UNIVERSITI TEKNOLOGI MARA FAKULTI KEJURUTERAAN KIMIA UNIVERSITI TEKNOLOGI MARA FAKULTI KEJURUTERAAN KIMIA FOOD PRESERVATION TECHNOLOGY

UNIVERSITI TEKNOLOGI MARA

FAKULTI KEJURUTERAAN KIMIA

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UNIVERSITI TEKNOLOGI MARA

FAKULTI KEJURUTERAAN KIMIA

FOOD PRESERVATION TECHNOLOGY
(CBE648)
NAME : NUR ILHAM BINTI ZAINUDDIN
STUDENT ID : 2016250248
GROUP : EH2207C
EXPERIMENT TITLE : DETERMINATION OF TOTAL AEROBIC PLATE COUNT ON FRESH AND SPOILED FOOD
DATE PERFORMED : 11 OCTOBER 2018
SEMESTER : 7

No. Title Allocated Marks (%) Marks
1 Abstract 10
2 Introduction 15
3 Literature Review 15
4 Methodology 10
5 Results & Discussion 30
6 Conclusion & Recommendations 10
7 References 5
8 Appendices 5
TOTAL MARKS 100

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Date :
Abstract
The microorganism is present in our environment that cause an effect to foods by their biochemical activities carried under the ideal growth conditions and cannot be seen by eyes. It is becoming challenged and only with the assistance of the microscope, we can observe the presence of microorganism. In this experiment, aerobic plate counter (APC) is used to observe and calculate the number of colony count forms on the spoiled and fresh sample of bread and milk. The spoiled bread has the highest number of colony count, which are 999 because it has been exposed to air for a long period of time. However, because of some limitations of APC, no accumulation of the colony does not indicate that there are no pathogen has affected the sample.

Introduction
Overview
Food spoilage is a process that causing foods not suitable for human consumption due to changes in its characteristics such as texture, smell, taste or appearance and maybe certain of foods have formed of microorganism on it. Shelf life of food is the duration of food during its stable and retains quantities QUOTE “{Rawat, 2015 #32}” {Rawat, 2015}. The spoilage microorganisms rate can be influenced by factors like moisture content, appropriate temperature, pH and nutrients to grow in the food.

Problem Statement
Microorganism present in our environment which will affect the foods by biochemical activities carried under the ideal growth conditions. Human eyes can not resolve microbes that are too small to be seen which is less than 0.1 mm in diameter without any help of a microscope QUOTE “{Fung, 2009 #37}” {Fung, 2009}. It becomes challenging to find a way to prevent the activities and growth of microorganism in food for microbiologists, engineer and technologist QUOTE “{Rawat, 2015 #32}” {Rawat, 2015}. Thus, this experiment is conducted to study the total aerobic count (TAC) to determine the number of in the fresh and spoil milk and bread using streaking process.

Objective
To determine total aerobic plate count on fresh and spoiled milk and bread by using streaking process.

Literature Review
The result in chemical, physical, biochemical, mechanical, organoleptical, microbiological and others are contributing to the food spoiled. However, it is very hard to classify food spoilage especially when the culture itself has various ideas on constitutes edible or nonedible food such as cheese. With some alteration and adoption process, the taste of the foods can be changed and people tend to love food from another culture. Food can be considered as fresh or not fresh is by depending on their conditions. For instance, for fresh fruits they are usually juicy and crispy compared to the rotten fruit; fresh vegetable is usually newly harvested and firm while vegetable not fresh is stored and wilted; and fresh bread is moist and fresh compare to spoil bread QUOTE “{Fung, 2009 #37}” {Fung, 2009}. As known, milk contains lactobacillus bacteria will use lactose to gain its energy and produce lactic acid, which causing the spoilage of milk and makes the milk become sour QUOTE “{Y*, 2017 #35}” {Y*, 2017}. Microbes can grow slowly or inactive at low temperature, which with the refrigeration method, it can prolong the lag phase and the microbe growth rate will decrease and it also needs high water activity thus keeping products in dry condition will preserve them.

For the analysis of food spoilage, it is crucial to have a proper sampling procedure which the microbiological need to be grouped as solid, liquid, surface or air samples in order to have more useful data analysis. The conventional ‘standard plate count method’ has been used for 100 years ago where it includes media preparation, sample dilution, sample plating with general selective agar, plate incubation at specific temperature and colony counters after 48 hours in incubators. There are various manipulative parameters used such as volume of sample to be plated, the selection of agar, incubation time, temperature and gaseous environments and others. QUOTE “{Fung, 2009 #37}” {Fung, 2009}
The aerobic plate counter (APC) also known as aerobic colony count is a test apply to determine the level of microorganism in food when it being mixed with agar containing nutrients. APC is used in evaluating the food quality which depends on the number of bacteria as an indicator of poor sanitation of equipment and utensils or problems with control of the process or ingredients. For example, APC used to assess the adequacy of moisture control during the drying process in dried food where for meats, to check the condition of incoming carcasses to potentially identify suppliers who prove those with excessively high counts. APC can be performed in several ways, such as using pour plate, spread plate or spiral plating techniques. In findings the dilution of countable colony, volumes of test solution dilutions is fixed when using spread plates and pour plate while for spiral plate, liquid extract of foods is applied in a spiral track to the surface of rotating agar plate. Colony counter usually used with a spiral plate to determine CFU/g QUOTE “{Lihua, 2008 #31}” {Lihua, 2008}.

Methodology
For liquid sample;
Fresh and spoil liquid sample was prepared.

Gloves were worn and sanitized with hand sanitizer to avoid contamination.

Petri dish was labelled on the bottom plate to preserve area to observe the growth.

Fresh liquid samples were poured into petri dishes.

The sterile L-shape was dipped into the sample and streak in 360 ?.

Then, the sterile L-shape was dipped in distilled water to remove a liquid sample trace.

Step 3-6 was repeated for spoiled liquid sample.

The petri dish was sealed with parafilm tape after streaking.

The petri dishes were kept inverted and incubated in an incubator for 20 hours at 37 ?C.

The next 20 hours, the petri dishes were taken out from the incubator and the number of colonies was counted by using a colony counter.

The amount of colony form was observed and recorded.

For solid sample;
Fresh and spoil bread sample was prepared.

A sterile cotton swab used to take a bit sample of fresh bread.

The sample of bread was streaked on the surface of the agar.

Step 2-3 was repeated for spoiled bread sample.

The petri dish was sealed with parafilm tape after streaking.

The petri dishes were kept inverted and incubated in an incubator for 20 hours at 37 ?C.

The next 20 hours, the petri dishes were taken out from the incubator and the number of colonies was counted by using a colony counter.

The amount of colony form was observed and recorded.

Result and Discussion
Food Sample Aerobic Plate Counter (APC)
Fresh Spoil
Milk 0 208
Bread 598 999
Table 5.1: Result of Aerobic Plate Counter for fresh and spoil samples.

Figure 5.1: Milk sample (fresh and spoil)

Figure 5.2: Bread sample (fresh and spoil)

In this experiment, aerobic plate count method (APC) is used to calculate the number of microorganisms. Fresh bread shows slightly higher of colony count comparison to spoiled milk. From here, we can say that fresh bread has higher colony count due to poor in proper sanitation and has been infected before by microorganism. Even though the lower value of APC recorded, it does not count that the food as microbes free because APC is a poor indicator for microbes present. This is because this method is only taken into account of the visible colony, need a longer period of time for colony to grow and can cause some error in the process of counting colony if the colony form is a very large number.

Four plates of samples containing both fresh and spoil food is prepared. The samples used are bread and milk where the colony count is observed and counted for all of the agar plates. The spoiled bread shows highest colony count, which is 999 number of colony compare to the other samples; followed by fresh bread and spoiled milk which are 598 and 208 respectively. Fresh milk contains no accumulation of bacteria in 20 hours of incubation process.

Moreover, each of the plates has different conditions after the incubation process where it is depending on the period of the sample exposed to air. This streaking process is suitable for for heat sensitive bacteria, but also can cause bacteria to be killed when exposed to oxygen from the surrounding. Spoiled bread has a highest colony count because it exposed to air in a long time and more colony that’s been killed embedded in the sample. Fresh milk has a lowest colony count because it exposed to air in shortest time.
As known, some of spoilage organisms need oxygen, some of them are killed by oxygen and still others are facultative. To solve this problem, the change of plate to modifies atmosphere packaging become an option which can retard and prevent growth of microbe. These procedures must be assessed for compatibility with different foods so that there are no significant organoleptic changes in the foods caused by the treatment or preservative.

Conclusion and Recommendation
Conclusion
All in all, it is concluded that APC is a poor indicator of microbial present because of some limitations in that process. Lower value of APC does not indicate that the food is microbial free. However, it can be said that the value of of colony count depends on the condition of the plates. The spoiled food sample shows a higher number of colony count rather than fresh food sample and fresh food sample that has high value of the colony because of the poor sanitation while conducting the experiment.

Recommendations
Make sure to wear gloves and sanitize with hand sanitizer to avoid any contamination of microbial.

Use the suitable method to calculate the colony count to avoid error in counting the colony.

For fresh milk that has no accumulation within 20 hours of incubation process, it is advisable to incubate the sample for longer time.

Streak the agar one time only to avoid a lot of layers of food sample and make it difficult for colony counter later.

Open the packaging of fresh food right before starting the experiments to avoid contamination of food samples by bacteria.

References
Aerobic Plate Count – Murray Brown Labs. (n.d.). Retrieved from http://mb-labs.com/resources/aerobic-plate-count/Fung, D. Y. C. (2009). Food Spoilage, Preservation and Quality Control. Applied Microbiology: Agro/Food.

Lihua, F., ; Jun, S. (2008). Microbial quality assessment methods for fresh-cut fruits and vegetables. Stewart Postharvest Review, 4(3), 1-9. doi:10.2212/spr.2008.3.10
Rawat, S. (2015). Food Spoilage: Microorganisms and their prevention. Asian Journal of Plant Science and Research, 47-56.

Y, S. (2017). A Short Review on Milk Spoilage. Research and Reviews: Journal of Food and Dairy Technology.

Appendices

Figure 8.1: Colony counter
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Figure 8.2: Seal the plate with parafilm

Figure 8.3: Pour the fresh milk sample on agar

Figure 8.4: Streak the agar with sterile L-shape

Figure 8.5: Streak the agar with sterile cotton swab

Figure 8.6: Swab a bit of spoiled bread sample
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