Food Safety Measures for Milk - Assignment Example

Food Safety Measures for Milk A critical review of Implication of food safety measures on microbiological quality of raw and pasteurized milk Student Name 1. Introduction This essay is a critical review of the paper Implication of food safety measures on microbiological quality of raw and pasteurized milk, by Nada et al. (2012). The authors’ paper is an experimental research study that examines the effect of a system of quality improvement on the quality of raw and pasteurized milk in one of the largest dairy plants present in Serbia. The aim of this critical review is to consider the authors’ paper in detail, with respect to other papers in this field, in addition to experimental design and outcomes. It is argued that although the authors’ paper provides solid insight into the area of milk processing and suggests methods of improving the process, these methods are not tested effectively scientifically. Furthermore, the large range of changes made makes it impossible to determine which were effective and which were not. Finally, the lack of adequate controls obscures the overall themes of the paper, making it difficult to extrapolate the authors’ results or to determine accurately what was causing the observed trends. 2. Background As a product, milk is highly valuable for nutrition. However, this same nutritional value encourages the presence and growth of bacteria(Frank, 2009, pp. 281-283). There are many different aspects of the production chain of milk and dairy products that have the potential to lead to the contamination of the product by microorganisms(Te Giffel, Beumer, & Bonestroo, 1996). The most important area where contamination can occur is in raw milk. This can occur primarily through the equipment that is being used for storage, the milking process itself and transportation(Nastasijevic et al., 2009). Pasteurization was first developed in the 1850s(Weeks & Alcamo, 2008, p. 285), and involves heating milk above 100°C, which acts to deactivate bacteria(Smith & Hui, 2004, p. 92). Although the process of pasteurization is designed to remove any microorganisms from the milk, it is not fully successful(Christiansson, Bertilsson, & Svensson, 1999). This is because some types of bacteria are able to survive the product(Nada et al., 2012). For example, some organisms are able to create spores that survive the process of pasteurization, and re-infect the milk afterwards(Sorhaug & Stepaniak, 1997). It is estimated that between one and five percent of all bacterial outbreaks are the result of bacterial contamination of milk or milk products(Buyser et al., 2001). Because milk is so widely consumed, and is an important food product, both as milk itself and also incorporated into other dairy products, it is crucial that the quality of milk produced remains high and that it does not present a health risk to consumers. An area where there is significant potential for a human health risk is in the presence of pathogenic bacteria, especially those that escape the pasteurization process. One pathogen that has caused considerable concern is the presence of Mycobacterium paratuberculosis, which has been found both in raw and in pasteurized cow’s milk in the United Kingdom. This pathogen is dangerous because it is thought to have a role in Crohn’s disease. Because the organism is able to survive in the usual pasteurization temperatures, recommendations have been made to increase the overall time that milk is held at a high temperature during pasteurization(Grant, Ball, & Rowe, 2002). A second type of microorganism that has been found in milk and dairy products is Listeria monocytogens. Like, M. paratuberculosis this bacteria has the ability to survive the standard temperatures associated with pasteurization(Beckers, Soentoro, & Asch, 1987). These two examples show how important it is to examine the process of milk processing and pasteurization and determine what can be done to decrease the risk of harm to consumers. The difference in time between the two articles shows the ongoing nature of this problem. There are also other aspects of milk that lower its quality and can potentially cause harm such as temperature and acidity(Nada, et al., 2012). The concept of Hazard Analysis Critical Control Points (HACCP) is considered by many authors to be the best approach to use in order to ensure that food remains safe, regardless of what factors are threatening food safety. What critical control points are chosen ultimately depends on the study, how the pasteurization of raw milk and preventing recontamination following pasteurization are often considered to be two of the major points in the production of pasteurized milk, or milk product. Increasing management of risks at this point in the production cycle has the potential to significantly decrease the risk of treats to food safety(Silva et al., 2003). This form of regulation is the focus of the study by Nada et al. (2012), and the authors hoped that using this could significantly increase quality of milk in a large dairy plant that was the base of their research. 3. The Study In their study, the authors focus on the roles that HACCP and pre-requisite programs (PRPs) play in the prevention of food-borne disease through bacteria being present in milk and dairy products. In 2004, the European Union added regulations concerning that specifically focused on the HACCP system for food safety. The aim of the authors’ study was to examine how the increased PRPs, which occurred as part of this regulation, affected the microbiological quality of raw milk that was supplied to a large dairy plant in Serbia. Additionally, the authors examined what influence this system had on the quality of pasteurized milk from the plant. The authors believed that through the incorporation of these programs, the quality of the milk that the plant pasteurized would increase, as would the quality of raw milk that it received from suppliers. As such, the study had two distinct components, pasteurized milk and raw milk. Each involved a different set of PRPs to be developed and distinct critical control points. This was crucial because improving the processes involved in raw milk involved changes at the level of individual farmers, while pasteurization was within the plant itself. The authors argued that the use of PRPs was crucial for the successful implementation of a HACCP system, based on the arguments by Sperber(1998), who believed that an HACCP system was ineffective on its own. 3.1 Methodology The study was undertaken over a period of four years, from 2006 to 2009. Both raw and pasteurized samples were collected and examined. The period of study took into account the time prior to the implementation of the HACCP system, during the implementation and after infrastructure investments had occurred. Quality was measured differently for each type of milk. The acidity and temperature of the samples of raw milk were examined, as well as the somatic cell count and whether antibiotics were present. In comparison, pasteurized milk was examined for the present of specific bacteria species. Both types of milk were also analyzed for their total plate count (TPC). These methods allowed the authors to examine the quality of milk over the four-year period and to determine how this changed as the HACCP requirements were introduced. One of the advantages of this type of methodology is that it produces a way of directly comparing between different time periods and milk samples in a quantitative way. To analyze the results, the authors broke down the measures into categories that described the quality of the milk. For somatic cell count and TPC, the authors created four classes, although the intervals between the classes were not even. The determination of these classes was achieved based on a paper by Petrovic et al.(2006). To examine the conformity of milk to the requirements of acidity, temperature and antibiotics, the authors calculated the percentage of milk that did and did not meet the specifications. The values that the authors used for this was >6.8°SH and 10°C for acidity and temperature respectively. Antibiotics used a presence/absence measure. Thus, to examine most of these factors, the authors used a single measure, where either the milk was suitable or it was not. How close the milk was to these values was not considered. 3.2 Results The authors compared the values of TPC and somatic cell count observed in the raw milk to the requirements of the European Union and the Serbian regulation (which had been in place prior to the study). The authors found that in the first year of the study more than 55% of the milk was class III, which would not have been accepted under even the Serbian standards (which were lower than the European Union standards). Additionally, only 36% of the milk was considered to be high quality. With the introduction of the HACCP, the values began to change, and in 2009, only 20.3% of the milk was of class III. Furthermore, the percentage of class I and above milk increased from 36.5% to 53.7% in the same period. The authors argued that the poor quality of raw milk was related to the hygienic conditions that cows were present in, as well as the overall condition of the farm. This was supported by one study that the authors cited, which found a negative correlation between milk quality and washing the bulk tank or clipping udder hair (Elmoslemany et al., 2010). Another study considered that improper cleaning was the most important aspect of raw milk quality (Reinemann et al., 2000). To bypass these problems, there were a large number of improvements made at the level of the dairy plant. The authors report that a team for implementing good agricultural practices (GAP) was implemented. This involved establishing PRPs for many different aspects of farm work, and educating farmers about disease transmission and its effect. Storage of milk was also organized to ensure an adequate storage temperature. Finally, the plant focused on reducing its number of individual suppliers and increasing the quality of the products provided. During the process involved with implementing HACCP, a number of problems were identified by the company with carrying out the PRPs. This involved the creation of an investment plan to allow the company to meet the requirements of this certification. As for raw milk, there were a large number of different PRPs developed for pasteurized milk. In addition, milk pasteurization and reception were identified as being crucially important as control points for the process. The authors of the study focused on the milk pasteurization process, and found that there was a significant decrease in TPC for pasteurized milk between the initial implementation of HACCP and eight months after. Although it was significant, the size of this difference was small. (3.32 to 3.11 log CFU/ml). The authors argued that this difference was small because the processes involved in improving pasteurization had already been put into place prior to the HACCP implementation. After the HACCP implementation had been in place for eight months, the decline in TPC was more pronounced, and the TCP was 2.81 log CFU/ml. All tests for bacteria were negative both before and after HACCP implementation. Aerobic plate count also varied, and there was a decrease in aerobic plate count from 4.6 to 2.6 log CFU/ml. 3.3 Discussion and Limitations In their study, the authors showed that the implementation of PRPs the ability to increase the quality of raw and pasteurized milk for the company. The authors suggest that the research indicates that the HACCP system is an effective method of providing a mechanism of monitoring within the factory and for ensuring corrective actions are taken when required. The authors emphasize that the development of PRPs is crucial to this system working, as is improvement in procedures of sanitation and hygiene in the factor and investments in equipment. However, there are many aspects of the authors’ results that are not discussed in their findings. An interesting aspect of the study was the pattern that was observed in the quality of raw milk that was observed. The first component of this was that there was a trend of increasing milk quality from 2006 to 2008, with percentage of milk in the lowest class (III class) decreasing, and the percentages in the next highest classes (II class and I class) increasing. These trends were not strong, and the differences were two or three percent each year. It is likely that these differences were not statistically significant, so it appears reasonable that the authors did not discuss these trends. Nevertheless, one trend that occurred during this time is contrary to the authors’ predictions and explanations. For the first three years of the study, the percentage of milk that was in the highest quality class actually decreased. This percentage was 21.30 in 2006, and had decreased to 15.54% by 2008, before showing a big jump to 31% in 2009. The authors do not discuss this pattern, but it suggests that there may be additional effects occurring that are not explained by the HACCP system increasing quality of milk. One of the limitations of this study was that the authors did not make use of statistical tests when considering raw milk, although they did so for pasteurized milk. Because of this, there was no way to account for variance between one year and the next. What this meant was that there was no way of determining whether the changes were significant or whether they were within a normal level of variation. Another important aspect that neither the tests for raw milk nor those for pasteurized take into account other factors that could potentially be confounding. For example, this study takes place over a four-year period and follows the progression of the company and its milk quality. The authors do not examine what effects the change in time had on milk quality. It could be that this actually increased for other factories over the same time period because of external factors that had little to do with the study that was occurring within the plant. There is not much difference in percentages in the years 2006-2008. However, after this point, there is a dramatic decrease in the percentage of milk in the III class, and a strong increase in the percentage of milk in each of the other classes. This suggests that there was something specific that drove this strong change between 2008 and 2009. However, the authors do not evaluate this this. Their results and discussion focus on the fact that the values change between 2006 and 2009. The authors do not make their time line clear in the study, and this make interpretation of what processes caused these changes difficult to determine. If 2009 mostly represents the eight months after implementation that the authors discuss, then this jump is reasonable, however it does not explain what the previous years entailed. It is more likely that 2006 represented the pre-intervention phase, 2007 or 2008 was the eight months following implementation, and some point after this was the period where investments had been made. If this were the case, it would suggest that the HACCP system did little to improve quality, but instead it was the investments that the factory made. The authors argue that the investments acted in conjunction with the HACCP system and the development of PRPs to create an environment that significantly improved the quality of both raw and pasteurized milk. However, because of the way that they undertook their testing there is no way to determine what aspects of the intervention were effective and what were not. Furthermore, as discussed above, the lack of statistical testing for raw milk, and controls for both types of milk suggest that the results may not be as strong as they appear. Finally, the authors’ study considered only a single plant, which is not likely to be representative of the rest of the plants within the region. This is for two reasons. Firstly, using a single sample means that no variation between plants can be considered. Therefore, the results found in this study might not apply to other dairy plants because of factors such as different protocols or procedures involved in running the plant. Secondly, the plant that was considered in this study was one of the largest in the region. This means that it is likely to have different aspects from other plants in the region. Thus, the authors’ claims apply to the plant studied and perhaps others of a similar size, but cannot be generalized further. 4.0 Relationship to Other Literature Other studies have also examined the quality of raw and pasteurized milk, especially in relation to the presence or absence of microbes. For example, in Ireland, a study examined a random sample of raw and pasteurized milk. Throughout the study, 253 different sampling visits were undertaken to milk processing plants, ranging from four to 16 visits per plant, related to the size of the plant. The conditions for pasteurization of each sample was recorded, as well as the presence or absence of the bacteria of interest (O'Reilly et al., 2004). The benefit of this type of study was that the authors were able to obtain an accurate image of the quality of the milk, through the use of random selection. This meant that the observations from the study could be generalized to Irish raw and pasteurized milk throughout the country. This example shows an effective method of sampling that has been used in the past to generate a more comprehensive picture. The conclusions that the authors developed in their study agreed with the results of other studies. For example, Kassem et al. (2002)also found a decrease in the plate count for pasteurized milk, although the high standard deviation limited the effectiveness of their results. Likewise, Janzekovic et al. (2008)also reported that cleaning appeared to increase the quality of milk, an effect that the authors observed. The ability of an HACCP system and improved PRPs to improve food safety has been demonstrated in a number of other studies, as well as the current one. In particular, the author cited one study where the implementation of this type of system improved the quality of ice cream, in terms of the microbes that were present(Kokkinakis et al., 2008). Another study showed that HACCP could improve restaurant meals(Soriano et al., 2002). This approach would not have been fully useful in this study, as the authors aimed to see whether the incorporation of a HACCP program would increase the quality of milk from the milk plant studied. However, it would have provided a good indication of where the milk standards of the plant were in relation to the rest of the country. This would have helped to create a more accurate context for the study. If analysis of milk throughout the region, or even the immediate area was carried out at intervals, then this would provide a comparison for the results of the study. For example, if information of milk quality from several plants that did not have the HACCP implementation was available, then it would be possible to see whether the trends differed. In theory, milk quality should have increased for the site being studied and remained constant for the control sites. This would have helped to show that the conclusions of this study were legitimate, and were not influenced by some external variable. 5.0 Conclusion In their study, Nada et al. (2012) investigate the use of PRPs and HACCP over a four-year period, with the desire that the system would result in an increase in quality of the milk produced. As a result of their study, and the large number of changes that they instigated, the authors did observe a decrease in the level of TPC in pasteurized milk and an increase in quality for raw milk. These results suggest that the changes that were made were influential in increasing quality of the milk and also the safety. However, despite these resoundingly positive results, the study was subject to significant limitations, that make their conclusions weaker, and also limit how generalizable their outcomes are. The authors do not statistically analyze their outcomes for raw milk, and do not consider many of the trends that occur throughout their data. They also do not clearly identify the time progression of their study, which makes interpretation difficult. In addition, the large number of different changes they incorporated make the practical application of their conclusions difficult, as their study does not give any indication as to which ones were effective and which were not. Finally, the fact that the authors do not use any external controls makes it difficult to validate their results, and suggests that there could have been an external factor influencing the observed trend. Thus, the study by Nada et al. (2012) is a good case study of an effective increase in quality and safety of milk, however, the practical value of the study is limited. Works Cited Beckers, H., Soentoro, P., & Asch, D. (1987). The occurrence of Listeria monocytogenes in soft cheeses and raw milk and its resistance to heat. International Journal of Food Microbiology, 4(3), 249-256. Buyser, M., Dufour, B., Maire, M., & Lafarge, V. (2001). Implication of milk and milk products in food-borne diseases in France and in different industralised countries. International Journal of Food Microbiology, 667(1-2), 1-17. Christiansson, A., Bertilsson, J., & Svensson, B. (1999). Bacillus cereus spores in raw milk: Factors affecting the contamination of milk during the grazing period. Journal of Dairy Science, 82(2), 305-314. Elmoslemany, A., Keefe, G., Dohoo, I., Wichtel, J., Stryhn, H., & Dingwell, R. (2010). The association between bulk tank milk analysis for raw milk quality and on-farm management practices. Preventive Veterinary Medicine, 95(1-2), 32-40. Frank, J. (2009). Milk and dairy products. In P. Doyle, R. Beuchat, & J. Montville, Food Microbiology - Fundamentals and Frontiers. Washington DC: ASM Press. Grant, I., Ball, H., & Rowe, M. (2002). Incidence of Mycobacterium paratuberculosis in bulk raw and commercially pasteurized cow's milk from approved dairy processing establishments in the United Kingdom. Applied and Environmental Microbiology, 68(5), 2428-2435. Janzekovic, M., Mursec, B., Vindis, P., & Cus, F. (2008). Energy saving in milk processing. Journal of Achievement in Materials and Manufacturing Engineering, 33(2), 191-194. Kassem, M., Salem, E., & Ahwal, A. S. (2002). Application of hazard analysis and critical control point in dairy industry. La Revue de Sante de la Meditarranee orientale, 8(1), 114-128. Kokkinakis, E., Fragkiadakis, G., Ioakeimidi, S., Giankoulof, I., & Kokkinaki, A. (2008). Microbiological quality of ice cream after HACCP implementation: A factory case study. Czech Journal of Food Science, 26(5), 383-391. Nada, S., Ilija, D., Igor, T., Jelena, M., & Ruzica, G. (2012). Implication of food safety measures on microbiological quality of raw and pasteurized milk. Food Control, 728-731. Nastasijevic, I., Mitrovic, R., Popovic, K., Tubic, M., & Buncic, S. (2009). The effects of a non-intervention HACCP implementation on process hygiene indicators on bovine and porcine carcasses. Meso, 11(4), 232-239. O'Reilly, C., O'Connor, L., Anderson, W., Harvey, P., Grant, I., Donaghy, J., et al. (2004). Surveillance of bulk raw and commercially pasteurized cows' milk from approved Irish liquid-milk pasteurization plants to determine the incidence of Mycobacterium paratuberculosis. Applied Environmental Microbiology, 70(9), 5138-5144. Petrovic, M., Petrovic, M., Nenadovic, G., Kurcubic, V., & Marinkov, G. (2006). Chemical - microbiological quality parameters of raw cow milk. Biotechnology in Animal Husbandry, 22(5-6), 109-119. Reinemann, D., Mein, G., Bray, D., Reid, D., & Britt, J. (2000). Troubleshooting high bacteria counts in farm milk. Dairy Food and Environmental Sanitation, 20(8), 606-611. Silva, I., Almeida, R., Alves, M., & Almeida, P. (2003). Occurrence of Listeria spp. in critical control points and the environment of Minas Frescal cheese processing. International Journal of Food Microbiology, 81, 241-248. Smith, J., & Hui, Y. (2004). Food processing: Principles and applications. Ames, Iowa: Blackwell Publishing. Sorhaug, T., & Stepaniak, L. (1997). Psychotrophs and their enzymes in milk and dairy products: Quality aspects. Trends in Food Science & Technology, 8(2), 35-41. Soriano, J., Rico, H., Molto, J., & Manes, J. (2002). Effect of introduction of HACCP on the microbiological quality of some restaurant meals. Food Control, 13(4-5), 253-261. Sperber, W. (1998). Auditing and verification of food safety and HACCP. Food Control, 9(2-3), 157-162. Te Giffel, M., Beumer, R., & Bonestroo, M. R. (1996). Incidence and characterization of Bacillus cerus in two dairy processing plants. Netherlands Milk & Dairy Journal, 50, 479-492. Weeks, B., & Alcamo, I. (2008). Microbes and Society (2nd ed.). Sudbury, MA: Jones and Bartlett. Wouters, J., Ayad, E., Hugenholtz, J., & Smit, G. (2002). Microbes from raw milk for fermented dairy products. International Dairy Journal, 12(2-3), 91-109. Read More