A comparison between organic and conventionally grown carrots

prepared on cutting boards sanitized in various ways

By: Crystal Hamelburg and Tomasz Perlinski

Hypothesis

Organic carrots should exhibit a higher quantity of microbial growth than their conventional counterparts, even after the application of various sanitizers.

Introduction

• There were two main objectives of this study:

• The first objective involved testing the efficacy of three different sanitizers used to clean cutting boards purposely contaminated with Escherichia coli.

• The second objective was to compare the quantity of E.Coli contamination present on organic and conventionally grown carrots prepared on the cutting boards after the application of the disinfectants.

Materials and Methods

Media Preparation

• 40 g of Tryptic Soy Agar was weighed out on a balance and slowly added to 1.0 L of distilled water, while the flask was stirred with a stir bar (directions obtained directly from the bottle)

• The media was placed into the autoclave on a Liquid 9 setting for 45 minutes at 121°C

• 56 plates were poured for the two trials conducted

Materials and Methods

Sample Preparation

Carrots were washed with warm tap water and dawn dish

soap

A borer, forceps, and scissors were autoclaved and used to

obtain the carrot cores

Carrot cores were obtained under a sterile hood and placed into sterile weigh

boats

Materials and Methods

Cutting Board Preparation

A used cutting board was obtained from Texas Roadhouse, cut into four roughly equal

boards, and sterilized under UV light for 2 hours. .

Each board was divided into 6 sections and labeled the “control, bleach, Eco-San, and

lime.”

Materials and Methods

Disinfectants

Control: Sterile Distilled Water

1% Bleach Solution 50% Diluted Eco-San

Lime Essential Oil (1 mL Lime +

2 mL dH2O)(10 mL dH2O+10 mL Eco San)

Materials and Methods

Pre and Post experiment procedures and testing

• Four separate sterile cotton swabs were used to test each cutting board prior to the application

of any E.coli to ensure that they were free from contamination that would skew the results. • Four Additional samples were collected after the application of each disinfectant.

Materials and Methods

Application of Escherichia coli and DisinfectantsA McFarland standard was used to prepare the E.Coli cells

0.5 mL of E.coli was transferred using a sterile pipette to each section of the four cutting boards

The bacteria was spread all over each section of the cutting board using a sterile cotton swab

The bacteria were given 10 minutes to dry before 0.5 mL of each respective sanitizer was applied to each respective section

Materials and Methods

Incorporation of carrot core samples and consequent plating on TSA plates

Giant Organic

Shoprite Organic

Weis Organic

Giant Conventional

Shoprite Conventional

Weis Conventional

• Carrot cores were spread around about an inch forward and then back again with forceps.

• The Bunsen burner was used to sterilize the forceps after each carrot core application.

Materials and Methods

Colony Quantification

Control Bleach Eco-San Lime Essential Oil

Materials and Methods

Gram Stains

Gram stains were performed on the E.coli Bacteria after they were given a 24 hour incubation

period.

The TSA plates that showed growth were tested using

the standard gram stain procedure.

This allowed the quantification of any sort of contamination.

Results

Figure 5: Sample gram stains from colony forming carrot samples. Photographs of gram stains, showing E. coli (gram negative) colonies that formed from carrot core swabs. A – Sample gram stain of carrot

swab used on control (dH2O) cutting board; B - Bleach treated cutting

board, C – Eco-San treated cutting board, and D – Lime treated cutting board.

Gram Stains

Results

Table 1: Colony Quantification of Experiment I. The number of colonies that formed from the carrot swabs after the 24 hour incubation period (standard conditions).

*Using a streak plate method and counted using naked eye.

Table 2: Colony Quantification of Experiment II. The number of colonies that formed from the carrot swabs after the 24 hour incubation period (standard conditions).

*Using a streak plate method and counted using naked eye.

Colony Counts

Experiment I

Carrots Control (dH2O) Bleach Eco-San Lime

Giant Organic TNTC 0 0 5

Giant Conventional TNTC 0 0 TNTC

Shoprite Organic 16 0 0 TNTCShoprite Conventional TNTC 0 0 TNTC

Weis Organic 0 0 0 TNTC

Weis Conventional 2 0 0 TNTC

Experiment II

Carrots Control (dH2O) Bleach Eco-San Lime

Giant Organic TNTC 2 0 0

Giant Conventional TNTC 0 0 0

Shoprite Organic 83 6 0 0Shoprite Conventional TNTC 0 0 0

Weis Organic 28 0 0 42

Weis Conventional TNTC 0 1 0

Results

Sanitizer Effectiveness

Control Bleach EcoSan Lime0

1

2

3

4

5

0

5 5

2

Scal

e of

Eff

ecti

vene

ss

Figure 1: Sanitizer Effectiveness Scale. The effectiveness of sanitizers used compared to the control, using a 1-5 scale. (0 = Not effective, 5 = Very effective)

*Effectiveness refers to the number of colonies formed, 0-20 CFU’s is considered very effective.

The most effective sanitizers were Bleach and Eco-

San.

The lime’s effectiveness varied

between experiments, but was not very effective in either

case.

Results

Pre and Post Experiment Testing

Control Bleach EcoSan Lime

1

0 0 0

Figure 2: Cutting Board Cleanliness Before the start of the experiment. A sample of each cutting board was plated on TSA to evaluate the effectiveness of cutting board sterilization under the UV light in a laminar flow biological hood for approximately 2 hours. Any colony growth after a 24 incubation period was noted.

Control Bleach EcoSan Lime

+330

40 11

Figure 3: Cutting Board Cleanliness 10 minutes after applying Sanitizers. A sample of each cutting board was plated on TSA to evaluate the effectiveness of the sanitizers before applying the carrot samples. Any colony growth after a 24 incubation period was noted.

Results

Organic vs. Conventionally Grown Carrot Cores

Figure 4: Microbial Growth Comparison between Organic and Conventional Carrots. The number of each carrot category that had colony formation was summed together to determine the total number of organic carrot growth to conventional carrot growth out of a possible 24 samples. For example, every time there was growth on a TSA plate it was counted as “1”.

Discussion

Eco-San was found to be the most

effective.

Bleach was also found to be the most effective.

Lime essential oil was found to be

the least effective.

Effectiveness of Sanitizers The results of this experiment have shown that plastic cutting boards can be effectively cleaned with the use of various sanitizers that may help to prevent cross contamination.

Discussion

Overall, it was observed that organic carrots exhibited more microbial growth.

Conventional carrots are often associated with the application of chemical fertilizers, genetic modification, hormones, pesticides, and residues in food.

Microbial growth comparison between organic and conventional produce

Discussion

Typically, the use of the external portion of the carrots were utilized for experimental procedures in the literature that was explored.

However, our experiment used aseptic carrot cores, but was still consistent with theories that stated organic microbial growth would be higher than conventional carrot growth, despite the differences in methods.

Literature Comparison

Questions