PurePress

sep 2021 - jun 2022 | design research, new product design

Home cooks tend to avoid deep-frying, and we found that the biggest sources of friction were the clean up and waste from dealing with a large volume of contaminated oil. In a team with 4 other engineering students, I conceptualized and developed a new product that extends the lifespan of used cooking oil (UCO). We focused not only on improving the post-cooking cleanup workflow, but also finding an area of differentiation by addressing oil degradation, innovating upon typical oil filters which only target sediment.
screenshot of purepress CAD
Why do current products fall short?
The common belief that existing solutions operate on is that simply filtering sediment from UCO is enough to make it reusable. We found that the more you fry with the same oil, the thicker, smellier, and darker it gets.  Food fried with this older oil also tastes worse, coming out burnt and acrid. Something had to be happening to the oil that causes it to deteriorate with each fry, something that filtering alone cannot solve.
My Contributions
I led the design research and patent analysis, while also contributing to benchmarking, testing, prototyping, and manufacturing considerations. I focused on exploring gelatin as a novel method of filtration, which led to researching the root cause and effects of oil degradation during deep-frying and uncovering our competitive advantage.
Home Cook Insights
To get a better understanding of the relationship home cooks have with deep frying, we conducted user observations and interviews, summarizing our insights in a journey map with painpoints.
User interview insightful quotes
Home cook journey map, with pain points

While we found that almost half of the interviewed home cooks reused their oil, only a third of them filtered their oil before storing and reuse. And those that followed best practices questioned if it was even worth it, because they only got 2 more reuses before having to throw it out. Could this be a sign of a new product opportunity?

Determining Project Scope

Disposing of oil is one of the major problems, even if it is inevitable.  Users would either pour UCO down the sink or into a container and throw it into the trash. Both of these options are terrible: one causes billions of dollars of clogged pipes, and the other just moves it to a landfill. There are proper oil disposal services, but those are unfortunately only available to restaurants. So instead of trying to find a better way to dispose of oil, could we find a way to extend its lifespan past 3 uses?

Why focus on extending the lifespan of used cooking oil?

  1. Reduces quantity of oil going into sewage or landfills
  2. Reduces frequency of purchasing oil, reducing cost
  3. Makes food "tastier" (according to fry cooks...)

This let us to our revised ideal usage map, indicating the need for a product that filters, extends, stores, and indicates the usability of UCO.

Updated journey map, indicating critical functions

Benchmarking

To assess the current market and as a starting point for prototyping and to see how effective current products are in filtering, extending, storing, and checking the quality of UCO, we benchmarked available oil filtration products as well as coffee products, whose filtration mechanisms could be insightful.
Product benchmarking overview
Benchmarking results
Conclusions from benchmarking

Gelatin Filtration

With a better understanding of existing filtering methods, we got to work exploring ideas through prototypes. While my teammates focused on determining if a mechanical advantage could improve the filtration workflow, I focused on exploring a novel solution: gelatin filtration. Would a biodegradable and solid gelatin matrix (0.5-4.0 µm pore size) work better than metal screens (>37 µm pore size) at trapping the smaller food particulate (<200 µm) more susceptible to burning?
Reasoning behind gelatin explorationGelatin ideationGelatin prototypes

These attempts were promising, and demonstrated that gelatin did set separately from the used cooking oil, trapping sediment within the matrix. However, I ran into a number of issues with keeping results consistent: no matter what I tried, I couldn't figure out how to repeat the results of these first tests, with the gelatin forming less of a set gel and more of a combined paste with the oil. I reached out to SMEs, who were unfortunately unable to pinpoint why this was happening. However, they mentioned that while gelatin is theoretically more effective at trapping sediment than metal screens, filtration itself wouldn't improve oil quality. This got me thinking: instead of simply slowing down the rate at which oil degrades, could we find a way of reversing the effects of oil degradation and treat the root cause?

Selection of gelatin trials

5 of 12 gelatin process experiments, adjusting mixing temperatures, distribution method, and setting temperatures to determine controlling factors

Understanding Frying Oil Degradation

The root causes of oil degradation are two biochemical processes occurring during frying: oxidation and hydrolysis. When coming into contact with a food's intrinsic moisture and the oxygen from the air, hot oil molecules break down into smaller compounds. Simply put, these undesirable polar molecules are responsible for the deteriorating taste, color, and viscosity of UCO. In other words, if there was a way to remove polar molecules, we could reduce oil degradation, thus extending its lifespan.

This meant two things. Firstly, it finally gave us a direction to innovate, and led us to look at adsorbent agents, which attract and stick to polar molecules (this is same reason why activated carbon is effective in purifying water). Secondly, it gave us a metric to test our prototypes to, where we would use the Testo 270 to measure total polar molecule percentage (TPM%). If our prototypes empirically reduced the TPM%, we could quantifiably say that our product not only filters oil, but actively reduces its "age", extending its usable lifespan!

Testo table for TPM%

Defining Specifications

Focusing our scope to a two-part system that filters, treats, and stores UCO for reuse, I reviewed relevant patents. From analyzing patent similarity by comparing patent claims, we identified areas of differentiation, and defined a set of metrics and target specifications that our product needed to meet.

Selected patents
Patent analysis results: areas of possible innovation and differentiation
Target specs
Final Design
We decided to move forwards with a filter design with a pressing mechanism, with the understanding that driving UCO through the filter with pressure would improve the filtration workflow; as well as a double-walled storage container that the filter fit onto. We modified our prototypes to include an adsorbent agent, with the two available food-safe ones being bleached earth and activated carbon.
PurePress prototypeCAD v1 CAD v2CAD v3 CAD v4CAD Final

Validation

With a final design, all that was left was to validate our claims of providing a set of products that filters, treats, and stores UCO for multiple reuses.  Our competitive advantage hinges upon the product's ability to reduce TPM% in accordance with our target specification, but our data started to not make sense.

In our testing of bleached earth, we found that it was able to reduce TPM% by 2.5%. This stood out in a comparison with a controlled sample of untreated UCO and other substances, none of which were adsorbent agents.
Evaluating adsorbents

Comparing this to activated carbon, it seemed that the carbon was more effective, although only slightly. Since activated carbon filters were more available, we chose this option.

Although these numbers seemed low, we felt it was enough of a measurable impact that it indicated probable success. As such, we prepared more UCO by frying 12lbs of battered chicken wings without cleaning the oil, as mentioned in one of the patents I reviewed. In doing so, we uncovered a concerning result: the TPM% readings seemed to improve as the oil was used more. This was the exact opposite of what we had predicted based on our understanding of oil degradation, and even after recalibration, as well as a temperature retesting, none of our data made sense to us.

Batch Fried Chicken TPM% Test

Retest after Calibration

Temperature Retest

Without any response from the manufacturers of the Testo 270 we used to measure TPM% and no other way to validate the PurePress, we ended the project with a product concept that worked in theory, but was unproven in practice. A disappointing end to what was otherwise an invaluable experience in learning how to explore new product opportunities.

While we weren't able to take it as far as we would've liked to, I still truly believe that there is a legitimate product here. I would love to revisit this in the future with a fresh perspective and with closer collaboration with experts.  I am extremely proud of my team for the effort we put into our vision, and for uncovering an exciting new product concept.

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