HONOURABLE MENTION

Prewashed VS Unwashed lettuce

Is Unwashed Lettuce Cleaner Than Prewashed?
Max.B
Grade 7

Hypothesis

My big question: Is pre-washed lettuce cleaner than unwashed lettuce washed by yourself?

 

 

Hypothesis: I think that unwashed lettuce and washing it yourself will be cleaner than prewashed lettuce because who knows how clean the water is that they wash in (see research).

 

Research

 The reason I think that buying unwashed lettuce and washing it will be cleaner is based on the fact that on the website for the lettuce it does not say what they washed it in? I mean it could be chemicals that are dangerous! Let me walk you through how the lettuce gets to the store. First, it is grown in a large greenhouse and the crops are sprayed with pesticides like Imidacloprid and Mandipropamid which are two of the most common ones used on lettuce. Some lettuce has been found with over 50 pesticides. Once Picked by someone (their hands could be very dirty) They are loaded onto a truck and taken to where they will be washed. They are probably washed in water but the water could have germs or they could be washing the lettuce in chemicals. Also, we don't know if they get all the pesticides off. Then they are loaded into the packages (which could be dirty) and are shipped off to the store. The other reason is that when you buy unwashed lettuce you can clean it as thoroughly as you want to try to get it as clean as possible. Some company's wash the lettuce in one big tube of water that the lettuce falls through and only switching the water every few days. Others have developed ways to spray water on the lettuce and use the same water over and over.

Variables

Variables:

 

Manipulated: 

 

-Washing procedure 

  •   (Prewashed) (Group A)
  •  (Prewashed and hand washed) (Group B)
  • (unwashed) (Group C)
  • (Unwashed and hand washed) (Group D)



 

Controlled:

  • distilled water
  • Petri dishes
  • Agar
  • swabs   
  • Lettuce
  • Salad spinner



 

Responding: 

 

The Average number of bacterial colonies per petri dish for each group.

 

 

Procedure

Procedure:  

  1. Agar was prepared and poured into Petri dishes.
  2. Pre-washed lettuce was purchased and swabbed.
  3. The pre-washed lettuce was then soaked in water, drained, and spun in a salad spinner. This process was done twice, before swabbing again.

 

  1. Non-washed lettuce was purchased and swabbed.

The non-washed lettuce was then soaked in water, drained, and spun in a salad spinner. This process was done twice, before swabbing again.

 

  1. All swabs were wiped on agar-filled petri dishes in a zig-zag pattern.
  2. The petri dishes were incubated in a warm location.
  3. The petri dishes were examined every day at 8:00 PM and the bacterial colonies were counted for 10 days.
  4. After day 10 the petri dishes were safely disposed of.

 

 

Materials:

  • Seaweed Solution Laboratories Nutrient Agar kit

containing 20 sterile Petri dishes, 20 sterile swabs, and 16 grams of Nutrient Agar.

  •  170ml of Distilled water
  • President's choice brand spring mix blend of thoroughly washed Lettuce (Prewashed)
  • President's choice brand Live Lettuce(unwashed)
  • Tap water (to wash unwashed Lettuce)
  • Generic Salad tosser (to dry lettuce)
  • President's Choice Distilled water (to make the Agar)

Observations

Day 1

Jan 3


 

A1: Where swap touched a thousand of small see through colonies.

A2: Where swap touched a thousand of small yellow colonies. 

A3: Around 600 small see through colonies.

B1: Around a thousand see through colonies.

B2: Around a thousand see through colonies.

B3:Around a thousand see through colonies.

C1:Nothing

C2:Nothing

C3:Nothing

D1:Nothing

D2:Nothing

D3:Nothing

Salad Tosser:Nothing

Control:Nothing

 

Day 2

Jan 4


 

A1: All the dot’s have condensed into around 50 large one’s.

A2: A thousand of small yellow colonies. 

A3: All the dot’s have condensed into around 30 large one’s.

B1: All colonies have turned yellow.

B2:All the dot’s have condensed into around 60 large one’s.

B3:All the dot’s have condensed into around 70 large one’s.

C1: 20 see through.

C2:Nothing

C3:Nothing

D1: 10 See through.

D2: Nothing

D3:Nothing

Salad Tosser:Nothing

Control: Nothing


 

Day 3

Jan 5


 

A1:50 big white colonies, 10 small yellow colonies.

A2: A thousand small yellow colonies, 15 big white.

A3: All the dot’s have condensed into around 65 big colonies.

B1: Thousand small yellow colonies.

B2: 80 big white, 20 big yellow colonies, 4 small yellow colonies, 6 yellow stain-like one’s.

B3: 70 big white colonies, 6 smaller yellow colonies, 3 yellow stain-like one’s.

C1: 30 clear colonies, 20 medium yellow colonies.

C2: 2 white colonies, 1 yellow colony, 3 fan-like colonies.

C3: 4 white colonies, 1 yellow colony.

D1: 15 big white colonies, 2 medium yellow colonies.

D2: 17 big white colonies, 3 big yellow colonies.

D3: 27 big white colonies, 3 big yellow colonies.

Salad Tosser: Nothing

Control: Nothing


 

Day 4

Jan 6 

 

A1:64 big white colonies, 30 small yellow colonies.

A2:1000 small yellow colonies, 15 big white.

A3: 67 Big white, 22 small yellow. 

B1: Thousand small yellow colonies. 

B2: 83 big white colonies, 43 big yellow colonies, 37th small yellow colonies, 8 stain like colonies. 

B3: 76 big white colonies,8 small yellow colonies, three stain like colonies. 

C1:42 white colonies, 31 big yellow colonies, 157 small yellow colonies, one big white colony. 

C2: 5 white colonies, one mushroom - like Colony, 10 fan-like colonies with black dots, 6 yellow colonies.

C3:23 white colonies, for small yellow colonies. 

D1: 23 big white colonies, 6 big yellow colonies.

D2:30 big white colonies, 6 big yellow colonies.

D3: Thirty-One big white colonies_three big yellow colonies.

Salad Tosser: Nothing

Control: nothing 


 

Day 5

Jan 7

 

A1:67 big white colonies, 33 small yellow colonies. 

A2: 1000 small yellow colonies, 20 big white colonies, one weird Blobby colony. 

A3:Nochange

B1:Nochange

B2: 87 big white colonies, 51 big yellow colonies, 37 small yellow colonies, 8 staine like colonies.

B3: Nochange

C1: Nochange

C2: 5 white colonies, 1 mushroom like colony, 10 fan like colonies with black dots,6 yellow colonies.

C3:Nochange

D1: 41 big white colonies, 16 big yellow colonies.

D2: Nochange

D3:Nochange

Salad Tosser:Nochange

Control:Nochange


 

Day 6

Jan 8

 

A1: Nochange

A2: 54 small yellow colonies, 23 big white colonies, one weird Blobby colony.

A3: 82 big white colonies, 25 small yellow colonies.

B1: All the yellow turn to White.

B2: nochange

B3: Nochange

C1: 47 white colonies, for TV yellow colonies, 172 small yellow colonies.

C2: Nochange

C3: 37 white colonies, 18th small yellow colonies.

D1: Nochange

D2: 42 big white colonies, 7 big yellow colonies.

D3: 34 big white colonies, seven big yellow colonies.

Salad Tosser:  4 yellow Mini 3 mini white one fan with black. Mini. 

Control: One white super mini.


 

Day 7

Jan 9

 

A1: 83 big white colonies, 34 small yellow , 1 big yellow.

A2: 1000 small yellow colonies,1 big white blob-like colony.

A3:Nochange

B1: 1 white blob-like colonies, 1000 small white colonies.

B2:Nochange

B3: 80 big white colonies, 3 small yellow colonies,3 white stain-like colonies.

C1: Nochange

C2: 26 yellow colonies, 3 white mushroom-like colonies, 10 fan-like colonies with black dots, 2 white colonies. 

C3: 52 big white colonies, 18 small yellow colonies, 4 pink, 2 white stain like colonies.

D1:43 white colonies, 4 fan-like with black dots colonies, 15 big yellow.

D2:45 big white colonies, 7 big yellow colonies, 

D3:37 big white colonies 14 big yellow colonies. 

Salad Tosser:5 yellow mini colonies, for many white colonies, 1 fan-like colony with black dot.

Control: 1 white mini.


 

Day 8

Jan 10

 

A1:Nochange

A2:1000 small yellow colonies,1 weird blog Colony, 37 big white colonies.

A3:Nochange

B1:Nochange

B2: 90 big white colonies, 51 big yellow colonies, 38th small yellow colonies, 8 seem like colonies.

B3:Nochange

C1: 50 big white colonies, 41 big yellow colonies, 172 small yellow colonies.

C2: Nochange

C3: 52 White colonies, 21 small yellow colonies for pink colonies to White stain like colonies. 

D1:Nochange

D2:Nochange

D3:Nochange

Salad Tosser:Nochange

Control:Nochange


 

Day 9

Jan 11 

 

A1:87 big white colonies, 34 small yellow colonies, 2 big yellow colonies.

A2:  57  big yellow colonies, 1 blob-like Colony, 40 big white colonies.

A3:193 big white colonies, 28 small yellow colonies. 

B1:8 White fleck looking colonies 72 big white colonies. 

B2:40 big white colonies Karma 9 Sulekha looking colonies, 64 big yellow colonies, 38th small yellow colonies, 11 small yellow. 

B3:83 big white colonies, 19th small yellow colonies, 8 stain-like colonies.

C1: 50 big white colonies, 57 big yellow colonies, 105 small yellow colonies.

C2: 29 yellow colonies, 4 white mushroom-like colonies with black dots.

C3:Nochange

D1:52 White colonies, for white colonies with black dots,  29 big yellow colonies.

D2:Nochange

D3: 40 big white colonies, 12 yellow colonies (some of the yellow turned white).

Salad Tosser: Nochange

Control: Nochange


 

Day 10

Jan 12

 

A1:104 big white colonies, 57 small yellow colonies, three big yellow colonies.

A2: 57 big yellow colonies, one weird blob like Colony, 67 big white colonies.

A3: 102 big white colonies, 39 small yellow colonies.

B1: 47 fleck looking colonies, 72 big white colonies.

B2: 62 big white colonies, 14 Fleck looking colonies, 57 big yellow colonies, 45 small yellow colonies, 23 stained like colonies.

B3: 83 big white Colonies, 26 small yellow colonies, 8 stain-like colonies. 

C1:50 big white colonies, 82 big yellow colonies, 207 small yellow colonies, 3 Fan like colonies White.

C2: 29 yellow colonies, 5 white mushroom-like colonies, 11 fan-like colonies with black dot. 

C3:83 white colonies, 53 small yellow colonies, 7 pink colonies , to stain like colonies White. 

D1:50 white colonies, five of them with black dots, 32 big yellow colonies.

D2:57 big white colonies, seven big yellow colonies, one mushroom like Colony yellow.

D3: 48 big white colonies, 12 big yellow colonies, one with black dot.

Salad Tosser:Nochange

Control: Nochange

 

Analysis

A Average B Average C average D average
0 0 0 0
45 23 7 10
65 62 20 22
89 81 41 36
89 99 46 42
107 103 62 49
107 112 71 55
107 118 84 55
180 136 95 62
186 171 119 80
  A1 A2 A3 B1 B2 B3 C1 C2 C3 D1 D2 D3 Control Saled Tosser
Day 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Day 2 50 54 30 0 0 70 20 0 0 10 12 9 0 0
Day 3   69 65 47 60 79 50 6 5 17 20 30 0 0
Day 4 92 69 89 47 110 87 75 22 27 39 36 34 0 0
Day 5 100 73 89 49 160 87 75 36 27 57 36 34 0 7
Day 6 100 77 107 52 169 87 95 36 55 57 49 41 1 7
Day 7 117 85 107 72 170 95 95 41 76 62 52 51 1 10
Day 8 117 94 107 83 176 95 111 62 79 62 52 51 1 10
Day 9 123 95 180 97 180 130 140 67 79 82 52 53 1 11
Day 10 164 122 186 149 186 177 140 88 129 85 73 81 1 13

Conclusion

Conclusion: Pre-washing lettuce does not reduce bacterial growth in fact it seems to increase bacterial growth. Handwashing does seem to reduce bacterial growth.

 

Application

Application's: The most effective way to get clean lettuce is to buy unwashed lettuce and wash the lettuce yourself. This has been proven to be more effective then prewashed lettuce.

Sources Of Error

Ways that this project could have had Errors are:

1.There could have been contamation by me.

2.There could have been cross-contamantion  because they were stored together

3 .The agar (bacteria food) could have been defective.

4. The petre dishes could have not been sterial.

5. The colonies are very small the counting my not be perfect.

Acknowledgement

My Grandfather for helping me edit.

My Mother for proofreading. 

My teachers Mrs. Saville and Mr Ryan for helping me through this.