Food Lab 1

March 24, 2018 | Author: Nurul Syaheerah | Category: Foods, Experiment, Nuclear Magnetic Resonance, Bacteria, Agar
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Short Description

Food science...


Food Preservation Technology Name

: Amalina binti Abdul Halim

Student ID

: 2015837512

Topic 1

: Introduction to Food Preservation

Experiment 1 : Determination of total aerobic plate count (including yeast & moulds) on fresh and

spoiled food (milk/juices/any solid food)

Date of Start : 13 October 2016 (Thursday) Date of Check : 14 October 2016 (Friday)

1.1 Introduction From this experiment, it can be said that the objectives or aims are as follows: 1.1.1) To determine the total amount of colony on spoiled milk, spoiled milo, apple and cake by using a quantitative analysis of aerobic plate count 1.1.2) To compare the amount of colony between spoiled food and fresh food Bacteria is one of the biggest challenge to our daily food supply especially in the food industry and market. We struggle to prevent our food supply from being spoiled by the activities of bacteria and also other micro-organisms to our food. The effects of consuming spoiled food can be detrimental to humans health and can cause diseases such as nausea, headache, vomiting and many more. There are a lot of methods to determine the amount of colony that exists in a food sample, whether by qualitative or by quantitative analysis that have been adapted from methods recommended by the ICMSF, AOAC, FDA, APHA and Health Canada [2]. In this experiment, the method used to know how much colony exist in a particular sample is known as the aerobic plate count which is a quantitative type of analysis which is very simple to

be run. Food sample will be tested by transferring them onto a medium such as agar in a petri dish, incubated overnight then examined using a colony counter where we get a rough amount of the colonies that exist in the petri dish. The experiment can also be creatively done by also testing out fresh food together with spoiled food to see a comparison in terms of the number of colonies exist. Generally, spoiled food would have more colonies than unspoiled food. This experiment is sensitive to any types of germs and bacteria as well hence the experiment needs to be conducted with precaution so that hands are sanitised and equipments are sterilised throughout the experiment to get a more accurate result. The reasons for us to have experiments like this or any type of food analysis is because we want to meet a certain quality or set point of food to be consumed by humans, to have a rough estimation of the food’s life span, to examine the quality of the food and for health purposes. These analysis are also known as microbial food analysis [4]. The food industry especially needs to be really careful with these kinds of analysis because they need to provide the best food out of the factory into the customer’s tummy. Any carelessness while handling food can give out effects to customers and can ruin their business. As consumers, we too need to be concern about the quality of our food so that we stay healthy and gain enough nutritions that we essentially need in our daily life. This simple experiment was preceded using the following equipments and materials: 1.1.3) Materials - Spoiled Milk - Spoiled Milo - Newly Opened Cake - Apple - Agar - Hand Sanitiser

1.1.4) Equipments - Wire Loop - Bunsen Burner - Test Tubes - Petri Dishes - Tape - Incubator -Colony Counter

Figure 1.1: Hand Sanitiser, Bunsen Burner & Wire Loop used in experiment

Figure 1.2: A colony counter is used to count the bacterial colony observed.

1.2 Literature Review 1.2.1 Food Analysis Food analysis is generally a type of discipline dealing with methods to characterise the properties of food and also their elements. These procedures are analytical and are used to provide us with details about variety of characteristics, composition, viscosity, density, physiochemical properties and many more attributes [4]. Basically, these analysis tells us the quality of a certain tested food sample. There are different types of food analysis that are used to test quality of food. It is very important to choose the most suitable analytical technique of food analysis according to what kind of properties that needs to be tested and also what type of food that wants to be tested as well. In order to choose a suitable food analysis, some selection criteria could be evaluated such as precision, accuracy, cost, speed, sensitivity and many more [5]. Some of the commonly known food analysis are spectroscopic, nuclear magnetic resonance (NMR), infrared (IR), atomic spectroscopy (AS), biological, electrochemical, gas chromatography (GC), flow injection analysis (FIA) and many more [6]. 1.2.2 Microbial Analysis of Food Microbial Food Analysis is a type of food analysis that examines the acceptability of a food based on the existence or amount of microorganisms including parasites, and/or quantity of their toxins/metabolites, per unit(s) of mass, volume, area or lot [4]. Aerobic plate count is an example of a microbial food analysis besides presumptive coliform count, Escherichia coli count and Enterobacteriaceae count. 1.2.3 Aerobic Plate Count According to Scott Sutton, a plate count analysis is one of the best interpretation of an approximation of the number of cells present in a food sample where a linear range for common bacterial counts on standard sized plates (for example: agar in a petri dish) is established. However, there could also be unusual plate count situations hence should be covered by a standard operating procedure (SOP).In order to make counting of bacterias easy, some rounding

and average rules can also be used especially to those petri dish which is crowded or those with combined colonies. Plate counting can have a significant effect towards product specifications and process controls [7]. Basically, aerobic plate count is the population of colonies produced on an agar in a petri dish under defined incubation temperature and time. It is al known with other names such as colony count, standard plate count, total bacterial count and many more. It is operated based on the principles that there is an assumption that microbial cells present in a sample smeared onto an agar medium will develop into visible, separated colonies and each cell, spore or clump or chain of cells gives rise to a single colony [4].

! Figure 1.3: An example of the procedures of an aerobic plate count

1.3 Methodology 1.3.1

Spoiled and fresh food samples are prepared for the experiment


Gloves are being worn and sprayed with hand sanitiser to avoid any contamination to the




A suitable amount of liquid sample is poured into small beaker/test tubes.


A wire loop is heated using a bunsen burner until it starts to become red to make sure that

it is

disinfected to not contaminate the liquid sample.

Figure 1.4: Wire loop is being heated 1.3.5

The wire loop is then dipped into the liquid sample and smeared onto a petri dish

containing agar.

Figure 1.5: Wire loop dipped into liquid sample is being smeared onto agar in petri dish. 1.3.6 sample

After that, the wire loop is dipped into distilled water to remove any traces of the liquid

Figure 1.6: Cotton bud that has scrubbed solid food sample is smeared on agar in petri dish 1.3.7

Steps 1.3.3 until 1.3.6 are repeated for other liquid samples.


Solid samples are prepared and cut into small or suitable amount.


A cotton bud is used to scrub the surface of the solid sample.

1.3.10 The cotton bud is then smeared onto a petri dish containing agar. 1.3.11 Steps 1.3.8 until 1.3.10 are repeated for other solid samples using new cotton buds. 1.3.12 All petri dishes are secured with tape and labelled with the correct type of food sample. 1.3.13 The petri dishes are then kept inside an incubator overnight with the agar facing down. 1.3.14 The next day, the petri dishes are examined and the colony is counted by using a colony counter. 1.3.15 The amount of colony for each petri dishes are observed and recorded.

! Figure 1.7: Colony amount being observed, counted & recorded after overnight incubated.

1.4 Results & Discussion 1.4.1 Results Table 1.1: Amount of colony counted and recorded for every type of food sample. Type of food sample

Amount of Colony

Spoiled Milk


Spoiled Milo






1.4.2 Discussion According to the data obtained from the experiment, the colony amount counted using a colony counter is as table 1.1 above. From the tabulated data, we can see that the spoiled milk has the most amount of colony which is as much as 1013 colony, while the least colony recorded is apple. The spoiled milo has the second most colony which is 859 and the newly opened cake contains 46 colony at third place amongst the 4 type of food samples tested. The colony amount shows which type of food sample in the experiment produces more bacterial growth than the other. Those with more colony produces more bacterial growth than those who have less of them. The spoiled milk and milo produces the most bacterial growth probably because of the condition it is left at is not suitable to preserve it from making sure the bacterial activities are inactive to not spoil the drinks. For this experiment, both milk and milo were kept at room condition for around 24 hours making bacterial growth activated. If both of these drinks were refrigerated, the the bacterial growth would be inactive or retarded and they can be preserved for a longer span of time. Milks or milk-based drinks are usually preserved by using canning, pasteurising, drying and many more to make sure that it has a longer duration of life span and to attain its natural nutrients.

As for the cake, we are surprised to know that it has quite an amount of colony. The cake has just been opened from its plastic packaging for the experiment. However, it could be that the cake was opened for quite long before it is being tested. This shows that the cake has been contaminated by germs or microorganisms in the air when it was being watched with the cotton bud, then onto the agar in the petri dish. As the cake’s texture is spongy, contamination is much easier to happen as the surface area of the cake is large. A fresh newly opened food should have less colony that what has been recorded for the cake in the experiment but the amount recorded is still low if compared to the spoiled drinks tested. The lowest amount of colony counted and recorded was the apple with only 6 colonies. The apple seemed a bit old on the outside but it has the least amount of bacteria amongst all the food tested. This shows that the apple is very well preserved and least contaminated. By looking at the amount of colony present in each food sample. We can say that both of the milk and also milo is not safe to be consumed. If consumed, they can cause bad health effects to human such as food poisoning having symptoms like nausea, vomiting, stomach ache, headache and many more. According to Ochs, Carol (2015), anyone who drinks milk past the expiration date, is exposed to the risk of getting food poisoning from unhealthy bacteria that might have grown in the milk. As for the cake and the apple, they are safe to be consumed but precautions still need to be taken to make sure of their quality. Washing the hands and checking expiry dates of food everytime before eating can ensure that you are eating fresh and unspoiled food.

1.5 Conclusion & Recommendation 1.5.1 Conclusion As a conclusion of this experiment, it can be said that spoiled food has a bad quality and the condition can deteriorate according to time. If it is consumed, it can cause a lot of bad health effects towards the consumer. However, fresh food can also contain bacterial growth when it is not handled in a good food handling discipline from hands or environment. Food analysis such as the aerobic plate count is significant to food producers and also consumers to make sure that only great quality food is being produced and consumed in the past, present and the future because food is the main source of our nutrients. From the experiment, the spoiled milk produced most bacterial colonies, followed by spoiled milo, newly opened cake and last but not least the apple. 1.5.2 Recommendation Recommendations are needed to make sure the experiments are preceded in a way that it provides us with accurate results or at least with less alterations of factors affecting the results obtained. The following are the recommendations that could be taken to improve the findings of this experiment in the future : - Always wear gloves throughout the experiment to make sure that the food sample is not affected by germs already on the palms of the hands. - If fresh food samples are in the form of any packaging such as plastics, tubes, box and many more, only open the package right before the food sample needs to be tested. Leaving the food sample exposed to the air for quite a long time can lead to contamination of the food sample by bacteria of environment or air. - Always sanitise the gloves before starting the experiment to avoid any contamination. - Remember to heat the wire loop before dipping it onto the samples and washing it inside clean water/distilled water after dipping onto the samples to sterile it.

- Do not smear too much or a lot of layers of the food sample onto the agar in the petri dish to not make the colony growth too much and makes it hard to be counted later. - Take ample time to count the colony using the colony counter to avoid any miscounts.

1.6 References 1. Ochs, Carol. (2015) Livestrong Foundation, Consequences of Drinking Expired Milk, http:// Retrieved at 20 October 2016. 2. U.S. Food & Drug Administration , Center for Food Safety & Applied Nutrition Bacteriological Analytical Manual Online January 2001 3. OAC. 2001. Bacteriological Analytical Manual (Online) Chapter 14, Bacillus cereus. USDA, Center for Food Safety and Applied Nutrition. 4. Rachitha Wickramasinghe (n.d.), Dept. of Health Sciences The Open University of Sri Lanka. Aerobic plate count, PCC/ ECC and Enterobacteriaceae count. 5. D.W. Gruenwedel and J.R. Whitaker, Marcel Dekker. Food Analysis: Principles and Techniques (1998) 6. A. Golcu, A. M. Haji Shabani, and I. Miksik (2012), Food Analysis: Present, Future, and Foodomics . Laboratory of Foodomics, Institute of Food Science Research (CIAL), CSIC, Nicolas Cabrera 9, Campus de Cantoblanco, 28049 Madrid, Spain. ISRN Analytical Chemistry Volume 2012 (2012), Article ID 801607, 16 pages. Retrieved from: http:// 7. Scott Sutton (2011), Microbiological Topics: Accuracy of Plate Counts, JOURNAL OF VALIDATION TECHNOLOGY (SUMMER 2011), Volume 17, No. 3.

1.7 Appendices









Figure 1.8 : The food tested out for this experiment 1 are as follows; (1) spoiled milk, (2) spoiled milo drink, (3) newly opened cake, (4) apple.





Figure 1.9: The colony observed for the food sample tested are as follows; (1) Spoiled Milk, (2) Spoiled Milo, (3) Newly Opened Cake, (4) Apple

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