****Food Microbiology Laboratory question****, **********Questions********** (PL
ID: 208326 • Letter: #
Question
****Food Microbiology Laboratory question****,
**********Questions********** (PLease help me to figure out the answers after reading/ using following text, thx a lot)
1. Introduce what is Standard plate count and how it works in this lab
2. Deeply analyse and explain the result of this lab (results is provide in the following text)
---------------------
Laboratory: Microbiological analysis of food products (Standard plate count)
Used media: Brain-heart Infusion Agar
Brain Heart Infusion (BHI) Agar is a general-purpose medium suitable for the cultivation of a wide variety of organism types, including bacteria, yeasts and molds. BHI Agar derives its nutrients from the brain heart infusion, peptone and dextrose components. The peptones and infusion are sources of organic nitrogen, carbon, sulfur, vitamins and trace substances. Dextrose is a carbohydrate source that microorganisms utilize by fermentative action. The medium is buffered with the effect of disodium phosphate.
Ingredients: Beef brain and heart, peptone, dextrose, disodium phosphate
---------------------
Food products used: 2 Char sui samples (Store at 4°C and room temperature for 20 hours)
---------------------
Procedure:
1.1 Label 5 sterile petri dishes 10-2, 10-3, 10-4, 10-5, 10-6 (1 set); prepare 2 sets for each food sample (A total of 20 plates for 2 food samples).
1.2 Place 20 g of the food sample in the stomacher plastic bag
1.3 Use the dilution scheme shown in Figure 3, add 180 ml of sterile water to the bag/blender. This is a 1:10 dilution (10-1)
1.4 Place the bag in the stomacher, mix at medium speed for 30 seconds.
1.5 Pour the liquid of the mixture into a 50 ml Falcon tube.
1.6 Pipette 1 ml of this 10-1 to a 9 ml sterile water. This is a 1:100 dilution (10-2).
1.7 Mix well the 10-2 dilution by vortex, pipette 1 ml of 10-2 to a new 9 ml sterile water. This is a 1:1,000 dilution (10-3).
1.8 Before pipetting, mix well each dilution by vortex.
1.9 Repeat step 1.6 to obtain 1:10,000 dilution (10-4) to 1:1,000,000 dilution (10-6).
1.10 Pipette 0.1 ml of the suspension from the 50 ml Falcon tube (containing the blended food sample) to the bottom of the plate marked 10-2.
1.11 Pipette 0.1 ml of 10-2 dilution to the bottom of the plate marked 10-3.
1.12 Repeat step 1.11 for 10-3 to 10-6 dilution according to Figure. 3
1.13 Add 15 ml of cooled molten BHI agar to all plates.
1.14 Swirl the plates gently 20 times on the bench-top. The goal is to disperse the bacterial cells throughout the agar so you will get isolated colonies when incubated.
1.15 Allow agar in plates to solidify. Then invert and incubate the plates at 37oC.
1.16 After 24 hours of incubation, count the colonies in the BHI agar plates.
---------------------
Results:
10-2
10-3
10-4
10-5
10-6
Plate 1
RT
TNTC
37
3
0
0
4 ºC
77
11
0
0
0
Plate 2
RT
TNTC
31
2
1
0
4 ºC
111
5
0
3
0
SPC calculation as follows:
For the Char Siu sample stored at room temperature,
N = (37+3+31+2+1) / [(1 x 2) + (0.1 x 2) x 10-3]
= 74 / 0.0022
=3.36 x 104
SPC Round off to two significant = 30000
For the Char Siu sample stored at 4 ºC,
N = (77+11+111+5+3) / [(1 x 2) + (0.1 x 2) x 10-2]
= 207 / 0.022
=9.41 x 103
SPC Round off to two significant = 9000
---------------------
10-2
10-3
10-4
10-5
10-6
Plate 1
RT
TNTC
37
3
0
0
4 ºC
77
11
0
0
0
Plate 2
RT
TNTC
31
2
1
0
4 ºC
111
5
0
3
0
1ml 1ml 20 g food sample180 ml sterile water (10) 1ml 1ml 1ml -6 9 (10) 9 (10) 9 (10) 9(10 2 9 (10) 0.1ml 0.1ml 0.1ml 0.1ml 0.1ml 10 10 10 10 10 Fie 3. Dilution scheme for SPCsExplanation / Answer
Question 1 answered
Standard Plate Count allows us to find out the possible presence of microbes in samples and find out if the food or the production process is carried out in a hygienic way ( if the spc is found within safe limits). Here in this lab we are trying to find out microbe count that grows in the samples from 4degrees and room temperatures to quantify activated or inactivated forms of microbes present. If the count is to be found par the safe limits then the food or the production space would be qualified as foul.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.