Driven by curiosity about strawberry prices and consumer experience, Squirrel-SouthEast aims to provide scientific insights and solutions for the loss and waste issues faced in the food supply chain. During the research process, we found that strawberries are highly susceptible to damage during transportation and storage, with a loss rate reaching 20%–30%. This finding allowed us, at the very beginning of the project conception, to focus on how to use technological and management innovations to reduce losses during transport, improve the circulation efficiency of agricultural products, and achieve a safe, accessible, and sustainable supply chain solution.

Stakeholders

At the beginning of the project, the Squirrel-SouthEast team clarified a core task through brainstorming:

To truly understand the reasons behind high strawberry prices, relying solely on literature or online information is insufficient. We must engage directly with the real industry chain and have in-depth conversations with various people related to strawberries.

Starting from the complete chain of strawberry harvesting, transportation, storage, and sales, we listed the interview targets: orchard owners and farmers, logistics personnel in the transportation link, fruit wholesalers and retailers, as well as intermediary brokerage companies. At the same time, we realized that proposing scientifically reasonable solutions also requires consulting relevant experts, such as researchers at agricultural institutes and mentors in biology laboratories, to help us assess the feasibility of using synthetic biology to reduce losses.

We plan to use one-on-one interviews, focusing on open-ended questions, allowing interviewees to fully express their experiences and opinions. During the interviews, we can not only collect first-hand data, but also, through recommendations from interviewees, identify more groups worth contacting, gradually expanding the breadth and depth of our research.

Interview Targets and Outline

• Orchard Owners / Farmers: Understand the process of strawberry cultivation to harvesting, post-harvest handling methods, and their perspectives on strawberry loss and sales models.
• Transportation / Logistics Personnel: Understand the main causes of loss during strawberry transportation, the differences between cold chain and ambient transportation, as well as transportation costs and potential improvements.
• Wholesalers / Retailers / Intermediary Brokerage Companies: Understand the loss rate of strawberries in circulation, pricing logic, market demand, and the challenges they face in storage and sales.
• Consumers: Understand the factors they pay most attention to when purchasing strawberries (freshness, price, taste, etc.), and their acceptance of high strawberry prices.
• Agricultural Institutes / Researchers / Laboratory Experts: Understand the current research progress in strawberry preservation and transportation, and the feasibility and potential risks of using synthetic biology to reduce losses.

Survey Questionnaire

At the beginning of the project, we designed and distributed a survey through the online platform Wenjuanxing, focusing on the key factors consumers pay attention to when purchasing strawberries. The results showed that for most consumers, freshness is the most valued quality, followed by price. This finding made us realize that maintaining strawberry freshness while reducing price is a problem we need to consider and solve.

However, we also realized that relying solely on survey data limits the scope of participants, mainly to consumers themselves. To gain a deeper understanding of the issues behind the strawberry supply chain, such as transportation loss, pricing logic, or preservation technology, surveys alone are insufficient. Therefore, we need to conduct one-on-one in-depth interviews to obtain more comprehensive, authentic feedback and insights.

Interviews with Farmers

In the initial research, we noticed that strawberries experience a high loss rate during transportation and storage, which not only drives up market prices but also affects the consumer purchasing experience. This issue prompted us to consider whether we could find entry points to reduce loss by gaining a deeper understanding of the strawberry supply chain.

We first visited strawberry farms and conducted face-to-face communication with farmers. The farmers told us that they usually prefer not to sell strawberries on a large scale, as strawberries are not easy to preserve. To ensure freshness, they tend to organize “pick-your-own” activities, allowing consumers to directly pick strawberries. In this model, farmers only need to handle cultivation and maintenance, while the transportation link is completely bypassed. If they choose to sell the strawberries, they do not bear the transportation loss and thus have no concerns about it.

Through communication with farmers, we gained an understanding of the upstream end of the supply chain: the farmers’ strategy mainly focuses on avoiding transportation loss risks rather than actively solving the problem. The high transportation loss is also one of the reasons for high strawberry prices, so we need to pay attention to the subsequent circulation stages. With this insight, we decided to extend the research focus downstream in the supply chain to explore the challenges they face.

Large-Scale Strawberry Companies

In the interviews with farmers, we found that they often use “pick-your-own” activities to avoid losses during transportation and storage. However, when strawberries enter the scaled-up market, transportation and preservation inevitably become key challenges. This made us realize that large strawberry companies may have higher demands for supply chain stability and preservation technology.

With this in mind, we visited large strawberry companies. Company representatives emphasized that their main concerns are supply chain efficiency, loss rates, and brand reputation. Since strawberries are highly perishable, losses during transportation and storage not only cause direct economic losses but also affect supply stability and brand image.

Through this exchange, we learned that large strawberry companies hope to use new technologies to extend the shelf life of strawberries. This can not only reduce losses and lower costs, but also ensure stable market supply and reasonable pricing, thereby further enhancing the market competitiveness of the company. Our next step is to interview transportation personnel to gain a deeper understanding of the causes of loss in the logistics link and the potential for improvement.

Interviews with Transportation Personnel

Loss of strawberries during transportation is one of the key reasons for high prices. Since the supply chain is a critical link in maintaining market stability, the actual experiences and needs of transportation personnel can provide us with new perspectives to understand the problem.

We interviewed personnel engaged in strawberry logistics and transportation. They indicated that their main concerns are whether the transportation process is sufficiently streamlined and how responsibility is assigned in case of damage or delays. From their perspective, strawberries are very “delicate” goods, and once problems occur during transportation, it is often difficult to clarify responsibility, which increases their burden.

Through the communication, we learned that transportation personnel hope that strawberries could become more “worry-free”. If shelf life is extended and pressure resistance improved, losses during transportation would decrease, and their work stress would be reduced accordingly. This led us to initially focus on how to extend strawberry shelf life through scientific methods.

Interviews with Retailers

In the preliminary research, we had already identified the multiple challenges that strawberries face during harvesting, transportation, and wholesale. When strawberries enter the end-market, their performance on shelves also determines sales effectiveness and the consumer experience. Therefore, we realized that the retail stage is another critical link that requires our attention.

We interviewed fruit retailers. They indicated that the key factors they care about include shelf life, appearance, and loss rate. Once strawberries spoil or lose their fresh luster, they are not only difficult to sell but also directly affect consumer purchasing willingness.

Through the communication, we learned that if the rate of spoilage can be effectively slowed down, fruit retailers can extend the selling period, achieve higher profits, and reduce losses. In addition, this can prevent consumer complaints about strawberries going bad quickly after purchase, improving the purchasing experience and repurchase rate. This further reinforces our focus on “extending shelf life”.

Engineered Bacteria Design

Professor Yao from the Agricultural Institute

During the literature review, we learned that the main challenge in strawberry spoilage is that it is difficult to fundamentally prevent decay. However, when spoilage-causing pathogenic fungi appear, strawberries release a series of characteristic volatile organic compounds (VOCs), including alcohols, esters, aldehydes, and ethylene. The types and concentrations of these compounds change as spoilage progresses, making them reliable spoilage signals.

This led us to an idea: could we detect these signals to timely identify and remove spoiled strawberries, thereby preventing “bad strawberries” from infecting healthy ones?

With this idea in mind, we had an in-depth discussion with Professor Yao from the Agricultural Institute. Professor Yao affirmed our approach of tackling the problem from the “detection—prevention of spread” perspective, noting that it is more practically operable. At the same time, he suggested that we could screen a series of natural promoters that are sensitive to environmental stress or specific signaling molecules to serve as detection elements. Regarding the output method, he advised us not to be limited to the traditional fluorescent protein approach, as it is not intuitive for end users. Instead, we could consider using visible pigment molecules as an alternative to make the detection results immediately clear.

Through this exchange, we gained two key insights:

• Validation of the detection concept: By identifying the VOCs released during strawberry spoilage, we can quickly screen out spoiled individuals, achieving an overall preventive effect.
• Clearer design direction: In subsequent designs, we plan to screen natural promoters (e.g., recA, grpE, soxS, lasI) and systematically evaluate their response characteristics, selecting candidate elements with the highest sensitivity and specificity to spoilage-related VOCs. At the same time, we constructed a violacein synthesis system based on the Chromobacterium violaceum vioABCDE gene cluster to achieve visibly intuitive detection results.

Professor Zhu

During the literature review, we noticed that post-harvest strawberries are highly susceptible to spoilage, primarily due to the combined effects of pathogenic microbial infection, unfavorable environmental conditions, and the intrinsic fragility of the fruit. Adverse environmental factors further exacerbate disease development. For example, high humidity promotes pathogen spore germination and adhesion, while forming a water film on the fruit surface that facilitates fungal invasion. Poor ventilation or fluctuating temperature and humidity can lead to the accumulation of metabolic gases such as carbon dioxide and ethylene, weakening the fruit’s defense response and triggering a chain spread of disease.

Since fungi are the main driver of spoilage, we began to consider whether disrupting fungal cell walls could be an effective strategy to suppress spoilage.

With this approach in mind, we consulted Professor Zhu. He pointed out that the main pathogenic fungi responsible for post-harvest strawberry spoilage (such as Botrytis cinerea and soft rot fungi) rely on chitin and β-glucan to form their cell walls, maintaining structural stability and defense functions. At the same time, the extracellular polysaccharide matrix (EPS) enhances fungal adhesion and biofilm formation. Professor Zhu suggested that we could use chitinase and glucanase to target these two types of polysaccharides, and synergistically disrupt the EPS, thereby weakening fungal cell wall integrity and infectivity, ultimately suppressing post-harvest strawberry spoilage and its spread.

Through this discussion, we developed a clear design plan:

• Enzyme production by engineered bacteria: Design E. coli to heterologously express chitinase and glucanase.
• Formulated application: Prepare the purified enzyme solution as a spray, applied directly to the strawberry surface after harvest, covering areas likely to come into contact with pathogenic fungi.
• Mechanism of action: Chitinase and glucanase work synergistically to disrupt fungal cell walls and EPS, thereby reducing infectivity and delaying or preventing spoilage spread.

Hardware Design

Our ultimate goal is to construct a comprehensive solution for strawberry spoilage. While designing the engineered bacteria, we simultaneously began conceptualizing and developing hardware to achieve real-time detection and early warning of strawberry spoilage.

First-Generation System: Laboratory Basic Version

In the process of exploring strawberry spoilage, we attempted to explore hardware-based detection. Initially, we designed a very simple device: using a large suction flask, a gas pump, and tubing to extract and collect the gas surrounding the strawberries. However, this device relied on laboratory glassware, required professional knowledge to operate, and lacked temperature control, making it difficult for non-experts to use. This made us realize that if we want to truly apply the system, we must consider the final usage scenarios from the start, such as strawberry storage warehouses and market vendor environments.

Based on this reflection, we plan to interview hardware design manufacturers. Through communication with professional manufacturers, we hope to learn how to upgrade the current rudimentary prototype into a more practical product: improving the ease of use, stability, and safety, while adapting it to real storage, transportation, and sales scenarios.

Second-Generation System: Factory and Vendor Applicable Version

Interview with Hardware Manufacturers

After completing the first-generation hardware prototype, we found multiple limitations in practical applications: glassware is fragile, operation is complex, non-experts find it difficult to use, and it lacks the ability to quantify spoilage levels. We hope that through further design optimization, the device can become more robust, more intuitive, and effective in strawberry storage and sales scenarios. Since our own hardware design capabilities are limited, we decided to seek advice from professional hardware manufacturers.

In our communication with hardware manufacturers, we introduced our first-generation design concept and asked for suggestions on improvement. Based on their experience, the manufacturers proposed several practical optimization suggestions:

• Test tube optimization: Replace glass test tubes with plastic test tubes with threaded interfaces, which are not only safer and more durable but also facilitate gas flow.
• Series structure: Design a device with four test tubes in series, allowing gas to flow sequentially. By observing the color changes in different tubes, a correspondence between the “number of color changes” and the degree of spoilage can be established using a concentration gradient.
• Time control module: Add a time control function to the device to accurately record and compare the time dimension of gas accumulation and reactions.

Through this interview, we realized:

• Hardware must not only be usable but also user-friendly. In terms of material selection, avoid fragile laboratory equipment and instead use more robust and reusable components.
• The core logic of the device should align with user needs. For example, the series test tube design provides users with a visual readout of spoilage levels, rather than just a binary detection of “yes/no”.
• Modular functionality is the future direction. Adding time control, temperature and humidity monitoring, and even wireless data transmission modules can transform the device from a laboratory tool into a practical industrial product.

This also informs the concept and upgrade for our third-generation hardware.

Second-Generation System

We optimized our hardware design in several aspects:

• Plastic test tubes: Replaced fragile glass tubes, making the device safer and easier to operate.
• Series structure: Introduced four tubes in sequence, where color changes provide a visual and intuitive indication of the spoilage degree.
• Time control: Added a compensation mechanism to adapt to different temperature conditions, ensuring more accurate detection.
• Application scenarios: Designed for use in warehouses and vendor stalls, enabling real-time assessment of spoilage risk.

For more details, please refer to our Hardware Design page.

Third-Generation System: Transport-Compatible Version

From our early-stage research, we found that the transportation stage is the most critical phase where strawberry loss frequently occurs. Therefore, ensuring that our device is adaptable to transport scenarios is especially important. To achieve this, we plan to interview transport personnel in order to gain a deeper understanding of their practical needs.

During interviews, transport personnel pointed out that our current product is still not convenient enough. In the transport process, they prefer to use a portable detection device rather than a bulky system that relies on laboratory conditions. This feedback made us realize that product design should not remain at the laboratory prototype stage, but must also address the practical application needs of the transportation stage. Therefore, portability and miniaturization must become key directions in device iteration, ensuring it can truly function in transport scenarios.

Third-Generation System Design

We recognized that applying the device in transportation scenarios requires it to be more portable, more stable, and capable of withstanding environmental fluctuations during transit. This insight drove us to consider how we could further optimize the design based on the second-generation system, ensuring better adaptability and practicality in real-world use.

We brought our prototype to the School of Biomedical Engineering at Shanghai Jiao Tong University and consulted with field experts. Under their guidance, we finalized the overall product design and, based on practical application needs, integrated several additional functional modules.

This step not only ensured that our system was scientifically robust, but also aligned the design with real-world scenarios, making the device more feasible for future industrial application.

In the third-generation design, we achieved the following optimizations:

• Power adaptation: Replaced plug-in power supply with a portable power source to meet the needs of transportation scenarios without fixed power access.
• Vibration testing: Simulated braking and bumping conditions during transportation without altering the structure, ensuring device stability.
• Insulation system: Designed a simple insulated box (including a carrying bag, insulation layer, aluminum-plastic film, and heating pad) to maintain an internal temperature of 37 °C, preserving engineered bacteria activity and preventing detection failure caused by low temperatures.
• This version of the design is not only functionally improved but also better aligned with the practical application scenarios of strawberry transportation and storage.

For more details, please refer to our Hardware Design page.

Finally, we brought our product to consult 3D modeling experts. We hope that the next generation of hardware can achieve automated operation, digital readout, and network-based monitoring, so that quality monitoring of strawberries and other perishable foods can become as common and reliable as using a thermometer. Therefore, we need to integrate all components, and the experts provided us with guidance in 3D modeling, offering direction for our future design.

Summary

Our first-generation hardware was mainly used to verify the basic concept; the second generation improved safety and functionality; the third generation was further adapted to real-world application scenarios. Looking ahead, we will continue to iterate in the directions of miniaturization, intelligent design, and cost optimization, promoting the development of the device into a truly implementable comprehensive solution for strawberry preservation and decay detection.

Farmers

In the preliminary research, we found that farmers generally adopt the “pick-and-sell on-site” model to avoid the high losses of strawberries during transportation and storage. This made us wonder: if we introduced our device to the farmers, would they show interest in detection and preservation technologies, thereby potentially changing the traditional sales model?

We interviewed farmers with our product prototype and design plan. They acknowledged the feasibility of our device for strawberry detection, recognizing that it could indeed achieve effective monitoring. However, they also expressed reluctance to use such a device. The reasons include:

• Sales model: They still prefer the “pick-and-sell on-site” approach, which avoids transport losses, so they don’t see the need to introduce a detection step.
• Operational complexity: They believe the device workflow is too complicated and not as straightforward as their current method.
• Knowledge threshold: Due to limited technical knowledge, they lack confidence in operating and maintaining the device.

Through this discussion, we realized:

• Limited farmer demand: Their sales model makes the attractiveness of the detection device relatively low for them.
• Shift in promotion focus: Rather than promoting the device to farmers, it is more effective to focus on strawberry companies, transportation stages, and retailers, where there is a greater need to extend shelf life and reduce losses.
• Importance of education and outreach: Feedback from farmers also reminds us that in future promotion, it is necessary to conduct more science popularization and training for grassroots workers, helping them gradually understand and accept the value of new technologies.

Interview with Transport Personnel

In our preliminary research, we found that strawberries experience significant losses during transportation, which is one of the main reasons for their high market prices. We aim to interview transport personnel to understand the challenges they face in actual operations and to evaluate whether our device can meet the needs of this stage in the supply chain.

We presented our device design concept to transport personnel. During the discussion, they first affirmed our idea, recognizing that the direction of reducing strawberry losses through detection and early warning is valuable. However, they also provided some suggestions:

• The device should be more compact and portable, allowing for easy use during transportation.
• The functionality should be simplified as much as possible to avoid adding extra burden.

From this conversation, we gained two important insights:

• The concept is feasible, but further optimization is needed.
• The iteration direction is clear: the device should evolve towards portability, simplicity, and scenario-specific design, enabling transport personnel to truly use it effectively, affordably, and conveniently.

Customer

Note: The hardware shown in the figure is only a model and does not contain any engineered bacteria.

In our preliminary research, we found that consumer demand for strawberries is mainly focused on freshness and price. We aimed to introduce our product to consumers to verify whether they would accept this detection- and preservation-based solution.

We presented our design plan and product concept to the consumers. They generally expressed interest in this solution and believed that if it could effectively extend the shelf life of strawberries, it would greatly improve their purchasing experience. They also hoped that such a product could be launched as soon as possible and enter the market.

Strawberry Retailers

At the end of the supply chain, retailers interact directly with consumers. They are concerned not only with strawberry sales but also with customer feedback. We aimed to interview retailers to understand their attitudes toward our detection- and preservation-based solution and to learn about their needs in real-world sales scenarios.

We presented our product concept and design plan to strawberry retailers. They expressed approval of the idea, noting that if it could truly extend the shelf life of strawberries, it would not only reduce losses but also prevent customer complaints such as “they spoil too quickly after purchase.” They also expressed expectations, hoping that this solution could be implemented and applied in the market as soon as possible.

Through this exchange, we confirmed the high recognition of our solution among retailers. Their feedback further validated that extending shelf life and reducing losses are practically meaningful goals, and highlighted the demand for such a product at the retail stage.

Through systematic interviews with farmers, large strawberry companies, transport personnel, retailers, consumers, and experts, we gradually built a comprehensive understanding of the strawberry supply chain.

• Farmers focus on risk reduction and prefer “pick-and-sell on-site”.
• Companies care about supply chain efficiency and brand reputation.
• Transport personnel desire portable devices that reduce operational burden.
• Retailers and consumers expect extended shelf life and maintained freshness.
• Experts provided guidance on detecting spoilage signals and inhibiting pathogenic fungi.

Integrating all this feedback, we recognize that maintaining freshness and reducing losses are shared needs across the entire supply chain. Looking ahead, we will continue to iterate on engineered bacteria design and hardware devices, advancing towards miniaturization, portability, and intelligent design, with the goal of creating a truly implementable comprehensive solution for strawberry spoilage detection and preservation.