Exp 1-Aerobic Plate Count

UNIVERSITI TEKNOLOGI MARA FAKULTI KEJURUTERAAN KIMIA FOOD PRESERVATION TECHNOLOGY (CBE648) ____________________________________________________________________________________

NAME STUDENT ID GROUP EXPERIMENT TITLE DATE PERFORMED SEMESTER

No. 1 2 3 4 5 6 7 8

MOHAMAD AFIQ IKHWAN BIN MOHD NOOR VELAN 2015476476 EH2205C

Determination of total aerobic plate count (including yeast and moulds) on fresh and spoiled food (milk/ juices/ any solid food) 12 OCT 2017 5

Title Abstract Introduction Literature Review Methodology Results & Discussion Conclusion & Recommendations References Appendices TOTAL MARKS

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Allocated Marks (%) 10 15 15 10 30 10 5 5 100

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Contents 1.0

ABSTRACT .........................................................................................................................................................3

1.1

INTRODUCTION ................................................................................................................................................3

1.2

LITERATURE REVIEW.........................................................................................................................................6

1.3

METHODOLOGY ................................................................................................................................................8

1.4

RESULTS & DISCUSSION ....................................................................................................................................9

1.5

CONCLUSIONS ................................................................................................................................................12

1.6

RECOMMENDATIONS .....................................................................................................................................12

1.7

REFERRENCE ...................................................................................................................................................13

1.8

APPENDICES ....................................................................................................................................................14

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1.0 ABSTRACT This experiment was conducted to analyze the aerobic plate counts (APCs) for fresh and spoiled food and to study the aerobic plate count mechanism and important. This experiment was conducted firstly by preparing the sample of food and then the food is being smeared on an agar medium inside a petri dish and then being kept in an incubator shaker for 24 hours. After 24 hours, the sample of the product being analyze using colony counter devices. The result shows that, the spoiled for recorded high value of APCs while fresh food show small value of APCs. This means that, the spoilage occurs on the spoiled food while fresh food also presents small amount of microorganism in it. Aerobic plate count is one of the enumeration technique used in microbiology to count the microorganism in foods sample but the question is, is it enough just by using number to determine the quality of food, is it can be applied on all system.

1.1 INTRODUCTION Bacteria, yeasts, molds and viruses are the tiniest living things on earth that was termed as microorganism. There are thousands of species of bacteria, but all are single-celled and fall into three basic shapes: spherical, straight rods, and spiral rods. Bacteria are the most important microorganisms to the food processing. Most are harmless, many are highly beneficial, some indicate the probable presence of filth, disease organisms, spoilage and a few cause diseases. Yeasts are oval-shaped and slightly larger than bacteria. They reproduce most often by budding. In budding each cell can produce several buds, or swellings, which break away to form new, fully formed daughter cells while Molds as found on bread, fruit, damp paper, or other surfaces are actually composed of millions of microscopic cells joined together to form chains. The chains usually have numerous branches, called hyphae. Molds can thrive in conditions too adverse for bacteria or yeasts. They reproduce by spores that are frequently present as green or black masses on the protruding hyphae.

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Food industry frequently being hit by simple spoilage caused by these microorganism, especially bacteria, yeasts and molds. This microorganism can infect all sorts types of food such as dry food, fermented food, pickled food and refrigerated food. There are many foodborne diseases caused by colonies of this bacteria such as Escherichia Coli, Salmonella and Staphylococcus Aureus. This can lead to many health problems.

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There are a lot of methods can be used to determine the amount of colony that exists in a food sample, whether by qualitative or by quantitative analysis. Redigel, petrifilm, spiral plate system, isogrid and aerobic plate count, this is all the technique that can be used to determine the number of bacteria colonies in selected food.

Spiral plate system

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Petrifilm

Isogrid

Aerobic plate count

This experiment was conducted to determine the bacteria colony that presence on fresh food and spoiled food. Aerobic plate count (APC) is the colony counting technique used in this experiment. The aerobic plate count (APC) measures only that fraction of the bacterial flora that is able to grow to visible colonies under the arbitrary test conditions provided in the time period allowed. It does not measure the total bacterial population in a food sample, but is the best estimate. Depending on the circumstances, a high APC may indicate that a food has been grossly mishandled or that it contains a poor-quality ingredient. Interpretation depends on knowing what the normal APC is for each food. The purpose of this experiment is to have a rough estimation on food quality because in industrial application this analysis is important for the food processing unit so that they will supply the best food to the customer because there are many cases related to foodborne diseases outbreak related to this microorganism.

1.2 LITERATURE REVIEW In microbiology, there are various methods used to determine the number of colonial of microorganism. Many researches had been conducted on the enumeration of microorganism through various technique. There are two main reasons why many microbiologists have their attention on this subject. First is the lax of accuracy and precision on measurement that has lid up this perception to further studies and for the second reasons is they want to introduce alternate microbiological methods into the lab. As we know aerobic plate count is one of the microorganism colonies counting methods. First, the ranges in common acceptance for countable numbers of colonies on plate are 30-300 and 6|P a g e

25-250. Breed and Dotterrer published a seminal paper on this topic in 1916. They set out to determine the limit in number of colonies that may be allowed to grow on plate without introducing serious errors in connection with the proposed revisions of standard methods of milk analysis. They point out that “the kind of bacteria in the material under examination will have an influence on the size of colonies, and consequently, on the number that can develop on a plate.”.

Other than that, a research has been conducted to compare the enumeration technique

The

numbers of aerobic bacteria from chicken, ground beef, ground pork, shelled pecan, raw milk, thyme, and flour (20 samples from each food) were determined by four alternative viable cell count methods (Redigel, Petrifilm, Spiral Plate System, and Isogrid) to ascertain the effectiveness of these methods in providing viable cell counts compared with the widely used Aerobic Plate Count (APC) method. The results indicated that all five methods were highly comparable (r=0.97 and higher, with the exception of Petrifilm versus Spiral Plate System, which was 0.88) and exhibited a high degree of accuracy and agreement. Thus, the four alternative methods were found to provide accurate aerobic bacterial counts of foods compared with the APC method.

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1.3 METHODOLOGY Part 1: For liquid foods. I. II.

The fresh and spoiled liquid food was prepared. Gloves was worn and sanitized with hand sanitizer to avoid any contamination to the food samples.

III.

A suitable amount of the liquid foods was poured into respective small beaker or test tube.

IV.

A wire inoculation loop was heated up to sterilize the tip to ensure the aseptic technique was preserved.

V.

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

VI.

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

VII. VIII.

Steps 3 until 6 are repeated for other liquid samples. All petri dishes are secured with tape and labelled with the correct type of food sample.

IX.

The petri dishes are then kept inside an incubator overnight with the agar facing down. 1

X.

The next day, the petri dishes are examined and the colony is counted by using a colony counter.

XI.

The amount of colony for each petri dishes are observed and recorded.

Part 2: For solid foods I. II.

Solid food samples were prepared and being cut into small or suitable amount. A cotton bud is used to scrub the surface of the solid sample.

III.

The cotton bud is then smeared onto a petri dish containing agar.

IV.

Steps 1 until 3 are repeated for other solid samples using new cotton buds.

V.

All petri dishes are secured with tape and labelled with the correct type of food sample.

VI.

The petri dishes are then kept inside an incubator overnight with the agar facing down. 1

VII.

The next day, the petri dishes are examined and the colony is counted by using a colony counter.

VIII.

The amount of colony for each petri dishes are observed and recorded.

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1.4 RESULTS & DISCUSSION Food Sample

Aerobic Plate Count (APC) Fresh

Spoiled

Grape Fruits

5

55

Bread

10

59

Figure 1.4.1: Results for experiment 1

Figure 1.4.2: Fresh Food Results

Figure 1.4.3: Spoiled Food Results

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This experiment was conducted to determine the colonies of the microorganism presents in food samples by using the aerobic plate count method. Based on result tabulated in table 1.4.1, it shows that Grapes shows 5 colonies for fresh one while 55 represents the spoiled one. Besides that, Bread record 10 count for fresh one and 59 for spoiled one. Therefore, it can be said that fresh grape is still good because of its low count of APC and recorded high count for spoiled grape that represents it has been totally unsafe to be consumed. Furthermore, bread shows the same pattern but a slightly higher than grape for both spoiled and fresh ones. The fresh food still recorded some value maybe due to lack of proper sanitation and due to it was taken from the same sources so the food has already been infected with the microorganism as in the spoiled one. However, we cannot directly say that the low value of APC means pathogen free because APC is a poor indicator of safety in most instances, since they do not directly correlate to the presence of pathogens or toxins. However, some products or ingredients showing excessively or unusually high APCs may reasonably be assumed to be potential health hazards, pending pathogen screening results. However, some products or ingredients showing excessively or unusually high APCs may reasonably be assumed to be potential health hazards.

APC can be used to gauge sanitary quality, organoleptic acceptability, adherence to good manufacturing practices, and to a lesser extent, as an indicator of safety. APC may also provide information regarding shelf life or impending organoleptic change in a food.

Interpretation of the APC results must take into consideration knowledge of the product and whether a high APC is expected.

Depending on the situation, APC can be valuable in evaluating food quality. Large numbers of bacteria may be an indication may be an indication of poor sanitation or problems with process control or ingredients. Certain products, such as those produced through fermentation, naturally have a high APC. Again, low APC numbers do not equate to an absence of pathogens. Often, it is necessary to assay foods for specific pathogens or spoilage organisms before ruling on food safety or food quality.

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Quality and safety guidelines or specifications are often applied to raw materials and finished goods. Using APC for ingredients may or may not be appropriate as a quality indicator. A food manufacturer’s decision to apply APC guidelines on ingredients must be based on the ingredient’s effect on the finished product. For instance, in dried foods, APC can be used as a means of assessing the adequacy of moisture control during the drying process. For meats, APC can be used to check to the condition of incoming carcasses to potentially identify suppliers who prove those with excessively high counts. APC can also be used to evaluate sanitary conditions of equipment and utensils. This can be done during processing to monitor buildup and after sanitation to gauge its effectiveness.

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1.5 CONCLUSIONS In conclusion, aerobic plate count is a good mechanism to detect poor sanitation, spoilage and quality control. A high APCs shows that it contains high colonies of microorganism but it depends on situation of what kind of food, what is the process (eg: fermentation that usually contains high APCs) and what the raw material and end product of the foods. From this experiment it can be said that the spoiled food shows high APCs value that represents the spoilage of food has occurred while the fresh food still collects some value of APCs maybe due to lack of proper sanitation while conducting the experiment and due to the food sample is taken from the sample sources so the fresh one may be already infected by those microorganism as in the spoiled food.

1.6 RECOMMENDATIONS  

   

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 to preserve the aseptic technique. 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.

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1.7 REFERRENCE 

Breed, R and WD Dotterrer. 1916. The Number of Colonies Allowable On Satisfactory Agar Plates. J Bacteriol. 1:321-331



Food Technology and Processing. Retrived from 6/11/2017 on: http://aggiehorticulture.tamu.edu/food-technology/food-processing-entrepreneurs/microbiology-offood/



The Journal of Applied Poultry Research, Volume 25, Issue 1, 1 March 2016, Pages 48– 53



Tomasiewicz, D.M.et al. 1980. The Most Suitable Number of Colonies on Plates for Counting. J Food Prot. 43(4):282-286



USP. 2006. Microbial Examination of Nonsterile Products: Microbial Enumeration Tests. USP 29 Suppl 2. August 1, 2006. United States Pharmacopeial Convention. pp. 3757-3759.



VICKI S. CHAIN and DANIEL Y.C. FUNG (1991) Comparison of Redigel, Petrifilm, Spiral Plate System, Isogrid, and Aerobic Plate Count for Determining the Numbers of Aerobic Bacteria in Selected Foods. Journal of Food Protection: March 1991, Vol. 54, No. 3, pp. 208-211.

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1.8 APPENDICES

Figure 1.8.1: Plate Counter

Figure 1.8.3: Spoiled Food

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Figure 1.8.2: Fresh Food

Figure 1.8.4: Agar medium on a petri dish

Figure 1.8.6: Incubator Shaker

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