This coincides with fact that experiment 4 had the greatest amount of heat applied to the milk treatment and experiment 2 coincides with the least amount of heat being applied to the milk treatment. If you need assistance with writing your essay, our professional essay writing service is here to help! This example concludes Nataliya’s story that started in How Microbes Grow and Oxygen Requirements for Microbial Growth.. The generation time for most of the pathogenic bacteria, such as … The curdling process of milk occurred more quickly at warmer temperatures compared to cold temperature, therefore only the samples in the cupboard developed curd (Moncel, 2014). The protein in milk also provides a source of carbon the bacteria can use, in addition to lactose, as a fuel source. However in milk, as the lactobacilli population grew rapidly, the amount of lactic acid increased greatly also, considering that these bacteria broke down the lactose in milk and released a by-product of lactic acid. Disclaimer: This work has been submitted by a university student. Milk contained various compounds, the main ones being fat, protein, and sugar. The growth of all microbes was characterized by the appearance of logphase after 12 hours in all the milk types tested, which shows that the optimal time period for growth of the tested isolates is ranging between 12 – 48 hours and this means provision of enzymes for … This process allowed new gene combinations to be introduced which may provide the daughter cells a better chance of adapting to the changing conditions. Most bacteria preferred to live in a pH value of 7; neutral. Milk has ideal conditions for bacterial growth having high water content, plentiful nutrients, and a pH level that’s very close to neutral (6.4-6.8). %PDF-1.3 %���� The factors that control the rate of bacterial growth discovered in this experiment could be applied to everyday life. Bacteria reproduce when one cell splits into two cells through a process called binary fission. This was because both the warm temperature and the close to neutral pH level provided the bacteria in milk, lactobacilli, with a favourable environment for reproduction allowing more bacteria to ferment lactose which produced more lactic acid and increased the acidity of the milk (“Microbiology,” 2014). RESULTS Experiments with raw milk as inoculum. This is not an example of the work produced by our Essay Writing Service. It was concluded that milk is an ideal setting for the reproduction of bacteria due to its high water content, pH value close to 7, and ingredients. A preliminary experiment showed that two of the powders and one of the syrups had high bacterial counts, and the others had low counts. Study for free with our range of university lectures! Whereas, the milk samples in the fridge had less amount of lactic acid present and produced a faint or no sour odour (Chua, 2008). You can test the effectiveness of different soaps by treating different petri dishes with "dirty" hands before washing and "clean" hands after washing. Milk contains a significant amount of protein, a nutrient made of nitrogen-rich amino acids. During this method of asexual reproduction, the single DNA molecule would replicate to create a copy of its original single chromosome. Company Registration No: 4964706. The lactobacillus bacteria existent in milk fermented the carbohydrates such as glucose and lactose in milk into lactic acid. Several food agencies reported that at temperatures between 5 to 60°C several foodborne bacteria were able to grow; this was referred as the “danger zone.” This fact explained the reason behind the extremely slow rate of bacterial reproduction in the fridge milk samples considering that refrigerators were usually kept under 4°C to inhibit rapid bacterial growth in the foods. If the factors were considered, one would be able to control the growth of bacteria. Growth over the course of the 5-week experiment in the 19 different groups of recipient mice ranged from 107 to 156% of the starting weight (averaged per group; table S6A). of incubation is indicated (Figure 1). However, milk is unique with respect to its sugar. This was because of the difference in the amounts of lactic acid present in the two groups of samples. First, the prediction ability was performed only with parameters estimated from individual growth curves of E. coli, S. aureus and the lactic acid bacteria in milk (Dataset 1, 21 experiments). *You can also browse our support articles here >, To understand the favourable and unfavourable conditions for bacterial reproduction, To monitor and compare the rate of bacterial growth in milk stored at warm and cool temperatures. The final stage of bacterial growth byBacillus The temperature was taken for each sample of milk and recorded in the appropriate observation table. at 55C on the growth of microorganisms in the 0.1 m MF systems used for milk protein fractionation. of growth of the bacteria in differently pretreated milks were carried out on the basis of these data. 100 0 obj <>stream These errors affected the analysis greatly since the information wasn’t specific and accurate. Reference this. The donor bacterium would transfer all or part of its chromosome to the receiving bacterium. 57 0 obj <> endobj 4 glass cups each with a different type of milk sample were placed in the fridge. You can view samples of our professional work here. Biology The test tube with the methylene blue is your test sample. Experiments were conducted using a simplified human milk spoilage model based on goat's milk as a human milk surrogate, spiked with a single bacterial strain (Staphylococcus epidermidis), in which pH and carbon dioxide (CO 2) concentration were measured along with bacteria count over 160 hr. Additionally, these organisms came in several different shapes; the most common being cocci (round), bacilli (rod-shaped), and spirilli (spiral shaped) (“Classification of bacteria,” 2012).Each shape offered distinctive advantages. Extreme freezing can stop bacterial growth and/or kill bacteria altogether. Registered Data Controller No: Z1821391. Foods which were kept in warmer temperatures such as in the oven for at least a day or two should not be consumed; they might be hazardous to one’s health considering that warm temperatures encourage bacterial reproduction. Also, different individuals might interpret the colours differently and for the buttermilk and whole milk, the values of the exact pH levels weren’t recorded. Bacteria were the only living organisms that existed on Earth for approximately 3.5 billion years implying that these prokaryotic organisms were able to survive through all the harsh climate changes in Earth’s history. They could be photoautotrophic, photoheterotrophic, chemoautotrophic, or chemo- heterotrophic. Any scientific information contained within this essay should not be treated as fact, this content is to be used for educational purposes only and may contain factual inaccuracies or be out of date. Chocolate milk had about 10g of sugar per 100mL (“Chocolate milk,” 2014), whole milk had about 5.2 grams (“Nutrition facts,” 2014), skim milk had 4.9g (“Skim milk,” 2014), and buttermilk with a 5 g sugar content per 100mL (“Buttermilk,” 2014). endstream endobj startxref The Kingdom Bacteria consisted of anaerobic unicellular microorganisms with exceptional abilities of adapting to wide ranges of environment conditions. V2 = volume of the inoculums (in this experiment, 50 ml) Substitute the values in the equation and V1 was calculated. The milk samples kept in the cupboards for six days produced a pungent sour odour while the samples in the fridge had no or a faint sour smell. Or, you can press a variety of common objects like coins, combs, etc. If it takes 20 minutes to 2 hours, then there are 4 to 20 million organisms/ml of milk. This lowered the pH level greatly which caused the death of bacteria. 74 0 obj <>/Filter/FlateDecode/ID[<51743C8C586D7346A2AE8CB8467C70D2>]/Index[57 44]/Info 56 0 R/Length 91/Prev 1615106/Root 58 0 R/Size 101/Type/XRef/W[1 2 1]>>stream The other 4 glass cups filled with different types of milk samples were placed in a cupboard/cabinet. Bacteria count correlated highly with CO 2 but not with pH. All work is written to order. Furthermore, foods should be kept refrigerated in order to inhibit bacterial growth. 8 observation tables were created; 2 tables for each type of milk; fridge vs. cupboard. influence of mastitis on the total bacteria count of bulk milk depends on type of bacteria, the stage of infection and the percent of the herd infected. Hence, the clumps of a cheese-like substance that was formed at the end of the experiment in the cupboard samples were protein (casein) molecules. Therefore, after a few days the pH values of buttermilk sample in the cupboards increased as more bacteria died and stopped producing lactic acid. The pH values were another factor that affected the bacterial reproduction in the milk samples. The results of the experiments showed that primarily heat treatment and, to a minor extent, fat content of milk influenced the growth parameters of both bacterial strains, especially Lb. Procedure: In this experiment, you will qualitatively assess the presence of bacteria in milk using the methylene blue reductase test. As bacteria grow and reproduce in milk, the pH level of milk drops. Clinical Focus: Nataliya, Resolution. Some grew in pair (diplo), some in clusters (staphylo), and others grew in a chain (strepto) (“Bacterial shapes and,” 2014). The pH levels of all the milk samples excluding the buttermilk, were very close the neutral, therefore they encouraged bacterial growth. Milk was an emulsified colloid where the protein molecules are suspended and dispersed within a water-based solution. In this lab everything went as originally planned. The most common bacteria found in milk were the lactobacilli. From -30 degrees C (-22 degrees F) and below, bacteria growth slows rapidly. To export a reference to this article please select a referencing stye below: If you are the original writer of this essay and no longer wish to have your work published on UKEssays.com then please: Our academic writing and marking services can help you! Pathogenic bacteria induced food poisoning such asBacillus cereus whereas spoilage bacteria were only capable of producing pungent odours, unappetizing flavours, and changes in texture and appearance of milk. In this type of experiment, bacteria is transferred directly to the prepared petri plate via direct contact. When the chemical indicator, methylene blue, is added to the milk, the milk is turned blue. The pH level was taken for each milk sample and recorded in the appropriate observation table. Instead, their DNA floats in a tangle inside the cell. of bacterial growth while experiment 2 had the least amount of bacterial growth. The results collected after the six day period of observation revealed that factors which influenced the rate of bacterial growth were temperature, pH level, moisture and the amount of food sources available. 6 . A few factors were temperature, pH levels, water content, and available food sources. A physical property of acids was sourness, therefore considering that there were more lactobacilli bacteria in the cupboard samples breaking down sugar and producing lactic acid as a by-product, there was a greater quantity of acid in the samples forming the strong sour smell. Using the kitchen tongs remove the test tube caps from the pot, and cap the test tubes. Lastly, the sharp sour odour of the cupboard samples after a few days were produced by the lactic acid present in the milk. Among the samples left in the cupboard, the skim milk and chocolate milk showed the greatest amount of difference in appearance from day 0; the beginning, to day 6; the end of the experiment. Errors which occurred during this experiment included inaccurate measurements of the pH values considering that the colours of the red litmus paper strip were difficult to differentiate. A description of the appearance of the milk samples were made and noted in the appropriate observation table. Subsequently, the model was extended with the average competition coefficients (E-BR–GD model) that represented quantitative relations among the populations. h��Yko۸�+�x/����(�w�4MP���-����č_��n�_�gH��C�[g��PH��"yΜ�x+2ᝐy.�*h�p9�BjiE�PZ-��j%���L���5J#�ɍ�C� m%�y��˜�s�60m��"��x4�J� ;�6C?��x�ȭ�Ƣt�exy�3΋/ �a��x���[��NU�~�V�=����5�G�H�(. 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