100 American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) ISSN (Print) 2313-4410, ISSN (Online) 2313-4402 © Global Society of Scientific Research and Researchers http://asrjetsjournal.org/ Physico-chemical, Microbiological Parameters and Adulteration in Processed Dairy Products in Pakistan Sibghat Ullaha, Muhammad Tariq Zebb*, Muhammad Ayazc, Muhammad Tahir Khand, Siraj Ahmade, Aziz Ullah Noorf, Kausar Zebg, Farman Ullahh, Baitullah Khani, Muhammad Nauman-ul-Islamj, Naveed Ullahk, Ihsanullah Khanl, Faizul Hassanm, Ihsan uddinn, Haneefur Rehmano, Faiza Ashrafp a,I,o,pFoot and Mouth Disease Research Center, Veterinary Research Institute, Peshawar, Pakistan. b,m,nVeterinary Research and Disease Investigation Center, Swat, Pakistan. cUniversity of Veterinary & Animal Sciences, Lahore, Pakistan. dMuhammad ali Jinnah University, Pakistan. eVeterinary Research Institute, Peshawar, Pakistan. fHazara University, Mansehra, Pakistan. gL&DD department, KPK, Peshawar, Pakistan. hLasbella University, Balochistan, Pakistan. iLivestock Research and Developmental Station, Surezai, Peshawar, Pakistan. jThe University of Agriculture Peshawar, Khyber Pakhtunkhwa, Pakistan. bEmail:drtariqzeb@yahoo.com Abstract Adulteration of dairy products with chemicals such as Caustic soda, Urea, Antibiotics and Microbiological contamination (high Total plate count, Coliform count and S. aureus) in processed dairy products samples constitute a potential public health hazard. A study was carried out to determine the microbiological quality and adulteration in various processed dairy products from various brands prevalent in the market. ------------------------------------------------------------------------ * Corresponding author. http://asrjetsjournal.org/ American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2016) Volume 25, No 1, pp 100-112 101 Samples of different dairy products including: (i) Yogurt, (ii) Cheese, (iii) Butter, (iv) Ice cream and v) Milk powder were collected from various places and processed in the laboratory for physic-chemical, microbiological and adultration analysis was carried out. (i)Yogurt samples from different Brands showed non-significant (P>0.05) difference in Total Plate Count (TPC), Coliform Count (CC) whereas significant (P<0.05) difference was observed in Streptococcus aureus Count (SAC), (ii) Cheese samples showed non-significant (P>0.05) difference in TPC whereas significant (P<0.05) difference was observed in SAC, (iii) Butter samples showed significant (P<0.05) difference in TPC, CC and SAC, (iv) Ice cream samples showed significant (P<0.05) difference in TPC, CC and SAC; and (v) Milk powder from various brands showed non-significant (P>0.05) difference in CC and SAC. All dairy products were negative for chemical adulterants tests i.e. urea, formaldehyde, neutralizers, starch, boric acid, quaternary ammonium compounds, while H2O2 was slightly positive in yogurt, milk powder and Ice cream samples of different brands. It is concluded that the dairy product in the market are safe from adulterants. Further butter and ice cream are showing a significant TPC, CC, and SAC. Key words: Physico-chemical quality; Microbial quality; chemical adulterants; dairy products. 1. Introduction In 2002 Pakistan was producing 32 million tons of milk that was slightly rise than Germany [5]. There is a great potential for dairy industry but the sector operates mostly in the informal economy and needs a consistent effort to formalize and be able to contribute better to the national economy. There are hardly 15 milk processing plant (mainly UHT fluid milk, milk powder and yogurt in Pakistan). Only about 3 percent milk is being processed and 97 percent is consumed as raw milk [14] . Milk and dairy products are one of the most important food products that enjoy special significance in terms of its various nutritional properties such as protein, lactose, fat, minerals and vitamins. Many studies have been made on its constituents and physicochemical characteristics [21]. Milk and dairy products form a significant part of the diet in many countries and a substantial part of food expenditure goes on milk and dairy products. Basic public health and hygienic considerations require that consumer be provided with safe and pure milk that is hygienically clean and unadulterated. Suppliers of milk and milk in Pakistan dairy industry appear to have found three ways to increase their margin from the sale of milk, 1) Addition of water 2) Removal of valuable components i.e. milk fat 3) A combination of one and two with the addition of additives, such as starch, to increase the total solids [20]. Sometime adulteration of milk is made by addition of chemicals i.e. caustic soda, urea and antibiotics which can cause serious health problem such as cancer, diabetes and kidney failure [7] and ultimately affect the health of our nation. Adulteration of milk and dairy products is one of the most serious issues in the dairy industry and causes economic losses and major health problems to consumers. Due to the limited numbers of large dairy farms, milk handling processes in the traditional system are unhygienic and there is insufficient enforcement of standards, resulting in poor quality milk products. In order to keep milk safe middleman adds ice to the milk. In addition, American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2016) Volume 25, No 1, pp 100-112 102 microbiological contamination occurs due to addition of ice in the milk [2]. The middleman increases the milk quantity by adding water, vegetable oil, whey powder and other ingredients to increase the solids of the milk. Antibiotics and Hydrogen peroxide are often used as preservatives [5]. The adulterants in milk include water, starch, vegetable oil, whey powder and hazardous substances such as antibiotics, caustic soda, urea, formalin, detergents and other chemical preservatives. Adulteration in milk and dairy products is a serious public health hazard and is a very serious problem in Pakistan. Keeping in view these facts, the present study was planned with the objectives to study the microbiological quality of dairy products and to determine the chemical adulterants and residues in dairy products. 2. Materials and methods 2.1 Collection of samples The dairy product samples were collected from the market and then physicochemical, microbiological, and adulteration analyses were performed at Quality Control Laboratory, University of Veterinary and Animal Sciences (UVAS), Lahore. Three samples of each brand were collected from local market Lahore. Yoghurt samples from Haleeb and Nestle brands, Cheese samples from Nurpur Dairies, Haleeb and Adams, Butter samples from Gourmet, Haleeb and Nestle, milk powder samples from two different brands namely, Nurpur Dairies and Haleeb whereas, Ice cream samples were collected of three different brands namely, Gourmet, Walls and Yummy of cup types. 2.2 Sampling procedure Dairy product samples were collected in clean sterilized containers and put in ice chest, whereas milk powder was collected in zip polythene bag. These samples were transported for analysis to Quality Control Laboratory, University of Veterinary and Animal Sciences, Lahore. 2.3 Sterilization All glassware like pipette, test tubes, Petri dishes, beakers, and flasks were thoroughly cleaned and sterilized in an oven at 1800C for 2 hours. All media and solutions were prepared in distilled water and autoclaved at 1210C at 15 lb pressure for 15 minutes using the procedure of [3]. 2.4 Microbiological tests Dairy product samples were tested for Total plate count, Coliform count, Staphylococcus aureus, and Yeast and Mould count by the methods prescribed by [3]. 2.5 Sample preparation Prepared the dilution blanks by pipetting 9 ml of Phosphate Buffer Solution (PBS) into sterile test tubes. Dairy American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2016) Volume 25, No 1, pp 100-112 103 product sample was taken with 1 ml sterilized pipette and added into first dilution blank, and then shake the test tube 25 times in 1-foot arc within 7 seconds and then 1ml is transferred to the next dilution blank. Continued the same procedures as the required dilution obtained according to procedure of [3]. 2.6 Total plate count The Total plate count (TPC) is intended to indicate the level of microorganisms in the product. Plate count agar media (Table1) was used for the determination of Total Plate Count in dairy product samples as described in [3]. 2.7 Colony counting Colonies were counted from the plates showing the colonies between 20-200 with the help of colony counter [3]. Viable bacterial count = Average number of colonies × dilution factor 2.8 Coliform count Violet Red Bile Agar (VRB) media (Table 2) was used for determination of Coliform count in dairy product samples. Media was prepared by following the procedure of manufacturer (Oxoid) [3]. 2.9 Staphylococcus aureus count Baired Parker Agar media (Table 3) was used to determine the Staphylococcus aureus count in dairy product samples. Media was prepared according to (Oxoid) for preparation of plates were poured and the spread plate method was used as described in` [3]. 2.10 Yeast and mould Saborad Dextrose Agar media (Table 5) was used for determination of yeast and mould in dairy product samples. Media was prepared by following the procedure of manufacturer (Oxoid) [3]. 2.11 Chemical Adulterants Detection Tests 2.11.1 Formaldehyde Adulteration of Formaldehyde was determined by mixing 02 ml sample of dairy products with 90% solution of sulfuric acid. Development of yellow color at the junction of two layers indicated the presence of formaldehyde. 2.11.2 Boric acid For the detection of Boric Acid adulteration, 5 ml dairy product samples were taken in a test tube and 1 ml of concentrated hydrochloric acid was added, contents of test tube were mixed well for 1 minute and a strip of American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2016) Volume 25, No 1, pp 100-112 104 turmeric paper was dipped into the acidified dairy products and development of red color exhibited the presence of boric acid. 2.11.3 Hydrogen peroxide Presence of hydrogen peroxide was detected by mixing 1% Valeduum Peroxide in 6% sulfuric acid solution. Appearance of pink color was the evidence of adulteration of dairy products with hydrogen peroxide. 2.11.4 Starch Presence of starch in dairy products was determined by adding 1ml (1 %) iodine solution in 3 ml dairy product samples. Presence of blue color indicated the presence of starch. 2.11.5 Neutralizer (sodium carbonates, sodium bi carbonates and sodium hydroxide) Adulteration of neutralizers was estimated by mixing 1 ml of various dairy products sample with 1 ml Rosalic acid solution (1 % in distilled water). Development of red color indicated the adulteration of dairy products with neutralizers. 2.11.6 Urea Adulteration of urea was detected by adding 01 ml 1.60% Para Dimethyl Benzaldehyde prepared in concentrated Hydrochloric Acid. Development of yellow color indicated the adulteration of dairy products with urea. 2.11.7 Quaternary Ammonium Compounds Five ml of dairy products were taken in a centrifuge tube, 5 ml of tetra chloroethane and 2 ml of lactic acid solution was added and test tube was stopped and shaken vigorously for One minute, 02 ml of standard sodium hydroxide solution was added and centrifugation was done at 3200 r.p.m. for 5 minutes. Remove the top layer by decantation. Pipette out 2 ml of aliquot of tetra chloroethane in a test tube. Add 0.5 ml of citric acid buffer and 0.2 ml of eosin solution. Cork the tube and shake vigorously. Observe the color. Pink or red color in the tetra chloroethane indicates presence of QAC. Adulteration tests were performed by following the procedures of [6]. 2.12 Statistical analysis The data thus obtained were statistically analyzed to compare the parameters of study through analysis of variance technique [16] and the means were compared through LSD whereas the comparison between dried milk samples and yoghurt samples were done through student’s t- test. American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2016) Volume 25, No 1, pp 100-112 105 3. Results and discussion 3.1 Microbiological Tests 3.1.1 Total Plate Count The highest recorded mean of Total plate count was (4.60+0.627) log cfu/g in yoghurt samples of Haleeb brand and lowest was (4.49+0.498) log cfu/g in Nestle brand. ANOVA showed non-significant (P>0.05) difference in Total plate count of yoghurt samples. These results are agreed with Lin and his colleagues. [13] who reported maximum increase (P<0.05) in Total plate counts that ranged from 6.0-7.0 to 7.5-9.1 log cfu/g. Salisu and his colleagues.[18] also reported the mean total aerobic plate count (TAPC) was 3.37 x 104 cfu/ml while the range was 2.66 x 104 ± 8.3 x 103 to 1.13 x 105 ± 1.17 x 105 cfu/ml of yoghurt. The highest recorded mean of Total plate count was (4.93+1.128) log cfu/g in cheese samples of Nurpur brand while, lowest was (3.31+0.10) log cfu/g observed in Haleeb brand. ANOVA showed non-significant (P>0.05) difference of Total plate count in cheese samples of different brands. Our results are in agreement with [15] and Suleiman [19] who found that the mean Total plate counts/g, log10, in the fresh U.S. and Canadian cheeses were 3.54 and 5.22, and total viable count 1.0×104 c.f.u/g respectively. The highest mean of Total plate count recorded was (5.39+0.524) log cfu/g in butter samples of Gourmet brand and lowest was (3.67+0.349) log cfu/g in Nestle brand. There was significant (P<0.05) difference in Total plate count of butter samples. These results are similar to the reported by [22] who found Aerobic plate counts that ranged from 1.7 to 3.5 log cfu/g in butter samples. The highest recorded mean of Total plate count was (5.76+0.69) log cfu/g in ice cream samples of Gourmet brand and lowest was (4.31+0.275) log cfu/g in Walls brand. ANOVA showed the significant (P<0.05) difference in Total plate count of ice cream samples of different brands Table 1 and 2. 3.1.2 Coliform Count The highest mean of Coliform count was (3.85+0.442) log cfu/g in yoghurt samples of Haleeb brand and lowest was (3.28+0.07) log cfu/g observed in Nestle brand. ANOVA table showed non-significant (P>0.05) difference of Coliform count in yoghurt samples of different brands. The results of present studies regarding Coliform count is not in line with [11] who did not report Coliform count in yoghurts made from fresh or frozen milks. Ifeanyi and his colleagues. [9] reported the coliform count in the yoghurt samples were high; 4.4 x 105 CFU/ml. The highest recorded mean of Coliform count was (5.28+0.759) log cfu/g in cheese samples of Nurpur brands and lowest (3.38+0.110) cfu/log g were observed in Haleeb brand. ANOVA showed significant (P<0.05) difference of Coliform count in cheese samples of different brands. Conversely to our results, [1] did not report Coliform count in cheese while Hussein and his colleagues. [8] find out the the coliform count was high in locally produced cheese log 3.34 compared to the imported one log 3.09. The highest mean of Coliform recorded was (4.53+0.732) log cfu/g in butter samples of Gourmet brand and lowest was (3.38+0.013) log cfu/g observed in Nestle brand. ANOVA showed the significant difference of Coliform count in butter samples of different brands. The highest mean of Coliform recorded was (5.41+0.616) log cfu/g in ice cream samples of Gourmet brand and American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2016) Volume 25, No 1, pp 100-112 106 lowest was (3.79+0.37) log cfu/g observed in Walls brand. Similar results were reported by [12] who manufactured three ice creams with flavors of vanilla, chocolate and strawberry and observed Coliform counts with the level of 1.7 to 2.4 log cfu/g. ANOVA showed significant (P<0.05) difference of Coliform count in Ice cream samples. The highest mean of Coliform recorded was (4.16+0.826) log cfu/g in milk powder samples of Nurpur brand and lowest was (3.95+0.873) log cfu/g observed in Haleeb brand. ANOVA showed non- significant (P>0.05) difference of Coliform count among milk powder samples of different brands (Table 3). Table 1: Analysis of variance of microbiological tests in yoghurt samples of different brands Yoghurt Cheese SO V D iff er en ce M ea n sq ua re F P va lu e di ff er en ce M ea n sq ua re F P va lu e TPC - b/w groups 1 1.493 4.680 0.059 2 2.540 2.830 0.136 Error 4 0.319 6 0.897 Total 5 8 Coliform -b/w groups 1 0.859 3.632 0.092 2 2.989 9.519 0.013 Error 4 0.236 6 0.314 Total 5 8 Staph aureus - b/w groups 1 5.154 10.511 0.010 2 0.806 8.182 0.019 Error 4 0.245 6 0.098 Total 5 8 3.1.3 Staphylococcus aureus count The highest recorded mean of Staph aureus was (4.52+0.557) log cfu/g in yoghurt samples of Haleeb brand and lowest was (3.63+0.079) log cfu/g in Nestle brand. ANOVA revealed significant (P<0.05) difference of Staph aureus of yoghurt samples. The highest mean of Staph aureus recorded was (4.64+1.132) log cfu/g in cheese samples of Nurpur brands and lowest was (3.61+0.16) log cfu/g in Haleeb brand. American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2016) Volume 25, No 1, pp 100-112 107 ANOVA showed significant (P<0.05) difference of Staph. Aureus count in cheese samples of different brands. Present results are in agreement with [17] who reported S. aureus counts were 5.16 log cfu/g in control cheese samples. The highest mean of Staph aureus recorded was (5.35+0.736) log cfu/g in butter samples of Gourmet brand and lowest was (3.60+0.167) log cfu/g in Nestle brand. Table 2: Mean (±S.E) total plate count, coliform Staph aureus count in yoghurt samples of different brands There was significant (P<0.05) difference of Staph. Aureus count of butter samples. The highest mean of Staph aureus recorded was (6.38+0.536) log cfu/g in ice cream samples of Gourmet brand and lowest was (3.90+0.048) log cfu/g in Walls brand. ANOVA revealed significant (P<0.05) difference of Staph. Aureus Count in ice cream samples. The highest mean of Staph aureus recorded was (4.89+0.299) log cfu/g in milk powder samples of Nurpur brand and lowest value (4.43+0.425 log cfu/g) was observed in Haleeb brand. ANOVA revealed non-significant (P>0.05) difference of Staph. Aureus count among milk powder samples of different brands (Table 4). 3.1.4 Yeast and Mould Count Yeast and Mold count in cheese samples of Nurpur brand was 2.5×104 /g and 4.3×103/g in Haleeb samples. In case of Gourmet butter, Yeast and mould count was3.1×104/g, while samples of Nestle showed 3.7×103/g. [4] reported high Yeast count 106–107 cfu/g in yoghurt and cheese samples, while lower counts found in cream, butter and ice cream. Sample Total Plate Count Coliform count Staph aureus count Means + S.E Min Max Means + S.E Min Max Means + S.E Min Max Haleeb Yoghurt 4.60 +0.627 4.14 5.32 3.85+0.442 3.54 4.36 4.52 +0.557 3.88 4.86 Nestle Yoghurt 4.49 +0.498 4.17 5.07 3.28+0.070 3.22 3.36 3.63 +0.079 3.54 3.69 Adams Cheese 4.88 +1.186 4.64 5.59 4.85+0.594 4.46 5.54 4.10 +0.517 3.51 4.44 Haleeb Cheese 3.31 +0.100 3.94 3.41 3.38+0.110 3.27 3.49 3.61 +0.16 3.51 3.71 Nurpur Cheese 4.93 +1.128 4.80 5.61 5.28+0.759 4.41 5.74 4.64 +1.132 4.53 4.79 American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2016) Volume 25, No 1, pp 100-112 108 3.1.5 Chemical Adulterants Detection Tests Haleeb and Nestle yoghurt brands were negative for chemical adulterants tests i.e. urea, formaldehyde, neutralizers, starch, boric acid, quaternary ammonium compounds, while H2O2 was detected slightly positive in both yoghurt samples of Haleeb and Nestle Table 5. Similarly all the chemical adulterants tests were negative for milk powder samples of Haleeb and Nurpur brands while slightly positive for H2O2. Results about ice cream samples showed that all the ice cream samples were negative for chemical adulterants tests while slightly positive for H2O2. Our study agreed with [10] who reported similar adulterants in dairy products. Table 3: Analysis of variance of microbiological tests in butter samples of different brands. Butter Samples Ice cream Samples Milk powder SO V D iff er en ce M ea n sq ua re F P va lu e D iff er en ce M ea n sq ua re F P va lu e D iff er en ce M ea n sq ua re F P va lu e TPC - b/w groups 2 2.482 10.275 0.0115 2 2.073 6.338 0.033 1 1.297 3.22 0.147 Error 6 0.241 6 0.327 4 0.402 Total 8 8 5 Coliform -b/w groups 2 2.482 10.275 0.011 2 2.273 6.676 0.029 1 0.064 0.088 0.780 Error 6 0.241 6 0.340 4 0.723 Total 8 8 5 Staph aureus - b/w groups 2 2.317 11.408 0.009 2 4.712 15.667 0.004 1 0.326 2.419 0.195 Error 6 0.203 6 0.300 4 0.135 Total 8 8 5 American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2016) Volume 25, No 1, pp 100-112 109 Table 4: Mean (±S.E) total plate count and coliform count in butter samples of different brands Table 5: Chemical adulterants in yoghurt samples of different brands Total Plate Count Coliform count Staph aureus count Samples Means + S.E Min Max Means + S.E Mi n Ma x Means + S.E Min Max Gourme t Butter 5.39 +0.524 4.79 5.76 5.21+0.112 5.1 3 5.3 3 5.35 +0.736 4.51 5.85 Haleeb Butter 5.05 +0.572 4.66 5.71 5.36+0.342 5.2 8 5.4 5 4.58 +0.196 4.36 4.71 Nestle Butter 3.67 +0.349 3.41 4.07 4.79+0.327 4.5 2 5.1 7 3.60 +0.167 3.41 3.71 gourmet , ice cream 5.76 +0.690 5.34 4.56 5.41+0.616 4.7 1 5.8 6 6.38 +0.536 5.76 6.85 Walls ice cream 4.31 +0.275 4.11 4.63 3.79+0.370 3.5 1 4.2 1 3.90 +0.480 3.49 4.43 Yummy ice cream 4.33 +0.654 3.62 4.91 4.05+0.710 3.3 4 4.7 6 4.85 +0.595 4.27 5.46 Haleeb milk powder 3.94 +0.638 3.54 4.68 3.95+0.873 3.3 9 4.9 6 4.43 +0.425 3.96 4.79 Nurpur milk powder 4.87 +0.630 4.25 5.51 4.16+0.826 3.2 1 4.7 1 4.89 +0.299 4.65 5.23 Yoghurt Nurpur Urea Formaldehyde H2O2 Neutralizers Starch Boric Acid QAC Yoghurt Haleeb –ve –ve +ve –ve –ve –ve –ve Yoghurt Nestle –ve –ve +ve –ve –ve –ve –ve Milk powder Nurpur –ve –ve +ve –ve –ve –ve –ve Milk powder Haleeb –ve –ve +ve –ve –ve –ve –ve Ice cream Gourmet –ve –ve +ve –ve –ve –ve –ve Ice cream Walls –ve –ve +ve –ve –ve –ve –ve Ice cream Yummy -ve –ve +ve –ve –ve –ve –ve American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2016) Volume 25, No 1, pp 100-112 110 4. Conclusion On the basis of present findings, it is concluded that multiple factors can markedly affect the quality of dairy products. Adulteration of dairy products with chemicals such as Caustic soda, Urea, Antibiotics and Microbiological contamination such as Total plate count, Coliform count and Staphylococcus aureus in processed dairy products samples constitute a potential public health hazard. Acknowledgments The authors of paper are thankful to the staff of University Diagnostic Laboratory (UDL), University of Veterinary and Animal Sciences (UVAS), Lahore, for providing the laboratory facility and technical inputs to undertake the study. Funding/Support The study was conducted at the University Diagnostic Laboratory, UVAS, Lahore, Pakistan. Declarations The authors of the manuscript declare that they have no conflict of interest. References [1] Albenzio M, Santillo A, Caroprese M, Braghieri A, Sevi A, Napolitano F (2013) Composition and sensory profiling of probiotic Scamorza ewe milk cheese. Journal of dairy science 96:2792-2800 [2] Bansal P, Bansal N (1997) Synthetic Milk: Genesis, Current Status And Options. Current science 73:904-905 [3] Feldsine P, Abeyta C, Andrews WH (2002) AOAC International methods committee guidelines for validation of qualitative and quantitative food microbiological official methods of analysis. Journal of AOAC International 85:1187-1200 [4] Fleet GH, Mian M (1987) The occurrence and growth of yeasts in dairy products. International Journal of Food Microbiology 4:145-155 [5] Garcia O, Mahmood K, Hemme T (2003) A review of milk production in Pakistan with particular emphasis on small-scale producers. [6] Ghatak S, Sánchez-Fung JR (2007) Monetary economics in developing countries. Palgrave Macmillan [7] Haasnoot W, Smits NG, Kemmers-Voncken AE, Bremer MG (2004) Fast biosensor immunoassays for the detection of cows' milk in the milk of ewes and goats. Journal of Dairy Research 71:322-329 [8] Hussein FS, El Zubeir IM, Fadlelmoula AA (2011) Quality evaluation of imported and locally produced processed cheese in Sudan. Jordan Journal of Biological Sciences 4:231-236 [9] Ifeanyi V, Ihesiaba E, Muomaife O, Ikenga C (2013) Assessment of microbiological quality of yogurt sold by street vendors in onitsha metropolis, Anambra State, Nigeria. British Microbiology Research Journal 3:198 [10] Jha S, Matsuoka T (2004) Detection of adulterants in milk using near infrared spectroscopy. Journal of American Scientific Research Journal for Engineering, Technology, and Sciences (ASRJETS) (2016) Volume 25, No 1, pp 100-112 111 Food Science and Technolog,Mysore 41:313-316 [11] Katsiari MC, Voutsinas LP, Kondyli E (2002) Manufacture of yoghurt from stored frozen sheep’s milk. Food chemistry 77:413-420 [12] Lee J-W, Kim H-J, Yoon Y, Kim J-H, Ham J-S, Byun M-W, Baek M, Jo C, Shin M-G (2009) Manufacture of ice cream with improved microbiological safety by using gamma irradiation. Radiation Physics and Chemistry 78:593-595 [13] Lin TY, Lin C-W, Lee C-H (1999) Conjugated linoleic acid concentration as affected by lactic cultures and added linoleic acid. Food Chemistry 67:1-5 [14] Malik A (2008) Dairy sector lacks policy focus. Net, Ed Daily Dawn, Jan 28 [15] Piccinin DM, Shelef LA (1995) Survival of Listeria monocytogenes in cottage cheese. Journal of Food Protection® 58:128-131 [16] Robert S, Torrie J, Dickey D (1997) Principles and procedures of statistics: a biometrical approach. McGraw-Hill, New York [17] Rodrıguez E, Calzada J, Arqués J, Rodrıguez J, Nunez M, Medina M (2005) Antimicrobial activity of pediocin-producing Lactococcus lactis on Listeria monocytogenes, Staphylococcus aureus and Escherichia coli O157: H7 in cheese. International Dairy Journal 15:51-57 [18] Salisu M, Junaidu A, Mohammed A, Lamidi O, Suleiman A, Goska D, Mustapha H, Madziga I, Yusuf M, Sani R (2016) MICROBIOLOGICAL QUALITY ASSESSMENT OF COMMERCIALLY PREPARED YOGHURT RETAILED IN SOKOTO STATE, NORTHWESTERN NIGERIA. Journal of Animal Production Research 28:78-83 [19] Sulieman AME, Eljack AS, Salih ZA (2012) Quality Evaluation of “Ricotta” Cheese Produced at Laboratory Level. International Journal of Food Science and Nutrition Engineering 2:108-112 [20] Tipu M, Altaf I, Ashfaq M, Siddique S (2007) Monitoring of chemical adulterants and hygienic status of market milk. Handbook published by Quality Control Laboratory, Univ. Vet. Anim Sci, Lahore, Pakistan pp 7 [21] Walstra P, Wouters JT, Geurts TJ (2005) Dairy science and technology. CRC press [22] Zhao T, Doyle MP, Berg DE (2000) Fate of Campylobacter jejuni in butter. Journal of Food Protection® 63:120-122