Food spoilage

NOR DIYANA BINTI MOHAMAD 2015839542 EH2205G

ABSTRACT Metabolic process that causes food to be undesirable and not suitable for consumption is a term of food spoilage.The purpose of conducting this experiment is to determine the total aerobic plate count(including yeast and moulds) on fresh milk,spoiled milk,fresh papaya and spoiled papaya.The methods involve are streaking by loop and swabbing by cotton bud.Both method are simple and easy to perform.4 sample of food were tested which are fresh milk,spoiled milk,fresh papaya and spoiled milk.The result obtained show that fresh milk has zero colony count meanwhile spoiled milk recorded has the highest colony count which is 280 this is due to presence of microorganism.

1.0 INTRODUCTION 1.1 Research background Food spoilage can be defined as the changes occur in food that deteriorate the quality of food. Flavour, color, texture start to change as the food become spoil. Food spoilage can be divided into three categories which are physical, biological and chemical. Major cause of food spoilage is because of presence microorganism such as yeast,bacteria,and molds.Food spoilage also occur due to environment factor, as the food exposed to air and oxygen,the oxidation occur and it will give effect on vitamin A,vitamin C and other constituents of food.eating food that already spoiled can make people sick,the symptom occur from food poisoning is nausea,vomit,stomach ache and other illness that make us feel not comfortable. 1.2 Objective The purpose of this experiment is conduct to determine the total aerobic plate count(including yeast and moulds) on fresh milk,spoiled milk,fresh papaya and spoiled papaya

1.3 Problem statements In performing this task,we used streaking and swabbing method. Streaking method is easy,simple,and fast.The streaking technique is for isolation of bacterial cultures into distinct separate colonies.Swabbing method is easy to perform, inexpensive,well suited to flexible,uneven and heavily contaminated surfaces

2.0 LITERATURE REVIEW 2.1 Food spoilage Food spoilage can damage the texture,flavour and the original nutritional value of the food itself.This food spoilage can be harm to people who eat it. 2.2 Causes of food spoilage There are several factor that cause food spoilage occurred.Activity of organism,action of nation enzyme,chemical reactions of the constituents of food can contribute to spoilage of food. 2.2.1 Activity of microorganism Microorganism is around us.They are living in the soil,water,sair,skin of cattle that are capable to spoil the food.Microorganism can be divided into three 3 types which are yeast,moulds,and bacteria 2.2.2.1 Yeast True yeast and false yeast are types of yeast.Yeast growth can cause fermentation.Fermentation is also known as true yeast.Alcohol and carbon dioxide gas are produced from the metabolism of sugar of true yeast.Meanwhile the false yeast is only survive in food that have high sugar and acid environment

2.2.2.2 Moulds

Moulds can forming spore at dry condition.They can start growth cycle at dry condition.People can be sick when eating food that has mould,starts to feel nausea and vomit.Moulds are found in pickle,jams,jellies and can be destroyed at high temperature. 2.2.2.3 Bacteria Spore forming and non spore forming are types of bacteria that cause food spoilage.They are round shaped and spiral shaped microorganism.Bacteria usually prefer low acid food. In order to destroy bacteria spores in a relatively short period of time, low acid foods must be processed for the appropriate length of time at 116°C (240°F) in a pressure canner. (Temperatures higher than 100°C [212°F] can be obtained only by pressure canning.). 2.2.2 Action of native enzyme The growing of enzyme in animal and platnt food are due to lack of contro, mechanism in the harvested plant food or slaughtered animal.Ripening and browning are example of native enzyme. 2.2.3 Chemical reaction The quality of food worsen due to chemical reactions of the constituens of food.Exposure to atmospheric air can cause unsaturated fatty acid component undergo oxidation,thus increase oxidative rancidity in fat rich foods. 2.3 Food preservation Preservation is a technique to prevent the growth of bacteria,yeast,or other microorganism that can slow down the oxidation process which can leads to rancidity.Many process can be used for preservation of food.Pasteurization and artificial food additives are example food preservation technique

2.3.1 Pasteurization This process is mainly applied in dairy product. In this method, milk is heated at about 70 °C for 15 to 30 seconds to kill the bacteria present in it and cooling it quickly to 10 °C to prevent the remaining bacteria from growing.(Nummer,2012)

2.3.2 Artificial food additives Vitamin C are categorized under antioxidant for artificial food additives.Antimicrobial and chelating agent are type of artificial food additives

3.0 METHODOLOGY For this experiment, each group must prepared at least 2 samples which is fresh food and spoiled food. Our group prepared 4 samples from two different types of food which are milk and papaya. First of all, we prepared milk and papaya and left it opened in room temperature for about 2 or 3 days before experiment is conducted. This is to prepared spoiled food sample and for the fresh food sample we prepared it on the day we conduct experiment. So, the total sample we prepared are 4 sample which are fresh milk, spoiled milk, fresh papaya and spoiled papaya. On the day experiment these 4 sample were testing on the plate agar. For this method we need bunsen burner, loop, ethanol, cotton bud, and plate agar. First of all we need to spray our hand with some ethanol but no directly, we should wore gloves first this to prevent infection of bacteria. The loop is used for liquid sample (milk) using streaking method The loop is dipped into water to remove impurities, The loop that already dipped with water is being apply on flame to sterile and dry the water and it is dipped into food sample (fresh milk, spoiled milk).Using the loop that attach with food sample already, we streaked out over the surface of plate agar in a zigzag pattern line on the plate agar,so that the food sample is absorbed on the plate agar. Then the plate agar is incubate in incubator for 24hours,For the solid sample(papaya )we used swabbing method means that took some sample with cotton bud and follow the procedure like the liquid sample. After 24 hours .the plate agar is put in colony counter and start to count the colony appeared in food sample.

4.0 RESULT Food sample Fresh milk Spoiled milk Fresh papaya

Colony bacteria count 0 208 169

Spoiled papaya

44

Colony count vs food sample Colony count

0 208 169

44

Food sample

Graph 1 : The graph below shows the colony counted for each sample

5.0 DISCUSSION Based on result obtain, fresh result recorded zero colony bacteria found. Fresh milk does not exposed to light and air that can cause oxidation reaction. The quality of milk can be maintain if it is not exposed to light and air. Fresh milk contain inhibitor e.g lactoterrin and lactoperoxide,these inhibitors is responsible to ensure that no bacterial formed in first to three hours after milking process at ambient temperature. The original quality of the milk can be maintained at cooling to 4o C,this method is used to obtain good quality of milk for processing and consumption.

In the spoiled milk,colony bacteria counted was 208.For the spoiled milk,we left it opened for about three days.The quality of milk is start to detetriote as it is exposed to light and air.Air and oxygen can gives dentrimental effect on vitamin A,C,food color,flavour and other constitents.Exposure to light can destruct the protein in milk.In spoiled milk, Common microorganism found which is yeast and molds that change the texture, flavour, and nutritional of milk.Milk undergoes heat treatment pasteurization to kill the microbes that can cause food spoilage but certain bacteria strains is still survive even at high temperature. (Shackford,2012).According to research paenibacillus bacteria found in spoiled milk,this kind of bacteria is responsible for spoiling the milk and curding as well. For the fresh solid sample which is papaya.It is found 169 colony of bacteria.the environmental effect cause the bacteria is found.Bacteria is living in the low acid food,at moist area and such as fruits and vegetable,this show that bacteria is still exist at fresh fruit.Number of colony found in fresh papaya is much higher than spoiled papaya because fresh papaya has high moisture content which can lead the bacterial growth.This fresh sample exposed to light and air that can contribute to oxidation reaction. The spoiled papaya recorded about 44colony bacteria.We left it freely at the room temperature for about three days.The fruits start to rotten and dry.Yeast and molds are the bacteria found in the fruits.Yeast grow faster than molds,thus yeast initiate the fruit spoilage.Molds degrading the complex polysaccharide in cell walls and rinds.The spoiled papaya is already peeled which is the skin of papaya is not protected cause the bacteria is easy to form.Low number of colony bacteria is found compared to fresh papaya due to environmental effects and also the chemical reaction.The texture.flavor and the nutritional inside the papaya is totally change.

6.0 CONCLUSION From the experiment conduct which to determine the total aerobic plate count(including yeast and moulds) on fresh milk,spoiled milk,fresh papaya and spoiled milk.The result obtained show that the spoiled milk and the spoiled papaya has large number of colony bacteria found.This conclude that microorganism (yeast and molds) are easily growth in spoiled food.The factors that cause food spoilage is due to microorganism ,environmental effect and action of enzyme but the microorganism is contribute the large factor of spoilage food seems it is everywhere areound us and easily growth.So,in order to

keed food from spoilage,the right preservation technique should be conduct so that quality of food can be kept longer.

7.0 RECOMMENDATION During the experiment,they are several precaution that should be considered.First of all,make sure our hand is clean before experiment is started this is to ensure that no bacteria or microorganism is affected the result.Beside that,when draw a line using loop or cotton bud,it is better not to do overlapping line,the right technique is to draw in zigzag pattern this is to ease the count of colony bacteria and the isolated bacteria can be seen clearly.

8.0 REFERENCES ’Microbial testing procedure’.Retrieved from http://faculty.weber.edu/coberg/class/3853/3853%20Microbial%20Testing %20Procedures. htm

Rawat.S, ( 2015), ‘Food spoilage and their prevention ‘ .Retrieved from https://www.imedpub.com/articles/food-spoilage-microorganisms-and-theirprevention.pdf

‘Milk processing’. Retrieved from http://www.fao.org/agriculture/dairy-gateway/milk-processing/milkpreservation/en/#.WAqW6Oh97IU

Shackford.S. (2012,July 17) ‘Dairy researchers identify bacteria spoiler in milk’.Retrieved from http://www.news.cornell.edu/stories/2012/07/scientists-find-new-culprits-spoil-milk

Cliver.D (2008,May 5 ).Retrieved from http://www.madsci.org/posts/archives/2008-05/1210051357.Mi.r.html

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