Using Grapefruit to Explore my Food System

I find the individual stories about each food fascinating. Each individual food ingredient has its unique story about which comes from its history, science, cultural influences, and supply chain etc. There are so many books and articles written about different foods including salt, cod, tomato, apples, bananas, milk, and bread. Many food scientists spend their whole careers studying the behavior of one ingredient such as salt, sugar, gelatin etc. Or in my case, one reaction; the Maillard reaction causes the colors, flavors and aromas we love during and after toasting, grilling, roasting, and baking our food. 

Grapefruit Introduction

Half a pink grapefruit
Grapefruit from Fresno CA. Image by CDavies

Late last year (2021) a friend from Fresno, CA, sent me a box of grapefruit from a tree in her back garden.


Fresh ruby grapefruit. 

My mouth is watering at the memory. 

I am quite envious of Californians who can grow citrus in their gardens. 

Grapefruit are less popular than oranges because they are very sour and tart. They are considered a breakfast fruit and usually we eat them by cutting them in half and sprinkling with brown sugar before grilling or broiling the top to melt the sugar. There is even a grapefruit spoon to help remove the flesh from the peel.

In this article, I explore grapefruit from a scientific perspective and from food systems perspective.

Grapefruit Science

In this section, I share two interesting science facts make grapefruit a challenging food to eat:

  1. Grapefruit and drug interactions
  2. Grapefruit bitterness and genetics

Grapefruit and Drug Interactions

When we take drugs or eat compounds that our body considers as toxic, there is a process for inactivating them. Most of the drugs we take are metabolized by cytochrome P450, a family of more than 50 enzymes found throughout the body, especially in the liver as it is the main organ involved in detoxification. 

In the initial steps of detoxification, called Phase 1 Liver Detoxification, fat soluble toxins, such as drugs and alcohol, are hydrolyzed, reduced, oxidized etc. by cytochrome P450 enzymes. 

In Phase 2 Liver Detoxification, other enzymes further metabolize them into water soluble waste compounds which are excreted in our urine. 

The drug detoxification process is very efficient and pharmaceutical researchers assume that 90% of drugs are inactivated by cytochrome P450 system. Thus, pharmacologists work out drug doses based on the fact that only 10% will be effective.

Grapefruit is now a well known inhibitor of the  cytochrome P450-mediated metabolism of drugs. Grapefruit contains lots of furanocoumarins, compounds that interfere with cytochrome P450, switching it off. This is a problem because if you take some drugs with grapefruit, the detoxification process is inhibited and 100% of the drug may enter our blood stream. For some drugs, this could be fatal as listed here and these drugs come with a warning to avoid grapefruit. Thus, grapefruit is forbidden from the diet of people taking these drugs.

Oxycodone cytochrome P450 metabolic pathway. Image from Aegis Labs

Grapefruit and Bitterness

All citrus fruit contain sugar and citric acid, as well as other organic acids, such as ascorbic acid, which we know better as Vitamin C. 

The balance between sweetness and acidity gives us the tastes we expect when we bit into a slice of citrus fruit. Thus, lemon juice is more acidic than orange juice and oranges have more sugar than lemons.  pH is one way we measure acidity; the lower the pH the more acid – lemons have an approximate pH 2.30, oranges pH is around 4.35 and grapefruit are in the middle with a pH 3.38 (ref).  Yet grapefruit are more bitter than lemons because they also contain a bitter compound called naringin. 

Our response to tastes like bitterness is genetic; some of us are more sensitive than others and some people do not find grapefruit bitter at all! These genetic differences may also influence whether you like IPA beer. Another genetic taste response is whether you find cilantro soapy. 

You can test to see if you are sensitive to bitter flavors by trying one of the two main taste tests for bitterness sensitivity: Phenylthiocarbamide (PTC) and 6-n-propylthiouracil (PROP). Most people who find grapefruit bitter are PROP sensitive individuals.

Not to fret if you are a supertaster for bitter; as some of us who are sensitive to bitter flavors we seek out bitter flavors and we still love grapefruit.

Grapefruit and Food Systems

As well as their science being fascinating, the history of grapefruits is also strange. Unlike most citrus fruit, which originate from Asia, grapefruits are originally from Barbados where citrus fruits were planted all over by Europeans without any consideration of their ability to easily crossbreed. The citrus trees were probably excited to have a climate in which they could grow with limited pests.

Three citrus fruits widely spread from Asia were the citron, the pomelo, and the mandarin. Grapefruit are thought to be a cross between the pomelo and a sweet orange, which itself is a hybrid of pomelo and mandarin. 

Today, China is the biggest producer of grapefruit producing over 5,000,000 tons per year in 2017 and 2018. In contrast, the US and Mexico each produced about half a million tons of grapefruit. 

I am excited that I now know more about the grapefruits my friend sent me from her tree in Fresno, CA.

Explore Your Food

You too can explore your food system more by researching one of the foods you ate today and let me know what you find out in the comments.

Here are some questions to get you started:

  • Why you chose to eat this food?
  • Look up your food in the Food Central Database and find out its nutritional content.
  • Search the internet to find out some interesting facts about your food. 
  • Do you know where your food came from? 
    • Where did you get it from?
    • If you bought it, where did the retailer obtain it from?
    • If your food is fresh fruit or vegetables, where was it typically grown? 
    • Whose cuisine is it traditionally part of? 
  • If it is a pre-made food, do you know how it is made?  Could you make it at home?

What Hope 2021 Gave Me For 2022


White woman with brown curly hair smiling wearing a white-grey shawl over her shoulders. There are plants and pictures in the background.
I knitted a silk scarf in 2021. It will be giving me comfort in 2022, Image by cdavies

Phew! Goodbye 2021 and don’t slam the door on your way out.

Right, good riddance to a difficult year and let’s shut the book on what happened!

Not so fast. 

I find it helpful to look back to remember what I achieved in the last 12 months and have a moments of celebration. Perhaps I learned something that I can take forward to give me hope to make 2022 better. 

Don’t let Stop Food Waste Day Distract You

April 28th 2021 is National Stop Food Waste Day. Food waste is a problem with approximately 30-40% of food grown not being eaten. This amounts to over 133 billion pounds of food and over $161 billion. There are some amazing comparisons at to what this means in real terms as well as recognizing that the wasted food cost energy, labor and water to grow and also caused the release of greenhouse gases. Additionally 1 in 8 American children are going to bed hungry and they could benefit if wasted food is recovered. Wasted food ends up in landfills where it rots releasing methane, a greenhouse gas. 

Where does all this excess food come from? Wasted food is considered to belong to two categories

  • “Food waste” which is food thrown out by grocery stores, restaurants or consumers
  • “Food loss” occurs before food reaches consumer as a result of loss during production, storage, processing, manufacturing and distribution

Stop Food Waste Day focuses mostly on what we can do as consumers, as individuals. The comforting story around food waste is that we, as individuals, can do something about all this waste. There is a lot of pressure for us to plan our meals, store our food properly so that it has a good shelf life, to eat compost, to save leftovers, to freeze food if we can’t eat it all now.  Yeah! Just make sure we eat all the food we buy and then we’ll be good! Hmm, not so fast. 

Many of the suggestions are based on us having the luxuries of time, money, and space. We can’t all freeze leftovers, some of us can’t even prepare food where we live. Those of us in small apartments may find it hard to compost and if we did, what do with the compost once we have it. We don’t all have space to grow our own food.

If we consider the EPA’s Food Recovery Hierarchy we find that food recovery is not a solution that can be carried out only on an individual level. Yes, we can be more organized, buy less, and make sure we are using everything we buy. But don’t worry about tossing out that limp cucumber in your fridge.

Additionally, as Alicia Kennedy wrote in her newsletter, over and over again we are expected to pick up the pieces after government and big business have messed up. Where are the voices suggesting that businesses should produce less food? Where are the regulations limiting the serving sizes at restaurants?

There is a lot of good coming from concern with food waste. Food entrepreneurs like Toast Ale are making beer from old bread. Upcycled Food Association is supporting companies who are interested in recovering and upcycling the parts of food that would normally end up in landfill. Some local municipalities are collecting food wasted for composting.

We live in world where the food system deliberately produces excess cheap food. Farmers are encouraged to grow in excess and only the best makes it to the supermarket. Food manufacturers create processed packaged food with long shelf lifes so that essentially they are flooding the market. Encouraged by the overwhelming choices: ten varieties of apples, over 20 different types of bread and “buy three get one free” type deals, we buy too much because along with this over abundance we live in a world which emphasizes a scarcity mindset. Thus, we buy too much, we let food spoil, we get confused about best before dates, and we throw food away that if only we had used a little bit of planning or forethought we could have prevented.

The biggest issue here is how much excess food is grown and processed. To have a complete reduction in food waste we need a different economic system. One where poverty doesn’t exist and food companies are discouraged from producing cheap food. We need an economic model that isn’t dependent on cheap things; including cheap energy, cheap food, and cheap labor. Do we want a food system where we don’t have to choose between ten different apple varieties outside of harvest season? If we truly don’t want food waste we have to accept that we cannot have so much choice and abundance, while thinking with a scarcity mindset.

We saw last year the risk of having a just-in-time food system. When we switched overnight from a food service-restaurant based system to one where we all had to cook at home, we found shortages of essentials and saw farmers having to throw away crops that would normally have been bought by food service companies like Sodexo and Compass Group. We also saw farmers killing their animals as they were too large for the meatpack houses. These had been closed for cleaning and refitting after initial massive outbreaks of Covid-19 raged through their facilities. Globally food shortages and price increases caused by Covid-19 have continued to today.

Image shows picture of fast food and food waste and says "Wasting food is costing us lives! and "40% of food is wasted.
Food waste costs lives!

I find the paternalistic approach of donating recovered food to food pantries and food banks, so that it “feeds the hungry” troubling and reminds me of concerns raised by Andy Fisher in Big Hunger. This also ignores the effect of poverty and allows us and food companies to feel food about the excess production of food. These issues around food waste are discussed in a great article by Austin Bryniarski.  It is great that countries like Italy have laws that mean leftover food from supermarkets must be donated so that it doesn’t end up in landfill. Except it allows us to ignore the fact that there are HUNGRY PEOPLE in Italy. Focusing on food waste allows us to ignore the fact that farmworkers are treated badly and that there is systemic racism within the current food system

I want to give a call to action to not forget that we need to make the food system stronger; more equitable, sustainable, and resilient. While this is the most important. I also realize that we tend to prefer action we can do now. So start looking at our own food use, help and/or donate to a local gleaning group or food pantry to recover food from farmers and supermarkets. While doing this work, don’t forget that food waste is part of the large food system which we need to start changing too. 

Lack of Resilience in the Food System

Food Safety: The Connection between Leafy Greens, Workers’ Rights, and Cattle

In fall 2020 there was an outbreak of Shiga toxin producing E. coli (STEC) O157:H7 linked to consumers eating leafy greens; most notably Romaine lettuce. In fall 2019; there was a recall of Romaine lettuce due to STEC O157:H7; this outbreak meant that for Thanksgiving, pumpkin pie was healthier than salad. In fact, when we look back over the last ten years, forty outbreaks from STEC O157:H7 on leafy greens were identified. Romaine lettuce was responsible for more than half of these outbreaks. This comes at a huge cost as between 2009 and 2018 there were 1,212 illnesses, 77 cases of hemolytic uremic syndrome, and 8 deaths. 

Lettuce growing in a field; looks safe to eat.
Lettuce Image from Pixabay

Conversation with Wayne Proberts Part 5: Future of the Food System

This is part five and the final part of a multi-part overview of an interview I did with Wayne Robert in August 2020. Here you can find Part 1Part 2, Part 3 and Part 4 here.

A view of a market stall with lots of colorful fruit and vegetables.
Where we get our food from is an important decision. Image from Pixabay.

At the end of the interview we discussed changes we thought would happen to the food system. In particular we considered the strengths of the current food system that sustain us while we continue to make change.

People feel somewhere in their gut that we were going the wrong way as a society; we got to go another way. And part of how we’re going to express it is with food, we’re going to grow more food in our backyards. We’re gonna buy more local food, have connections with our local farmers. And I think the food movement is going to be pushing in very new directions after COVID.

Wayne Roberts August 2020

In Conversation with Wayne Roberts. Part 4: Pushback from Scientists

This is part four of a multi-part review of an interview I did with Wayne Robert in August 2020. Here you can find Part 1 and Part 2 and Part 3.

photo of Wayne whose interview I am reviewing here

We discussed the fact that I started writing my book because I couldn’t find how to use my food science technical knowledge as a food systems change maker. I am still looking at how to get food scientists and agricultural scientists to work with food systems change makers so we can work together to make the food system more sustainable and resilient. Wayne responded with memories of how his proposals weren’t popular with scientists and he disagreed with their work which brought in technology, pesticides, tractors, mechanization to farming and food processing. He isn’t the only food systems changemaker who has a problem with science and scientists!

In Conversation with Wayne Roberts: Part 3: Food in the Public Interest

This is part three of a multi-part review of an interview I did with Wayne Robert in August 2020. Sadly Wayne passed away in January 2021. Reading through the interview we did for my book gives me hope for the future. Here you can find Part 1 and Part 2.

Food is a public interest issue.

Wayne Roberts, Interview August 2020
photo of Wayne whose interview I am reviewing here
Wayne Roberts Food Systems Leader

In 2019 in America more than 35 million of us struggled with food insecurity. This increased during the COVID-19 pandemic to 42 million people of which 13 million were children. At the same time 42% of us are obese and 3000 people per year die from foodborne illness.

In 2019 we paid farmers $22 billion in subsidies and trade related aid. These subsidies mostly go to farmers who are growing corn and soy. This is when farm bankruptcies increased. Why can’t farmers make a profit?

In 2019 medical costs for obesity, heart disease, and diabetes which are mostly diet-related are in the region of $10 billion. This is a public health crisis.

Part 2: “The symbolism of food is local”

This is part two of a multi-part review of an interview I did with Wayne Robert in August 2020. Sadly Wayne passed away in January 2021. Reading through the interview we did for my book gives me hope for the future. You can find Part 1 here.

The most significant quote of the interview was “The symbolism of food is local.” and in this post I  explore Wayne’s role in building a local food movement in Toronto and his support of others around the world to do the same in their communities. He was manager of the Toronto Food Policy Council which was the first food policy council in a big city. There are now 350 food policy councils throughout Canada and North America. 

A food policy council is an organized group of stakeholders from various sectors that may be sanctioned by a government body or may exist independently of government, which works to address food systems issues and needs at the local (city/municipality or county), state/provincial, regional or Native American/First Nations levels though policy. He came to food policy after working in the labor movement and the attitudes there had a huge influence on how he approached food systems change. 

“I used to be in the labor movement and in the labor movement, the practice that was followed was called leap frogging which is: This group gets x. Now our group deserves the same. Then we jump back and forth. So I wanted to get that game going in city food policy. ”

This led to a discussion on the size of the food industry as a whole because few people recognize that food is one of the biggest employers in a city and is the third largest industry. 

[.T]he fact is, it’s true in every city, the biggest employer in every city is food. […] because you add together waiters and waitresses and usually there’s some local food processing. Toronto is the one of the biggest food processing centers in North America and there’s a lot of manufacturing employment. And when people think of it only as agriculture, they don’t think the city as the center of food employment.”

We discussed my challenges teaching food science and having to recognize that the jobs for my students were with the multinational corporations and, not even if they were interested, with smaller local businesses or with changing the food system. This became a personal problem when I left academia to have a more direct, grassroots influence on the food system. 

“The Food moment, by its nature, is a local movement. “The symbolism of food is local. You know, it’s mom and grandma making meals and eating with friends and, you know, much more intimate. It’s not thought of as the auto industry or some other impersonal industry, industry. It’s thought of in a personal way.”

Local and regional food have been shown to be essential during the pandemic. In my search for a local food movement, I’ve volunteered with both the Philadelphia Food Advisory Council and with the New Haven Food Policy Council. I often wish there was one locally and every so often I talk to people about starting one, so a couple of years ago, I started the Cumberland County Food Systems Change Group. If you are interested in knowing more about your local food movement, you may search for a local food policy council here.

A Conversation with Wayne Roberts. Part 1: Introduction and Three Streams to Food Thinking

Back in August 2020, I was fortunate to interview Wayne Roberts, before he unexpectedly passed away in January, for my book, Food Science and Food Systems: A Call for Change. I was delighted when he agreed because I found his perspective on the food system refreshing. 

Wayne was a Canadian food policy analyst and writer. He was the manager of the Toronto Food Policy Council from 2000-2010. Before becoming a food policy leader, he was a labor and environmental activist. As he explains in the Introduction to The No-Nonsense Guide to World Food, he stumbled into food activism because he felt stuck working with the environmental movement. He thought that “food could offer a way ahead, for the simple reason that eating demands that individuals make food decisions several times a day. Transport systems and energy systems don’t do that; here, your only choice is to take or leave what’s offered.”.

In our conversation, Wayne and I covered a diverse range of topics including food’s symbolism as a local movement and, why food must be in the public interest, and how this led to a push back from scientists.

Three Streams to Food Thinking

For me, one of our most interesting discussion points that Wayne raised was that he considered that there were three streams to food thinking. 

“My recent career has been centered around the idea that there are three streams to food thinking: Agriculture, and the supply chain. The other is nutrition, which is basically a concept of food as a fuel that feeds the engine and then, I consider there’s a third field, which is the human side of food, the people side of food. I’ve been trying to develop a notion of this as a distinctive field within food studies, what I call people centered or existential policy.”

In our conversation, we didn’t take this much further as it lead into a discussion on attitudes to science that I will explore in a later post. I see Wayne’s three streams of food thinking as ways that food studies could be divided:

  1. Agriculture and supply chain
  2. Nutrition
  3. People-centered

I find this interesting as I would personally, as a food scientist, divide the first category into more sub-categories. As someone who is professionally a food safety consultant whose research passion is in food chemistry, I am thinking about how my work fits into these three categories. Yes, they easily fit into the first category, if you consider food science an agricultural science. It wasn’t until I moved to the US that I found that food science was considered a subset of agricultural science. In the UK, Food Science departments are mostly part of the sciences along with chemistry. In the US, food science is part of the agricultural Land Grant mission of many public universities. 

For a mass produced food system, understanding food chemistry is important if you want to ensure that consumers get the healthiest, most nutritious food, so that is a way that food science influences the second category. The separation of nutrition and food science is, in my experience, a hard one for the layperson to understand as for most people food is food. It doesn’t matter to most people how the food gets to their plate, just that it is safe and healthy when it does. As someone who has both a nutrition and food science background, I explain the difference, with a joke that food scientists stop worrying about the food once it has been eaten and that is when nutritionists start worrying about food. 

The People-centered steam is newer to me. Food policy is very important to a food safety consultant. My business started as a way to support small and midsize food businesses comply with the new Food Safety Modernization Act regulations. Food policy also influences where my clients can make and package their foods. New Jersey for example, doesn’t allow any food to be made in a private kitchen, whereas in Pennsylvania, there is a cottage food law that covers jams and jellies and baked goods. 

We can use people centered thinking as an opportunity to look at local food systems. Many people I talk to about food systems are interested in strengthening their local food system and buy regional foods as much as possible. The increase in people who, during the pandemic, opted for Community Supported Agriculture (CSA) to buy food directly from a local farm is a sign of the value of local food systems. 

How do the three different streams of food thinking affect your life? If you are a food business, think beyond the science and manufacturing and look at how you overlap with nutrition if you are producing a particularly healthy food, and never forget that food policy is important!

What If

The one question I am always asking myself when I am writing food safety plans for my clients “What If?”:

  • What if the temperature isn’t exactly at 165 F when cooking chicken?
  • What if the sanitizer concentration is slightly less than the manufacturer recommends?
  • What if the food safety plan is only followed for every other batch?
  • What if colleagues turn up to work unwell?

And I worry. I worry about two things mostly:

  • My client’s customers and consumers
  • My client.

Customers and Consumers

Imagine: a child or an older adult having Salmonella from undercooked chicken

Undercooked chicken may cause foodborne illness
Cooking and manufacturing correctly stops food poisoning. Image from Pixabay

I am a food consumer and I am assuming you are one too! We all eat and, unless we are completely living off the grid, we buy food and food ingredients. We assume that food is safe for us to eat. Thus, selling food comes with a huge responsibility, whether you are selling directly to consumers, through Amazon or Facebook marketplaces; or through a distributor or supermarket. Small and large food producers, cooks, and manufacturers have a responsibility to create and sell food that is the highest quality possible which includes safety. 

When I think about consumers, my “What If” pictures someone, possibly a child or an older adult having Salmonella from undercooked chicken, suffering anaphylaxis from eating misbranded food because the label wasn’t checked for allergens, or breaking a tooth on a piece of metal because the blades of the blender went unchecked. There are lots of stories of people who have suffered from foodborne illness in the US as they affect one in six Americans annually. 

As a food manufacturer or producer, how can we make sure that your product is safe and not about to become part of a foodborne illness story? 

Food Producers and Manufacturers

Recalls are a bad way to manage food safety.

Check lists will help with food recalls
Keep your food safe and never use your recall plan. Deedster from Pixabay

I have this image in my mind of my clients undergoing a recall because they didn’t follow their food safety plan and their Good Manufacturing Practices. This happens to all food producers – I just read about Nestle recalling 381 tons of hot pockets because they contain foreign material such as glass and hard plastic. I am certain that Nestle has a very robust food safety program. Unfortunately, one consumer, that we know of, suffered minor oral injury. So what might have gone wrong? Did the X-ray machine fail? I am sure Nestle’s QA and Food Safety team are looking for the cause.. 

Recalls are a bad way to manage food safety. Not only are food recalls risky for the consumer, they are also costly. A typical food recall has been calculated to cost businesses $10 million in direct costs alone. That excludes costs from the loss of sales, loss of brand integrity and trust, liabilities fees, and increased insurance costs. 

Not to mention the cost to the people who made ill by eating contaminated food.

One of the challenges with “What If” is that we don’t have enough data. We don’t know for certain what would happen if the sanitizer concentration is slightly less than it should be one day. We don’t know if we will cause a foodborne outbreak if we only check the temperature of every other batch. Should we take the risk of a recall if our X-ray machine or metal detector stops working?

Due to my What Ifs, I tell my clients that they MUST NOT cut corners with food safety; to me it is just too risky. The recommendations in a food safety program are there for a reason. 

Which of your What Ifs are you uncertain about? Where are the potential risks in your food production processes? Book a call today so we can start working on your food safety program and making high quality, safe food for your consumers.