in the cheese sample obtained from El Rahad city while, the lowest salt contents was recorded in the Kazgail city (Table 1). Variations were observed in fat contents of the cheese in different areas. The results were not in accordance with those reported by Elkhider19 and Topcu and Saldamli20 who found 12.8 and 11.79% fat (35.45% of dry matter), respectively. The high average fat contents in this study could be due to high fat contents of the milk used for cheese making. Average protein contents of the collected cheese samples was 20.41%.
These results agree with a previous study conducted by Abdalla21. However, these results disagree with those of Ceylan et al.22; Lemya et al.23 and El Owni and Hamid2. Average water soluble protein contents of collected cheese sample was 0.36%. This finding is lower than the result of a previous study conducted by Tarakci and Kucukoner24.
In several areas, variations were observed in fat contents of the cheese. The findings of the present study agree with the results of Nuser25. From the results it is obvious that the fat, protein, total solids and moisture contents of white cheese (Gibna Mudaffara) satisfied the Sudanese standard for cheese while the acidity didn't satisfy the quality.
Table 2 shows that total viable count was the highest in the Gibna Mudaffara samples obtained from El Rahad and the lowest in the samples which were obtained from Abuharaz. The highest Coliform bacteria count was recorded for the Mudaffara cheese samples from Kazgail, while the lowest was found in cheese samples obtained from Abuharaz. However, significant variations (p<0.001) were found in Coliform counts of the cheese samples among producers in El Obaied and Abuharaz and El Rahad city.
The highest molds and yeast counts were recorded for cheese samples obtained form Abuharaz, while the lowest was recorded for a cheese samples from El Obaied. Molds and yeast counts of the cheese were significantly (p<0.001) different in different areas. The difference in the chemical composition and microbial load could be attributed to variation in the chemical composition of raw milk used for cheese manufacturing or difference in manufacturing process and marketing methods, since there is no standard procedure for cheese manufacturing in Sudan.
Microorganisms play an important role in the deterioration of dairy products and in the ripening of some types of cheese25. The spoilage organisms in cheese and dairy products are coliforms, yeasts and molds, propionic acid bacteria, fecal streptococci, lactococic lactic acid and psychrotrophic bacteria22. The spoilage microorganisms differ greatly in dairy products due to the selective effect of practices followed in production, formulation, processing, packaging, storage, distribution and handling26. Raw milk may contain a wide variety of pathogenic organisms. They may be derived from an infected (mastitic) udder, the faeces or other excreta of infected cows or symptomless (carrier), cows, human sources, a contaminated environment or dairy equipment. The group includes Staph aureus, Streptococcus spp, Salmonella, E. Coli, Listeria monocytogenes, etc. If pathogens survive during cheese manufacturing process, it may result in food poisoning due to the ingestion of cheese contaminated with pathogenic organisms and their enterotoxins. Mold species are essential for ripening of specific varieties of cheese but mold growth on most cheeses is undesirable. It spoils the appearance, can impart musty flavor and may produce mycotoxins27.
Coliform contamination of cheese, particularly fecal coliforms, is an indication of direct or indirect fecal contamination and is seen as a mirror of the degree of non-compliance with many hygiene standards during processing and marketing28. Osman4 examined the microbiological properties of Sudanese white cheese and found that the total count of bacteria, coliforms and molds, as well as the yeasts of the cheese samples, increased significantly at the beginning of storage (p≤0.05) and the time of storage decreased towards the end of the year, only Staphylococcus aureus was detected on day zero and disappeared completely during the storage period. Salmonella were not found. Ceylan et al.22 examined the microbiological quality of white cheese and found that the average number of coliforms was 5.99 log CFU g–1; the high content of coliforms was attributed to post-contamination during storage. Recently, due to increase in population, the cheese (Gibna Mudaffara) industry has become a common sight without supervision or quality, Sudanese white cheese is delivered to the market immediately after processing under inadequate conditions such as poor handling technique, inappropriate packaging materials and lack of adequate storage facilities. However, dairy products including cheese must be safe, acceptable and should meet consumer's satisfaction2,29. Different factors that influence the quality and nutritive value of white cheese include composition of food materials, the natural of the compounds, the type of packaging system and the preservative used30.
CONCLUSION
Both rural and urban residents in Sudan rely on traditional fermented foods as their primary source of sustenance. Dairy products accelerate the economic growth. In Sudan, white cheese is produced under inadequate conditions. Its quality is neither checked nor controlled. Lack of adequate storage facilities, inappropriate packaging material and poor handling technique increase the risk of spoilage of dairy products.