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. Here: α-hemolysis (S. mitis, L); β-hemolysis (S. pyogenes, M); γ-hemolysis (also called non-hemolytic, S. salivarius, R). These errors would’ve altered the observations that were made significantly. V2 = volume of the inoculums (in this experiment, 50 ml) Substitute the values in the equation and V1 was calculated. Milk is a good source of all principal nutrients, including carbon, nitrogen and macro-minerals. The lactobacillus bacteria existent in milk fermented the carbohydrates such as glucose and lactose in milk into lactic acid. From simple essay plans, through to full dissertations, you can guarantee we have a service perfectly matched to your needs. Generation time is the time required for a bacterium to give rise to two daughter cells under optimum conditions. 354 Bacterial Changes in Milk garded-is proven by careful milk dealers and dairymen every- where, and laboratory studies have amply demonstrated that clean milk, kept cold, is more apt to lose organisms during the first twenty-four to forty-eight hours than to gain them. A population of bacteria could increase greatly in a fairly little amount of time considering that they reproduce exponentially. Coccus had protection against drying out, bacillus bacteria had great surface area for nutrients absorption and spirilla bacteria were able to travel through fluids with ease. Place the methylene blue in one of the test tubes. Moreover, bacteria commonly grew in distinguishing arrangements. Oct. 1, 1925 Bacterial Count of Milk and Cream 699 In contrast with centrifugally separated cream, gravity separated cream shows a much higher percentage increase in bacterial count over whole milk. A description of the appearance of the milk samples were made and noted in the appropriate observation table. Furthermore, research showed that food bacteria reproduce the quickest at temperatures ranging between 21 and 47°C. 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 … They are different from plant and animal cells because they dont have a distinct, membrane-enclosed nucleus containing genetic material. The most significant factor proven in this experiment was temperature. There were also other types of reproduction that bacteria go through such as transformation, transduction, and spore formation (Galbraith et al., 2001). The pH level was taken for each milk sample and recorded in the appropriate observation table. Bacteria count correlated highly with CO 2 but not with pH. Reference this. 57 0 obj <> endobj It could be concluded that several factors influenced the bacterial growth rate in milk. Bacteria require nitrogen to synthesize new proteins as they increase their population during growth. 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 353. 6 . and growth. Furthermore, the results could’ve been different depending on how each individual perceived the changes that had occurred to the milk samples. Take the lid off of the Petri dish (the lid is larger than the dish) and carefully cover the bottom-half of … At this point, the milk would be more vulnerable spoilage caused by mould and yeast which are able to survive in pH values below 4.5, extremely acid conditions (“What pH is,” 2012). The other 4 glass cups were labeled as; whole, skim, butter, and chocolate as well. 4 glass cups each with a different type of milk sample were placed in the fridge. The receiving cell would then undergo binary fission with the new gene content to produce more cells with this new gene combination. If it takes 20 minutes to 2 hours, then there are 4 to 20 million organisms/ml of milk. Lastly, the sharp sour odour of the cupboard samples after a few days were produced by the lactic acid present in the milk. This was what happened at the molecular level when milk developed curd. VAT Registration No: 842417633. Membranes2020, 10, 326 3 of 11 The purpose was to identify at which filtration temperature the hygiene conditions could be kept under control in the range of 10 to 20C, and therefore, to define how the production time between Growth of the bacterial flora of the milk itself was inhibited when powder or syrup was added, except with one syrup (S) which … Looking for a flexible role? Fission occurs rapidly in as little as 20 minu… Milk contains a significant amount of protein, a nutrient made of nitrogen-rich amino acids. The results after the six day observation period showed that the four types of milk which are kept in the fridge underwent little to no changes in appearance, odour, pH level or colour, whereas the milk that were left in the cupboards presented drastic changes in all aspects. The protein in milk also provides a source of carbon the bacteria can use, in addition to lactose, as a fuel source. We've received widespread press coverage since 2003, Your UKEssays purchase is secure and we're rated 4.4/5 on reviews.co.uk. This suggests that non- refrigerated milk increases the growth of bacteria in milk, compared to refrigerated milk. All samples of milk dropped in pH levels and it seemed like by the fourth day, all samples kept in the cupboards had produced a cheese-like solid substance that was surrounded by a thin liquid residue. Therefore, the greater amount of available food supply, the faster the bacteria multiply in the milk (“What is lactobacillus?,” 2014). Furthermore, the lactobacilli bacteria existent in milk produced lactic acid by fermenting the sugars in milk. The most common bacteria found in milk were the lactobacilli. All science fair projects This experiment was testing how effective natural plant extracts are as antibiotics by placing a mixture of the bacteria and natural plant extract combined together with milk and measured the diameter of the bacterial colony in the agar plate and compared it a mixture of only milk and the bacteria without the plant extract to see if the plant extract was effective in killing the bacteria. In this lab everything went as originally planned. 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). This process allowed new gene combinations to be introduced which may provide the daughter cells a better chance of adapting to the changing conditions. Lightened agar around bacterial growth = complete blood cell lysis (S. pyogenes) The amount of blood cell lysis by the bacteria results in a different color in the media. "B����`��_�@���ϸ�@� ,S The pH values were another factor that affected the bacterial reproduction in the milk samples. The generation time for most of the pathogenic bacteria, such as … 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. There were several factors that affect the rate of bacterial growth. 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