STUDIES ON THE AIR QUALITY IN A DAIRY PROCESSING PLANT

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1 STUDIES ON THE AIR QUALITY IN A DAIRY PROCESSING PLANT K. Radha* and Lakshmi S. Nath Department of Dairy science, College of Veterinary and Animal sciences, Mannuthy, Kerala Received : Accepted : ABSTRACT Microbial quality of air in a dairy processing plant was evaluated to ascertain the contribution of air as a source of contamination and spoilage of milk and milk products. The mean total aerobic counts obtained in the air by sedimentation method were ± 3.82, ± 4.17 and ± 3.53 cfu/ m 2 in raw milk reception dock, pasteurization room and product preparation room respectively. The respective mean total coliform counts were 1.52 ± 0.14, 0.66 ± 0.08 and 0.99 ± 0.16 cfu/ m 2. Total coliform count observed in the raw milk reception dock was significantly higher (P< 0.01) than the other areas. The mean Staphylococcal counts were 2.52 ± 0.10, 3.84 ± 0.31and 5.82 ± 0.30 cfu/ m 2. The product preparation room showed highest mean Staphylococcal counts followed by pasteurization room and raw milk reception dock. The mean yeast and mould counts obtained were 5.42 ± 0.39, 3.84 ± 0.31and 5.82 ± 0.30 cfu/ m 2 in raw milk reception dock, pasteurization room and product preparation room respectively. Effect of fumigation on the microbial quality of air in the dairy processing area was also studied by comparing the microbial load in the air before and after fumigation. Fumigation practice followed in the dairy processing area was highly effective against total aerobic organisms, coliforms, and Staphylococci but not very effective in the case of yeast and moulds. Key words: Air quality, Dairy processing area, Microbial load in air, microbial quality of air INTRODUCTION Air quality inside the dairy processing area influences the microbial quality of milk and milk products. Dairy products are highly susceptible to contamination by airborne microorganisms. Microbial air quality in processing and packaging areas is a critical control point in the processing of dairy products, since airborne contamination reduces shelf-life and may serve as a vehicle for transmitting spoilage and pathogenic organisms. Every precaution should therefore be taken to prevent airborne contamination of the product during and after processing (Mostert and Jooste, 2002). Airborne microorganisms in dairy plants include bacteria, moulds, yeasts and viruses. The main sources of airborne organisms in the dairy processing area includes the activity of factory * Corresponding author radhavet@gmail.com. Ind. J. Vet. & Anim. Sci. Res., 43 (5) , September - October

2 personnel, dairy equipments, floor drains, ventilation and air-conditioning systems, packaging materials and water when applied under pressure in the cleaning and sanitizing procedures. Equipment surfaces can also support the growth of microorganisms and become a source of contamination for the aerosols in the processing areas. Spore-forming bacteria and fungi are able to survive in bio aerosols and stay viable for a longer time in the air. Water used in open circulation systems is a significant source of airborne microbial populations and the spray from cooling towers, if contaminated, may also be a possible source of certain pathogens and consequently, airborne contamination. Installation of air filters, application of UV irradiation and regular chemical disinfection (bactericidal, fungicidal and viricidal agents) of air can be applied to critical areas to control airborne microorganisms. However, research works carried out in this area are very much limited in our country. Hence this study is proposed to evaluate the quality of air in the processing area of a dairy plant. 347 MATERIALS AND METHODS The number of airborne microorganisms in milk processing areas of a dairy plant was evaluated by sedimentation method (Direct settling plate technique).the air samples for the study were collected from the University Dairy Plant, Kerala Veterinary and Animal Sciences University. The areas included in the study were milk reception dock, pasteurization and product preparation rooms. Aerobic plate count, yeast and mould count, total coliform count and Staphylococcal count were determined by the methods prescribed by American Public Health Association (Hickey et al. 1992). The experiment was conducted by collecting 50 samples from each area. Studies on the air quality in a diary processing area Effect of fumigation on the microbial quality of air in the dairy processing area was also studied by comparing the microbial load in the air before and after fumigation. The data obtained were analyzed by using ANOVA followed by Duncan multiple range tests. Independent sample test was done to study the effect of fumigation (Snedecor and Cochran 1994). RESULTS AND DISCUSSION The mean total aerobic counts obtained in the air by sedimentation method were ± 3.82, ± 4.17 and ± 3.53 cfu/ m 2 in raw milk reception dock, pasteurization room and product preparation room respectively (Table No.1). The total aerobic counts among different processing areas analyzed by ANOVA shows that there is no significant (P>0.05) difference between different areas of processing. The product preparation room showed highest mean total aerobic count followed by raw milk reception dock and pasteurization room. This can be attributed to the higher personnel activity in the product preparation room and raw milk reception dock when compared to the pasteurization room. The total aerobic counts obtained from different areas were within the standards prescribed for culture settling plate technique by APHA (30 cfu/cm 2 / week). Studies conducted by Salustiano et al., (2003) have shown that temperature and presence of steam affects the microbial number in the air due to environmental variations at the processing areas in a working day. The mean total aerobic counts reported by them were 73.6cfu/ m 3, 64.9cfu/ m 3, 46.9 cfu/ m 3 and 37.6 cfu / m 3 in milk reception room, pasteurization room, butter preparation and cheese preparation rooms respectively. In this study, total aerobic counts in the product Ind. J. Vet. & Anim. Sci. Res., 43 (5) , September - October 2014

3 preparation rooms were significantly lower than the other areas. However, this trend was not seen in our study. Prejit et al., (2007) studied the microbial air contamination in pasteurization and packaging rooms of a dairy plant. They have reported a total viable count which ranged from cfu/ft 2 /min in pasteurization room and cfu /ft 2 / min in packaging room. Dioguardi and Franzetti (2010) evaluated the microbial air contamination in cheese making room and skimming milk room in ten dairy plants. Among them, only three dairies showed a total bacterial count less than 50 cfu/m 3. The mean total coliform counts obtained in the air by sedimentation method were 1.52 ± 0.14, 0.66 ± 0.08 and 0.99 ± 0.16 cfu/ m 2 in raw milk reception dock, pasteurization room and product preparation room respectively (Table No.2). Total coliform count observed in the raw milk reception dock was significantly higher (P< 0.01) than the pasteurization room and product preparation room. This can be attributed to the location of the raw milk reception dock which directly opens into the outside environment and higher personnel activity when compared to the other areas. Radha and Lakshmi dairies studied. The total coliform counts obtained in our study are lower than those reported by the previous workers. Hence, it can be considered that the microbial air quality with regard to the coliform organisms is comparatively good in the dairy plant evaluated in our study. The mean Staphylococcal counts obtained in the air by sedimentation method were 2.52 ± 0.10, 3.84 ± 0.31and 5.82 ± 0.30 cfu/ m 2 in raw milk reception dock, pasteurization room and product preparation room respectively (Table No.3). The Staphylococcal count among different processing areas analyzed by Duncan test gave significantly higher values for (P< 0.01) product preparation room when compared with raw milk reception dock and pasteurization room. This can be attributed to the higher personnel activity in the product preparation room. People were considered to be the major aerosol producers in a processing plant. As people speak, breath, sneeze and cough, bacteria are released into the air. Ren and Frank(1992) evaluated air samples from two fluid milk processing plants and two icecream plants for the potential sources of aerosol contamination. According to them, the drains, water spraying system and personnel activity were associated with the significant increase in Staphylococcal count. According to the literature, several factors may contribute to air contamination at the processing areas of a dairy plant. Among them, dairy plant localization, contamination Salustiano et al., (2003) obtained sources, ventilation system and manufacturing Staphylococcus aureus count ranged between practices play a vital role in determining the 1 and 4.3 cfu/ m 3 in the milk packaging room. microbial load. Salustiano et al., (2003) The microbial air quality with respect to the reported total coliform counts between 1 and 3 Staphylococcal organisms was comparatively cfu/ m 3 in a dairy processing plant. Dioguardi low in the product preparation room of the dairy and Franzetti (2010) evaluated the microbial plant and it may be attributed to the higher air contamination in cheese making room and personnel activity coupled with high humidity skimming milk room in ten dairy plants. in that area. Coliforms were absent in seven of the ten Ind. J. Vet. & Anim. Sci. Res., 43 (5) , September - October

4 The mean yeast and mould counts obtained in the air by sedimentation method were 5.42 ± 0.39, 3.84 ± 0.31and 5.82 ± 0.30 cfu/ m 2 in raw milk reception dock, pasteurization room and product preparation room respectively (Table No.4). The yeast and mould count among different processing areas analyzed by Duncan test gave significantly higher values for (P< 0.01) product preparation room when compared with the other two areas. This can be due to the higher personnel activity in these areas. A positive relationship between worker activity and airborne yeasts and moulds was reported by many previous workers. Kang and Frank (1990) have suggested acceptable yeast and mould count in the food processing areas between cfu / m 3. According to Lück and Gavron (1990) acceptable yeast and mould count in the processing areas was <50 cfu /m 3. Salustiano et al., (2003) detected the presence of yeast and mould from the air with in the processing areas in a dairy plant by using the sedimentation technique and a one-stage air sampler. They have observed yeast and mould count in milk reception room, pasteurization room, butter preparation room and cheese preparation room. The values were 21.7 cfu/ m 3, 31.4 cfu/ m 3, 39.6 cfu/ m 3, 45.2 cfu/ m 3 respectively. Belestioids et al., (2011) isolated Cladosporium spp., Penicillium spp. and yeasts by the classical microbiological methods and molecular typing techniques in a Greek dairy plant. The mean viable fungal load was cfu/m 3 in outdoor air samples and 69.8 cfu/m 3 and cfu/m 3 in samples from the two indoor locations. The values obtained in our study were lesser than the results reported by the above authors. The results were also within the limit 349 Studies on the air quality in a diary processing area prescribed by Lück and Gavron (1990). Hence, it can be concluded that the microbial air quality with regard to the yeast and mould count was comparatively good in the dairy plant evaluated in the present study. Raw milk reception dock : The mean total aerobic count, total coliform count, Staphylococcal count and yeast and mould count obtained in the air by sedimentation method before fumigation were ± 5.80, 8.67 ± 1.30, ± 1.46 and 6.78 ± 0.79 and the counts after fumigation were ± 2.23, 2.15 ± 0.43, 6.00 ± 0.53, and 5.12 ± 0.43 cfu/ m 2 respectively (Table No.5). There was a significant (p d 0.01) reduction in the total aerobic count, total coliform count and Staphylococcal count after fumigation. But, no significant reduction in yeast and mould count was observed after fumigation. Pasteurization room : The mean total aerobic count, total coliform count, Staphylococcal count and yeast and mould count obtained in the air by sedimentation method before fumigation were ± 7.12, 1.60 ± 0.37, ± 2.96, 4.70 ± 0.65 and the counts obtained after fumigation were ± 1.13, 0.63 ± 0.11, 7.30 ±0.48 and 3.63 ± 0.34 cfu/ m 2 respectively (Table No.6). There was a significant (p d 0.01) reduction in the total aerobic count, total coliform count and Staphylococcal count after fumigation. But no significant reduction in yeast and mould count was observed after fumigation. Product preparation room : The mean total aerobic count, total coliform count, Staphylococcal count and yeast and mould count obtained in the air by sedimentation method before fumigation were ± 4.78, ± 0.71, ± 2.96 and5.75 ± 0.92 and the counts obtained after fumigation were Ind. J. Vet. & Anim. Sci. Res., 43 (5) , September - October 2014

5 Radha and Lakshmi ± 2.15, 0.71 ± 0.09, 7.30 ± 0.48 and 5.83 ± 0.32 cfu/ m 2 respectively (Table No.7). There was a highly significant reduction in the total aerobic count, total coliform count (p d 0.01) and Staphylococcal count (p d 0.05) after fumigation. But no significant reduction in yeast and mould count was observed after fumigation. The overall air quality with respect to the total aerobic count, coliform count and yeast and mould count was good in all the dairy processing areas evaluated in the dairy plant. The result indicates that the fumigation practice followed in the dairy processing area was highly effective against total aerobic organisms, coliforms and Staphylococci but not very effective in the case of yeast and moulds. Staphylococcal count was slightly higher in the product preparation room. Hence it is recommended that the air quality with respect to the Staphylococcal count in the product preparation room may be improved by adopting suitable measures to control the humidity as well as the activity of personnel s working in the room. Fumigation practices may be modified to reduce the yeast and mould count. The fumigation practices can be modified to reduce the yeast and mould count. This result also emphasizes for the need of frequent fumigation of different dairy processing areas to maintain a low microbial load in the air. Table 1. Total aerobic count (cfu/m 2 ) in different processing areas of a dairy plant Area of sample collection Mean ± S.E Raw milk reception dock ± 3.82 Pasteurization room ± 4.17 Product preparation room ± 3.53 F- value ns (p<0.05) ns : Non significant Table 2. Total coliform count (cfu/ m 2) in different processing areas of a ddairy plant Area of sample collection Raw milk reception dock Pasteurization room Product preparation room F-Value Mean ± S.E 1.52 ± 0.14 a 0.66 ± 0.08 b 0.99 ± 0.16 b **(P<0.01) ** Significant at 0.01 level Means bearing same letter as superscript do not differ significantly. Ind. J. Vet. & Anim. Sci. Res., 43 (5) , September - October

6 Studies on the air quality in a diary processing area Table 3. Staphylococcal count (cfu/ m 2) in different processing areas of a dairy plant Area of sample collection Raw milk reception dock Pasteurization room Product preparation room F-Value Mean ± S.E 2.52 ± 0.10 b 3.84 ± 0.31 b 5.82 ± 0.30 a **( P<0.01) ** Significant at 0.01 level Means bearing same letter as superscript do not differ significantly Table 4. Yeast and mould count (cfu/ m 2) in different processing areas of a dairy plant Area of sample collection Raw milk reception dock Pasteurization room Product preparation room F-value Mean ± S.E 5.42 ± 0.39 a 3.84 ± 0.31 b 5.82 ± a 9.520** (P<0.01) ** Significant at 0.01 level Means bearing same letter as superscript do not differ significantly. Table 5. Effect of fumigation on microbial counts in the raw milk reception dock Parameters Before fumigation After fumigation t-value cfu/ m2) cfu/ m2) Total aerobic count ± ± ** Total coliform count 8.67 ± ± ** Staphylococcal count ± ± ** Yeast and mould count 6.78 ± ± **Significant at 1% level. 351 Ind. J. Vet. & Anim. Sci. Res., 43 (5) , September - October 2014

7 Radha and Lakshmi Table 6. Effect of fumigation on microbial counts in the pasteurization room Parameters Before fumigation After fumigation t-value cfu/ m2) cfu/ m2) Total aerobic count ± ± ** Total coliform count 1.60 ± ± ** Staphylococcal count ± ± ** Yeast and mould count 4.70 ± ± **Significant at 1% level. Table 7. Effect of fumigation on microbial counts in the product preparation room Parameters Before fumigation After fumigation t-value cfu/ m2) cfu/ m2) Total aerobic count ± ± ** Total coliform count ± ± ** Staphylococcal count ± ± * Yeast and mould count 5.75 ± ± **Significant at 1% level. *Significant at 5% level REFERENCES Belestioids, E., Ghikas, D. and Kalantzi Incorporation of microbiological and molecular methods in HACCP monitoring scheme of moulds and yeasts in a Greek Dairy Plant: A case study -11 th International congress on Engineering and Food (ICEF11), Procedia Food Sciences, Dioguardi, L. and Franzetti, L Influence of environmental conditions and building structure on food quality-a survey of handcrafted dairies in Northern Italy. Food control. 21: Hickley, P.K., Beckeheimer, C.E and Parrow, T.1992.Microbiological tests for equipment, containers, water and air. Ind. J. Vet. & Anim. Sci. Res., 43 (5) , September - October

8 Studies on the air quality in a diary processing area Standard methods for the examination of Dairy products. (16 th Ed). American Public Health Association, Washington DC.pp Kang,Y.J. and Frank, F.J Characteristics of biological aerosols in dairy processing plants. Journal of Dairy Sciences, 73: Luck,H and Garvon,1990. Quality control in the dairy industry. In: Robinson, R.K (ed.) Dairy Microbiology- the Microbiology of Milk products, 2 nd Ed.pp.2: Elsevier Applied Science, London. Mostert, J.F. and Jooste, P.J In: Robinson R.K. (ed) Quality control in the dairy industry. Dairy Microbiology Handbook. (3 rd Ed.). John Wiley and Sons, New York, pp Prejit, Nanu, E. and Latha, C Microbial quality assurance of Milk during production, processing and marketing. Am. Journal of Food Technology, 2: Ren, T.J. and Frank, F.J Sampling of microbiological aerosols at various locations in fluid milk and ice cream plants. Journal of Food Protect. 55: Salustiano, C.V., Andrade, J. N., Brandao, S.C., Azeredo, R. and Mandlima, S.M Microbiological air quality of processing area in a dairy plant as evaluated by the sedimentation technique and a one stage air sampler. Braz. Journal of Microbiology, 34: Snedecor, G. W. and Cochran, W. G Statistical methods. 8 th Ed. The lowa state university, Ames, Lowa, pp Ind. J. Vet. & Anim. Sci. Res., 43 (5) , September - October 2014