The strategic deployment of free food samples and promotional loyalty schemes represents a significant investment within the marketing industry, which claimed a spend of 2.2 billion dollars on general product sampling in 2009, a trend that continued to rise as late as 2015. In the context of food choices, the primary drivers of consumer behavior are price and taste, making sampling a critical tool for businesses attempting to introduce new products that consumers would not typically purchase. This is especially pertinent for the plant-based sector, where vegetarian and vegan options are often met with consumer hesitation due to concerns regarding taste. Retailers and global food brands have signaled this importance through aggressive growth targets; for instance, Tesco established a goal to increase plant-based sales by 300% between 2020 and 2025, while entities such as Starbucks and Burger King have committed to expanding their plant-based offerings.
Despite these industry claims and the proliferation of sampling, rigorous empirical evidence remains mixed. While some marketing services claim sales conversions can reach as high as 90%, peer-reviewed evidence on the actual effectiveness and sustainability of these effects is limited. Research conducted in Brazil and Malaysia indicated that consumers reported a higher likelihood of trialing new supermarket products when free samples were provided, but these results relied on self-reported data rather than observed behavior and may be influenced by cultural differences specific to those regions. To address these gaps, a stepped wedge trial was implemented in 2022 within blue-collar workplace food outlets to determine if free samples and loyalty cards could shift consumption patterns toward plant-based meals.
Trial Design and Implementation Framework
The 2022 intervention was structured as a stepped wedge trial combined with a process evaluation. This specific design was selected to maximize statistical power given the constraints of the number of participating outlets. The trial was executed via a workplace food outlet operator serving blue-collar environments across the country.
The timeline for the study was strictly defined, running over a four-week period from August 1st to August 28th, 2022. To establish a baseline and measure the long-term impact, data collection extended beyond the active intervention phase. Baseline data were collected for the four weeks preceding the trial, from July 4th to July 31st, 2022. Following the conclusion of the trial, data were collected for an additional five weeks, spanning August 29th to October 2nd, 2022.
The transition from the control phase to the intervention phase occurred in three distinct sequences. These sequences entered the intervention in three steps:
- Week 1: The first group transitioned on August 1st.
- Week 2: The second group transitioned on August 8th.
- Week 3: The third group transitioned on August 15th.
A total of 29 sites completed the trial. The distribution of these sites across the sequences was as follows:
- Sequence 1: 9 sites.
- Sequence 2: 10 sites.
- Sequence 3: 10 sites.
Intervention Mechanisms and Operationalization
The trial employed two primary promotional tools: free samples and loyalty cards. These were designed to lower the barrier to entry for plant-based options by addressing taste concerns and incentivizing repeat purchases.
Free Sample Deployment
The free sample component was focused on the first week of the intervention. Fieldworkers were deployed into the food outlets to distribute samples of one of the vegan or vegetarian meals available that day. The specific meals offered varied by outlet. To maximize the impact, sampling occurred during the periods of highest footfall, specifically on Tuesdays, Wednesdays, and Fridays during lunchtime.
The use of fieldworkers ensured that the samples were actively handed to customers, rather than left as self-service options. This operational choice aimed to directly counter the consumer fear that plant-based foods might not taste appealing.
Loyalty Card Structure
Loyalty cards were made available in each food outlet for the entire duration of the intervention. Depending on the sequence in which a site entered the trial, the duration of the loyalty card availability lasted for two, three, or four weeks.
The loyalty system was designed with an "endowed progress" mechanism to increase the psychological appeal and the likelihood of completion. The structure was as follows:
- Qualifying Action: Customers received a stamp for every vegan or vegetarian hot meal or baguette ordered during lunch and dinner periods.
- Reward Threshold: A total of four stamps were required to exchange the card for a free meal.
- Endowed Progress: The first stamp was provided automatically upon receipt of the card.
- Practical Requirement: Because of the first free stamp, customers only needed to purchase three qualifying plant-based meals to earn the reward.
- Reward Flexibility: The free meal earned could be any meal of the customer's choice, whether it was vegan, vegetarian, or otherwise.
- Redemption Window: The rewards remained valid until September 25th, 2022, which was one month after the intervention period ended.
Baseline Sales Data and Site Variations
Before the implementation of the interventions, baseline data were collected to understand existing consumption patterns in the blue-collar workplace environments.
On average, a food outlet sold approximately 66 meals daily. Of these, plant-based meals accounted for an average of 19 sales per day, which represented 30.4% of all daily options sold. While the numbers were generally consistent across the three sequences, Sequence 1 exhibited a lower mean for both the number of plant-based options sold daily and the proportion of plant-based options sold.
This variation in Sequence 1 was primarily attributed to a single outlier, Food Outlet 32, which reported a significantly lower average of 4.1 plant-based options sold daily and a proportion of only 6.1%.
Quantitative Results and Statistical Analysis
The primary objective of the trial was to determine if the interventions would increase the volume of plant-based sales. The results indicated that neither the free samples nor the loyalty cards produced a statistically significant effect.
Free Sample Impact
The volume of plant-based sales on days when free samples were distributed did not differ significantly from the baseline period. The statistical analysis provided the following values:
- Coefficient: -0.53.
- 95% Confidence Interval: [-3.43, 2.36].
- P-value: .718.
Loyalty Card Impact
Similarly, the volume of sales on days where only the loyalty card intervention was active showed no statistically significant increase. The statistical analysis provided the following values:
- Coefficient: 0.33.
- 95% Confidence Interval: [-2.73, 3.38].
- P-value: .834.
To ensure the robustness of these findings, an alternative model was utilized that incorporated day-of-the-week fixed effects instead of date fixed effects. This adjustment was made to better capture weekly seasonality, yet it confirmed the initial result that the interventions did not significantly alter sales volumes.
Process Evaluation and Qualitative Findings
To understand why the interventions failed to produce statistically significant results, a process evaluation was conducted. This included interviews with food outlet managers, staff from six outlets, and six fieldworkers responsible for distribution. Additionally, intercept interviews were conducted with customers at two sites in each sequence.
Consumer Behavior and Taste
The process evaluation revealed that customers who tried the free samples generally liked the taste of the plant-based meals. This indicates that the intervention successfully addressed the perceived barrier of taste. However, liking the sample did not translate into a purchase.
The qualitative data highlighted several reasons why samples did not lead to sales:
- Habitual Preference: Many customers preferred to eat their usual meal despite liking the sample.
- External Factors: Some customers had brought their own lunch from home.
- Resistance to Change: The data suggests that habits are difficult to break, and the preference for a regular meal outweighed the positive experience of a sample.
Operational Constraints
The evaluation also noted that the efficacy of the sample intervention may have been limited by the operationalization of the food offered. The meals provided as samples were limited to what the food outlets were already producing and what the outlets decided could be portioned into samples. The researchers had no influence over the specific meals selected for sampling, which may have impacted the results.
Summary of Intervention Data
The following table provides a structured overview of the trial's parameters and outcomes.
| Parameter | Detail |
|---|---|
| Trial Period | August 1 - August 28, 2022 |
| Baseline Period | July 4 - July 31, 2022 |
| Post-Intervention Period | August 29 - October 2, 2022 |
| Total Participating Sites | 29 |
| Sequence 1 Sites | 9 |
| Sequence 2 Sites | 10 |
| Sequence 3 Sites | 10 |
| Average Daily Meals (Baseline) | 66 |
| Average Daily Plant-Based Meals | 19 (30.4%) |
| Sample Distribution Days | Tuesday, Wednesday, Friday |
| Loyalty Card Requirement | 4 stamps (1 endowed, 3 purchased) |
| Loyalty Reward | Any meal of choice |
| Sample Sales Effect (p-value) | .718 |
| Loyalty Sales Effect (p-value) | .834 |
Analysis of Behavioral Drivers in Food Choice
The results of the 2022 trial underscore a critical tension in food marketing: the difference between product acceptance and behavioral change. The study confirms that while free samples can effectively remove the "taste barrier"—the fear that a plant-based product will not be palatable—this removal is not sufficient to override established eating habits.
In the blue-collar workplace environment, food choice is heavily governed by habit. Even when consumers expressed that they liked the sample, the psychological and practical pull of their "usual" meal remained the dominant factor. This suggests that the marketing industry's focus on sampling as a conversion tool may be overestimating the role of taste as the sole barrier to adoption. While taste is one of the two most important determinants alongside price, the role of habit acts as a tertiary, and potentially more powerful, barrier.
Furthermore, the failure of the loyalty card intervention—which utilized an endowed progress model to reduce the perceived effort required to earn a reward—suggests that financial or reward-based incentives may also be insufficient to break deep-seated dietary habits in this demographic. The fact that the reward could be any meal, not just a plant-based one, was intended to attract a broader range of customers, yet it did not result in a statistically significant increase in plant-based sales.
This analysis indicates that for plant-based interventions to be successful in workplace settings, they may need to move beyond simple sampling and loyalty rewards. The lack of significance in both the sample-led and loyalty-led groups suggests that the "trial" phase of a new product is distinct from the "adoption" phase. Sampling can trigger a trial, but adoption requires a shift in habit that may necessitate more comprehensive behavioral interventions.