Potato Dextrose Agar Lab Report

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Potato Dextrose Agar

1. 39.0 g of potato dextrose agar powder was dissolved in a litre of sterile distilled water on the hot plate.
2. pH of the solution was adjusted to 5.6 ± 0.2 by adding NaOH or HCl and was immediately transferred into the Schott bottle to be autoclaved at 121 ° C for 15 minutes
3. Prepared medium was stored in 4° C chiller

Plate Count Agar or Total Plate Count

1. 22.5 g of plate count agar powder was dissolved in a litre of sterile distilled water on the hot plate
2. pH of the solution was adjusted to 7.0 ± 0.2 by adding NaOH or HCl and was immediately transferred into the Schott bottle to be autoclaved at 121 ° C for 15 minutes
3. Prepared medium was stored in 4° C chiller

Lauryl Sulphate Broth
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It is a solution that maintains the osmotic balance for bacteria. It also used in the microbial control of apparatus by the rinse and swab method.
Stomaching process used in this experiment offers as a useful alternatives to blending in preparing food samples for microbiological analysis but according by data presented om 30 types of food tested, the efficiency of stomachers varies based on the type of food being examined. Since most of the pineapple products tested is either in liquid or semi-solid form, stomaching is the most suitable way to make food homogenate(Andrews et al, 1977). Besides that, in this analysis process we used serial dilution method. Serial dilution is the repeated dilution of a solution to amplify the dilution factor quickly. It is commonly performed in experiments requiring highly dilute solutions with great accuracy such as those involving concentration curves on a logarithmic scale or involving experiments to determine density of bacteria
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Firstly, by using pipette, one ml of food homogenate was transferred into a universal bottle containing 9ml of Ringer solution and labelled as 10-2 or dilution 2, 10-1 is dilution 1 which is the food homogenate.
2. Content of the bottle was then mixed using shaker approximately 10 seconds
3. 1ml of 10-2 was pipetted into a new universal bottle containing 9ml of Ringer solution to make 10-3 dilution
4. Again, content of the bottle was mixed by using shaker for approximately 10 seconds
5. Similar processes can be repeated if more dilution series are needed

Note: all processes were done in laminar airflow and aseptic methods were applied

Microbial Identification and Enumeration Using Pour Plate Method

Objective:

To identify availability and quantity of various microbes in different type of microbial culture media

Materials

Micropipette (100-100µl), consumable petri dishes, Bunsen burner, shaker, incubator 25°C and incubator 37° C. The following materials were prepared prior of this experiment:universal bottles filled with Ringer solutpn, food homogenateof canned pineapple, microbial culture media: BCA, PDA, TPC and lauryl sulphate broth

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