Food Safety Consumer Research Project: 

Meal Preparation Experiment Related to Thermometer Use 

Executive Summary 

May 2018 

The Food Safety and Inspection Service (FSIS) of the U.S. Department of Agriculture (USDA) contracted 

with RTI International and its subcontractor North Carolina State University (NCSU) to conduct meal 

preparation studies to evaluate consumer food handling behaviors in a test kitchen. The research team 

is conducting five separate iterations of the meal preparation study to address a specific consumer 

behavior and to determine the effectiveness of a behavior change intervention. The meal preparation 

studies are part of a larger 5-year annual study that also includes focus groups (two iterations) and web 

surveys (two iterations). This report describes the results of the first iteration of the meal preparation 

study that examined consumers’ use of food thermometers when cooking ground turkey patties. 

The study was conducted in six test kitchen facilities located in the metro Raleigh–Durham area of North 

Carolina and Smithfield, North Carolina, a rural location. Before preparing the meal, a randomized 

treatment group watched the 3-minute USDA food safety video “The Importance of Cooking to a Safe 

Internal Temperature and How to Use a Food Thermometer.” In each test kitchen, six cameras recorded 

participants’ actions at various locations throughout the kitchen and recorded the meal preparation 

from beginning to end. Participants in the control and treatment groups were observed while cooking 

turkey burgers (spiked with the harmless tracer bacteriophage MS2) and preparing a chef’s salad to 

determine whether they used a thermometer on the turkey products and whether they adhered to 

other food safety behaviors throughout the meal preparation. Following meal preparation and cleaning, 

the study team collected microbiological samples from surfaces and lettuce and analyzed the samples 

for prevalence and level of MS2. Participants participated in a post-observation interview to collect 

information on their usual food preparation practices and possible predictors of behavior change. A 

total of 383 people participated in the study (201 control, 182 treatment). The results for the control 

group, which describes consumer behavior without direct exposure to the video, and the treatment 

group are presented and described below. 

Key Findings 

o Viewing the USDA video on thermometer use immediately before food preparation encouraged 

participants to follow USDA-recommended use of a food thermometer for checking doneness of 

raw poultry. 

o Reported food thermometer ownership (61 to 63%) was similar to results reported in the 2016 

FDA Food Safety Survey, in which 67% of consumers reported owning a thermometer (see 

Figure 1). 
 

 

 

 

 

 

 

 

 

 

80% 

70% 

60% 

50% 

40% 

30% 

20% 

10% 

0% 

90% 

80% 

70% 

60% 

50% 

40% 

30% 

20% 

10% 

0% 

75%· 

61% 63% 

Thermometer ownership (self-reported) Used a thermometer 

 Control (n = 201)  Treatment (n = 182) 

52%* 

23% 

Placed thermometer in correct location 

(among total attempts) 

Control (n = 168) 

Treatment (n = 322) 

82%* 

Checked both patties 

(among thermometer users) 

Control (n = 60) 

Treatment (n = 128) 

 Control  Treatment 

o Participants who viewed the 

video (i.e., treatment group) 

were twice as likely to use a 

thermometer to check the 

doneness of the turkey 

patties compared with those 

who were not exposed to 

the video (i.e., control 

group) (75 vs. 34%) (see 

Figure 1). 

o Participants in the treatment 

group were twice as likely to 

place the thermometer in 

the correct location (i.e., the 

side of the patty to reach the 

center and coldest spot) 

compared with the control 

group (52 vs. 23% of 

attempts for thermometer 

placement) (see Figure 2). 

o Participants in the treatment 

group were more likely than 

participants in the control 

group to cook the patties to 

at least 165°F based on the 

initial thermometer reading 

(73 vs. 54%). 

o Use of other indicators of 

doneness was common 

among control group 

participants; most relied on 

only touch (the firmness or 

texture of the burger) or 

color and touch. 

o In the post-observation 

interviews, 66% of 

treatment-group 

participants stated that 

watching the video 

influenced their cooking 

behavior in the kitchen; of 

these participants, 61% reported using a thermometer as a result of watching the video. 

o Proper handwashing, which was not addressed in the video watched by the treatment group, 

needs improvement. For the treatment group, there were 1,054 cases in which a handwashing 

event was needed to decrease the risk of cross-contamination (e.g., before meal preparation 

* Differences between two groups statistically significant at 

p < .001 

Figure 1. Thermometer Ownership (Self-reported) and Use 

* Differences between two groups statistically significant at 

p < .001 

Figure 2. Correctly Used Thermometer 
 

 

 

 

 

 

 

90% 

80% 

70% 

60% 

50% 

40% 

30% 

20% 

10% 

0% 

Did not wet 

hands 

35% 

31% 

30% 

25% 

20% 

15% 

10% 

5% 

0% 

33% 

0.8% 

- 2% 

 

Attempts 

Control (n = 1,195)  Treatment (n 

Successful 

= 1,054) 

attempts 

-

83% 

76% 

24% 

Ii 

Did not use soap Did not ru b 

hands with soap 

for at least 20 

1% 1% 

Did not ri nse 

hands with 

water 

i i 

Did not dry 

hands 

23% 

16% 

I 

Dried hands 

with surface 

other tha n 

seconds disposable 

towe l 

 Control (n = 355)  Treatment (n = 327) 

and after handling raw 

product). For these cases, 

participants attempted to 

wash their hands about onethird (33%) of the time. 

Results were similar for 

control group participants, in 

which participants 

attempted to wash their 

hands 31% of the time when 

required (see Figure 3). 

o Among attempted 

handwashing events, very 

few included all steps 

necessary to be considered 

an adequate handwashing 

event (defined by the Centers for Disease Control and Prevention’s recommended steps); 2% for 

the treatment group and less than 1% for the control group (see Figure 3). 

o The most common reason for unsuccessful handwashing was not rubbing hands with soap for at 

least 20 seconds (76% in the control group and 83% in the treatment group), followed by not 

wetting hands with water (40% in the control group and 44% in the treatment group). There 

were no significant differences between the treatment and control groups (see Figure 4). 

Figure 3. Handwashing Attempts among Required Events 

Figure 4. Reasons for Unsuccessful Handwashing Attempts 

o Approximately 48% of control group participants contaminated spice containers (e.g., salt and 

pepper shakers) they touched during the preparation of the preformed turkey burgers, and 5% 

contaminated the lettuce used to prepare the salad, a ready-to-eat food (see Figure 5). This rate 
 

% 

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ro 

..., 

C 40% 0 

u 

Q) 

u 

C 

~ 30% ro 

> 

~ CL 

20% 

11% 

10% 

0% 

Refrigerator 

handle 

5.47 ± 0.38· 

(n = 199) 

48% 

11% 

Spice containers Faucet handle 

6.28 ± 0.83b 5.51 ± 0.47· 

(n = 199) (n = 199) 

6% 

Mobile device 

5.54 ± 1.51 C 

(n = 35) 

5% 

Salad 

-

lettuce 

5.64 ± 0.74d 

(n = 199) 

60 

c 

of contamination of the salad indicates that cross-contamination was not necessarily frequent 

but did occur with some regularity, which could be a significant area of concern when 

extrapolated nationally. Results for the treatment group (not shown) were similar. 

a Level of contamination ± SD, log genome copies/handle 

b Level of contamination ± SD, log genome copies/bottle 

Level of contamination ± SD, log genome copies/device 

d Level of contamination (SD), log genome copies/18–25g 

Figure 5. Prevalence of MS2 Contamination for Four Kitchen Locations and Salad 

Lettuce (Control Group Participants)